BBC tuning help needed

[hotrod56cars]

I just got my engine back from the rebuilder and it's running like crap. It's been over 20 years since I've messed with a "hot rod" engine and it's becoming obvious I've forgotten more than I remember.
'69 Chevy 427 forged crank, stock rods, Sealed Power domed forged pistons, '69 427 101cc closed chamber heads, about 11:1 compression, Schnieder JB4 cam (510 gross lift, 310 gross duration), Pete Jackson gear drive, HEI distributor with a Hypertech coil, Accel wires, Autolite plugs, Holley Strip Dominator intake, Holley blue electric fuel pump and reg (6 psi at any given RPM), Holley 800 DP w/mechanical secondaries (fresh rebuild by a pro with alcohol gaskets in it), 91 octane gas.
When I first fired up the engine it was very snappy with no hesitation. My engine's builder told me to set the timing at 36 degree's total which I did several days later. In those several days I would fire the engine up just because I liked the way it sounded :D but it seemed to be slowly running crappier and crappier. The total timing set at 36 degree's put my initial timing at 20 degree's which broke the nose on my starter, yesterday I replaced the starter and moved the initial timing to 10 degree's. It just keeps running worse and worse the more I mess with it/run it. A friend commented last night that he saw flames shooting out the headers. I'm thinking it's a fuel problem (too lean) but I don't have a clue (it seems) as to what I'm doing. I'm leaning towards a vacuum leak as the culprit. The guy that built my carb is well known in the area and he jetted my carb for my application.
At this point when the pedal is stabbed the engine dies. It sounds very rough, "choppy" if you will, it refuses to idle below 800 RPM and although I know I don't want it to idle that low in a jet boat, shouldn't it be able to idle below 800 RPM out of the water and not hooked up to the jet drive? What kind of aresol spray (carb cleaner, WD40, etc.) can I use to check for vacuum leaks that won't stain my parts? I want to do a plug check, should I do it at idle or at higher RPM's, or both?
Any advice out here? Where else should I "look" besides a vacuum leak?

[ck7684]

hmmm, I'm no expert but I would look towards a vacuum leak, possible around the intake gaskets. I'm just taking a guess seeing as it's a new engine that was running great when you got it. The front and rear of the intake is usually just RTV'd
Did this thing idle at or below 800 when you first got it? I think mine idles around 1000 and I may have less duration than yours...

[victorfb]

first off, only use a spray to check for a vacume leak if you really have to. vacume guages are cheap at almost any autoparts store.
the fact that this engine was running well prior leads me to believe you have something else rather than a vacume leak. cam going flat, contamination in the carb, ?,?,? start at the basics and check your plugs, take a compression check of all cylinders, check your electrical system (plugs wires cap and rotar ect), check the carb and filter, make sure no jets are clogged, check valve train and clearances (lash).

[thatguy]

first off, only use a spray to check for a vacume leak if you really have to. vacume guages are cheap at almost any autoparts store.
the fact that this engine was running well prior leads me to believe you have something else rather than a vacume leak. cam going flat, contamination in the carb, ?,?,? start at the basics and check your plugs, take a compression check of all cylinders, check your electrical system (plugs wires cap and rotar ect), check the carb and filter, make sure no jets are clogged, check valve train and clearances (lash).
Cam would be my first guess, since it just happened to me EXACTLY how you describe.
Pull covers and see if any rockers are loose. If not, RE-CURVE distributer.
I have 12 initial, 36 total. All in at 3200RPM (MSD)
Tommy

[Mr. Crusader 83]

Timing at Idel is nothing. You only need to worry about total advanced timing. Set it back to 36degress total. Then pull you valve covers and make sure all your rockers are moving the same amount.
Also with a fresh motor. Did you or the builder break in the cam? If not it could be going flat. When my cam went flat it back fired out the carb.

