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Old 01-29-2004, 08:23 PM
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Please Help with my combo

I have a 355 sbc that is going together right now.
I have:
TRW forged pistons .200 dome
292 duration comp magnum hydr. flat tappet cam 501 lift
434 cast heads (305 heads) bowel hogged to 64cc with 202 160 valves springs good to 510 lift
single plane vic jr intake
edelbrock 750 performer carb


I need too know a couple things

1. will i have a bad time with the piston to valve clearance?
2. it should be about 11.78:1 compression at least thats my calculations, what grade fuel do i need to run.
3. is this cam going to be real big? its the one that i bought becasue it was reccomended by comp. and I am running power brakes. will it idle roughly.

any help on these topics would be great but other tips and hints on my build would be great as well.

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Old 01-29-2004, 08:33 PM
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Re: Please Help with my combo

Quote:
Originally posted by 1985fiero
I have a 355 sbc that is going together right now.
I have:
TRW forged pistons .200 dome
292 duration comp magnum hydr. flat tappet cam 501 lift
434 cast heads (305 heads) bowel hogged to 64cc with 202 160 valves springs good to 510 lift
single plane vic jr intake
edelbrock 750 performer carb


I need too know a couple things

1. will i have a bad time with the piston to valve clearance?
2. it should be about 11.78:1 compression at least thats my calculations, what grade fuel do i need to run.
3. is this cam going to be real big? its the one that i bought becasue it was reccomended by comp. and I am running power brakes. will it idle roughly.

any help on these topics would be great but other tips and hints on my build would be great as well.
Depending on your valve reliefs, I would think you piston to valve clearance will be okay. Clay the piston during assembly to be safe.

11.78:1 is way too much on pump gas with an iron head. A larger cam won't help your problem either. I don't know what octane you will need. Whatever it is, it won't be at your local gas station. If you don't run race gas that engine won't live long.

That cam is pretty small if you are looking at it from a performance perspective.

It might lope a little.
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Old 01-29-2004, 08:44 PM
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thanks for that reply. but a 292 duration cam with a 501 lift on a hydr flat tappet cam. is pretty big. I think. I mean correct my theory if i am incorrect. 110 lobe seperation. i this is weak please give me a hydr flat tappet reccomendation

-dan

and what grade fuel should i run. 11.7:1 is usually borderline for pump gas i thought but no personal experience. i was thinking 93 octane plus a octane boost of 2-3 points

dan
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Old 01-29-2004, 08:55 PM
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That is still pretty small. I can't really recommend a cam until you get to a reasonable compression. Compression is one of the biggest concerns when choosing a cam.

11.7:1 would be really hard to run with aluminum heads. You would need massive combustion chamber, piston, and general engine mods. Octane boost won't even come close to helping.

I run 11:1 with an iron head. It took a lot of research, time, and money to make it work. It is really pushing the limits.
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Old 01-29-2004, 09:07 PM
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Quote:
Originally posted by lluciano77
That is still pretty small. I can't really recommend a cam until you get to a reasonable compression. Compression is one of the biggest concerns when choosing a cam.

11.7:1 would be really hard to run with aluminum heads. You would need massive combustion chamber, piston, and general engine mods. Octane boost won't even come close to helping.

I run 11:1 with an iron head. It took a lot of research, time, and money to make it work. It is really pushing the limits.

ok you said aluminum heads, i will be running irons see post 1. however 11.7:1 is the compression ratio and it has to be reasonable becasue that is what a .220 dome 355 piston equated out to be with 64cc combustion chambers. I geuss I dont understand about cams becasue this matches well i think. and comp cams reccomended along with crane a duration and lift with this lobe seperation. I am just trying to get advice from with someone running this combo or some information on the questions asked. I do appreciate the suggestions and help.


dan
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Old 01-29-2004, 09:17 PM
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What I meant was that with aluminum heads you can get away with about a half a point more compression. So even if you were to change to aluminum heads at that compression you will still detonate.

The size of the cam performance wise is probably okay for what you want. Because of the compression you are running you cannot run that cam. Your engine will not last very long as it stands. Unless you either use different pistons or get heads with larger cc chambers, your engine will die a quick death. It will detonate until your pistons and/or gaskets blow out.
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Old 01-29-2004, 09:34 PM
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i dont understand what you are saying but if i am running race gas and whats wrong with 11.5:1 compression? and that is the largest hydr cam i can run..... with the lift and i dont want a solid cam. and I just need to run a tougher head gasket. I know people out there run high compression sbc with iron heads and hydr cams and last. I dont see what you are saying. pinging and detonation will happen if the fuel is not up to par and how will the engine live short>?
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Old 01-29-2004, 10:18 PM
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You don't have to take my word for it. I'm just trying to stop you from making a big mistake. I suggest you do some more research before spending the $$$. Otherwise, this is what it will sound when you run that engine:





http://www.usmemorialday.org/audio/bugltaps.mp3
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Old 01-29-2004, 10:37 PM
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Not trying to ruin things for ya and Im saying this as friendly advice, but that combo is severely mismatched.

