QuestionQUESTION: My 79 Deville has had its engine/trans set up for racing. About 450 HP, 500 lbft @3200RPM. Edlebrock intake, full race cam, electronic ignition, headers, shifter kit, the works by Caddy specilist in Albuquerque.
Problem is hard to start cold (crank a long time) but fast start when warm. Runs great cold, but in hot weather stalls after 10-15 miles. I've changed carb fuel rods, tried fuel pressure regulator. System has low vacuum at low rpm. When running well, 0-60 in 8, qt in 11 or less. On a sustained pull it falters but keeps accelerating. Checked timing, and several different vacuum advance settings. It was a new carb (4 bbl). Any suggestions to get it to run smoother, start easier? If this is too far off your expedertise I understand.
ANSWER: Oooopps ! For some reason your primary question went to my spam filter, then your follow up arrived in my regular inbox.
Nearly any engine with a full race cam is hard to start when cold. The valves are open during part of the compression stroke. It's also why you have low vacuum at low RPM. Nature of the beast.
You can try new plugs and wires, new coil , modulator, and rotor in the distributor (I'm assuming you have a typical HEI ignition), and you might try a 'cool can' for the fuel.
It sounds like you have a heat related gremlin, but it could be as simple as vapor lock, or fuel starvation for another reason. Or it could be the coil I mentioned above. The stalling after a few minutes leads me to believe the vapor lock theory. To cure that you need to find a way to cool the fuel , hence the cool can, or run some extra metal line through an area away from engine heat. I once took some extra copper and wound it around a beer can several times , making a cooling coil. People thought I was nuts but it cured a severe vapor lock on my 51 Plymouth.
Here's what I suggest:
First; determine if the carb is adaquate for the size engine , that's a BIG motor. Ask the tech guys at Summit Racing, 1-330-630-3030.
SEcond; check your fuel pressure with a guage during the periods of stalling, and during your acceleration runs. It should stay around 4--5 PSI
Third: The stalling after 15 minutes. Does it cure itself if you slow down? If so , you're probably starving from simply not having enough in the float bowl, check the float setting certainly, but also go back to fuel pressure. Sometimes an electric pump solves those troubles, Summit Racing again, has a Carter pump for about $60.00 that should do nicely. I don't recommend Holly products, simply cuz I've had bad luck with them too often, and they're overpriced. Try those things and see what happens, I am happy to help further if needed
Good luck
Dan Liddy
Sarasota, Florida
---------- FOLLOW-UP ----------
QUESTION: The carb is OEM for the 502. The fuel metering rods have been change twice to get more gas flowing. I have an over size main fuel pump (mechanical) that drives the fuel regulator valve. The ignition is a high performace electronic unit. All parts new with the engine rebuild.
On the warm stall, pumping the gas will bring it back, or just restart in N while coasting works. THe line is in the original location, front of the engine from the pump, barely misses the belt/block then to one of the support struts where the regulator is, then a short jump to the carb input. On full throtle, it shifts to second @ 55 and third @ 90. Haven't found a road long enough to find ultimate top end, but past 140 on the GPS @ half mile, poor speedo only goes to 85. Kids in their rice paddy 4's and 6's think its gramps in his old car, till they try a challenge and get smoke and noise hit I kick it past them :-) And for the punks with rap or junk on their radio, 3400 watts of back end speakers/amps to toot some song they wouldn't like. :-) I painted it GM metalic gold (was GM yellow) GM color.
Thanks for the tips, will see how it works when its warm enough to crawl under the hood. BTW, it still gets 15 mpg @ 70.
Do you know of any shop in the Chicago area that knows carbs well? or do a dyno tune?
Regards,
Henry
AnswerYou wrote <<On the warm stall, pumping the gas will bring it back, or just restart in N while coasting works. Te line is in the original location, front of the engine from the pump, barely misses the belt/block then to one of the support struts where the regulator is, then a short jump to the carb input. >>
Leads me to believe you're having a starvation problem. Because it takes 15 minutes to occur I suspect vapor lock. Do something to lengthen the fuel supply line, see if there is a way to enlarge it (to -8 Aeroquip hose ) while we're at it. and find a way to get some cool air to it. When you call Summit Tech line, ask them about vapor lock too- - -their tech guys are really great and very knowledgable
RE: Chicago - - in a word , no, I live in Florida and stay as far away from the north as I can. Been to Chitown once for 3 days in February. Not again !
Keep trying - - you'll get it eventually.
Dan
