Thread: Pedal down engine dies

Tweet

Hey guys,i have a small problem.....but i want get into that here.Instead i need help with my car.As some of you probly know i have a bucket with a 350 chev motor and a 671 blower.Now she starts up eazy as,2 pumps and whammo,idles sweet azz,and even runs o.k,but the moment i slam the go pedal to the floor she coughs and splutters and dies.WHY???.Is it a vaccuum leak or am i trying to push too much gas into the stock 350 and flooding it.Please help me as i dearly need to start burning some rubber.

Cheers KIWI

Thanks for the reply Richard.It has been doing it since i put the Blower on.Bought it as a complete unit had been running on a mild 400ci in a 57 Chevy which was occassionnally dragged.Come to think of it it may be running lean,i remember now he ended up melting a couple of pistons...OOOOO scary.Could the leaning out be caused by a vaccuum leak?

Cheers Daryl

Hey Denny, 2 600 holleys

Cheers Daryl

Thanks for the help,i will check it out and see if the problem goes away.I am running a new unilite electronic dissie,no points.

Cheers KIWI

you may also want to check your power valves, so that they close at a higher vacume and that they have the window type hole rather than the drilled round hole, the big square window type flows more fuel.

Originally posted by Kiwi T
Hey guys,i have a small problem.....but i want get into that here.Instead i need help with my car.As some of you probly know i have a bucket with a 350 chev motor and a 671 blower.Now she starts up eazy as,2 pumps and whammo,idles sweet azz,and even runs o.k,but the moment i slam the go pedal to the floor she coughs and splutters and dies.WHY???.Is it a vaccuum leak or am i trying to push too much gas into the stock 350 and flooding it.Please help me as i dearly need to start burning some rubber.

Cheers KIWI

check to be sure your're not lean like everybody says Kiwi T, because you're better off rich than lean, but i ran a blower on the st. for 20 yrs, i burnt a lot of holes in a lot of pistons but it was going like a bat out hell when it blew, the only time i had a blown motor to fall on its face is the first holly carb. i ran , when you kicked the blower in it would sink the floats in the carb. and bog the motor down until you backed off the accl. a little then it would go. put the blower floats in no more problem. the way i found mine was i ran it one time without the breathers on the carbs. and when it fell on its face you could see raw gas coming out the top of the carb. and being sucked down into the motor. Something to think about because I spent a ton of money trying to fix it before I found the problem.

Actually looking back on a few of my holley blower carb notes, some other fixes. Change the small 30cc accellerator pumps for the big 50cc units, change the punp shooters up to the larger sizes, and get a holley accellerator pump cam kit, you want to skew the whole fuel delivery curve over so that you get the maximum fuel delivery down the throats of the primary bores to cover that big slug of air that tha blower gulps down. Then fine tune back from there by reading your plugs, better to run rich and work back rather than burn up a piston and pull rebuild your moter.

If you can give me your jet, shooter,and powervalve sizes. Segedins should be open tomorrow and the new year break still has 3 days left in it.

Originally posted by southerner
Actually looking back on a few of my holley blower carb notes, some other fixes. Change the small 30cc accellerator pumps for the big 50cc units, change the punp shooters up to the larger sizes, and get a holley accellerator pump cam kit, you want to skew the whole fuel delivery curve over so that you get the maximum fuel delivery down the throats of the primary bores to cover that big slug of air that tha blower gulps down. Then fine tune back from there by reading your plugs, better to run rich and work back rather than burn up a piston and pull rebuild your moter.

If you can give me your jet, shooter,and powervalve sizes. Segedins should be open tomorrow and the new year break still has 3 days left in it.

am i the only one thats had the floats to sink on him. when i talked to holly he knew what i needed, they are called none sinkable floats.

Originally posted by lt1s10
am i the only one thats had the floats to sink on him. when i talked to holly he knew what i needed, they are called none sinkable floats.

