I'm having a time. Anyway:
First I'll tell you about the '87 convertible. Has been running great, smooth, very clean car, I've had for about 4 months now, 92K miles. On the way home from work today, sudden-death. Quit while accelerating onto the freeway. Tried to start, figured sudden stop like that, spark or fuel problems. Sparking fine. Opened the fuel-rail pressure check valve and got a squirt of fuel. Tried to start again, sputter, sputter. Tried until battery almost dead. After towing home, I held open the fuel check valve on the fuel rail while the Mrs. cranked the engine. Hmmm, no fuel squirting. So, I messed with the gas tank opening and had her turn the ignition on while listening for a fuel pump sound, It made a little whir sound. Bingo, now the fuel rail is squirting again. And, all the sudden the car runs like nothing was ever wrong. Is this a fuel pump going bad? Anyone seen behavior like this before?

Now onto the 85 coupe. This ones a story. Bought the car expecting to rebuild it because the broker said his "mechanic" said the engine was shot. No specifics other than it overheats.

Well, we replaced the radiator and temp sensors and it no longer overheats at all. But, the water is REALLY rusty and mucky, so maybe a head cracked or gasket, I can't beleive that was all. So, we did a compression check last night. All 8 went from 100-120 on comp stroke one to 150-160psi on comp stroke four. From what I'm reading, this is perfect. I did it with the engine cold though, does that make the test irrelevant? Should I still have a full leak down done? What else can I look for? When I rev to about 2K Rpm there's a suspicious vibration, but it could be due to the cam, poor timing, or bad custom wiring.

Here's what's in the mystery '85s engine: Looks like GM heads with casting number GI85 462624. MSD-6A, NOS Powershot, A Wolverine Cam. Stock computer. The plugs where thick and black with carbon, it's running way too rich. The rest appears to be stock with some very sloppy assembly and wiring.

Here's the Cam spec sheet, what kind of computer changes will be needed to accomodate this? I can burn the PROM:
cam lift:int.305,exh.305
valve lift:int.458,exh.458
lobe ctrs:int.105,exh.115
adv dur:284int.,284exh.
.050 dur:218int.,218exh.
adv timing:
BTC-36 ABC-68 BBC-76 ATC-28
.050 timing:
BTC-4 ABC-34 BBC-44 ATC- -6

Let me know your opinions on these problems. I hope I wasn't to "wordy"
Joe

 

Oh ya. I forgot to mention on the '87s fuel problem, I had just filled the tank, and it was about 100 degrees outside and the car had been in the sun. Do these have vaporlock problems?

 

Joe, I have not seen any vaporlock problems on my 87. Have you changed your fuel filter? I think the only way to check out the fuel pump is to put a gauge on the valve and read the pressure. Haynes says it should be 34-39 psi. Regards Jim

 

sounds like the fuel pump is going out. dont let it strand you besides its easy to change. the car needs over 50 pounds of f/p to start.

 

As far as the 85 I see a lot of rusty coolant systems on these cars. Flush it out until the water is clean. Remove the overflow tank and fill it with water and stick a rag in it and a long screwdriver and clean out the muck in it. :cheers: :chevy :cheers: :chevy :cheers: :chevy :cheers: :chevy :cheers: :chevy

 

The 87 sounds like a fuel pump. My 89 did almost the same thing.

 

Check the motor oil on the 85. You should probably check all the wiring to make sure it goes where it supposed to go. Check the bulbs in the dash too. They get removed/covered when people don't want the buyer to see problems.

That NOS powershot is a bit worrysome. If the previous owner was as careless with the nitrous as the rest of the motor you may find some surprises in the bottom of the pan. I'd be real tempted to pull the pan and check a few things a main and rod bearing. Check the front main bearing since it gets the most abuse.

The suspicious vibration could be bad motor mounts, missing, too much advance, or bad balancer.

You 87 may have a bad fuel pump, flaky/intermittent connections, bad relay, and or oil pressure switch. I am usually suspicious about the connections when its intermittent like your is. Change the fuel filter if its been on for a while.

The cam should require a higher idle speed, more lower rpm spark advance and some fiddling with the fuel air at WOT. From the specs, its got a 110 LSA which is a bit narrow for an emission engine.

 

Thanks for all the input. I've replaced the fuel filter(nobody warned me what a JOB that was with the convertible cross bars in the way :boxing ) and replaced the relay just to be sure. I also figured how to hot wire the pump so If it strands me again, I can jump it until it starts running again. If it does, I'll replace it.

On the 85, we've double flushed it, now have cleaner running through it for about 10 run-hours, so it aught to be nice and clean. Replaced plugs and wires, now we are preparing to check timing.

On the cam, you mentioned:
The cam should require a higher idle speed, more lower rpm spark advance and some fiddling with the fuel air at WOT. From the specs, its got a 110 LSA which is a bit narrow for an emission engine.

What is LSA? We are gutting the cat and removing all the AIR pipes. We don't worry about passing emissions testing here. I'm about to start fiddling with the PROM settings. What role does this "LSA" play in my computer adjustments?

Thanks again, everybody!