# Advice on 69 engine rebuild that has 74 Block with 4x Heads



## PMaurer (Jan 6, 2021)

Looking for some advice on how I should approach an engine rebuild on my 69. 

Some background: it's been in the family since '98. Bought it from my older brother about 5 years ago. Prior to 98, at some point the original engine got swapped out. It has a 74 481988 YH block #256754 (haven't been able to find this 256 number correlating with any Pontiac #) , with 4X heads (K053). Appears to be the original 69 intake (9794284 - F239) with a 76 Q-jet (17056212ABH 2866). Runs decent, but the rear main seal is leaking. Figured while I had the engine apart for the rear seal, it be a good time to refresh the engine. Car has 98K miles on the odometer, don't have any work history on this engine. My brother did not do any engine work in the time that he had it.

My research suggests that the YH block with the 4X heads produces 175 HP. I'd like to get back to at least the original HP the car came with. It's an automatic and the PHS docs note it came with a YS block, which would have had 62 heads for 350hp. Suggested approach? My understanding is that the YH and YS blocks are the same, so assuming I should be able to stick with this block and just upgrade the cam and heads? Get the 62's, or aftermarket heads? Any reason, other than getting back to a 69 block and originality, that I should look for a YS block? I plan on going thru the rotating assembly as well. Anything else here I should consider with this engine in it's current setup as part of the rebuild?

I know it's pretty open-ended, any suggests appreciated.


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## PontiacJim (Dec 29, 2012)

PMaurer said:


> Looking for some advice on how I should approach an engine rebuild on my 69.
> 
> Some background: it's been in the family since '98. Bought it from my older brother about 5 years ago. Prior to 98, at some point the original engine got swapped out. It has a 74 481988 YH block #256754 (haven't been able to find this 256 number correlating with any Pontiac #) , with 4X heads (K053). Appears to be the original 69 intake (9794284 - F239) with a 76 Q-jet (17056212ABH 2866). Runs decent, but the rear main seal is leaking. Figured while I had the engine apart for the rear seal, it be a good time to refresh the engine. Car has 98K miles on the odometer, don't have any work history on this engine. My brother did not do any engine work in the time that he had it.
> 
> ...


How big is your budget for the rebuild? $6,000 - $12,000?


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## PMaurer (Jan 6, 2021)

Hey Jim - 
Yeah, guess I should have provided that detail . The 6-12 range is manageable budget-wise, but would prefer to stay within the 6-8K range. Would that be too restrictive in my options?


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## Old Man Taylor (May 9, 2011)

You first need to be more specific about your objectives. Will it be on the highway a lot? Do you care about the gas mileage? How important is power to you? Do you want it to look and/or sound stock? The hardest thing to do is come up with realistic objectives. For example, you're not going to get 600 horsepower and good gas mileage.


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## PontiacJim (Dec 29, 2012)

As pointed out by OMT, many questions need answering as to what you want out of the engine and what kind of performance you are looking to have. We are not trying to be tough on you, just get a flavor for what you are expecting from the build so we can throw out good suggestions.

I see no problem getting 400-425 HP out of what you have, no need to buy #62 heads unless you have to have them. Compression dictates octane and higher octane = more $$$. Bigger HP can also means drivetrain & suspension upgrades which is more $$$.

6-8K should be doable, and depending on your parts selection and HP wants, I'd shoot for under 6K.


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## PMaurer (Jan 6, 2021)

Thanks Jim and OMT - certainly didn't take it as a negative at all. I took a little time to think about what I am looking for and let me know if you need more:

I'd say the 375-400 hp would about right - a bit over the stock output to offset the A/C (when I get the factory setup back in).
Enough to enjoy a bit of laying down the rubber from a stop light every now a then, chirp the wheels , but not enough
to put the transmission and rear end into additional stress needing major updates. The transmission was rebuilt several years ago and shifts strong. 
My brother mentioned a quick shift kit put on it when it was rebuilt, and the rear diff was gone thru last year.
Love a nice rumble out of the exhaust. It sounds pretty good the way it is right now, sounds great outside as well as inside.
Definitely more a cruiser/daily driver than anything else. Good highway manners a plus. Not looking to race at all, just attend the occasional show.
I've already put a Hotchkis TVS and enjoying the much improved stability and handling dynamics. Guess I am looking for
something similar in the area of the engine. 

Hope I've given you enough details. Let me know if you need more and I'll noodle on it some more.

Thanks!


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## PontiacJim (Dec 29, 2012)

PMaurer said:


> Thanks Jim and OMT - certainly didn't take it as a negative at all. I took a little time to think about what I am looking for and let me know if you need more:
> 
> I'd say the 375-400 hp would about right - a bit over the stock output to offset the A/C (when I get the factory setup back in).
> Enough to enjoy a bit of laying down the rubber from a stop light every now a then, chirp the wheels , but not enough
> ...