[hotrod56cars]

cam going flat is a possibility. I originaly built this engine myself, in the 23 minute cam break-in I got a lot of water in the oil. The engine builder said my cam looked and measured fine when he rebuilt the engine after me, but water in the oil can't be good for a new cam... I'll check the rocker arms for play after work today, as well as all of the other rec.'s. Thanks!

[Mr. Crusader 83]

I have a 468 with closed chamber heads and two holley 750's. My buddy tuned it all in for me lastnight. At idel it at 1100rpms, on the trailer.

[thatguy]

Timing at Idel is nothing. You only need to worry about total advanced timing. Set it back to 36degress total. Then pull you valve covers and make sure all your rockers are moving the same amount.
Also with a fresh motor. Did you or the builder break in the cam? If not it could be going flat. When my cam went flat it back fired out the carb.
Initial does matter if he is breaking starters off. I respectfully must disagree with you on this.
Tommy

[pw_Tony]

Try running it without the valve covers on to try and check me make sure they're all moving around the same amount, the rockers. Just cover everything up so you don't make a mess

[hotrod56cars]

first off, only use a spray to check for a vacume leak if you really have to. vacume guages are cheap at almost any autoparts store...
With the cam being a non-stock cam, how much vacuum should I be looking for?

[thatguy]

Try running it without the valve covers on to try and check me make sure they're all moving around the same amount, the rockers. Just cover everything up so you don't make a mess
That was my first clue when mine went flat. But I used a remote starter trigger instead of running it.

[Mr. Crusader 83]

Try running it without the valve covers on to try and check me make sure they're all moving around the same amount, the rockers. Just cover everything up so you don't make a mess
Just go to Checkers and get the metal clips that go on the rockers. They are like 2 bucks and then oil wont go everywhere.

[ck7684]

Cam going flat is a definate possibilty too...sometimes I assume that everyone has a roller nowadays...
Also, make sure the cam is for the correct year block. If I remember correctly, the early BBC cams have a groove for oiling...
"Big blocks, cast in 1965 and '66, used a "grooved" rear cam bearing with a matching "groove" in the rear journal of the camshaft itself. This groove provided an oil passage to the lifter oil galleries. 1967 model and later Mark IV blocks have an annular groove oiling passage cast into the block itself. The blocks cast from the '67 model year on use a smooth, non-grooved cam bearing and the rear cam journal for these '67 and later blocks is smooth and does not use a grooved rear cam journal. The reason this is important is that if the wrong cam bearing gets used in the '65-'66 blocks, no oil gets to the lifter galleries or up to the rocker arms. The '65-'66 grooved cam bearing has three oil holes to feed the cam journal and the two lifter gallery passages. The '67 and later cam bearing is smooth and only has one oiling hole in it. A few of the cam makers will provide a big block cam with the groove cut in the rear camshaft journal, but you can have your machinist cut a groove that is 3/16" wide and 7/64" deep in the center of the rear cam journal if you have a big block cast in the '65 or '66 model year."

[ck7684]

I also found this...
"If you are building a big block Chevy with a flat tappet cam, (solid or hydraulic lifters) be careful during the initial engine break in. It is very easy to lose a cam lobe and lifter during initial break in. This is especially true with a higher than stock lift cam and higher pressure valve springs. The increased pushrod angles found on the BBC and poor preparation can make cam lobe failure after initial fireup a distinct possibility. You can help prevent this cam lobe failure by making sure the engine is prelubed prior to intial fireup. Use a good high pressure lube on the cam lobes and lifter bottoms during assembly. If possible use a lighter pressure stock valve spring (or if using a valve spring with multiple springs, take out some of the inner springs) to intially run the engine. Then switch to the heavier pressure springs after break in. When the engine is first fired up, keep the engine rpms at 2,500 or above, don't let the engine idle for 20 minutes or longer. This keeps lots of oil splashing up on the cam lobes. Make sure the engine can be run for this time period by having enough fuel available, ignition timing set correctly, coolant available for the motor, valve lash set correctly, etc. The idea is not to crank the motor over excessively before it starts up for the first time. If your BBC flat tappet cam survives this initial break in period, it will be good to go for many miles. After the initial engine breakin, drain the oil and change the oil filter. Roller cams generally do not suffer these types of cam lobe failures during initial engine fireup.