1. Thats a 244 @ .050 cam in a 350. I think that cam is way too big. You'll need a split duration cam for all but the best aftermarket heads(AFR, BRODIX, ETC.)

2. Those heads are very poor flowing, bad swirl, etc. even though they got big valves. I would definately invest in a better set of heads.

3. I would run a dual plane intake over that single plane, UNLESS you get very good heads and use that rather large cam and want top end HP at the expense of low end torque.

The way it is now, it will be a dogg. The parts just dont match. But it sounds like you are not far to rethink it.
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Old 01-30-2004, 12:01 AM
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I agree...the 305 heads are terrible. They won't flow no matter what you do to them. The runner size and geometry slows the intake and exhaust flow more and more as demand increases. The rest of your combo is built towards high rpm air flow. Both the carb and the intake are meant to flow more air than you're going to force through the 305 castings hogged out or not. As for the compression...just get different heads with a larger combustion chamber. However, the static compression ratio has little to do with detonation...which will, by the way kill and engine quickly. Its more or less like running the piston into a wall when it hits that shock wave before TDC. Good luck, but be carefull.
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Old 01-30-2004, 12:07 AM
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Quote:
Originally posted by NathanK79
I agree...the 305 heads are terrible. They won't flow no matter what you do to them. The runner size and geometry slows the intake and exhaust flow more and more as demand increases. The rest of your combo is built towards high rpm air flow. Both the carb and the intake are meant to flow more air than you're going to force through the 305 castings hogged out or not. As for the compression...just get different heads with a larger combustion chamber. However, the static compression ratio has little to do with detonation...which will, by the way kill and engine quickly. Its more or less like running the piston into a wall when it hits that shock wave before TDC. Good luck, but be carefull.
Static compression has everything to do with detonation. High cylinder pressures cause pre-ignition. The cam timing, distributor timing, heat, mixture, etc. are also factors, but I would say the static compression would be the baseline figure.
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Old 01-30-2004, 06:28 AM
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so everyone agrees if i jump to a set of dart iron eagle heads with larger runners andcombustion chambers like 76cc or 72 my combo would work even with my cam???? As I have bought everything but could sell me heads.

dan

or another option is a dual plane performer intake and the same heads and cam the cam makes power at 3000 and the intake would match at that rpm and would work those heads. which one could work. i know the heads would be perferd but cost efficency i would rather the intake. but i am looking for a good intake

Last edited by 1985fiero; 01-30-2004 at 06:28 AM.
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Old 01-30-2004, 11:56 AM
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I would have to agree with everyone that the 305 heads are going to kill your performance. I would guess that the operating range on a 350 with 305 heads would be around idle to 4500 RPM at most. Iron eagle 200cc heads would be a good choice, but if you have the money to spend $800 on a set of those, I would consider saving up a little more and going with a set of AFR 195cc heads ($1250). this would help out not only with the flow issue, but with these heads being aluminum, it will also help out with the compression issue. No matter what heads you choose, I would recommend the Performer RPM Air gap intake. A single plane is too much for your application. With a 355, the AFR heads, and the cam you are using, you would be looking at between 450 and 500 hp. With the darts, 400-450. With the 305 heads, probably 225-250.

Adam
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Old 01-30-2004, 04:40 PM
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ok well i did alot of research. And I geuss I will stick with the 305 heads. for two good reasons

1. I have the flow readings on them
2. the only thing good on 305 engines, are the heads they used to use them in nascar and still use them in cricle track cars, they make good power becasue they flow real good, so i dont understand how everyone says bad about the flow.


and the intake is going to be a performer rpm and it matches the cams power making range. my cam is the right choice because it was reccomended by comp cams

its advertised duration is 292 and lobe seperation is 110 and lift is 501 ex and int.

with the air flow readings and cam specs on desktop dyno with a dual plane intake along with my short block and compression and a 750 carb makes 436 hp and 426 tq.

I know its only desktop dyno but the combo after all the research i have done will work. and also will run pump gas but i may run race gas. they are forged pistons and have run a 12.5:1 with pump gas and dissasembled it and showed no signs of detenation on the piston heads.... please give me any advice that is helpful i am not trying to knock anyone just trying to be constructive and get good advice on my combo.....

thanks dan
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Old 01-30-2004, 04:55 PM
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It's your engine, so build your engine the way you want.

I don't have any suggestions at all for you. You seem very determined to build your engine a particular way. Even though you have asked for suggestions and received Many very good ones; you come back with why you think everyone else is misinformed.

As I said above: Build it your way! ENJOY!!!
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