# Engine Combo Question



## 68gtohawk8369 (Oct 26, 2009)

I HAVE A 69 YD 400 WITH GOOD COMPRESSION IS IT POSSIBLE TO BOLT ON #16 1968 HEADS WITH AN EDELBROCK PERFORMER A SET OF HEADERS AND THE RIGHT SIZE CARB AND EXPECT SIGNIFICANT INCREASE IN PERFORMANCE? THE HEADS HAVE STAINLESS VALVES AND HAVE JUST BEEN REBUILT NO PORTING OR POLISHING JUST NEW GUIDES, SPRINGS, VALVES AND A 3 ANGLE VALVE JOB OR WOULD YOU HAVE TO SWAP OUT THE CAM TO SEE INPROVEMENT iM NOT EXPECTING IT TO BE A RACE CAR BUT HIGH 13'S WITH A 373 GEAR AND 2000 STALL CONVERTER WOULD BE NICE IS THIS POSSIBLE OR WHAT WOULD i HAVE TO DO IF THE HEADS ARE IN EXCELLANT SHAPE ARE THEY WORTH 1000.00? ANY COMMENTS WOULD BE HIGHLY APPRECIATED IM NEW TO THIS FORUM I FORGOT TO MENTION THE CAR IS A 68 GTO CONVERTIBLE


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## Too Many Projects (Nov 15, 2008)

Welcome to the forum. You don't say what heads are on there now so it's hard to tell if you will see any benefit from the head swap. If you will get larger valves and more compression, there will be the "potential" for better performance. Without knowing what cam you have it's hard to determine if a swap would get more power in the midrange either. Headers are always good for a few horse but the intake won't yield anymore performance than most stock 69 intakes because they already flow well. 
Have you run the car as it is now to get a baseline et ?


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## 68gtohawk8369 (Oct 26, 2009)

*pump gas freindly combo using #16 heads*

The engine is a stock 69 yd I looked it up its supposed to be 290 hp I guess what im trying to find out is first of all what you guys think on the 1000.00 price tag on the #16 heads ? I would think you would have to go with a higher lift cam any suggestions??? im looking to make in the 375 h.p range but it has to be a pump gas motor .Is it possible to use #16 heads and run pump gas or would they raise the compression ratio to high


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## Too Many Projects (Nov 15, 2008)

If the seats have been changed to hardened also, the price is about what I've been quoted to rebuild and upgrade a pair of old heads for modern fuel. That being said, usually used parts sell for a bit less than that. As far as the compression ratio going to high it depends on the heads you now have. Most of the 69 head info i find lists the cc's as very close to the #16's at 72, EXCEPT the #45 heads which are probably what you have and they are 90cc's. That much difference could be an issue. Someone with more experience with these numbers needs to join in. As far as a cam swap, yes, if you have the stock 290 hp cam in there, that change would yield much bigger results than just throwing on the heads. In fact, you could bump your performance with the current heads with a decent cam swap and 4 barrel carb. I would be more tempted to go that route than throw 1k at a set of heads with stainless valves you don't need. A less expensive head swap later could still be done to utilize the cam better.


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## geeteeohguy (Feb 2, 2008)

If you run the #16 heads, you will need to run 96 to 100 octane fuel to avoid engine damage. I was unable to run 72cc heads in sunny California due to detination issues. I ended up running a set of 87cc #15 heads, and it runs on 89 octane no problem. If you want to use the #16 heads, my recommendation would be to run dished pistons to increase your combustion chamber to 82 or 85cc, for 9--9.5 compression. The #16 heads will get you close to 11:1 compression with the stock pistons, not workable on today's pump gas. If running 100 octane is not a problem, it will put out tons of power with the high compression heads, though!


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## 68gtohawk8369 (Oct 26, 2009)

Thanks for the response thats what im hearing about the #16 heads I dont want that high of a compression ration I need a decent combonation to make 350- 375 horse not a race car but I do want it to sound and pull like an old muscle car should


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## jpdog357 (Feb 27, 2006)

Anyone with a recommendation on either a lead additive or octane booster? Is this an option in this case? I have a 71 YS 400 with #16 heads but no idea on cam and pistons as this is how I bought it.

Thanks,

Jason


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## xcmac26 (Dec 1, 2008)

to add to the mess, i've got a YD block that has the #16 heads. Only driven the thing a couple times and it was months ago but she runs just fine on high test pump gas. hope that helps some.


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## 68greengoat (Sep 15, 2005)

jpdog357 said:


> Anyone with a recommendation on either a lead additive or octane booster? Is this an option in this case? I have a 71 YS 400 with #16 heads but no idea on cam and pistons as this is how I bought it.
> 
> Thanks,
> 
> Jason


I've used 104 Maximum. The Maximum supposedly contains double the octane boost of the regular 104. Suppose to - reduce knocks, pings and hesitation, boost horsepower, clean and lubes fuel system/combustion system. "The only octane boost that doesn't contain harmful MMT". For whatever that's worth. I've used a few bottles and like it.....16 oz bottles


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## 68gtohawk8369 (Oct 26, 2009)

*Im not understanding completely the cc issue*

Ok if you go out and get 72 cc heads and then get dished pistons wouldnt that take away from the performance you are trying to acheive in the first place? How is it possible for some of the crate motors to acheive 400 plus hp on pump gas I was thinking of a couple differant ways to go the first being buying a crate motor , pontiacs seem overly expensive though . The second buying a seperate block or use the one in my car I would like it to be a weekend swao though . so I would rather build it on the side than drag the projct out . it seems from what I have read the 400 block is stronger than a 455 so the hot set up is having a 455 crank machined to fit in a 400 block I think rotating assembly's are 2000.00 for this then top it offf with the edelbrock 87cc alluminum heads I would go with the comp cam that has a similar if not exact specs as the ram air 4 cam a 750 or 780 carb and free flowing exhaust I think this could all be built for right around the 5k -5500 can anyone guess as to what kind of hp this combo would put out ?? the 3rd way to go for me is a lot cheaper than the previous 2 I I know a guy that has a fresh 335 horse 1967 gto engine its 10.75 to 1 though or right around there so here we go with the pump gas issue I already have an edelbrock intake :confused I know I have read there really isnt any performance gains from these although they weigh roughly 40 pounds less than stock and a brand new 600 hollley will this car be to small for the 335 horse gto engine


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## Too Many Projects (Nov 15, 2008)

A small cc head and proper dished piston will yield the same compression as an 87 cc head and a flat top piston. It's the comp ratio that matters, not how you get there. The dish would be so shallow as to not affect air flow in and out of the cylinder.


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## geeteeohguy (Feb 2, 2008)

Running dished pistons, you can use a high performance, good flowing, big-valved head, so yes, you do get good performance. I'm not into stroker motors, so you need to contact somebody who is, like Butler Performance. In my opinion, the aluminum 87cc heads are too big of a chamber for an aluminum head on a Pontiac: with aluminum, you can run one full compression point higher than and iron head, and you need to, to make up for aluminum's lack of thermal efficiency. Running 9-9.5 to 1 static with aluminum is too low in my opinion. A 600 CFM carb is too small for your 400. You need at least a 750 CFM, in my opinion.


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