350 compression ratio

[Andy H]

So i have a 350 Pontiac engine that is bored 030 over that was given to me and i´m trying to piece this thing together for my -64 Le Mans, its going to be a almost stock street engine with perhaps a small cam also have a Edelbrock performer intake that i intend to use with a 600cfm 4bbl carburetor.

I CCed one of the combustion chambers and it is 92CC so the compression ratio is going to be very low, probably around 7.5.

I would like to se something around 9.0-9.5 if possible and what i probably need is a cyl head with a chamber in the low70s cc so any idea what head to look for?

Found a pair of 1969 #47 heads from a 350 that i think is supposed to be 72cc.

67 #140 heads from a 326 is closed or open chamber and what size? all i find is a listing of 9,25 comp no cc numbers.

So what heads to look for and what to stay away from?  whats better closed or open chambers, does it matter?

 

[64 kiwi boni]

sounds like a good question for bear Andy👍, hope he see your post

[Frosty]

Andy - if you are looking for something in the 72-75cc range, here are a list of Pontiac heads to look for. The nice thing is the 400 and 428 heads will bolt to 350 engine with no problem. Further more, all of these heads have the desirable 2.11" intake and 1.77" exhaust valves. The Ram Air II, III, and IV heads are most like to the most expensive heads on the market, so unless I am trying to build a numbers matching engine, I would look for something else. The codes refer to casting numbers on the heads. MT stands for manual transmission and AT for automatic.

Based on the data below #16, 62, and 13 would be my first choices. However, if you find something else - clearly look at them.

Also, Edelbrock carries a 72cc heads for the Pontiac engine family.

https://www.summitracing.com/parts/edl-61599/make/pontiac

 

 

[Andy H]

Thank you Frosty, Wow that was a lot of good information,What is the difference between A/T and M/T heads? chamber size? and can you tell on the head?

You are listing a few 1967 heads was that a split year for open/ closed chambers? What is thoughts on open vs closed chambers?

Looking on Franks Pontiac website here in SoCal and all the Big valve heads go for around $800 or more but found two sets 1.94/1.66 heads with smaller chambers for $200-$400 is it worth the extra $ for the big valve head for a almost stock engine?  Also read somewhere about valve shrouding with big valve heads and a small bore 350, any truth to this?

The Edelbrock heads would be the way to go but comes with a pretty steep price tag unfortunately.

Any god ideas about other places to look for used heads?

 

[Frosty]

Hi Andy - sorry it took so long to get back to you. I didn't see a response to this until today.

For a near stock engine, closed vs open chamber heads will make marginal difference in performance.

As for non-2.11 heads, I would suggest the following:

That said, I would first look to find a set of 5C or 6X/6H heads, particular the 6X heads that were plentiful in the late 70s. You see 6X heads all the time at swap meets and online. If you can find a set of #18 (350 HO) heads, grab them. Again, heads from any 455 should be somewhat plentiful, but they may not be as cheap as other heads, as you have already discovered.

Also, just because Franks wants $800 for a set of heads, doesn't mean you should pay that unless you want them bad enough. Arm yourself with the list of heads you want. Check swap meets and Craigslist (both in and outside your local area) regularly. You'd be surprised what you will find out there. You might find a set for $200-500.

Since you are in Orange County California - 3 words - Pomona Swap Meet!!!! Learn to haggle. Cash is king. Brink a dolly or wagon to carry them in.

[Andy H]

Frosty- think i got i figured out, Pomona is something i did not think about and that's i good idea, have not been there in years and we also have Long Beach swap meet but not sure i want to do that right now with everything going on, to many people.

Found three cyl heads on Franks Pontiac's web site #15, #46 and #47 so i drove out there and brought my stuff to CC the heads right there (two hour drive) and they where very cool to let me do that right there, Checked the #47 heads first and What i found on line is that they are supposed to be 72cc or 73cc but not, they where right around 80cc so no.

Next up was a set of #46 heads from a 69 428 and what i found is that they are supposed to be 10:1 or 72cc and they turned out to be around 74cc so those are the ones i got, paid $450

That should put my compression right below 9:1 witch should be OK.

The heads turned out to be really nice and did not have to have a valve job at the machine shop, seats where nice and not to wide and the guides OK, the valves needed to be ground but the valves in my old head( same size) was good so i just used those instead and hand lapped them. (I used to do valve jobs at a dealer i worked for a long time ago)

Got the block back from the machine shop, one cyl sleeved and had to go from ,030 to .040.

Now i just need to pick a camshaft.looking at a comp cam xtreme energy 51-221-4 potentially.

Currently working on tapping the front oil galley holes.

I'll post some picture of the progress with the car when i get a chance ( and figure out how to upload pictures)

Thanks for replying

 

 

[Frosty]

Andy - happy to help a fellow Pontiac faithful. 

Congrats on your cylinder head purchase, sounds like you scored pretty good. One question I have - do the valve guides or seats look to be original? If so, they may not be able to handle today's unleaded gas and you may want/need to install hardened ones. Remember when these heads were new, leaded gas was everywhere. JUSTA food for thought as you prep your motor. 

Edited February 11, 2021 by Frosty

[Andy H]

Frosty- Have you had or seen any heads that has been severely damaged due to this?

