Wanted, Sbc Motor Mounts

[miketsouth]

I been talkin all this HP stuff and am going to prove it, one way or another. In order to do that, i got to install a SBC. Expecting HP similar to a stock BBC with a little less weight (of course that HP will be had at a little higher RPM to make up for the CID loss) Been studying camshaft design an properties. Havent got a clew. I know the basics, but how to apply them must take some experience. I have had good recommendations from those that know.
My options are:
Stringer mount from CP or Rex or Glen-i and lookin at $450 or so.
Rail or maybe stringer mount from someone who has some that they will let go of.
Rail mounts are presently in the boat, but i think stringer mounts will work at 24.2' between the stringers. I like the rail mounts and it dont look hard to convert them. Seems maybe the rail mounts stiffen it up somewhat. Little full lenth stringers, like 1"x3"
The one piece rear (no cover and brace) appeals to me.
Bling is up in the air. Perfect bling is nice, otherwise black paint will do.
If you have any offers, please write me a pm.
mikeT
'i taut i taw a puddy tat"
PS if you want to know the truth i am just a cheep SOB that wont afford a BBC. SBC's are cheep. Disposable cheep. I expect WOT with a SS 'B' AT to be about 5100 or so at 350HP. Could be as low as 300 at 4800 but most have given me hopes of the higher figure. It seems to be all in the cam. I do expect some better acceleration from less weight.
Very little will be done to help the engine live at this rpm. Good balance, deeper pan, constant oil pressure & temp monitoring .

[Jungle Boy]

Your hopes are a little high on your expected RPM with the HP you are planning to run. With 350 HP, you will most likely turning a "B" at about 4500 / 4600 RPM. This will obviously depend on your altitude and pump condition. I have 2 small blocks currently. One is a ZZ4 that's was mildly ported and dynoed at 405 HP. It turns a "B" impeller at 3400 ft @ 4700 RPM on a good day. The 434ci x 560 HP (dynoed) turns a "B" at 5400/5500 RPM again at 3400 ft.

[miketsouth]

Sea level, i think that makes a big difference in what HP will be produced.
As far as what RPM@HP I am basing this mostly on others' experience and the AT pump chart. At first i was shooting for lower WOT rpm to try to make the engine hold together a little longer or maybe be a little more efficient at cruise, but research and common sense shows it aint gonna happen, that is HP at low RPM with small CID no matter what cam.
No replacement for displacement as regards HP. If no displacement then RPM is necessary.
AT pump chart (http://www.americanturbine.com/information/impeller_chart_sd309.htm)
Also you might have a B legend, agressor or something that does not follow the berkeley pump chart (i keep hearing that a B is an A in some pumps). I find the this pump chart to be ok for 330HP on an A impeller. If i understand it right, loading also can change the RPM@HP too. Got a lot to learn. Camshaft selection has been, if not interesting, confusing. Again got a lot to learn.
I really dont know what will happen. It will happen, though.
mikeT

[JEThro]

Mike, I know what you're going thru about selecting a cam. I'm in the same boat. When you ask one of the jet "Gurus" about a cam for a SBC,they all seem to pause for a while to think that one out.
I put in a 350 towards the end of last season after I grenaded my 327. With a Berkeley 12JC and an "A" impeller, I maxed out at 4500rpm with the headers wet,4700rpm dry. Here's a link for more info. Jethro
http://www.79tahiti.freecyberzone.com/photo5.html

[Cas]

you want to really test it, put in a cam that will peak it's TQ at 2500 rpms. Then try a cam that will put out out peak TQ at 4500 rpms.
You will then get your answer and it's the same answer most already know.
Actually, save yourself so time and money, just put a cam in your engine now that will put out it's peak TQ at 2500. I bet you won't get near what you're getting now.
Bottom line, you want the most TQ you can get and have it peak in the 4500 rpm range or above.

[miketsouth]

That look very VERY nice Jethro. Wild WILD intake setup. I REALLY like the way that looks.
4500RPM on an A i suppose is about 290HP. And i would think with a standard berk and that boat about 56 to 59mph, with a tolerable efficient cruising fuel consumption.
I would also suspect that a B or C impeller might wake that setup WAY up. Might put you into a better part of the HP curve with maybe 375HP, if my calculations and understanding of how things work, and some appreciated advice from knowledgable sources is accurate.
I am not sure but camshaft selection may very important to match with the exhaust and RPM expected at WOT. After a certain lift and duration i THINK it has mostly to do when the intake valve opens.
Sure is nice to hear from someone that has done it before.
mikeT

[Jungle Boy]

Sea level will give you about 250 - 300 RPM over the 3400 ft I was stating, if the conditions are right. I have raced in both and we try to keep acurate records. Cas is right; Try to choose a cam that will perform up to and peak at around 4500/4800 rpm. Seen a few guys that have dropped a hotrod car SBC into their jetboats and they performed REAL bad. An RV cam could be concidered too, since your motor isn't built to run into the 5000 rpm plus area. I've pleasure boated and raced only small blocks and still think they are great for the lighter jetboats. 200 lbs less weight at the pump makes a big difference. :cool:

[sleekcraft76]

go for it mike!!!

