Hard starting 427 FE when hot 85C or 190F, and stumble on ramp turns

Learjockey1 · #1 (**permalink**) 07-30-2010, 01:17 AM

1) Upon shut down from a "coming home" idle (not a real hot soak), with engine up to temp, 85C or 190F, the car is hard starting with starter having to turn 4-5 seconds with maybe two to three pumps (strokes are long with two fours and progressive linkage) until combustion resulting in a little black smoke. Engine does not want to crank hot without pedal strokes. However, engine starts immediately and crisply when cold without maybe half a pump, if at all. It seems with the fuel vaporizing at operating temp and being more evenly distributed and not puddling in the intake being cold, it should be easier to start hot than cold. I do not have any intake leaks around the carbs, bowls set, and idle mix screws are balanced on all four sides for highest idle and smoothness. Engine runs good otherwise. What science is going on here?

2) Another problem: When I am in a moderately hard turns, such as attacking on/off-ramps, the carbs stumble. I want to keep the two fours and not switch to a 780 center float. Can these carbs be worked to stay even in the turns? I was thinking about going with a set of 2x4 Quick Fuel Carbs from Survival Motorsports later.

Any fixes or insight for these two problems??

undy · #2 (**permalink**) 07-30-2010, 04:32 AM

Quote:

Originally Posted by Learjockey1

1)
2) Another problem: When I am in a moderately hard turns, such as attacking on/off-ramps, the carbs stumble. I want to keep the two fours and not switch to a 780 center float. Can these carbs be worked to stay even in the turns? I was thinking about going with a set of 2x4 Quick Fuel Carbs from Survival Motorsports later.

Any fixes or insight for these two problems??

A bit of info on the Quick Fuels...

I worked with Quick Fuel personally to have those carbs custom built for my 482" Pond motor. After I got all the specs from QF I then bought them through Survival. Barry liked my setup so well he's selling the same setup on his site. The Carbs are essentially 750 cfm, 4160 style with side-hung bowls and replaceable rear jets complete with all the bells 'n whistles of true race carbs. The workmanship is amazing and the performance tremendous. There's no stumble or dead spots anywhere. Right out of the box they produced a measured 12.2 AFR @ WOT on a chassis dyno.

All that being said, they still suck in the twisties. You can't adjust that out of side hung float bowls. If you want a drag car then dual 4s work fine. If you want a track car run a "properly adjusted" single center hung 4 bbl.

There is one other alternative... You can get 2 center hung carbs and turn them 90 degrees on the manifold. There's a few suppliers out there for some trick linkage too. It doesn't score much for originality but it'll get the job done, in the straights or turns...

JBCOBRA · #3 (**permalink**) 07-30-2010, 07:09 AM

Hi Lear!
With regard to your re-starting issue, I believe that many have this problem as the fuel is literally boiling in the carbs while the car is parked. Then, upon restart, it takes a little while to get fresh, cool gas thru the system. Ethanol in the gas nowadays seems to compound the issue.
As for your turning issue, does anyone make road race style floats for those carbs?

lamaluv · #4 (**permalink**) 07-30-2010, 08:14 AM

I was having an issue with the carb stumbling on turns also. After analizing each step and a little help from a racing friend we solved the problem. It only happened when turning left and also with a quarter of a tank of gas or less. It was not float related. The fuel pick up was on the left bottom of the tank and when low on gas the fuel was sloshing away from the pick-up. We installed baffles and problem solved.

Dick

Tom Kirkham · #5 (**permalink**) 07-30-2010, 09:59 PM

A bypassing fuel regulator will help the hot start issue

Excaliber · #6 (**permalink**) 07-31-2010, 07:58 AM

Dual carbs and a stumble in a corner is going to be really tough, if not impossible, to get around. Those side hung floats either "starve" you or "run rich" depending on which way your turning.

There's a reason Shelby went with a single center pivot float for road racing, and it wasn't for more power. Many different tests show that clearly the dual fours made the best power for the FE.

I've done a couple of things that have helped, but still...

1. I put in a plastic baffle inside the float bowl area that limits "slosh" of the fuel into the venturi area. It's a Holley part that can be purchased. In my case, I had a couple of the baffles from some old carbs I had laying around and simply transferred them to my new carbs.

2. I added this make shift piece of copper tubing to help eliminate any fuel slosh that may be coming out of the main vent holes.

3. The biggest issue was lean in the corners from a jet size that was to small!!!! Simply increasing the jet size made a big difference right away.

4. Yup, don't let the tank get to low, that happened to me as well. When I get below a 1/4 tank it starves in the corners.

I'm talking about hard core auto cross here, much more of a problem than just regular on ramps.

Of course I should run a single for hard core auto cross, OK, I guess I'm not "that" hard core after all, 'cause I aint running a single, no way. I like my duals, warts and all.

601HP · #7 (**permalink**) 07-31-2010, 01:08 PM

I had the same problem this summer. Great cold starting. Devilish to start after it was fully warm.

One of the floats was adjusted too high. Adjusted it downward. End of problem.

David

FIA-ERA · #8 (**permalink**) 07-31-2010, 07:41 PM

Can't help much with the carb probs as I was just as frustrated with the carbs on a 67 GT500 project. I went back and forth on the Carl's ford and Survival carbs package. I ended up with the carbs from Barry (Survival Motorsports). Now, I just got the 600 cfm's as my engine is a little more than stock. The 750's may require some boring of the butterfly holes as they are bigger. I actually just got them installed today and after about 3 hrs of fiddling with them I got them working pretty good! The problem all along was there is an allen head adjustment on the vaccum secondaries that was holding the secondaries open!! The carbs are very nice and started up right out of the box. I think the jets are pretty darn close (gotta pull some plugs) and they perform well. The car was stumbling still and we narrowed it down to a bad coil! Fixed the coil, the car runs like a raped ape! Just amazing!

NOW, the only negative thing I have to say is it took almost 6 weeks to get these carbs so if your not patient... I called Barry every week for 4 weeks and it was after all of this did I realize he out sourced them to Quick Fuel. I don't blame him as they are VERY nice BUT it was frustrating for us both. It was worth the wait but man was that painful. If you want "originality" get Carl's, if you want "new technology with better performance" get Barry's. By the way Barry will get them to make you any type of carb you want! I'm strongly considering a 650 double pumper with LeMans bowls from Barry! PM with any more questions, Thanks Matt.

Learjockey1 · #9 (**permalink**) 08-02-2010, 05:46 AM

Thanks for your time Gentlemen, I appreciate the help and ideas!
I remember in my college years I had a 69 Firebird with a moderately built 400 with a Holley 600 and vacuum secondaries. I never noticed the stumble then and I had it set up and lowered for the twisties.

I will check the items you all prescribed.

I like to two fours, probably next best to a set of Webers,

I read a quote from a rodder in one of the recent car magazines.

"It is not how fast you go, but how you go fast"

Another perspective.