[Squirtcha?]

Cam would be my first guess, since it just happened to me EXACTLY how you describe.
Tommy
Unfortunately, I'd have to agree with Tommy here. Especially the way it's getting worse
the more you run it. Hope it's not the case though.

[hotrod56cars]

... Hope it's not the case though.
Me too!

[thatguy]

Unfortunately, I'd have to agree with Tommy here. Especially the way it's getting worse
the more you run it. Hope it's not the case though.
Exactly. I replaced the cam with an identical one (comp 284 extreme) new lifters, 11 qts. of Rotella, 2 bottles of Comp. break in lube, new filter, fired as soon as I hit the button. Held it at 2200 RPM for 30 full minutes. Worked great second time.
First time had 20 minute break in and maybe 30 additional minutes tuning it. When I pulled the first cam 4 lobes were GONE, 4 lifters were ate into the hollow part of the lifter and several more were on the way. I mean it absolutely DESTROYED the first cam.
I think the reasons for success the second time were several things.
1. Springs tend to loose a great deal of seat and open pressure after initial fire up. More so than after initial fire. (Well, at least in the same amount of running time)
2. extra qt. of oil. (Rotella, more good stuff in it)
3. doubled break in additive
4. LIMITED RPM to 2200. 2500 OR ABOVE is not conducive to success in BBC, IMHO. 2200, no more- no less. That worked for me.
The symptoms described leave little doubt that it is your cam, to me at least. Did he re-use the lifters that you had installed?
Tommy

[ck7684]

In the engines I've built, I've varied the rpm a bit from 2000-2500 during the break in time...

[Mr. Crusader 83]

I dont know about the cam going flat though. Dont they usually pop through the intake when a cams flat? Fire out the exhaust sounds more like timing and a leak somewhere.

[thatguy]

I am waiting with baited breath. Hope he doesn't go through that hassle!
Tommy

[VAMI]

Double check the intake bolts and carb base bolts.You need to pull the valve covers off.Do have the stamped rockers with the lock nuts?Those things will losen up.Check the rocker studs for tourqe.Spin the motor around and watch the pushrods at the guide plate area to see that they are all moving the same amount.Maybe you can have some good luck and just have a few rockers that backed off.

[Desert68]

You might also check the ignition system. Ignition troubles can have symptoms like you're seeing. Along these lines maybe pull the distributor to see if the gear is OK. Along with wiped out cam lobes there has been wiped out distributor gears. Zinc additives have been removed from many oils, blah, blah. Rotella is one that still has the good additives. The diesel rated oils still have the zinc additives. I also agree that 20 degrees initial is too much. 36 total seems fine, but like in a drag car you'd fine tune that with top end MPH. The 12 initial, all in by 3200 RPM sounds good, but I don't know boats. A typical street car hot rod would probably have it all in by 3000, maybe even by 2700 or 2800. The guy that said initial doesn't matter isn't wrong. Some guys set up a hard core motor with locked in timing and that's it. As far as vacuum, you listed the advertised duration, but that doesn't tell much - it varies so much from one cam company to the next. Do you know the .050 duration? If you know that, you should be able to get some sort of an idea on vacuum at idle. You get near 250 or 260 degrees duration @ .050 and you's got a pretty lumpy cam that won't have a lot of vacuum. Also see if you know the lobe separation - it also comes into play. That number should be something like 108, 110, 112, etc. I think somebody also mentioned checking for boken valvesprings. You could do a basic check by pulling the valve covers and turning the engine over by hand. One more thing could be a bent pushrod.

[El Prosecutor]

. . . A friend commented last night that he saw flames shooting out the headers.
At least there is an up side to it. That sounds pretty cool to me! :D
Seriously though, looks like you are getting some good input here, hope it works out soon.