I have seen this discussion in several palaces through the years but really not seen any heads that had severe problems with the seats/ guides.

I am not sure what it would cost to replace all the seats and guides and also with the price of purchasing the heads it must be getting close to just buying new aluminum heads?

I remember when they started with unleaded gas that this was a big topic, all old engines was going to die but don't think that it exactly worked out that way.

Yes these heads have the original seats but I'm not going to worry about it for now, it is not to bad to pull them off in the car if i have to and it will not be a daily driver so it will probably be OK

 

[64 kiwi boni]

4 hours ago, Andy H said:

Frosty- Have you had or seen any heads that has been severely damaged due to this?

I have seen this discussion in several palaces through the years but really not seen any heads that had severe problems with the seats/ guides.

I am not sure what it would cost to replace all the seats and guides and also with the price of purchasing the heads it must be getting close to just buying new aluminum heads?

I remember when they started with unleaded gas that this was a big topic, all old engines was going to die but don't think that it exactly worked out that way.

Yes these heads have the original seats but I'm not going to worry about it for now, it is not to bad to pull them off in the car if i have to and it will not be a daily driver so it will probably be OK

 

hmm, Andy don’t waste you time ... if you are going to put new heads on your engine , make sure they are right.👍

or you are wasting your time and money 

when I was young I bought some double hump fuelies, stuck them straight on my  327 in my 61 impala .. and they ran like shit !!

moral of the story 

when using old heads 

get them crack tested, check the face is flat , stick new valve seats and guides in em 

and make sure you have the right valves and set your springs to the correct rating  for your cam . 

Hell I would blend the bowls and runners with a dremal too . JustA cause I think it will make for a better flowing head 🍻🍻🍻

[TWO LANE BLACK TOP]

5 hours ago, 64 kiwi boni said:

hmm, Andy don’t waste you time ... if you are going to put new heads on your engine , make sure they are right.👍

or you are wasting your time and money 

when I was young I bought some double hump fuelies, stuck them straight on my  327 in my 61 impala .. and they ran like shit !!

moral of the story 

when using old heads 

get them crack tested, check the face is flat , stick new valve seats and guides in em 

and make sure you have the right valves and set your springs to the correct rating  for your cam . 

Hell I would blend the bowls and runners with a dremal too . JustA cause I think it will make for a better flowing head 🍻🍻🍻

I completely agree...That is a very sound strategy....Hard to go wrong by doing so...If the heads are in decent shape to begin with...Could be a very economically viable option....

Edited February 11, 2021 by TWO LANE BLACK TOP

[Frosty]

11 hours ago, Andy H said:

Frosty- Have you had or seen any heads that has been severely damaged due to this?

I have seen this discussion in several palaces through the years but really not seen any heads that had severe problems with the seats/ guides.

I am not sure what it would cost to replace all the seats and guides and also with the price of purchasing the heads it must be getting close to just buying new aluminum heads?

I remember when they started with unleaded gas that this was a big topic, all old engines was going to die but don't think that it exactly worked out that way.

Yes these heads have the original seats but I'm not going to worry about it for now, it is not to bad to pull them off in the car if i have to and it will not be a daily driver so it will probably be OK

 

Best advice I can give is to call around to your local machine shops and ask for quotes. Everything that Last Indian and I have suggested is in order for you to get the maximum power out of your heads and engine. Matching the springs, valves, guides, etc. to your engine and cam is crucial. I, for one, lack all the specialty tools to do all the necessary machine work.  So if doing all this adds another $300 to the bill, I know I took it to a professional to be done right.

Now is it possible for a machine shop to screw up a set of heads., yup, it sure is. That's why it is important you do your homework and you select reputable shops. Ask for references, especially for Pontiac work.

I make it habit to have the valve guides replaced on any used heads I get. I assume they are all from back in the day and don't run the risk of burning a valve and I replace the seats and guides. It's cheap insurance.

[Andy H]

Love this, great discussion guys, a lot of knowledge and experience here and also some opinions😄

Machine shops are getting hard to find especially good ones, used one for my 489 BB in my 32 3W but it is now gone, when i worked in the automotive repair shop we had a couple we used but also gone.

Franks Pontiac that i got my heads from lists them as cleaned and magnafluxed and it looked like they had been bead blasted or similar.

I think they will be fine for now, guides check OK and the pattern on the valves when i lapped them was good, they are flat, checked them with straight edge.

basically the worst that could happen is i need another set of gaskets if i need something done later.

 

 

[64 kiwi boni]

14 minutes ago, Andy H said:

Love this, great discussion guys, a lot of knowledge and experience here and also some opinions😄

Machine shops are getting hard to find especially good ones, used one for my 489 BB in my 32 3W but it is now gone, when i worked in the automotive repair shop we had a couple we used but also gone.

Franks Pontiac that i got my heads from lists them as cleaned and magnafluxed and it looked like they had been bead blasted or similar.

I think they will be fine for now, guides check OK and the pattern on the valves when i lapped them was good, they are flat, checked them with straight edge.

basically the worst that could happen is i need another set of gaskets if i need something done later.

 

 

sweet as Andy, you clearly know what to look for