Flattened Lobe on BBC, you were right!

[jrork]

Hey everyone,
If you followed my son and I's popping through the carb topic this is an extenstion of that.
Many of you pointed towards our problem as possibly a bad cam and sure enough, No.8 exhaust is gone. Crank it over and it hardly moves...
Swapping a cam I can do but I have one question.
With a Small Block Chevy, you have to drop the pan to get the timing cover off. I've never had to do this on any of our BBC's let alone a jet boat.
Do I have to drop the pan? If so, the only way I can see how you do that is to pull the motor. Does the pump have enough play in the U-joint that I can use my hoist and just pick up the motor enough to clear the pan and leave it hanging or do we have to pull the motor completely.
We have the tools but not the experiance on these jets to go it alone without using some of your experiance/knowledge.
Thanks to the many that helped us find the problem. John and Ian

[Chris J]

You do not have to completely remove the pan. You will need to loosen all the pan bolts and remove the front 3 or so on each side and drop the front of the pan down about 1". If you have to scape the old gaskets off have someone hold a shop vac close to the scapper to catch the debris before it falls into the pan.
NOTE: Most common reason for a bad cam lobe is that you had a piston to valve hit. There is 99.9% chance you have a SLIGHTLY bent #8 exhaust valve that is not closing completely which is why it is backfiring. I would remove the valve and have it checked. If you don't it will still backfire and possible hang up the valve again for another hit.
Good luck.

[Hal]

No you do not have to lower the pan to pull the timming cover on a big block. It does not have the the extra lip on it to hold the rubber seal like a small block does. You need to take the front two bolts out of the pan that go into the cover. It would'nt hurt to loosen a few bolts on each side to make it easier to put the cover back on. The best way to do it is use a razor knife and cut the pan gasket between the block and the cover before you remove the cover. That way you wont screw up your old pan gasket or seal when you pull off the cover. You should be able to just put on a new cover gasket, put some silicone gasket sealer on the rubber gasket and a bead on each side where you cut the pan gasket and you should be good to go. I would'nt worry to much about a bent valve unless you had just put a new cam in and did,nt check your valve clearance or maybe if you reved it up to 9 grand. Always install new lifters when you install a new cam. Good luck..
[ June 21, 2003, 01:07 PM: Message edited by: Hal ]

[jrork]

Okay, we have the cam out. The #8 exhaust is a mess.
I think the damage is from the putz that worked/owned it before. All other lobe/lifters look good. Probably didn't break it in properly.
Since we have it apart, were going to throw a new cam, lifters, timing chain set and a new manifold for our fresh 780 Holley.
This is your chance to spend someone else's money. What would you throw in it?.
Pictures of ruin cam soon to be posted in Image Center.

[jrork]

Okay, we have the cam out. The #8 exhaust is a mess.
I think the damage is from the putz that worked/owned it before. All other lobe/lifters look good. Probably didn't break it in properly.
Since we have it apart, were going to throw a new cam, lifters, timing chain set and a new manifold for our fresh 780 Holley.
This is your chance to spend someone else's money. What would you throw in it?.
Pictures of ruined cam soon to be posted in Image Center.

[comin' unscrewed]

All the metal filings that use to be a cam lobe have been circulating throughout your motor with the oil. (The filter can't catch 'em all :( ) I've had this happen a couple of times and each time I had to pull the motor, thoroughly clean all parts and replace the main, rod and cam bearings.

[Rondo]

Yep....you probably have metal in your bearings by now! I would pull the motor, drop the pan, and take a good look at a couple of the main bearings at least. No sense installing a new cam in a motor full of filings.
Also, your right,.... the last guy may not have broke in the cam correctly but you should check your valve springs for correct installed height and seat pressure. I think this is one of the most important things to do with a new cam.
Good luck with your project!!

[Rexone]

I agree, take the motor apart and clean it. Otherwise there's a good chance you'll be taking it apart again soon anyway.

[HammerDown]

STOP...the motor must come apart and fully cleaned out...trust me, don't short cut this procedure. With in 15 min. I wiped out my #8 Exhaust Lobe in my BBC last year...do it right...or do it again.

[sleekcraft76]

hammer you are so right it needs to come apart and be cleaned out!

[Cas]

Yes, pull the motor out and get the whole thing cleaned. I'm in the process of doing the same thing right now.
What I'm finding strange is how there are so many with the #8 exh lobe going south. My engine had 30+ hours on it since the freshening up last year so it wasn't a poor break in.
I spoke with my machinist about it the other day and he felt it was because #8 lifter possibly isn't getting enough oil? I'm not sure about that but since I'm not a pro, I can't really dispute it. All I know is my oil pump was pumping at 80lbs so I have my doubts on his theory.
My theory is since #8 is the closest to the oil pump that it could be the one that gets any grit first. Maybe something got in there that slowed the rotation of the lifter enough to heat up and wipe out the lobe?
With the engine being at the machine shop, I had him check all the lifter bores and they were all fine.
Back to the subject at hand.....pull the motor, you will be happy you did in the long run.

