# New cylinder heads for 1967 GTO / 400ci



## IceBolt (Jul 28, 2020)

Good morning GTO Gurus, i'm looking for options to replace my cylinder heads on 400ci / 4BBL....soon to be fuel-injected with Holley Sniper EFI. What would you recommend in terms of cylinder heads. Existing ones are necessarily bad, just looking for something with hardened valve seats...and maybe a little more performance. I see Edelbrock aluminum heads on Ames Performance / Summit but at $2800 per pair, that's just too pricey for me.

Any ideas for options? Either new, or rebuilt? Thanks.


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## CptTheAlex (Jul 17, 2015)

Which cylinder heads do you have on it currently? Anything aluminum is going to be pretty steep price wise, i have a set of Kaufmann's on mine. I had cast iron small valves that i had redone by a local shop. Depending on your location you might be able to find an engine/machine shop that could redo your current heads. What are you looking to get out of the engine?


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## IceBolt (Jul 28, 2020)

Pretty sure it's the original heads. Don't have to be aluminum, just looking for something with hardened steel valve seats, extra performance would be great but not at Aluminum prices!


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## O52 (Jan 27, 2019)

Unless you're puling a trailer, racing, or loading down the engine in some form or another, hardened seats aren't really necessary. Not to the expense anyway of buying replacement (71 and later) heads and having them rebuilt. By then you're approaching the cost of aluminum heads.
If you have the original heads they will have '670' cast into the center exhaust ports. IIRC the only big valve heads with a closed chamber design.


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## Jim K (Nov 17, 2020)

Ice,
with todays gasoline (lead free w/ethanol) Hardened seats are a good idea. Since they removed the lead way back in the early 70's hardened valve seats were necessary. While the most inexpensive way is to just have hardened valves/seats put into your existing heads (should be # 670 as O52 mentioned) you then have the issue of possibly too much compression ratio for Iron Pontiac heads. Those 670's are 72 CC which is somewhere north of 10:1. With todays gas the max CR you want for an older Pontiac Iron head is 9.5:1. At 10.5:1 you have detonation issues which tend to tear things up, punch holes in pistons, etc, etc... You can run those older heads but be prepared to run octane booster w/premium gasoline and that entails another set of issues over time as most Octane boosters are corrosive.


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## IceBolt (Jul 28, 2020)

@Jim K thanks for the feedback. I think i'll wait and save my pennies so I buy aluminum heads, eventually. I was thinking about hardened valve seats because of the lead-free issue you mention above. I'll check to see what kind of heads i have on there now, as you said, should be #670. How would I tell if the engine (with original 670 heads) is not running well on regular unleaded (and i am adding STP or Lucas Octane Booster)? I'm in California, so there is often 15% ethanol at the pump. What would the benefit of using premium do?.....just starting with higher octane? And do your suggestions change after i add fuel injection? Yes, it's my first GTO  but love it!


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## Jim K (Nov 17, 2020)

Sometimes it's very hard to tell how the older engines are reacting to todays gasoline. Often times you won't even hear the detonation ping but it IS still happening. Some folks have good luck with a mechanics stethoscope. Best way I know of is to pull the plugs and read the signs. Detonation typically will show up on the electrode insulator as dark spots. You can do a search online to give you more definitive info. There are companies out there that make upper cylinder lubricant you can add to your gas tank that performs the same function as lead used to. The ethanol issue is more around any rubber material or gaskets in the fuel system. Ethanol is nasty stuff (in my opinion one of the biggest lies ever sold to the public) and will attack items involved in the fuel system over time (hoses, diaphragms, gaskets, o-rings, valve seals, etc..) that are not of late model design to withstand that. Then there is the issue of algae......... Whole 'nother story that one is.
Using premium grade lessons your amount of detonation but, when this motor was built, it was not uncommon to find 95+ Octane. Today you're doing good to find 93. VP racing fuels makes a very good octane booster but it's a bit pricey @ 22$ a quart and the quart treats 10 gallons. There are others.. Fuel injection.. How you deliver the fuel doesn't much make a difference once it gets into the cylinder for combustion. Yes, you might have better volume control based on the mass air flow sensor but you still run the issue of detonation wich is a function of fuel octane and compression.
Hope this helps..