[QuickJet]

If you were just doing quick little start ups here and there, I doubt that it would flatten the cam to where you would notice it. First thing I thought of was the spark plugs. If you were just starting it here and there without any timing in it, you could soak a set of plugs pretty quick. Especially without heating the engine up. Also, was the HEI in the boat before? If you were previously running a points type, you are going to have to swap out the resistor wire to the distributor to a non resistor type.

[ol guy]

Hey hot rod just curious as to what oil you fired the motor on.

[thatguy]

You might also check the ignition system. Ignition troubles can have symptoms like you're seeing. Along these lines maybe pull the distributor to see if the gear is OK. Along with wiped out cam lobes there has been wiped out distributor gears. Zinc additives have been removed from many oils, blah, blah. Rotella is one that still has the good additives. The diesel rated oils still have the zinc additives. I also agree that 20 degrees initial is too much. 36 total seems fine, but like in a drag car you'd fine tune that with top end MPH. The 12 initial, all in by 3200 RPM sounds good, but I don't know boats. A typical street car hot rod would probably have it all in by 3000, maybe even by 2700 or 2800. The guy that said initial doesn't matter isn't wrong. Some guys set up a hard core motor with locked in timing and that's it. As far as vacuum, you listed the advertised duration, but that doesn't tell much - it varies so much from one cam company to the next. Do you know the .050 duration? If you know that, you should be able to get some sort of an idea on vacuum at idle. You get near 250 or 260 degrees duration @ .050 and you's got a pretty lumpy cam that won't have a lot of vacuum. Also see if you know the lobe separation - it also comes into play. That number should be something like 108, 110, 112, etc. I think somebody also mentioned checking for boken valvesprings. You could do a basic check by pulling the valve covers and turning the engine over by hand. One more thing could be a bent pushrod.
Yes, I am changing springs to have it all in by 2800. I have only ran my boat twice, so did not want to get too cowboy right of the bat!! :D :D

[pw_Tony]

Maybe try and get a water bottle and spray some water around the intake and base gasket, if the idle raises then it's a vacuum leak

[hotrod56cars]

Wow that's a lot of replies! Thanks! Just got off of work so I'm going to go check it out right now.
I broke the cam in on the last rebuild when I built it myself. That didn't go very well either. RPM's ranged from 2000 - 3500 for the 23 minutes it ran because I couldn't get the flockin thing to run right (wrong intake manifold gaskets/vacuum leaks), for the most part the range was more like 2500 - 3000. I used 9 quarts of Valvoline and 1 quart of Lucas oil addittive on the cam break-in.
Here I go...

[Desert68]

I meant to mention a break-in additive called GM EOS - General Motors Engine Oil Supplement. Good stuff - add one can to the oil - been around for years. I get it at Chevy dealers. Someone else mentioned a Comp Cams additive. Comp is one of the companies that really stepped up when so many people were seeing new cams getting wiped out. They helped bring out the info about the Zinc being removed from many oils. I imagine their stuff is good, too.
A few years ago I put an Ultradyne cam in an engine and their break-in instructions were to use only the inner springs for the break-in period, then add the outer springs. First time I had heard of that method. I didn't do it.

[hotrod56cars]

All the valves appear to be opening and closing at the same amount. When the engine is off and I check for real loose rocker arms (Pro Comp aluminum roller rockers) none of them are real loose, they all feel correct with no play (hydraulic flat tappet) up or down and I am able to "slide" them side to side with a feeler gauge type of a feel to them (only on the valves that are closed). I sprayed water all over the intake and carb with no change whatsoever. I've tried the initial timing at 0, at 6, at 10, and at 20. I'm going to put it around 14 and then mess with the carb. Popping out the exhaust, runs real rough, sounds choppy instead of lopey, I'm thinking it's running lean. Just got off the phone with the engine builder and he thinks it's timing, he said put the initial between 12 and 18.
This is my first boat with headers, I got 4 burns in the last half hour or so. :o
I must have missed something somewhere...
oh yea, it's got 9 quarts of Castrol and 1 quart of Schneider oil additive (for zinc content) in it right now.