[Moneypitt]

While you are cleaning/inspecting this BB, don't forget the oil pump. If any foriegn material got to the pan, the first thing to see it is the pump, and there isn't any filtering prior to the pump gears. Also beware of high oil pressure, you don't need 80 lbs, and you would be amazed at the power it takes to create that much oil pressure, 30-40 lbs warm is more than enough, volume not pressure is what keeps the parts cool. New pumps, right out of the box, even brand name super duper pumps, should be opened up and inspected for squarness, and gear end clearence. One more thing, make sure your distributor actually bottoms out on the intake boss, and not the oil pump drive shaft...... Moneypitt

[comin' unscrewed]

jrork:
Unscrewed,
I suppose the exhaust valve might not be opening but wouldn't the engine miss all the time? As it set's now, it idles sweet, and will run up to 2000rpm nicely if I accelerate slowly.
Still sound familiar? It be a great way of talking myself in to a new cam. Sorry I never got back to you on your first post. Chances are the affected valve was still opening slightly. At idle/low rpm the air/fuel charge and resulting cylinder pressure are comparatively small. Also at say 800 - 2000 rpm there is probably enough time to bleed off most of the exhaust gasses through the small valve opening. But when you get into the throttle you get significantly greater cylinder pressure and less time so there is a lot of pressure still present when the intake valve opens resulting in the audible "pop".
As to what to do now? I want to reiterate that there are no short cuts here. The old "Pay me now or pay me later" definately applies. Want proof? Run you finger through the puddle of oil at the back of either head where it drains back to the lifter valley. Then look at your finger under a light. See all the "glitter"? Now consider the path it took to reach the top of the motor. Through the pump, into the main oil galley, through the main bearings, up to the cam bearings, through the lifter gallies, through the lifters and up through the pushrods. You'll probably find that the piston skirts are scratched as well and there may even be metal between the rings and lands. Unless it's nitrided steel, the crank may be scratched too.
Now this sounds like a horror story but don't panic. The major engine components are probably all salvageable. What's important is to take nothing for granted. Take the entire motor apart and thoroughly inspect and clean it including dissambling the heads. (There's metal lurking between the springs/shims/dampers/retainers.)
Also, while you have it apart, check the following:
1. piston to valve clearence
2. installed height of all 16 springs
3. look for coil bind
4. oil pumps are relatively cheap, replace it
5. Is the crank scratched? It'll probably need at least a polish job.
6. Scratched piston skirts aren't a significant problem, but scratched ring lands can be. Have an experienced racing engine mechanic look at them and advise you.
7. After inspection, buy an engine brush set such as this from Summit Racing (http://store.summitracing.com/default.asp?target=search.asp&type=bykeyword&searchtype=both&part=brush+set). Remove the oil galley plugs from the block. Fill a 5 gallon bucket with hot water and a capful of liquid Tide. Put on your swim trunks and go to town on that engine block! Run the various brushes through all the oil passages in the motor. Then (and here's where the fun comes in wink ) rinse with lots of water at good pressure. I suggest a hose end that has a 1/4" outlet. Don't use one of the typical garden handles that adjust from a spray to a stream. It's kinda tough to direct the water right where you want it. Also, pressure washers may not produce enough volume to get the job done IMHO. You need pressure and volume. Anyway, force lots of water through all those oil passages and nooks and crannies. Then, repeat the whole proceedure 2 or 3 times. Dry thoroughly with compressed air.
If you're lucky the minimum repairs you're looking at are probably:
1. crank polishing
2. new main/rod/cam bearings
3. oil pump
4. gasket set
5. cam and lifter set (if you use a different grind than what was in there before, get the recommended springs too.)
Ok guys, what'd I forget?
Good luck John!
[ June 22, 2003, 08:32 AM: Message edited by: comin' unscrewed ]

[jrork]

All of these are good posts and I appreciate it. I have have tougher question that you guys will laugh at.
How do you disconnect the pump so we can pull the motor?
The only logical spot that I can see is that the u-joint within the bell housing but I can't see any way to work through that small inspection hole. Am I missing something obvious?

