Dead stock cam, what now? <long>

[Bye 87GN]

For a while I've been trying to diagnose a lack of power/detonation problem with my 86k mile driver GN. After fixing all the usual stuff (questionable coil pack, cracked header, etc) I had a suspicion that my stock cam was bad.

I got out the dial indicator and magnetic base and started on the driver's side (suspecting #3 exhaust of course). I measured the lift at the pushrod and valve ends of the rocker on a few valves, while turning the engine over by hand. When I got to #3 exhaust, I found a whopping lift of .080" at the valve stem <ouch>. I should have just looked at it while I was turning it over, I should have noticed that.

Anyway, the engine has never been apart and I was wondering what the feasibility would be of replacing the cam while the engine was in the car? I think I know the answer, but I'm hoping here. I would guess that the cam bearings should be replaced, and that that might not be possible while still in the car. I would at least check out the rod/main bearings, which would tell me if I was going to yank the engine or not.

Also, with an ultimate goal of 11.50s, what cam should I be looking at? Everything is stock now, but new turbo/injectors/convertor etc. will be future improvements.

Thanks for reading my novel!

 

[Bye 87GN]

Has anyone just replaced the cam/lifters while the engine was still in the car?

Did you replace the cam bearings? <how?>

 

[BM Computer Src]

Many people simply replace the cam while the engine is in the car. How many miles on the engine?

 

[Bye 87GN]

About 86,000 miles. It didn't happen all at once, either. Gradually over the past 3 years I'd say. I know the lobes had to go somewhere, hopefully it was slow enough for the oil filter to grab the particles, and not shred the main/rod bearings.

Compression tests show 150 or so on all cylinders, so rings etc. may not be gone.

 

[frankg]

Yeah you can change it in the car. Go with a 204-214 Speed-pro or 212-212 Comp Cam. If the cam bearings are bad pull the engine for that. Frank

 

[MSDGN]

Don't assume the cam bearings are bad...I pulled the stock cam out of my car(87 "T") and it had 148K miles on it...lobes were worn a little but none were wiped...cam bearings looked brand new...I went with a CC 206-206 and you can see what I'm running in my sig...can be done easily in the car...just make sure you degree it in and if flat tappet break it in properly...

 

[Bye 87GN]

Cool, thanks for the info. I'll check the rod/main bearings, then if they are OK, I'll pull the cam and check the cam bearings. If anything looks fishy, I'll pull the engine and start rebuilding. How can you inspect the rear cam bearing while it's still in the car?

Oh, any cam break-in tips?