[QuickJet]

All the valves appear to be opening and closing at the same amount. When the engine is off and I check for real loose rocker arms (Pro Comp aluminum roller rockers) none of them are real loose, they all feel correct with no play (hydraulic flat tappet) up or down and I am able to "slide" them side to side with a feeler gauge type of a feel to them (only on the valves that are closed). I sprayed water all over the intake and carb with no change whatsoever. I've tried the initial timing at 0, at 6, at 10, and at 20. I'm going to put it around 14 and then mess with the carb. Popping out the exhaust, runs real rough, sounds choppy instead of lopey, I'm thinking it's running lean. Just got off the phone with the engine builder and he thinks it's timing, he said put the initial between 12 and 18.
This is my first boat with headers, I got 4 burns in the last half hour or so. :o
I must have missed something somewhere...
oh yea, it's got 9 quarts of Castrol and 1 quart of Schneider oil additive (for zinc content) in it right now.
Are you sure that #'s 5 and 7 spark plug wires aren't crossed?

[49er]

Could Be A Flat Cam. I Would Also Check The Gas Make Sure It's Not Gone Bad, Water In The Gas Will Make It Run Like Sht Too.. Don't Know How Clean Your Tanks Are.

[Bense468]

Check all your ignition out first. Timing in a chevy is 18436572. Check cap and roter, plugs, simple stuff. If its still running like shit, it can be flat cam, or a hung valve

[Cas]

Check all your ignition out first. Timing in a chevy is 18436572. Check cap and roter, plugs, simple stuff. If its still running like shit, it can be flat cam, or a hung valve
spring bind can cause it also. Hopefully it's just water in the fuel system.

[bradbigsley]

i would pull the oil filter and cut it open.. if your cams flat youll know it

[hotrod56cars]

Long story short, it's the carb. I have the initial timng now at 18 initial, 36 total. More on the timing later.
Long story long, I broke in the cam with the engine after I built it, got water in the oil, had a engine builder rebuild it for me, got it back 2 1/2 months later, ran great, and within the next week of running it on the trailer runs like garbage. I pulled the front fuel bowl off of the carb and it's full of brown crap, looks like dirt. :confused: The guy that built my engine is going to clean it out for me for less than half of what the carb builder wanted. I'm trying to make one last river trip before it's past the season...
The timing. When I broke the cam in I was trying to use my "bought new on eBay from private seller's" MSD Marine distributer, MSD 6AL, and Blaster 2 coil. The MSD box is bad/defective and puts out a constant rapid fire spark just by hooking up the +12, ground, and the tach wire. So I'm hoping that I can "settle" and use the HEI until I can figure out how to go about and how much it's going to cost to fix the MSD 6AL. Anyway, the HEI that's on it now has initial timing at 18, total timing at 36 degree's. From idle to about 2200 RPM it's at 18 degree's, from 2200 to 4000 is the curve and stays constant from 4000 on at 36 degree's. Seems like the HEI's curve is short and comes in late. :confused:
At least my first thought was right, it is running lean. :D
So where's a thread on the best way to go about where you should set your timing without spending a month doing it?
THANKS! For all of you chiming in and trying to help me out. :)
.

