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Thread: Wanted, Sbc Motor Mounts

  1. #1
    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.
    '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 .

  2. #2
    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.

  3. #3
    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 (
    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.

  4. #4
    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

  5. #5
    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.

  6. #6
    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.

  7. #7
    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.

  8. #8
    go for it mike!!!

  9. #9
    I think Jim Brock has a set, his # is 818-890-1867.

  10. #10
    Originally posted by SPECTRABRENT
    I think Jim Brock has a set, his # is 818-890-1867.
    Ill give him a call, thanks

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