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## IceBolt (Jul 28, 2020)

Jim K said:


> Sometimes it's very hard to tell how the older engines are reacting to todays gasoline. Often times you won't even hear the detonation ping but it IS still happening. Some folks have good luck with a mechanics stethoscope. Best way I know of is to pull the plugs and read the signs. Detonation typically will show up on the electrode insulator as dark spots. You can do a search online to give you more definitive info. There are companies out there that make upper cylinder lubricant you can add to your gas tank that performs the same function as lead used to. The ethanol issue is more around any rubber material or gaskets in the fuel system. Ethanol is nasty stuff (in my opinion one of the biggest lies ever sold to the public) and will attack items involved in the fuel system over time (hoses, diaphragms, gaskets, o-rings, valve seals, etc..) that are not of late model design to withstand that. Then there is the issue of algae......... Whole 'nother story that one is.
> Using premium grade lessons your amount of detonation but, when this motor was built, it was not uncommon to find 95+ Octane. Today you're doing good to find 93. VP racing fuels makes a very good octane booster but it's a bit pricey @ 22$ a quart and the quart treats 10 gallons. There are others.. Fuel injection.. How you deliver the fuel doesn't much make a difference once it gets into the cylinder for combustion. Yes, you might have better volume control based on the mass air flow sensor but you still run the issue of detonation wich is a function of fuel octane and compression.
> Hope this helps..


Thanks, that's very helpful!


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## IceBolt (Jul 28, 2020)

BTW, some gas stations in the Bay Area sell "Racing Fuel" with 100 Octane....at $6.99 per gallon, that gets pricey quickly as well.


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## Pontiac George (Mar 11, 2020)

IceBolt said:


> Good morning GTO Gurus, i'm looking for options to replace my cylinder heads on 400ci / 4BBL....soon to be fuel-injected with Holley Sniper EFI. What would you recommend in terms of cylinder heads. Existing ones are necessarily bad, just looking for something with hardened valve seats...and maybe a little more performance. I see Edelbrock aluminum heads on Ames Performance / Summit but at $2800 per pair, that's just too pricey for me.
> 
> Any ideas for options? Either new, or rebuilt? Thanks.


i'd spring for the Edelbrock aluminum heads. i have them on three of my GTO's. They are awesome. the motors run cooler and have more pop. They are worth the money.


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## 1968gto421 (Mar 28, 2014)

There are other aluminum heads besides Edelbrock which are very good. One is Kauffman Racing, they have a great selection of heads which I find less expensive than Eddies. I've gotten some geat tech advice from Jeff Kauffman and I haven't bought heads yet.






Kauffman Racing Equipment


High Performance Pontiac Parts



www.krepower.com









Kauffman Racing Equipment


High Performance Pontiac Parts



www.krepower.com





Speedmaster heads are also out there and are the most affordable (said to be cast in China, finished here). Several members of the PY forum have used them and had positive things to say. They are frequently found on ebay.









Pontiac 400 455 215cc 72cc Ram Air IV Hydraulic Roller Assembled Cylinder Heads


SpecsBrand:SpeedmasterPart Number:PCE281.2165Part Type:Cylinder Heads Cylinder Head Style:AssembledCylinder Head Material:AluminumCylinder Head Finish:NaturalCombustion Chamber Volume (cc):72 ccCNC-Machined Combustion Chamber:YesIntake Runner Volume (cc):215 ccExhaust Runner Volume (cc):175...




speedmaster79.com










PY Online Forums - Bringing the Pontiac Hobby Together - View Single Post - High Performance Injun's New SpeedMaster Heads


PY Online Forums - The online meeting place for Pontiac Enthusiasts all over the world.



forums.maxperformanceinc.com





Considering I am going for some HP and torque,I feel aluminum is the way to go as I've priced a high quality rebuild of my 6X4 heads and its almost as much as aluminum, (Also with my back surgery problems, they would be easier to work with and install. I am tending toward the KRE's.)

Good luck, do your research and you will be happy


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## IceBolt (Jul 28, 2020)

Thanks for the alternatives! Time to do some research. Appreciate the help. In the meantime, ordered this from Amazon 12 pack for ~$60


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## Montreux (Mar 8, 2009)

Absolutely start with the highest pump gas octane you can find!! These cars were designed for 100 octane! The best you’ll find today is 91-93. With careful tuning and careful driving you can get by. Octane booster on top of 91 will let you tune for a little more power.