When you say sink do you mean the rate at what the fuel is sucked out of the bowls sucked the floats down . I used the 600 holleys but initially modified them to run a secondary metering block and decided what the heck ! pinced the big centre hung bowls of a spare sed of holley 780's and ran it as side hung setup, figuring that the bigger bowls held more gas.
so maybe me coming up with that idea i must of sidestepped the lead float deal . Looking at a holley book, these untitanic floats, are you talking about the plastic neaprene foam filled floats ?.

Originally posted by southerner
When you say sink do you mean the rate at what the fuel is sucked out of the bowls sucked the floats down . I used the 600 holleys but initially modified them to run a secondary metering block and decided what the heck ! pinced the big centre hung bowls of a spare sed of holley 780's and ran it as side hung setup, figuring that the bigger bowls held more gas.
so maybe me coming up with that idea i must of sidestepped the lead float deal . Looking at a holley book, these untitanic floats, are you talking about the plastic neaprene foam filled floats ?.

i knew you was gonna ask that but i cant remember which way it went, but like i said holly told me which float i needed and they were guarantee not to sink. the extra pressure the blower created in the carb. bowl would pull the float wide open until you let up on it a little and then the float would come back to the top and cut the fuel off. this would happen from a dead stand still. it sounds just like his problem. i think i had the cork and needed the metal ones.

Originally posted by DennyW
600 Holley :
Power Valves and Carburetors for Superchargers
These carburetors that are intended for use with superchargers, and have a unique capability that allows their power valves to reference the intake manifold vacuum below the supercharger. This allows the power valve to operate as it should, based off intake manifold vacuum. A power valve provides further enrichment to the main metering system under load (low vacuum) conditions. Without this external referencing, the power valve would be "reading" the supercharger boost pressure, which has no bearing on the engine load.
So, is these carbs for a charger for sure?

never knew i had a power valve problem, but i almose took the blower off on accont of the floats. the people at blower serv. told me there was no way a 471 blower would sink a float so i keeped looking for something else, but wouldnt you know it i had one that would.

What i can't understand is how come the blower set up is pigging out on my motor,which is a stock 350 when it was going o.k. on the mild 400.Granted it melted some pistons,but that was going full shit down the drag strip,it was not bogging when the throttle was slammed to the floor.The carbs have been tuned to run with a blower.I changed nothing,just bolted the complete unit,from carbs to manifold,straight on to the motor.I know the car it was in previously,and i know and trust the owner,and i rode in the car with the blower on,went like stink.Could it be my engine??

Cheers Daryl

i dont think its to lean i belive its to much for your motor. but if i say its to lean and you burn a hole in a piston then you say i told you wroug. if it was mine id take the linkage a loose from the back carb and try it with one carb. just try it from a stand still it wont hurt anything and it will def. lean it out. if its makes it worse then its to lean.

That is actually a great idea Mike,i will try that,might give me an idea of where i am without spending money on unneeded parts.And besides if i put a hole in a piston i can always blame you guys lol

Originally posted by Kiwi T
That is actually a great idea Mike,i will try that,might give me an idea of where i am without spending money on unneeded parts.And besides if i put a hole in a piston i can always blame you guys lol

its not gonna burn a hole in a piston from a dead stand still. you'er forgetting i burnt up a lot of pistons so i know what you can and cant do. the first blower i had was a 4-71 on a stock motor with 7 lbs. of boost, it had 1- 750 holly with no jets in the rear and 92 jets in the front, stock cam, 71/2 pistons. i went to the drags every week with it, and that was all the carb. i needed. i dont care what type cam, pistons, or heads you have when and if you get the right fuel and ign its gonna go. the leaner it is the faster it goes until you do burn a hole in a piston. to much fuel is the only thing that i saw would slow it down. because its got a blower dont mean its need a lot more fuel, that would depend on the motor, so it looks like if the blow is giving you 30% more power you would need 30% more fuel. 2 600 is a lot of fuel for a stock motor. how much boost are you running? i hope you have sense enough not to run through the 1/4 mile with the one carb. im talking trying from a dead stand still just to see if it helps the stumble or not. its not gonna hurt it unless you get into the higher rpms and you'll know right away.