[cobalt327]

Originally Posted by lmsport

Have you verified that the 350 and 400 heads in question are the same combustion chamber size. I have seen the same casting with a 20cc variation in CC volume, I suppose for use in different applications. I would measure and calculate the compression ratio and make sure it is no less than 9:1.

X2. From post #3:

If you want, post the casting number of the 400 heads you plan to use. There are a lot of difference in the chamber sizes among Pontiac heads. What you do NOT want is to put too large chambers on your 350. This will lower the CR too much.

[AndersonRacing44]

sorry it took so long to get back to you guys. ive been trying to find where my heads came from (aside what the guy told me =/)

but here are the casting numbers.

Center casting # 6H

Rear port # M4

and theres another set of numbers by the valve cover B256

[AndersonRacing44]

Also it has skrew in rocker studs.

[cobalt327]

Originally Posted by AndersonRacing44

sorry it took so long to get back to you guys. ive been trying to find where my heads came from (aside what the guy told me =/)

but here are the casting numbers.

Center casting # 6H

Rear port # M4

and theres another set of numbers by the valve cover B256

Everything I have points to the 6H as being a '76 455 head. The "B266" (02-26-76) date code would bear the year out. 455 engines in '76 had an advertised CR of 7.6, so will be basically unusable on a smaller displacement engine, as-is.

The 6H head should have a 2.11" intake and a 1.66" exhaust valve, screw in studs w/guide plates. This is of small consolation, considering the 114cc-plus combustion chamber size. If you mill them, you will get about a 10cc reduction per ~0.045" removed, so you'd need to remove 0.090" to get to around 94cc- or the size that a 6X-4 head for a 400 is stock.

Look over THIS page at Wallace Racing to see what the secondary ID is. They show you where to look, along w/the meaning. But I hold very little hope that the 6H will be anything but the 114cc-plus chamber 455 head.

Sorry, I wish there was something better to report.

[AndersonRacing44]

yea the secondary code is 6 so yea there the 114cc heads. I had a machine shop do a valve job on it and they also milled the head a little, i dont know how much they took off though. Well me and my dad had been tossing around the idea of just getting some high compression pistons if the compression ratio came out to low. With some new pistons im hoping to get anywhere from 9:1 or 10:1, you think it could be done?

[cobalt327]

Originally Posted by AndersonRacing44

yea the secondary code is 6 so yea there the 114cc heads. I had a machine shop do a valve job on it and they also milled the head a little, i dont know how much they took off though. Well me and my dad had been tossing around the idea of just getting some high compression pistons if the compression ratio came out to low. With some new pistons im hoping to get anywhere from 9:1 or 10:1, you think it could be done?

It can be done by using domed pistons, but w/the cost of a set of smaller chambered heads being quite a bit less than the cost of the pistons ($600-plus/set), I don't know if it will pay to use the 455 heads over a different set of heads.

If the 455 heads hadn't been to the shop, it would be a much easier decision.

[WDCreech]

Originally Posted by AndersonRacing44

yea the secondary code is 6 so yea there the 114cc heads. I had a machine shop do a valve job on it and they also milled the head a little, i dont know how much they took off though. Well me and my dad had been tossing around the idea of just getting some high compression pistons if the compression ratio came out to low. With some new pistons im hoping to get anywhere from 9:1 or 10:1, you think it could be done?

You would be better off finding a pair of 70s 400, 72-75 cc, big valve heads and use the neccesary dish piston to get the compression that you want.

[AndersonRacing44]

Well I got these heads for free, and I know the family that owns the machine shop so i can get more taken off these heads, not to much though. And its just a project engine so i think ill just save some cash and get pistons.
Thanks for your help though!
One more quick question, well guesstimation.
How much will this up my HP?
its just a 2bbl 350 pontiac, books say its 180-190hp
going to a 4bbl quadrajet from a BBC 454 and a stock pontiac 4bbl manifold.
the new heads 1.96 intakes to the 2.11 and 20cc less on the head.

kinda vague but any guesses? im thinking around 240?

[cobalt327]

Originally Posted by AndersonRacing44

Well I got these heads for free, and I know the family that owns the machine shop so i can get more taken off these heads, not to much though. And its just a project engine so i think ill just save some cash and get pistons.
Thanks for your help though!
One more quick question, well guesstimation.
How much will this up my HP?
its just a 2bbl 350 pontiac, books say its 180-190hp
going to a 4bbl quadrajet from a BBC 454 and a stock pontiac 4bbl manifold.
the new heads 1.96 intakes to the 2.11 and 20cc less on the head.

kinda vague but any guesses? im thinking around 240?

