Hi... I have a 73 olds cutlass Supreme and bought a set of 72 7A heads for it. I had the local machine shop replace all the valves, new valve stems and seats and shave the head down just a little to account for the newer thicker gasket they make today. I think these heads have 64cc combustion chambers vs the 80cc chambers on the number 8 heads on the car right now. I am not sure if they have rebuilt the engine. I bought the car 3 years ago and have been getting all the wore out parts replaced, brakes, muffler, front linkage etc. The carb was trash so I had it sent off and re-jetted for 6,000 ft elevation. The car is running pretty good right now. It might have a slightly bigger cam than stock put in years ago, I really don't know. I want to swap out the heads to get better hp and I read with the stock pistons in the engine now, the new heads should give me about 9:5 or so compression vs the 8.0 compression the 73 motor has now. My question is that if I only do a head swap do I need to replace the lifter rods or can I use the ones in the engine and other than the head bolts can I reuse the head gasket or should I buy a new set. I will be putting the high performance exhaust manifolds on from a 70 350,, they are new. reproduction.. Is there anything else I should replace and by putting these newly rebuilt heads on, do you think it will blow the bottom end out. This is a street cruiser and I don't plan on racing the car. I will probably upgrade the cam at a later date, but just wanted to replace the heads now without having to rebuild the motor. Like I said the motor is running pretty smooth with no issues... thank you

 

The 72 and 73 used the same pushrod ( lifter rods ) So you should be OK there.
A head gasket should NEVER be re-used.
The heads and the top of the block should be absolutely clean. Use a Roloc disc and a drill to polish them.
The head bolts may be re-used, if in good condition.
Use a torque wrench to tighten the head bolts in the order specified in the shop manual .
I usually torque the bolts to about half of the specified torque, then go around the order again and tighten them to full specified torque.

 

Thank you .... appreciate the information.... Heh, I grew up in Apopka Fla, my sister still lives there... small world huh... thanks again

 

I'll add a couple things to Charlie. Put rags in the cylinders and cover other open areas like the "valley" to keep that Scotch-brite dust out. Scotch-brite is an abrasive ! BROWN is coarsest, RED is next, GREEN is after that. GRAY and WHITE are the finest grit.

Run a bottoming tap down threaded holes. Use a new sharpening stone on the block head gasket surface to remove raised areas around threaded holes.

Finally blow out threaded hole and blow off head gasket surface and remove rags in cylinders. .

 

You won't be at 9.5 to 1. You will be lucky to be at 9 to 1 with standard Felpro head gaskets. Those heads are not 64cc, most are about 5cc bigger. The two sets of #8 heads, I measured were 77 to 78cc. So you gain 10cc uncut but you are going from a .017" to a .038" to .045" for most standard replacement head gaskets. I used milled #6 heads were actually 64cc with a regular .028 head gasket that is no longer available with the factory factory piston being .025" below deck put me right at 9 to 1, it ran really nice. You could try a .027" Cometic MLS head gasket to at least hit 9 to 1. You should be fine with the push rods but inspect the rocker arms for wear and replace as necessary. Good luck.

 

Thank You... I just checked again, these 7A heads are from a 72 Olds 350... here is the info on those heads: On a set of Olds 7A 350 cylinder heads, the combustion chambers are typically "wedge-shaped" with a volume around 64cc, though the exact size can vary slightly depending on the specific casting variation of the 7A head; this design is considered a classic "small block" Oldsmobile combustion chamber shape. I did have the heads shaved down to compensate for the thicker gaskets so I should be at 9:5 maybe a little higher.....I will try the Cometic .027 head gasket.. thanks for the info

 

Thank You !!

 

What he is saying is that although they are ADVERTISED as such, they typically do not measure out as such due to core shift and other manufacturing variables. Several have been measured and typically end up being closer to 70cc. Not going to lose much by cutting the head .030" in addition to the thinner gasket but you're still probably going to be closer to 9.0:1 than 9.5:1. I think I recall the calculation being 1cc for every .006? so, at .030, looking at 64cc or so. Don't know until you actually measure with the valve job complete and installed though, of course.