I tore apart my entire engine (92 speed density, 305 TPI, stock) replaced all seals, gaskets, reassembled.

The car starts and runs, but runs more poorly than before I stated to tear into motor. I added a 89 vette L98 cam cuz they have a little more duration (and price was right, free) and even more LSA. the increase in LSA should smooth the idle, but it idles poorly. I added an AFPR just incase I needed it, since I plan on running a wide-band on it when it runs better.

First, timing is not set since I haven't got a light (plan on getting someone to do it, trust me) any way, the cars starts without any problems. i have movedthe distributor to the sweet spot of quick starting for now. Anyway my fuel pressure without the engine running builds to 44 right now. With the engine running it is at 40 psi and the needle bounces a bit (+/- 1 psi). When I open the throttle the pressure drops of and doesn't really want to build back up. It is in the low to mid 30's with some throttle. I tightened the AFPR screw some, but all that did was raise the no run amd idle pressure, it still drops with the throttle. Move the distributor around and no changes. WTF? Any ideas?

 

fuel pump

 

Raised pressure more. Idles at 44, drops to 42 with throttle but holds at 42. No more dancing at idle either.

What does the vacuum hose that connects to the AFPR actually do??

 

The vacuum hose to the FPR indicates pressure in the intake manifold to the FPR. At idle, pressue is lower than atmosphere and the FPR reduces the fuel pressure, usually to about 33 psi. At WOT or with key on engine not running, pressure in the manifold is close to atmospheric and the FPR increases the fuel pressue to about 41.5 psi.

Do a search on fuel pressures. If you're getting 33 at idle and 42 at WOT/key-on, the FPR and fuel pump seem to be working correctly.

Several reasons for running rich. Recommend getting a timing light and setting that first.

A longer duration cam has lower vacuum than stock. This will signal to the ECM the engine is under load and requires more fuel. You need to make changes to the fuel tables within your BIN/prom.

 

The difference in cams is so small I don't suspect it being the cause of such a bad idle. The car shakes a lot.

More info, when accelerating (just normal driving) everything feels ok, until I get to fifth gear. Any load in 5th below 2000 RPM causes the car to shake violently. Once it builds to a higher engine speed it is fine.

The timing will be set when I get a day off (friday).

 

Car stopped starting, so more investigation was needed.

The pick-up coil was gone and the ignition module tested ok, but with some intermittant readings, so I bought an entire new distributor. I also put on the stock fuel pressure regulator.

As far as the shaking, I backed off all of the rockers and re-adjusted. Some of the passenger side rockers were wayyy too tight. I followed the service manual, but the engine had been apart too, so I think after the oil pressure was brought up, the adjustments were off (lifters all pumped up evenly). Anyway, I only gave the rockers 1/4 turn past zero lash.

And.....
WOW! This car runs really well now. I don't think the AFPR had any affect, I think just the pick-up coil and the loss of compression on the passenger bank due to the valve adjustments were the cause of the poor running.

The car is a lot stronger than when I bought it, although I only put a few miles on it before ripping into the engine. Actually, I have put on less than 500 miles since I bought it in February. Now that it is running (with no leaks!) I will drive it more.

I thought i would update this thread in case anyone finds some good information in here.

Final thoughts: This car took WAY too much money to get where it is. Also, the 3.08 rear really holds this car back...