I have been warned by a few people that a head swap on a high mileage motor is bad because the rings may not hold the higher compression. However, I do not plan on raising the compression. The heads I am lookin at are the SDPC Vortecs, its the kit, comes with the heads, and the manifold, the heads are already worked for the higher lift, and I was gonna toss a ZZ4 cam in it. The heads are the same stock 64 cc chamber, and I can imagine the head gasket being much thinner than the stock. The motor as of now doesnt consume much oil, cause its more of a weekend car, and I know that the valve seals are bad, always get that blue puff on startup. I use mobil 1 5w-30, and oil pressure has always been good.

Along with the new heads and manifold, I will also do new pushrods, and lifters, and 1.6 rr's will top it all off.

So would a compression test be manditory?

 

I dont think the rings will be a problem at all. However the block may have warped over time so i would check to make sure it is still flat. Otherwise your gonna have a hell of a time getting everything to seal up properly. A before and after compression test would be a good idea just to make sure everything is sealed properly but isnt really mandatory.

 

hadnt thought of the block being warped. I plan on doing all this work at home, but i guess that if the block is warped I'd have to yank it to have it decked.

 

I wouldnt assume that it is gonna be warped. Definatly check it before you yank the engine. Youll need a good staight edge(not a ruler) that is long enuf to go aroos the entire engine both straight and diagnally and a .009 inch feeler gauge. You shouldnt be able to get the feeler gauge under it at any spot.

 

any source where I can pich up a straight edge of that size? could use that now since my bro has his new motor stripped down to the bare block

 

try www.mcmaster.com

 

The "theory" is that the valves and rings have worn at the same rate. When you do a valve job or put new heads on, the valves will now be sealing better, cylinder pressures will rise ("higher compression") and the rings will be stressed more than they were before.

It's pretty much bunk. I put new heads on with 141k on the 305 shortblock 33 months and 23k miles ago, no problems with the rings.

Now, there was the valve job I did on the 396 back in '95. Also upgraded the cam a little over the factory stick. When I pulled the heads, I discovered scored cylinder walls, so I went ahead and pulled the pistons - only to discover several broken top piston rings. The previous rering by a highschool shop class didn't remove the ridge, and the new piston rings broke right away. After reaming the ridge, breaking the glaze, and putting in new rings (and new bearings for good measure), I discovered the new Melling high volume oil pump wouldn't clear the stock oil pan baffle. So, I put the stock one back in and put it all back together. 300 miles into the break-in with the Pep Boys oil in it, I got on it a little for the first time and wiped out all the new bearings - because it now pulled a lot harder with the better sealing valves (and perhaps the new cam) and the oil pump (and possibly the oil) didn't keep up.

So, that's a case where doing a valve job killed the lower end...