[HOSS]

Yeah, and now you might as well get Brodix heads, Manley Pro Flo`s, 871, 2 1050 Dominators, etc, etc. Or you could send the heads out to be reworked, shaved (bumps up compression), new main/rod bearings, Lunati cam, Torker intake(used cheap as hell), and probably not that crappy 780 but an 850. Look in Summit for some cheap ass Crane roller rockers. Paint everything a color to your liking. Sand any chrome (if its not rusted yet, it will) and paint it too. Chrome believe it or not doesn`t make you any faster. Although it does disapate heat quicker than painted surfaces. Since the motors out of course! Or you could by mine. :p
Burnt valves probably, bent no.
[ June 22, 2003, 08:37 AM: Message edited by: HOSS ]

[comin' unscrewed]

jrork:
All of these are good posts and I appreciate it. I have have tougher question that you guys will laugh at.
How do you disconnect the pump so we can pull the motor?
The only logical spot that I can see is that the u-joint within the bell housing but I can't see any way to work through that small inspection hole. Am I missing something obvious? Mine's got a foot long drive shaft between the motor and pump with a U-joint at each end so it's easy to pull the four bolts on the flex-plate end. But in any case, on my setup, the rear U-joint isn't retained to the pump shaft in any way. It just slides on and off about 2"-3".

[BK]

Unbolt the bell housing at the rear where it goes around the pump, after you unbolt the other mounts it will just slide off the shaft.

[Cas]

jrork:
All of these are good posts and I appreciate it. I have have tougher question that you guys will laugh at.
How do you disconnect the pump so we can pull the motor?
The only logical spot that I can see is that the u-joint within the bell housing but I can't see any way to work through that small inspection hole. Am I missing something obvious? If you have a 3 point mount, you can remove the 2 bolts holding the bell housing to the pump. Then remove the 4 or 6 bolts to the front motor mounts, hook it up to a hoist and as you're lifting push the engine forward. The drive shaft will slide off the shaft.
If you have a 4 point, remove all the bolts holding the engine in place, hook up the hoist and as you're lifting, push the engine forward and the drive shaft whould slide off the shaft. :)

[jrork]

Perfect, I was hoping it would be that but I wasn't sure.
We've got the hoist and stand already so this should be a piece of cake.
Thanks and stay tuned..

[malcolm]

Hey, good luck you guys. I'm gonna be heading up to my shop to get some more done on my engine in a bit. I looked you up on the map, that looks like a nice area over there. When I get mine running again I'll have to see how much a ferry ride is for a truck/boat. :)

[jrork]

Okay,
Weve got it out and apart.
Main and Rod bearings aren't great but could have been much worse. The journals should polish up good. There don't appear to be any big issues there.
The previous owner said that it only had 30 hours on it since rebuild and I tend to beleive it since I was expecting worse.
I'm going to drop the block and heads off at the shop tomorrow and get them working on cleaning this mess up.
The crank is a .010 .010.
Cylinders look good. I'll probably ball hone those to clean them up.
The oil pump is headed to the garbage can. I didn't even bother to open it up.
Thanks everybody

[Moneypitt]

before you pitch the pump take it apart and look at the wear on the cover. This MAY show that the dist. was NOT bottomed out on the intake, but was forcing the shaft into the gear and into the cover. Also, just an arc on the cover shows how far out of square the pump was machined. This is common, even in the high dollar brand name pumps. If you don't have "How to hotrod BBCs" by hp books, get one and read about the oil pumps for BBCs. different sizes etc. Remember this is the "HEART" of the engine, and can really make a difference. You can waste a lot of power with the wromg oil pump set up....Good luck... Moneypitt

[TIMINATOR]

DON'T BALL HONE IT!!!!!!! more good hone jobs have been ruined by ballhoning than everything else! A good, straight hone is important to making power, a ball hone just won't do it. We get motors in here that have been ballhoned for the same reason as yours,and they lose power,and use oil. Sometimes if they are run long enough the rings will wear into the walls and start to seal, sometimes not. if the ring seal aint broke,DON'T FIX IT!!!!!

[jrork]

Just a quick update on our boat.
We took everyones advise and pulled the motor completely apart and had it cleaned out.
We knocked in some brass freeze plugs, new Clevite bearings .010 on the main jounals and std. on the rod bearings. The journals were fine and polished up very nicely. The 40 over pistons were cleaned and reused. We did rering it and when the rings were measured they gapped out nicely.
We plunked in a new Moroso HV pump, hardened drive shaft, A Comp Cam, lifter and roller timing chain.
We still haven't gotten the heads back but they've been mag'd, surfaced, cleaned, valve seats, valve guides installed and will have matching Comp Cams valve :D springs, retainers and locks.
I got a good deal on some Crane long slot rockers so they are being added to the mix.
While we were at it, we dropped a Edelbrock Performer RPM intake in the mix and a new scoop from RexMarine.
I don't know if it will run any better but it sure will look good.........
Many thanks to all of you and especially Malcolm for all the help and advice.
Stay tuned as we hope to break in the cam this weekend.....