[SPECTRABRENT]

I think Jim Brock has a set, his # is 818-890-1867.
Brent

[miketsouth]

Originally posted by SPECTRABRENT
I think Jim Brock has a set, his # is 818-890-1867.
Brent
Ill give him a call, thanks

[miketsouth]

Originally posted by Jungle Boy
Sea level will give you about 250 - 300 RPM over the 3400 ft I was stating, if the conditions are right. I have raced in both and we try to keep acurate records. Cas is right; Try to choose a cam that will perform up to and peak at around 4500/4800 rpm. Seen a few guys that have dropped a hotrod car SBC into their jetboats and they performed REAL bad. An RV cam could be concidered too, since your motor isn't built to run into the 5000 rpm plus area. I've pleasure boated and raced only small blocks and still think they are great for the lighter jetboats. 200 lbs less weight at the pump makes a big difference. :cool:
Got to get the HP in the expected RPM range. I suppose the first mistake is to overcarburate. 600-650 ( i suppose) is just about right. 2nd mistake is to misjudge the HP absorption curve. 3rd mistake is to misjudge the exhaust. I am going to use the Comp XM270H or the XE274H. Impellers are easy to change. So easy in fact that i might just carry one with me like i did on my I/O...one for skiing and one for cruising. Got to keep the lift below .5
Exhaust will be nicson logs. To what i aint sure yet.
mikeT

[Cas]

xe274 would be a pretty good choice. Peak TQ is at 5000 but there is very little change starting at just over 4000. The dual pattern cams like that one usually work pretty good in a jet.
Match up a B, maybe even a BC and it'll go along pretty good, depending on the weight of the hull, of course.
Putting a set of 2.02 heads would do wonders too.

[miketsouth]

it is done. See here mikeT's disposable motor
XE274H installed straigh up (thankyou W...)
pre-79 4bolt 350 balanced engine +- gram....flexplate
76cc heads 1.94/1.60
9-1 compression
cheep hyperutectic pistons
10/10 crank
HEI ignition
Cheep Air Gap Manifold
600cfm square bore
Nicson Logs
OT extentions
American Turbine SS B
7qt oil pan/baffles/doors
Maybe a 19' PF, light-medium layup.
Stickers and decals to make up for the lost CID
I still think i am looking at about 5000rpm WOT and 63mph. I am told the RPM may be a little higher, i dont see it. I dont think there is enough HP there to do it.
Still need some stuff...i aint got the carb or the mounts yet, or the extensions off the logs. Little other stuff.
I do appreciate thems that are encouraging, and thank them. I also know thems that are discouraging a SB have very good and valid reasons to do so, and i thank them too.
time....time....time....
mikeT

[Oldsquirt]

Mike, hopefully you have included some funds in the budget for a dyno session.

[miketsouth]

No i havent. Never thought about it. Never done it or seen it done. It would be the ONLY way to find out what it is really going to do.
I was thinking that the impeller would be a good enough dyno for me. Matter of fact i was relying on it. Let me look into it. Thanks.
mikeT

[Oldsquirt]

Originally posted by miketsouth
....I was thinking that the impeller would be a good enough dyno for me...
Mike I don't think anybody out there can truly vouch for the accuracy of those impeller absorption curves. Are they accurate to +/- 1%, 5%, 10%.....?
At least if you dyno the engine, you will have one set of hard data to work with. Won't hurt to know that you have optimized the engine combo, either.

[Cas]

what's the specs on the xe270h? I went to the Comp Cams website and couldn't find that number. Found the xe268h and the xe274h but nothing in between.
There's 270h though.

[Duane HTP]

Mike T give me a ring. 316-794-8616. I've got the mounts and the carb.

[miketsouth]

My mistake XE274H. I was going to use the XM270H.
mikeT
Originally posted by Cas
what's the specs on the xe270h? I went to the Comp Cams website and couldn't find that number. Found the xe268h and the xe274h but nothing in between.
There's 270h though. http://compcams.com/Technical/Search/CamDetails.asp?PartNumber=12-246-3

[miketsouth]

Originally posted by OLDSQUIRT
Mike I don't think anybody out there can truly vouch for the accuracy of those impeller absorption curves. Are they accurate to +/- 1%, 5%, 10%.....?
At least if you dyno the engine, you will have one set of hard data to work with. Won't hurt to know that you have optimized the engine combo, either.
I dont know about their absolute accuracy. I am pretty sure that one could use engine RPM to see if changes made in jetting, timing, or other things were working, as long as nothing else changes.
I have asked many people what RPM their stock 454 BBC turned a berk 'A' and they all say the same thing 4600. This goes with the chart. Of course it couldnt be TOO accurate. Most people have a tach that is not THAT accurate.