[thatguy]

All the valves appear to be opening and closing at the same amount. When the engine is off and I check for real loose rocker arms (Pro Comp aluminum roller rockers) none of them are real loose, they all feel correct with no play (hydraulic flat tappet) up or down and I am able to "slide" them side to side with a feeler gauge type of a feel to them (only on the valves that are closed). I sprayed water all over the intake and carb with no change whatsoever. I've tried the initial timing at 0, at 6, at 10, and at 20. I'm going to put it around 14 and then mess with the carb. Popping out the exhaust, runs real rough, sounds choppy instead of lopey, I'm thinking it's running lean. Just got off the phone with the engine builder and he thinks it's timing, he said put the initial between 12 and 18.
This is my first boat with headers, I got 4 burns in the last half hour or so. :o
I must have missed something somewhere...
oh yea, it's got 9 quarts of Castrol and 1 quart of Schneider oil additive (for zinc content) in it right now.
Well, that is certianly promising about the rocker clearance.
Go down the list.
Plugs, wires, power valve, fuel pressue, coil?
I'd take that distributer in and have that bitch checked out and set up.
Tommy

[hotrod56cars]

Anyone have any tips on tuning a HEI distributer's timing curve?
.

[hotrod56cars]

Anyone have any tips on tuning a HEI distributer's timing curve?
Nevermind, I just found out it takes a machine to totaly recurve an HEI.
.

[49er]

Anyone have any tips on tuning a HEI distributer's timing curve?
.
I never liked distributers that had vacum or manual. Every hod rod I've never had i've always had the distributer locked out , it's easy to do just take the springs off and weld it to where it's at total advance. It's always worked great for me. The last boat I had I ran a HEI for a while and the first thing I did was lock it out. Set the timing where you want it (36) total is what i ran on my NA motor, always started right up never had any problems

[Squirtcha?]

Long story short, it's the carb. I have the initial timng now at 18 initial, 36 total. More on the timing later.
Long story long, I broke in the cam with the engine after I built it, got water in the oil, had a engine builder rebuild it for me, got it back 2 1/2 months later, ran great, and within the next week of running it on the trailer runs like garbage. I pulled the front fuel bowl off of the carb and it's full of brown crap, looks like dirt. :confused: The guy that built my engine is going to clean it out for me for less than half of what the carb builder wanted. I'm trying to make one last river trip before it's past the season...
The timing. When I broke the cam in I was trying to use my "bought new on eBay from private seller's" MSD Marine distributer, MSD 6AL, and Blaster 2 coil. The MSD box is bad/defective and puts out a constant rapid fire spark just by hooking up the +12, ground, and the tach wire. So I'm hoping that I can "settle" and use the HEI until I can figure out how to go about and how much it's going to cost to fix the MSD 6AL. Anyway, the HEI that's on it now has initial timing at 18, total timing at 36 degree's. From idle to about 2200 RPM it's at 18 degree's, from 2200 to 4000 is the curve and stays constant from 4000 on at 36 degree's. Seems like the HEI's curve is short and comes in late. :confused:
At least my first thought was right, it is running lean. :D
So where's a thread on the best way to go about where you should set your timing without spending a month doing it?
THANKS! For all of you chiming in and trying to help me out. :)
.
Congratulations on it not being anything major. Sounds like you still have some issues to iron out, but at least it's not a rebuild.
I'm sure you already realize this, but make sure to clean your tanks out.

[Bense468]

I've always locked my stuff out too. Jetboats rpm at the wack of the throttle.

[Desert68]

Nevermind, I just found out it takes a machine to totaly recurve an HEI.
.
You can do it with a timing light. One thing you might try that is quick and cheap is to get a recurve kit, use one light spring and one medium spring, keep the stock weights in it, then see what the curve looks like.

[H20MOFO]

Maybe I'm Up In The Night. My Bbc Is 11.5 To One With Aluminum Heads And It Won't Even Think About Runnin On 91, Are You Runnin Iron Heads Or Aluminum?

