I am looking to replace the 7A heads on my 86 Cutlass with a set of 5A heads. I know that the 7A heads are on engines with hydraulic roller lifters and the 5A's are on engines with hydraulic flat tappet lifters. My question is whether the pushrods and rocker shafts are interchangeable between the two head styles?

On another note, I have found conflicting information on the combustion chamber size on these two head styles. The Head FAQ referenced on this site says the 5A heads have 64cc chambers and the 7A heads have 67cc chambers. Another website has the chamber sizes swapped between the two. This information won't change my mind, but I would like to know which one is correct.

 

The push rods are shorter on the roller cam motor. Olds changed the push rods to a larger ball end around the time of the 307. I found that out swapping 5A heads on an Olds 350, push rods and rockers had to match. Those years should be the same rocker arms but check where the push rod sits, if flip flopping. Honestly, CC both sets of heads, they could vary a few CC from factory spec. Very few have CC'd 307 heads, it would be good info. The swirl port motor use a different piston and have slightly lower advertised compression. Good luck.

 

The published chamber volumes are the NHRA stock class blueprint numbers. As-cast heads can be 2-4cc larger than that, depending on the metal that had to be removed to surface the heads, cut the seats, etc. And if the heads have every been rebuilt, all bets are off. The 64 vs 67 distinction is within the manufacturing tolerance.

 

You'll probably want to swap intakes as well. That A5 for those 7A heads are small ports. You'll need an A4 aluminum or a cast iron equivalent from an older engine with "normal" port sizes. Aftermarket would probably work as well.

I know VIN 9 (442) springs are the same for 5A and 7A heads (along with diesel). So you could just swap the push rods, pivots and rocker arms as needed straight over from the 7A to the 5A heads and be good to go. There are no rocker "shafts" to speak of here. It's just pivots and rocker arms. Which share the same part numbers between the flat tappet and roller heads.

 

 

I plan on buying a Performer RPM intake when I change the heads. From what I have read, I will also need to gasket match the heads and intake also. The intake might be a bit of overkill for for the engine but I want to get rid of the adaptor and spacer I currently have under my Sniper EFI.

 

I have been looking for a VIN 9 camshaft (roller hyd) and I am not having any luck. I am not comfortable buying the $400+ one size fits all camshafts I have found on Summit and Jegs. If anybody can steer me in the right direction I would appreciate it.

 

Hopefully Mark(Cutlassefi) will chime in. You will want to stay mild on the cam unless you mill those 5A heads. A custom roller might be your best bet. Good luck.

 

I just so happen to have an uber-rare NOS 86-up VIN 9 roller camshaft I guess I can part with. GM P/N 22531804. Still in the box. Well, make that still in the tube.

$425.00 plus shipping to U.S. address.

As you're well aware, they do not grow on trees. Or in bushes. I'll have to locate it and drag it out. Hit me up if you're interested.

 

Please consider changing the entire engine. An Olds 350 or 403 is a good choice. I chose the 403 for my 88 Cutlass.

 

I did that as well for my 88, a 403. I should swapped the radiator and not used fancy under drive pulleys right off the bat, it liked to run hot. The 307 is reliable, as long as he is OK with maybe 200 hp, it is a good motor.

 

Thanks for the help everyone! I know a swap to a 350 or 403 might be the best bang for the buck, but the 307 has fairly low miles and I know the condition. Everything that I’m adding to the 307 can be swapped over to to a larger short block if I come across one and have the facilities to do an engine/drive train swap. I’ve also got the 200c transmission and the 7-1/2” rear end which would probably end up in pieces on the ground with the larger engine.

 

Yeah both are weak. The spider gears are the first of many weak links for 7.5" rear, they are soft. I exploded a set that took out my pinion. I picked up a used set of 3.42 gears out of a Astro Van, the spider gears looked worn and ready to fail from it as well. If you service the diff and they look questionable, Yukon has a properly hardened set available. I used them at the track with slicks after I broke the Powertrax No slip, they look like new after multiple runs. A short tail BOP TH350 is an easy swap for your 200C if it starts to go south. Do you have dual exhaust? An aftermarket dual hump crossmember would also allow a 2004R swap and something better than the factory 2.14 gears. The exhaust will be a nice gain as well and sound better. 200 HP should be there with exhaust and the cam swap. If you go with the HO or another mild cam, buy a quality Cloyes 9 way Billet timing set and degree the cam. Good luck.

 

I have replaced the 2.14 gears with 3.73’s and put in a posi so I hope that isn’t quite the weak link that it was stock. I did install headers along with a dual exhaust as one of the first projects on the car.

I installed a Holley Sniper EFI and ignition system which allowed me to gut all the wiring and hoses that went with the stock ECU. I am hoping wit the head, intake, and cam upgrade that I can get the horsepower well north of 200. I know that the low compression will hold me back and that it won’t be wise to wind it past 5,000 rpm.

 

I have replaced the 2.14 gears with 3.73’s and put in a posi so I hope that isn’t quite the weak link that it was stock. I did install headers along with a dual exhaust as one of the first projects on the car.

I installed a Holley Sniper EFI and ignition system which allowed me to gut all the wiring and hoses that went with the stock ECU. I am hoping wit the head, intake, and cam upgrade that I can get the horsepower well north of 200. I know that the low compression will hold me back and that it won’t be wise to wind it past 5,000 rpm.