The difference in valve size won't offset the CR loss- you will lose HP over the stock 350 heads, or at the very best, break even.

[WDCreech]

I concur with cobalt. With the heads from a 455, you will still have a dog, And you won't have decent throttle responce from a 4bbl carbuator, because of the puny cam that they put in the 2bbl 350s.

[AndersonRacing44]

Well...today i found some dissapointing news. there isnt really a mass produced high top piston for pontiac 350's, they would have to be custom and very expensive...

I can get a 455 for 200 bucks, all it is, is a short block though. Soposed to have new bearings and pistons etc. I would just transfer all the little things over from my 350 (oil pan, timing chain cover etc.)
Good buy?

[beertracker]

Originally Posted by cobalt327

Hey, BT.

You will be using polylocs without any other form of thread lock or jam nut. JUST the polyloc, alone.

The procedure used by the same Pontiac folks you cited above is HERE.

The method is shown by Bill Boyle is for an engine that's assembled and w/lifters full of oil. On an engine stand, unless you've primed the oiling system this isn't the case, so you'll want to stack small washers (or in some other way) to make a lifter solid. Or just use a Pontiac solid lifter.

This solid lifter is then used to do the procedure to see where the sweep of the rocker arm is, across the tip of the valve. You can add the amount of preload to the figure you get, or you can set up the lifter to have the required preload and use the adjustable pushrod length directly. Either way, your choice.
HERE is a page by Comp Cams that give some more info and insight to the procedure. It is worth reading, IMO.

At first it may seem a little complicated, and it may take a time or three to get a "feel" for what you're doing if you've never set the geometry/pushrod length before. But I assure you by the time you are done you will be a pro at it!

But I WILL say that only the rankest amateur HACK would ever presume to build a performance engine that had not had the valve train geometry verified. And that's all I have to say about that.

Personally, I like using blue machinists paste (below) to use on the valve tip instead of a Sharpie, but that's me- you may have no problem using the Sharpie/Magic Marker 'method'.

Hopefully some guys w/real engine building experience besides myself will add to what I've offered here- there are tricks guys use that work for them and some of those may help you w/your task at hand.

Good luck and feel free to ask whatever you want if something comes up.

Hey Colbalt327 & Group:

I read over the links above and learned quite a lot. I do have few more questions. I haven't replaced the stock Pontiac rocker nuts and (bottle neck) rocker studs yet but I am looking at these after market poly locks and rocker studs from Summit and wanted to get your opinion on them. Is this what I should buy?

http://www.summitracing.com/parts/MRG-920G/?rtype=10
http://www.summitracing.com/parts/ARP-134-7101/

Note the ARP rocker studs are for a Chevy and I have a POntiac 400; problem here?

Can I get by with just using poly locks with stock Pontiac bottle neck rocker studs?

Does the set screw on the poly locks bite into the rocker stud threads (either stock or ARP rocker studs) and effectively make the rocker stud a one adjustment item since the threads are damaged by the poly lock?

By going to ARP rocker studs will this require the use of tall valve covers?

Thanks,
BT

[WDCreech]

beertracker, I have seen the 3/8 studs break under stress. You need to get the BBC 7/16 studs and the appropiate lock nuts for any kind of performance.

[beertracker]

Originally Posted by WDCreech

beertracker, I have seen the 3/8 studs break under stress. You need to get the BBC 7/16 studs and the appropiate lock nuts for any kind of performance.

Ok, I found two 7/16 BBC studs from Summit. The difference between the two is Effective Stud Length; 1.75" or 1.90". Which one should I get or does it make any difference? Will the taller one with poly locks require the use of taller valve covers? I am trying to anticipate all the gotchas before tearing into the engine.

http://www.summitracing.com/parts/ARP-135-7101/
http://www.summitracing.com/parts/ARP-135-7102/

My horse power goal is 360hp. That's why I asked about using my stock bottle neck rocker studs and poly locks. At my horse power level is it necessary to use stronger rocker studs.

BT

[WDCreech]

I don't know for sure, but I would think that the shorter ones would work unless you were to run a very high lift cam. You might ask Summit Tech before you order.