[hotrod56cars]

I think I read somewhere that vacuum advance mech.'s are for mileage and for part throttle (that's why I didn't hook up the HEI's vacuum advance, is that why I'm not getting the amount of advance I thought I would get?), so with two responses telling me that I don't even need a mech. advance...
What's the mechanical advance for? What are the advantages and disadvantages of getting rid of the mechanical and vaccum advances all together?
By changing the springs on the mechanical advance I think it would change when the mechanical advance starts (and ends), but wouldn't change how much advance it will give, correct?
Iron heads, 101cc combustion chamber, closed chamber, oval port, 2.06 intake, 1.72 exhaust, 1969 L36 427 Corvette engine, seemed OK running on 91 on the trailer until it started having the problem's that created this post (dirty carb). I plan on dumping some race gas in with the pump gas before it hits the water, I just assumed running 91 wouldn't be a problem while it's still on the trailer with no load on it.

[Desert68]

What's the mechanical advance for? What are the advantages and disadvantages of getting rid of the mechanical and vaccum advances all together?
By changing the springs on the mechanical advance I think it would change when the mechanical advance starts (and ends), but wouldn't change how much advance it will give, correct?
I do not know boats - learning. My guess is you don't need/want a vacuum advance in a boat, at least not a jet boat. If it has one, you do not want it hooked up if you're using a timing light to check a curve. The comment about total advance is correct - the springs won't change the total, just the rate at which the advance changes.
I know zero about a locked distributor other than the timing is what it is set at, period, no change. My impression, right or wrong, is it's suited for an application where the engine basically goes from idle to wide open throttle, or close to it. Hard core stuff. Seems to me like I'd be worried about detonation at a lower RPM, heavy engine load situation with pump gas and 36 degrees of advance. But again, I don't know and have zero experience.
An L36 was originally 10.25:1 compression. Rebuild changes things. Were the heads shaved for flatness? How thick are the gaskets? Block decked? What pistons? Stuff like that. If you know it has flat-top pistons in it, my guess would be you should be safe with 91/92 pump gas.
Does someone have a carb you could borrow? That's a quick/easy way to rule out that part of things.

[thatguy]

I think I read somewhere that vacuum advance mech.'s are for mileage and for part throttle (that's why I didn't hook up the HEI's vacuum advance, is that why I'm not getting the amount of advance I thought I would get?), so with two responses telling me that I don't even need a mech. advance...
What's the mechanical advance for? What are the advantages and disadvantages of getting rid of the mechanical and vaccum advances all together?
By changing the springs on the mechanical advance I think it would change when the mechanical advance starts (and ends), but wouldn't change how much advance it will give, correct?
Iron heads, 101cc combustion chamber, closed chamber, oval port, 2.06 intake, 1.72 exhaust, 1969 L36 427 Corvette engine, seemed OK running on 91 on the trailer until it started having the problem's that created this post (dirty carb). I plan on dumping some race gas in with the pump gas before it hits the water, I just assumed running 91 wouldn't be a problem while it's still on the trailer with no load on it.
Right. On the MSD distributor you change a little bushing that sits on a little post under the weights. The wieghts lift off and then you can see thee limiter bushing. It is a stop. The smaller the bushing the more it lets the wieghts travel. Hence more advance curve. The springs control only the rate.
If you are at 10 at idle, for instance, with a bushing that allows 20 deg. mech. advance you will end up with 30 totaL. the springs will determine what RPM it is all in by.
So if , for instance you wanted 35 total, instead of setting the initial at 15 you would leave it at 10 but change the bushing to allow 5 more deg. of travel. Then change to a lighter spring so it would still all be in at the same time.
I can't tell you how to do it on an HEI. I have only ever used MSD's. They have color coded bushings and springs and a little chart that tells you the characteristics.
I would think that because your engine is getting worse as it runs that it is not necessarilly the set up, but something failing such as a coil, module or pickup magnet or eye. If in fact it is ignition related.
A quick spin on a distributor machine will tell a lot. Call your local auto electrical shop and see who can test it for you. Might end a lot of gues work.
Just be glad it doesn't look to be your cam. I was hooked up to the truck with the boat loaded for the maiden voyage when I discovered mine was shot. :(
Tommy

[hotrod56cars]