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## maw2078826 (May 1, 2020)

Recently rebuilt my Pontiac Tri-Power and the upper surface of the carbs air horns (all three) was encrusted with corn gas (Ethanol) residue...for me that's the absolute end of using anything with ethanol...which also encrusted my original gas tank...so I bought a new gas tank, and have been purchasing 100 octane gasoline from a local air field for both my GTO & my 442...I can now run more timing and not be concerned with destroying my carburetors. Haven't found ant booster products which work as well as 100 octane...and "real" gasoline is well worth the money. I long for the days when you could buy Sunoco 260 right out of the pump @ 106 leaded octane....those were the days.


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## Dukes67 (Jun 19, 2018)

maw2078826 said:


> Recently rebuilt my Pontiac Tri-Power and the upper surface of the carbs air horns (all three) was encrusted with corn gas (Ethanol) residue...for me that's the absolute end of using anything with ethanol...which also encrusted my original gas tank...so I bought a new gas tank, and have been purchasing 100 octane gasoline from a local air field for both my GTO & my 442...I can now run more timing and not be concerned with destroying my carburetors. Haven't found ant booster products which work as well as 100 octane...and "real" gasoline is well worth the money. I long for the days when you could buy Sunoco 260 right out of the pump @ 106 leaded octane....those were the days.


Burn what you feel comfortable with through your car but I would sway away from the 100LL personally. It’s loaded with a lot more lead than was originally found in auto gas. I saw a lot of evidence of caking lead while working on general aviation engines. It literally cakes onto the pistons, valves, plugs and exhaust tubes and is very corrosive. It’s also chemically optimized for 8500 and higher altitudes.


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## maw2078826 (May 1, 2020)

Dukes67 said:


> Burn what you feel comfortable with through your car but I would sway away from the 100LL personally. It’s loaded with a lot more lead than was originally found in auto gas. I saw a lot of evidence of caking lead while working on general aviation engines. It literally cakes onto the pistons, valves, plugs and exhaust tubes and is very corrosive. It’s also chemically optimized for 8500 and higher altitudes.


Interesting....didn't know that...However, I have seen no spark plug fouling (other than normal)...would you suggest mixing with 93 Octane?...They sell non ethanol 93 here also.


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## Dukes67 (Jun 19, 2018)

maw2078826 said:


> Interesting....didn't know that...However, I have seen no spark plug fouling (other than normal)...would you suggest mixing with 93 Octane?...They sell non ethanol 93 here also.


I know of people that used to mix 25%LL to 93 octane E-free. I couldn’t tell you what the inside of their combustion chamber looked like though? To take care of it in mine I ultimately built a lower compression (9.5) engine and had the seats replaced on the 670 heads. Prior to that I ran 93 e-free gas also and added octane booster or would buy the canned race gas. I also used a top cylinder lubricant that would help with the loss of lead. It depends on what your compression ratio is and if your heads have hardened seats in them.


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## maw2078826 (May 1, 2020)

Dukes67 said:


> I know of people that used to mix 25%LL to 93 octane E-free. I couldn’t tell you what the inside of their combustion chamber looked like though? To take care of it in mine I ultimately built a lower compression (9.5) engine and had the seats replaced on the 670 heads. Prior to that I ran 93 e-free gas also and added octane booster or would buy the canned race gas. I also used a top cylinder lubricant that would help with the loss of lead. It depends on what your compression ratio is and if your heads have hardened seats in them.


Thanks Dukes67...I'm running #16 heads with TRW power forged pistons...they have perhaps a 1/4" dish in them and at the time I built the engine, the machine shop told me I was running between 9.5 & 10 -to- one compression ratio...at 6 degrees advance I haven't noticed any detonation, but of course we all know it's not always audible...I'll give the mixture you suggest a try.


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## Dukes67 (Jun 19, 2018)

I run 93 ethanol free in mine with no issues. My compression is at 9.5. My timing all in is @ 34. Besides not hearing detonation (which cannot always be heard) I check for indications on the spark plugs. If you can find exactly what your dish was on your cylinders and associated work done on the heads, block deck, head cc, etc. you can run a compression calculation on your engine and adjust from there. I would also assume your seats were changed at overhaul making the need of lead unnecessary. To make the long story short I just personally don’t recommend running straight avgas except in airplanes. I also don’t recommend mogas in airplanes. I’ve seen it cause problems with them. Particularly vapor lock on low wing models.


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