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wildeman 06-08-2009 05:19 PM

355 chevy hp estimate
I just registered today and my first question is concerning my motor. I would like to hear estimated hp from various sources. I have a 355 chevy with S/R torquer heads (76cc) slightly ported and polished with 8.6:1 CR (catalog ref of piston p/n says with 76cc and .040 head gasket equals 8.6:1), Victor Jr. intake, Holley 750 vacuum secondaries, .490 lift both sides camshaft, 2.02 intake and 1.60 exhaust valves. The head gasket has been changed to a .015 steel shim gasket. I'm guessing around 360-375 at the crank because this was supposed to be a 400hp motor but I'm thinking that was with the 67cc torquer heads.

my87Z 06-08-2009 05:49 PM

to give you and estimate most would need to know more about the cam, adv duration, duration @ .050, LSA/LCA, you mention that a .015 head gasket is or was what was on it, but that a .040 makes 8.6:1, are you replacing the gaskets? if so before you go using a .015 gasket check you quench and if you dont have atleast .020 deck clearance then you will need a .040, world product heads used to be the heads to have about 10-15 yrs ago, but they are very outdated with todays iron heads, you also mention a single plane vic jr intake, i dont know the rest of the specs of the cam but this sounds a little mismatched, i would have gone with a eddy RPM intake or similar dual plane, and last a 750 holley is overkill for this motor, a 650 is more than enough to handle most 350's

wildeman 06-08-2009 06:14 PM

The .040 gasket was replaced with the .015 shim gasket to boost compression to around 9:1. Quench area was checked out and is okay. I don't have the cam specs except lift and total duration. The duration is adv 292 both sides. I have an old desktop dyno and looking at the graphs, there is not much difference between a dual plane and a single plane except at the very low end. The 650 would be great for the street, but this is not going to be a daily driver. Some track action, shows, and cruising are the goal, plus its a 3310 vacuum secondary not a double pumper.

dh79 06-08-2009 06:20 PM

My estimate would be about 350. Possibly a bit less even. It's a bit mismatched. More compression and a double pumper would match better with the victor jr. 400 hp is not as easy as people like to believe.

wildeman 06-08-2009 06:44 PM

Yeah, it does seem pretty hard to get that. I know the compression was low so that is why I went with a .015 shim gasket and hopefully achieve at least 9:1. I believe the double pumper would be overkill unless you are actually at the track all the time. The motor is in a 76 620 Datsun truck and I'm figuring 20% drivetrain loss which with your estimate would put around 280 at the wheels.

my87Z 06-08-2009 06:54 PM

a 292 duration cam should be around 240@ 050, but LSA/LCA are still very important, this is a decent amount of duration on a 350 and yes it is possible that the vic jr would work better, you'll just be bringing the powerband up some with the single plane, i would still be very cautious about the 015 head gasket, without machine work going from a 040 gasket to a 015 is a little crazy (if the quench was set up right to begin with)

if your quench was around 040 to begin with and now they have lowered it to 025 just to get a little cr out of it, that is stupid!, optimum quench is 035-044 you can go as high as 060 but i wouldn't, the smart thing would not have been to put a 015 gasket on but to never have bought the 76cc s/r's :rolleyes:

i would also be a little concerned about the cr with the cam chosen, but as i dont know the rest of the specs im not for sure i know the 292H comps cam want about a 10.0:1 cr, and you dont need a 750 to run this at the track, a 350 that will only rev to about 62-6400rpm will only need a 650, if you plan on hitting 7k i would advise a good 750 but you would still be fine with a 650

my87Z 06-08-2009 07:03 PM


Originally Posted by dh79
My estimate would be about 350. Possibly a bit less even. It's a bit mismatched. More compression and a double pumper would match better with the victor jr. 400 hp is not as easy as people like to believe.

