SBC build. compression, quinch and cam opinions wanted.
hi guys, i,m assembling my SBC 383 stroker build and would like some of you engine guys opinions.
forged flat top pistons.
aluminum heads, 190 CC intake ports, 64 CC chambers (now at 67 CC after smoothing and a mild polish.
cam yet to be selected.
1 7/8" long tube headers (yeah, i know, too big but the car is an early corvette and has the hooker chrome headers and sidepipes. they only come in one dia. and i'm not willing to change them.
single 4 BBL cross ram intake with either a 650 or 750 holley DP (i have both)
car will weigh between 2800 and 3000# when finished.
driveline is a 4.11 rear and a muncie 4 speed.
the car is going to be a fun street car and i'm not looking for max. horsepower. real world i'm looking for good performance between 2500-3000 to 5000-6000 (probably very seldome see 6000 on the street and never above).
i know the intake and exhaust are a compromise but that is what i'm running due to their looks and uniqueness.
here's what i would like your thoughts on:
i was going to run composition gaskets .039 compressed, but after assembling the short block i measured the pistons at TDC and they are down .024 in the hole. this would give me a compression of 10.24 and a quinch of.063 (which i don't like).
i can go with an .020 gasket which will give me a compression of 10.6 (a little high but remember aluminum heads) and a quinch of .044, i like this better, your thoughts???
with aluminum heads, 10.6 compression and .044 quinch i'm now looking at cams. it's going to be a flat tappet hydraulic. i'm looking a these 4:
234-234 duration, .488/.488 lift 114 LSA
234-244 duration, .488/.510 lift 114 LSA
230-230 duration, .480/.480 lift 110 LSA
244-244 duration, .501/.501 lift 110 LSA
all durations are at .050 lift.
which cam would you choose and why? if you want to recommend another cam feel free to and tell me why.
thanks guys :thumbup: i feel the more opinions the better.
i know there are some mismatched parts but i'm a retired corvette mechanic and know how to dial in/tune hi perf engines so please bear that in mind. :welcome:
i am building a similar motor for my 87 Z28 (385) and i used to have the summit cam with 282/292 224/234 .465/.488 with a 114 LSA
before i put this cam in i found out that 114 LSA actually lowered my hp/tq numbers, if i used the same came but with a 110 LSA my hp/tq number rose by about 10-15
i decided (with opinions from the guys on here) to go with the comp cams XE274: 274/286 230/236 .490/.490
since it is a stroked motor and that cam's power band is around 1800-5500 you make a butt ton of tq down low
i would stay away from the 114 LSA cams, what are the other 2 they sound like the 280H and the 292H
for my build everytime i sim a cam with more advertised duration than 282 my power numbers actually go down, for mine the XE274 the highest
I would actaully use a .015" head gasket that I believe FelPro makes, which would put you at a perfect .039" quench.
As far as the cam goes, running a hyd flat tappet is a bad idea IMO. If you have to use a cheap cam I'd step to a mech. flat tappet not only for the increased lift (which those ehads need) but also for the high RPM stability. YOu say you won't go over 6,000 but that compression is more suited to a max RPM of about 6500, which in most cases is still safe.
LSA was already brought up so I will say that a 383 usually likes a tighter LSA than a 350 due to the added stroke. As such I would even stay away from the 110 and steer more towards a 108-105 for the street. Also, your mismatched intake will bennefit from a tighter LSA.
This is a link to a hyd. cam that will give you peak power at about 6500 RPM
And here is a link to an almost ideal mech. cam- http://store.summitracing.com/partde...4&autoview=sku
This one is really nice, but I would use EDM lifters with it as cheap insurance, its a little agressive, also I'd install it about 4º advanced
If you use any of those I hope you have a solid car and enough common sense to not do insane speeds on the freeway because they will pull hard.
thank's for your reply's 87 Z and AP 72. no offence intiended. your cam suggestions are very close. but you are both in your 20's , i have been a corvette mechanic since the early 70s. now retired. i'm building a resto-mod 365 horse, 64 coupe and want input from the engine builders on this forum. come on you old professional experts, chime in. :thumbup:
I take no offense- a lot of engneers I work with do a doube take when they find out my age. The smart seasoned veterans are going to spec a very simmilar cam to the one I suggested though. The only difference may be that they run a wider LSA to keep it a hair more docile- something I think that a manual trans and 4.10s doesn't necessarily require.
I think the cam comes down to how much "hair of the dog" you want. Any cam's effects tend to appear milder as displacement goes up. As the LSA gets tighter, the rastier the idle becomes.
I don't think you've got a big concern with squish/quench distance as the cam overlap will spill a lot of exhaust into the mix at lower revs which calms the burn. The 4.11s give the engine a large amount leverage which reduces the tendency for detonation in the mid and upper ranges. So these characteristics will allow an optimum advance rate and amount even though the squish/quench is getting toward the high side of optimum. The other thing not discussed with squish/quench goes beyond the closeness of closure which is the area of the decks. Flat top pistons present a much larger surface than is present with circular dish designs and the heads you're using also feature a large surface, so one needs to consider that large surfaces will enhance the desired effects (especially that of quench) while allowing for a more piston to deck clearance. The larger clearance will surrender some squish, but given the ports are 190 ccs, this means mixture velocity for a 383 will be pretty high and that will enhance chamber turbulance covering much, if not all, the needed squish function.
thanks my87Z for the LSA input.
thanks AP72 for the cam suggestions-they are right on. i just don't want to adjust solid lifters (i did too much of that in the 70s on C2 vettes. guys would come in and say "adjust my solid lifter cam" i would ask" what cam do you have, they would say " i don't know" so i would have to figure out wether it was a 30/30 dontov cam , or a .027, or an .017 solid lifter cam (they all were a pain)
also AP72, i have much more high speed cars with much more HP, so i don't think my vette will be much of a problem. after all, how fast can you do with a 4.11 in the rear.
my pantera will top out at at 150 MPH+
THANKS OLD RED i put much value on your comments. :thumbup: .
I'd love to hear those side pipes!!
|All times are GMT -6. The time now is 12:32 PM.|
Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2015, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0 PL2
Copyright Hotrodders.com 1999 - 2012. All Rights Reserved.