OK, I think you provided enough info. I'd say you want pretty much a basic rebuild with a bit more attitude. I would keep what you presently have and build off of it as it'll save money and since the engine is not original anyway, why spend money for the high compression number correct heads when nothing else will be matching and no one really knows the difference, or cares when you show it off at car shows or cruise-ins. They know it's a GTO and know it sounds bad-ass, that's all most will be looking to see and hear.

Since you plan on A/C, I would go for an increase in torque over HP, which is how you build a Pontiac anyway - torque.

The best bang for your buck would be to go with a stroker kit, new cast crank, new forged rods, new forged pistons/rings, new bearings, balanced. Replaces all the 50 year old parts with new and upgrades them as well - so a solid bottom end to start.



https://butlerperformance.com/c-1459542-engine-components-internal-rotating-assemblies-stroker-kits-400-blocks-406-495-cu-in-butler-custom-rotating-assemblies.html



Butler 60PSI Pro oil pump & pick-up. New hardened oil pump shaft as well.



https://butlerperformance.com/i-24453827-butler-performance-pro-60psi-oil-pump-w-pickup-screen-bpi-m54ds-pro.html?ref=category:1234738



New harmonic balancer.



https://butlerperformance.com/i-24453461-powerbond-dayco-pontiac-1968-up-except-301-performance-street-4-bolt-harmonic-balancers-dampers-w-timing-marks-non-sfi-pbo-pb1056st.html?ref=category:1234723



What is needed is to know what "4X" heads you have as there are different offerings based on the engine application. There is a ID number/letter stamped on the head, but I will assume the engine is the 400AT "7H" head. Perfect for the larger 4.25" 461CI stroker engine with its 98 CC combustion chamber. My 1972 7K3 heads are 98 CC's on my 455 build and with the KB pistons and .027" Cometic head gaskets I am using, it'll be just a little over 9.0 compression. 

I used the online Wallace Compression Calculator to determine compression using the stroker kit, .030" over 400, 4.25" stroke, 98 CC head, Cometic .027" compressed head gasket, .020" deck height, 8 CC valve reliefs, 4.3" head gasket bore dia. It comes up as 9.06 compression. This is a good number for pump gas.

If you use the Felpro head gasket of .041", compression drops AND you don't get the important "squish/quench" between the flat area of the piston and flat area of the head. .041" + .020" = .061", where as .027" = .020" = .047" and is a better number with .040" ideal for street.



1974 All1974 All400 2bbl AT*4X*4H980.3008:1Screw-inIndividual1.961.66 1974 All1974 All400 4bbl AT*4X*7H980.3008:1Screw-inIndividual2.111.66 1974 All1974 All400 4bbl MT*4X*3H980.3008:1Screw-inIndividual2.111.66


Build the heads using RA IV length Ferrea stainless steel intake valves and exhaust valves - have the 1.66" exhaust valves opened to the 1.77" size. 3-angle valve job, clean up the bowls by smoothing, gasket match the intake ports and clean up the intake ports to remove any casting flash, casting parting lines, or rough areas - nothing fancy and no polishing, just cleaned up. Bronze valve guides & Viton valve seals. ARP 7/16" Big Block rocker arm studs to replace the factory bottle neck studs - and will need poly locks. New long-slot 1.5 ratio stamped steel rocker arms. Matching springs and retainers to work with cam selection.

Cam choice could be something like the Crower #60243






Pontiac Hydraulic Flat Tappet Camshaft


Pontiac 287-455 Compu-Pro Hydraulic Camshaft (284-Hdp)




www.crower.com





Q-jet and cast iron manifold.

Good quality ignition system and matching timing curve for your engine.

I would add a higher than stock (about 1,800 RPM for stock) torque converter and go with something near 2,500 RPM, but what is called a "tight" converter vs one of the "loose" slipping type converters.

Reproduction RA cast iron exhaust manifolds, 2.5" outlets and matching mandrel bent pipes.

There is more with all the small parts, but this is for the major assembly.

So this may be something to consider for a strong street build and get you where you want.

Others will throw out a few suggestions as well and you can get an idea of parts/pieces and then narrow down from there.


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## Droach6498 (Nov 1, 2020)

PontiacJim said:


> OK, I think you provided enough info. I'd say you want pretty much a basic rebuild with a bit more attitude. I would keep what you presently have and build off of it as it'll save money and since the engine is not original anyway, why spend money for the high compression number correct heads when nothing else will be matching and no one really knows the difference, or cares when you show it off at car shows or cruise-ins. They know it's a GTO and know it sounds bad-ass, that's all most will be looking to see and hear.
> 
> Since you plan on A/C, I would go for an increase in torque over HP, which is how you build a Pontiac anyway - torque.
> 
> ...