400hp is very easy if you mach your parts up right, with that cam (depending on the rest of the specs) a much better flowing set of heads, RHS pro-act, dart platinums, or afr 195's, 9.5:1/10:1, vic jr intake 650DP, quench set right at 040, then tune it all up correctly, you talking about 415hp all day long!

eric32 06-08-2009 07:27 PM

Cant say for the setup you got but with some dyno tests I have seen with a comp xtreme engergy mild grind flat tappet cam with around 218/224 @ 50 and a little less lift then that a 350 made around 340 plus hp with those set of heads with no port work done. The intake was a edelbrock dual plane performer. I would say you should have 325 to 350 easy. If you had world product sportsman II's and some better matching parts you could make over 400 hp easy. My setup is a 350, world sportsman 2's with edelbrock performer rpm, crane powermax hydraullic roller 284/292, 222/230 @50 with 513/ 528 lift. 9:2 to 1 CR with edelbrock 750 performer. Bottom end with flattop pistons and my block was decked etc to get me decent quench etc. My setup should make me around 400 or so. I had a super victor intake before and it was fine but after I went to a performer rpm I like the bottom end much better and did not really notice the difference too much on the top end. Like always you think your done with your motor and somwhere down the road you want to change something. It seems its always a work in progress.
Have fun on your build.

wildeman 06-09-2009 09:27 AM

1 Attachment(s)
Allright, I'm at home now (using computer at work last night). Here's what I got. The pistons ride approximately .020 - .025 in the hole (piston slap) so with the .015 gasket it should be okay. I know - its tight. I finally found cam specs. I messed up last night. The cam is .490 lift both sides, 292 adv duration with 230 @ .050 both sides. When originally bought, the motor was claimed to be a 400hp 355 and that was with the S/R torquer heads, Victor Jr., Holley carb, all the stuff I mentioned last night except I believe they probably used the 67cc head instead of the 76cc.

my87Z 06-09-2009 03:04 PM

well you said that you replaced the head gasket, are the heads still off, if so you can check the volume of the combustion chambers, can you see the part# or s/n# this should also tell you (this would be the best way) that would be a very important thing to know

about you cam, i tried to look up who might make it, and i cant find it (that doesn't mean much) i was trying to figure out the LSA/CL, 230 @ 050 on a 292 cam is a little low, but its not bad, on a 350 is should sound pretty nice, if you have th 67cc heads it's possible to have 380-390hp but i wouldn't expect much more than that (and that is tuned well) but if its the 76cc heads i would guess a bit lower

wildeman 06-09-2009 04:58 PM

I have the 76cc heads. Like you, I have also tried to find out who made the cam and there is not even any info on the end of the cam itself.

my87Z 06-09-2009 05:09 PM

what are your plans for this motor, are you happy with it, or do you plan on making some changes before it goes into the car/truck

wildeman 06-09-2009 05:24 PM

Well, right now its pretty much ready to put in the truck. Its been in once and drives really nice. Drove it up and down the street and burped it to about 3500 and it hooked up nice and smooth. My main consideration is torque. I believe I don't need a motor really strong at the bottom end because if there is a lot of torque it'll just go up in smoke because the truck only weighs around 2350 stock. The front clip has been replaced with a unit from chassis engineering, the rear has been narrowed and leaf springs removed (all weight reduction), but the rearend is ford 9" (weight gain) with 4.11s and ladder bars with track locator. I'll track it sometimes, show it sometimes and cruise. By the way, when I got the motor it was supposed to be 10:1, but like I said when I pulled the heads and crossed the piston # the speedpro cat said 8.6:1 with .040 gasket. In time, I'd like some aluminum heads or actually go to a 383.

my87Z 06-09-2009 06:18 PM

that should be a pretty quick truck, if your happy then go ahead pop her in there and have at it :thumbup:

eric32 06-09-2009 06:49 PM

This is only a suggestion and would not make that much difference but I would change over to a edelbrock rpm performer dual plane to go with that cam and I don't personally think your setup is that far out of match. Your cam is a cross between radical street and strip and performance daily driver. My cam I am sticking in has 284/292 advertised and 222/230 and its going in daily driver so yours is not that bad really. I say your engine should run very nice I just would change the intake to dual plain it would have a little more torque and still pull good all the way to about 6000 rpm with that cam. Have fun and enjoy it. I have another truck with a more way decked out setup and people still tell me I should have this or that. As long as you happy with it and things are matched up decent then why do you have to keep adding things too it. I was planning on redoing my other engine again but I really thought about it and whats wrong with the one I got already? So I am just leaving it along and changing out cam only.
Take care

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