454 - Chevelle Tech
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post #1 of 19 (permalink) Old Jan 22nd, 20, 2:22 PM Thread Starter
 
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454

I just picked up a complete used 454 for $400. 445 block casting, turns it has had a stock rebuild with .030 over flat tops with valve reliefs and 236 heads.my question is that I have a set of worked over 702 heads with big valves, port work and 97cc chambers. Just wondering about compession, valve clearance and matching a cam to set up.
Im already building a nice 489 for my chevelle, so this will go in my 69 4x4. Mostly play toy with occasional towing.
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post #2 of 19 (permalink) Old Jan 22nd, 20, 2:30 PM
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Gene
 
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Re: 454

oh, those 236- heads do stuff like THIS! ( see pic below) There are a couple of peanut port (PP) build threads here that may interest you.

I'm not familiar with the 702, although I know they're small chamber and would give you more compression. The 236-s are spot on the right head for a 1200-5000 rpm motor, and even more.

more compression ( which = TQ) , or more port TQ with the 236 PP heads? Personally, I may leave the 236's on there, but be somewhat picky about my camshaft. You can build compression with valve events.

Are you considering the extra expense of a hyd roller or staying flat tappet?
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post #3 of 19 (permalink) Old Jan 22nd, 20, 3:54 PM
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Re: 454

The 236 heads are the largest of the "peanut port" head and are decent torque heads. With the flat-top pistons and the 236 head you will be around 7.8:1 compression - not earth shattering by any stretch. The 702 heads are mid 60's closed chamber Large Oval ports, larger valves in them may actually reduce flow unless you unshroud them by grinding some of the chamber as the same time. With the flat-top pistons and 97cc chambers you will have around 9:1 compression.


Because you want to put it in a truck that will be a play toy and also used for towing, give thought to keeping the 236 heads and picking a cam low compression low end torque engines. If you had a set of the L29 Vortec heads, they would be ideal for what you want to do.
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post #4 of 19 (permalink) Old Jan 22nd, 20, 4:06 PM Thread Starter
 
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Thanks, I was so excited to finally use the 702s I never gave the 236s a second thought. I had these 702s built for my 489 but ended up getting a new pair of edelbrocks for crazy cheap.
If the factory 236 run decent I may use as is. I don't want to put money into them when the 702s are ready to go. Would stock 236s be compable to built 702s?
Probably looking for a 1500 -5500 flat tappet cam. (Can't afford a 2nd roller set up right now)
Flat t
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post #5 of 19 (permalink) Old Jan 22nd, 20, 4:41 PM
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Re: 454

Find somebody who can unshroud the valves reliably on the 702's. A Serdi valve machine would be ideal. You'll get fairly close to the flow of the open chamber head with a good bit better compression.

Gary Adrian
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post #6 of 19 (permalink) Old Jan 22nd, 20, 11:11 PM
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Re: 454

My mild ported 236's went [email protected] with flat top pistons @ 7.8 compression. They are great heads once reworked.
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post #7 of 19 (permalink) Old Jan 22nd, 20, 11:26 PM
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Re: 454

If you do change heads watch for P/V clearance, I bought an Isky 2.30 piston notch tool (PITA with engine in car) when I put 063 big valve heads on an 86 454, needed the depth and radius larger, I'd leave the 236 heads on


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post #8 of 19 (permalink) Old Jan 23rd, 20, 1:45 AM
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Re: 454

You have the 702 heads ready to go, use them. No need to build another set of heads! Check all your clearances. It'll run fine. As you said, it's just a toy.
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post #9 of 19 (permalink) Old Jan 23rd, 20, 7:50 AM
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Re: 454

True, if the 702 are fresh and the 236 need going thru. OK, I changed my mind, I'm with Rod. The "spend no more" option!

PS the 702 stock would have been crappy for a BBC stroker imho. Unless it was a low rpm wood truck motor.

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post #10 of 19 (permalink) Old Jan 23rd, 20, 8:59 AM
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Thumbs up Re: 454

Quote:
Originally Posted by 68Chevele View Post
My mild ported 236's went [email protected] with flat top pistons @ 7.8 compression. They are great heads once reworked.
I've been saying this for years but it goes unheard. You don't need big compression to go fast (well up to a point that is).. On the street, compression is a nuance. Its makes a engine hard to start in the heat, pingy and it doesn't let you run efficient timing. On my low compression 78 454 I am running 20 initial without any issues. That motor takes off like a rocket at that setting with all that torque. If I had 10:1 compression, it wouldn't start and it would ping like crazy. No way could I run 87 octane like I do now..
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post #11 of 19 (permalink) Old Jan 23rd, 20, 10:04 AM
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Re: 454

I say put the 702 heads on. I have a set on my 454 in the Chevelle now. For the RPM range you are looking at, I doubt any head will outperform another. The compression difference will help quite a bit.

Ray


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post #12 of 19 (permalink) Old Jan 23rd, 20, 11:08 AM
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Re: 454

Quote:
Originally Posted by 68Chevele View Post
My mild ported 236's went [email protected] with flat top pistons @ 7.8 compression. They are great heads once reworked.
What cam are you using?

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post #13 of 19 (permalink) Old Jan 23rd, 20, 12:36 PM
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Re: 454

The OP said : "Im already building a nice 489 for my chevelle, so this will go in my 69 4x4. Mostly play toy with occasional towing."
so which head will be better for use while towing ? The big valve,higher compression 702's or the 236 small port heads ?
I'm thinking the 236's may have recently had a going over as the 454 he picked up had a recent rebuild so that may effect any answers if they were rebuilt or not. That's a question the OP should answer.

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post #14 of 19 (permalink) Old Jan 23rd, 20, 1:40 PM Thread Starter
 
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I have a comp extreme 4x4 flat tappet
226/234 544/564 I didn't use for 489
Might be too hot, plus valve clearance?
I would like to stay in this series so I can use these lifters and the springs are already on 702s.
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post #15 of 19 (permalink) Old Jan 23rd, 20, 1:44 PM
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Re: 454

Quote:
Originally Posted by LaVelle View Post
What cam are you using?
On that pass I had the Comp Cams 282S in there. 561 lift 236 @.050 on a 110 LCA. It had the Air Gap on it. Would have liked to use my Crower tight LCA cam but the 236 heads did not allow for the right springs on the intake side. I have a much better set of 360 PP heads that have 2.19 and 1.88 that I ported. They are the next set of test heads, then I will test my Ported L-29 heads.


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