Dont put headers on it. Just redid my exhaust installed new headers wish I didnt.


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## Jared (Apr 19, 2013)

Make sure you check with the shop that does your heads. There are some parts availability issues right now, and from what the shop doing mine told me a couple weeks back, Pontiac valves are in short supply right now. I was also told that some cams and connecting rods are in short supply as well. Again, this is second hand information that I pass on. I ordered my cam months ago and it was not an issue back then. Also, be prepared to wait for the machine shop work. I am in the process of building a Pontiac engine too. The bottom end took almost six months to get back and the heads are 8 months in now (was told should be ready the end of this month or so). Basically, everything is going to take way longer than you expect. This was good for me since nothing from the engine that came out was reusable. The time allowed me to spread the cost over a longer time period. 

Your budget makes sense. My build is a bit more radial than yours. I haven't crunched the numbers exact (almost afraid to) but I figure total cost of the project is a little north of $10K.

X2 on the headers comment. RARE makes the RA style manifolds with larger collectors that will support a street application. That's what I am going with on mine.


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## Droach6498 (Nov 1, 2020)

Jared said:


> Make sure you check with the shop that does your heads. There are some parts availability issues right now, and from what the shop doing mine told me a couple weeks back, Pontiac valves are in short supply right now. I was also told that some cams and connecting rods are in short supply as well. Again, this is second hand information that I pass on. I ordered my cam months ago and it was not an issue back then. Also, be prepared to wait for the machine shop work. I am in the process of building a Pontiac engine too. The bottom end took almost six months to get back and the heads are 8 months in now (was told should be ready the end of this month or so). Basically, everything is going to take way longer than you expect. This was good for me since nothing from the engine that came out was reusable. The time allowed me to spread the cost over a longer time period.
> 
> Your budget makes sense. My build is a bit more radial than yours. I haven't crunched the numbers exact (almost afraid to) but I figure total cost of the project is a little north of $10K.
> 
> X2 on the headers comment. RARE makes the RA style manifolds with larger collectors that will support a street application. That's what I am going with on mine.


No suprise I oredered Rally I wheels and was told they were back ordered since July, this was in Jan. I did just get the though. Took about a month


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## PMaurer (Jan 6, 2021)

Hey Jim,

Thanks for the input! After figuring out where the stamping is, turns out I have the 4H heads. I am assuming I'd have to have the intake opened up to 2.11 along with the exhaust 1.77.
Pretty sure my current headers are toast with this project, and the exhaust system is up for consideration as well. Going to continue to build out my shopping list. Any other items I should consider while doing this project? You know "while the engine is out".

Much appreciated.


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## PontiacJim (Dec 29, 2012)

PMaurer said:


> Hey Jim,
> 
> Thanks for the input! After figuring out where the stamping is, turns out I have the 4H heads. I am assuming I'd have to have the intake opened up to 2.11 along with the exhaust 1.77.
> Pretty sure my current headers are toast with this project, and the exhaust system is up for consideration as well. Going to continue to build out my shopping list. Any other items I should consider while doing this project? You know "while the engine is out".
> ...


First thing is to have them cleaned and magnafluxed to make sure no cracks. If good, then you can move forward. Yes, you can install the 2.11/1.77 valves. This will provide some good metal for the seats. The machine shop should use a cutter to open up the throats to match the larger valves and should blend this in. You can add hardened seats to the exhaust valves if you want to. Different opinions on this, but I don't feel you need them with the stainless steel valves and fresh seats. Key is to have good margins on the valves which you will get with new valves. You can also use an additive called Defender Boost that has a lubricant that will help. I would not use it in every tankful, just every couple. Now if you plan on towing a camper behind your car and getting engine temps up while climbing hills, then hardened seats would be a good option.









Defender + Booster Fuel Additive


Defender + Booster Fuel Additive



drivenracingoil.com





As pointed out the 98 cc's should do well to keep compression down to the 9.0-9.3 range once you crunch all you numbers for deck height, valve relief CC's, bore size, etc.. You can mill the heads to reduce a few CC's if needed. I would have the machine shop measure 1 chamber with the new valves in place to get an accurate CC number. This can then be used to select a piston with matching valve relief CC's, assuming the piston is .020" down in the hole (deck height), or one that is "zero deck" if you go that route. Keep in mind to shoot for the .040" quench/squish distance, or close to it if possible. Again, you'll want to work with your engine machinist in selecting some of these parts or machine work to get you there.

You don't have to gasket match the intake ports or even smooth out/clean up the intake runners, but it can't hurt. No need to go crazy and polish or re-contour anything. A good 3-angle valve job is a plus, but you want to ensure good seat margins on the valves.

And all of which I pointed out earlier.


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