Right. On the MSD distributor you change a little bushing that sits on a little post under the weights. The wieghts lift off and then you can see thee limiter bushing. It is a stop. The smaller the bushing the more it lets the wieghts travel. Hence more advance curve. The springs control only the rate.
If you are at 10 at idle, for instance, with a bushing that allows 20 deg. mech. advance you will end up with 30 totaL. the springs will determine what RPM it is all in by.
So if , for instance you wanted 35 total, instead of setting the initial at 15 you would leave it at 10 but change the bushing to allow 5 more deg. of travel. Then change to a lighter spring so it would still all be in at the same time.
I can't tell you how to do it on an HEI. I have only ever used MSD's. They have color coded bushings and springs and a little chart that tells you the characteristics.
I would think that because your engine is getting worse as it runs that it is not necessarilly the set up, but something failing such as a coil, module or pickup magnet or eye. If in fact it is ignition related.
A quick spin on a distributor machine will tell a lot. Call your local auto electrical shop and see who can test it for you. Might end a lot of gues work.
Just be glad it doesn't look to be your cam. I was hooked up to the truck with the boat loaded for the maiden voyage when I discovered mine was shot. :(
Tommy
Yea, I'm very happy the cam appears to be good. :D
With the adjustability of MSD distributor's, it makes me wish I would have bought mine new. I'm sure they come with "extra parts" when they're new, right?
Anyone have any more thoughts on the advantages/disadvantages to locking out a distributor on a jet boat?
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[thatguy]

Yea, I'm very happy the cam appears to be good. :D
With the adjustability of MSD distributor's, it makes me wish I would have bought mine new. I'm sure they come with "extra parts" when they're new, right?
Anyone have any more thoughts on the advantages/disadvantages to locking out a distributor on a jet boat?
.
You know, I have never bought one new in box. They either came with what I bought or got them like new from somebody.
The one in my boat 454 is a ready to run Pro-Billet. Probably one of the most popular models. The bushing and spring kits are at any speed shop. Around $20.00 for a complete tuning kit. (bushings, springs, chart.)
Tommy

[hotrod56cars]

BBC tuning help wanted is an understeatement.
W.O.T. 3900 RPM
48.7 mph
rides like sh!t.
runs like sh!t.
place diverter AFU
bilgde pump problem, took on a lot of water, not a good combination.
burnt my forehead on super flockin hot headers.
severely disapointed

[thatguy]

BBC tuning help wanted is an understeatement.
W.O.T. 3900 RPM
48.7 mph
rides like sh!t.
runs like sh!t.
place diverter AFU
bilgde pump problem, took on a lot of water, not a good combination.
burnt my forehead on super flockin hot headers.
severely disapointed
Damn, sorry to hear that. Wish I was closer, would love to try to help you sort it out. Really souds like possible cam timing / ignition problems.
Tommy

[hotrod56cars]

I'll get back on it... ;) I'm thinking ignition problems. I'll get my MSD box fixed and ditch the HEI first.

[IMPATIENT 1]

BBC tuning help wanted is an understeatement.
W.O.T. 3900 RPM
48.7 mph
rides like sh!t.
runs like sh!t.
place diverter AFU
bilgde pump problem, took on a lot of water, not a good combination.
burnt my forehead on super flockin hot headers.
severely disapointed
ahhh man, ya just had a bad day on the water, we've all been there.:D even a bad day on the water is better than a good day at work;)

[pw_Tony]

BBC tuning help wanted is an understeatement.
W.O.T. 3900 RPM
48.7 mph
rides like sh!t.
runs like sh!t.
place diverter AFU
bilgde pump problem, took on a lot of water, not a good combination.
burnt my forehead on super flockin hot headers.
severely disapointed
Got any pics of your new bassett tattoo?

[hotrod56cars]

ahhh man, ya just had a bad day on the water, we've all been there.:D even a bad day on the water is better than a good day at work;)
I'll drink to that! :D
.

[hotrod56cars]

Got any pics of your new bassett tattoo?
Hell no, you'd have to pay me for a picture. :o :D
.