Going to pick up my DOHC next weekend!

[vinny]

Well I found what appears to be a pretty good deal on one. It sayes twin cam so I know its a early one. I'm gettin the engine of course, the transmission, wireing harness, and pcm.

The only drawback is that it's a high milage motor. Around 200K I think. The biggest concern I have is bore wear. How do the motors hold up with high miles? When I rebuilt the 2.8 in my Fiero I had to bore it .060 over. I was planning to put forged pistons in it in anticipation for a turbo later down the road. What do ya'll think? Fresh bore, forged pistons, ARP studs, and about 15psi! Just kidding maybe only 10psi. I'm unfamilier with this stuff so any advice would be great.

Thanks
Vinny

[z34phoenix]

these are high compression motors 10psi will take a lot of prep. other things to look at is wear on the cams, deff change the lifters, timing belt job w/ new pulleys

no clue how the valves hold up... deff new valve seals.
FYI i got 182k miles on mine and she is still runing nice. all depends on how the motor was taken care of.

[vinny]

The owner said the engine appears to have been taken care of. The very minimum I plan on doing is a ring and bearing swap. If it needs more I'll do it. When the time comes for me to concentrate on the motor ,trust me, I'm going to ask alot of questions

Thanks
Vinny

[pocket-rocket]

Compression on the early ones was 9.25:1 I believe. When the heads came off the 91 with around 130k miles, possibly 140k you could still see the factory cross hatch in the cylinders. I didn't drive that car easy either. When I got it, it had the 2nd tranny in it because it had a rebuilt tag on it. I went through 1 more 4T60-E before throwing a Getrag 284 at it. At 160-170k, I bet the cross hatch is still there. As far as egg shaped bores, I have no idea.

[fieromadman]

these are high compression motors 10psi will take a lot of prep.

You're kidding right? First off, 9.25-9.5:1 isn't that high of compression. Secondly, theres several of these engines running around with over 100K on them turboed. Thirdly Matt Hawkins is running 13 psi on a stock block with ARP bolts, polished combustion chambers, hyper pistons, and a box style intake mani. He has been running that for several years. BTW, he's got 415 WHP.

[91DOHC284]

i had 292 000 Km on my DOHC when i did the top end. i dont know how that relates im miles but when i did the top end at about 286 000 Km the cylinder walls still had the factory hone on them. they werent shiny, no lip, nothing. absolutly perfect. after i put the top end back on i did a leak down to see if the rings were sealing properly and each cylinder had exactly 2% leak. now that is damn good. and as for the valves and heads, i put new valve seals in cuz it was running a little blue and i lapped each valve in the lazy man way (with a drill). internal is all working fine, minus a noisy lifter so i agree with z34phenox when he sais new lifters. cams were all in good shape also.