help please new engine race's when started

[peglegs]

First start up on my rebuilt engine it race’s up to aprox. 3500 rpm? no tach.….back to idol up again back down to idol then i shut it off.

rebuilt 90 4.3 v/6, roller cam, after market HEI, electric fuel pump (not intank), changed fuel pump from a fixed 7 psi , said it was adjustable, to the one i have now that is adjustable fuel guage reads 3 ½ psi.

* visually no vacuum leak anywhere afraid to run it & spray carb cleaner to see if
engines rpm increase’s.

*#1 cyl was at TDC with pressure, timing mark on “0”, rotor at #1 spark plug.

* re-adjusted floats on new edlebrock.

im thinking its either the dizzy off or a vacuum leak somewhere if dizzy was off would it cause it race that high rpm?

[cableguy0]

Throttle is stuck open or you have a massive vacuum leak.

[crazy longhorn]

Straight up....I would bet an air leak. Vacuum does not leak ....it is the air that leaks into the vacuum system? Just messin with you guys on "terminology".... I probably did not spell it all properly, so feel free to toss it back Longhorn

[peglegs]

given the symptom of immediate rise in rpm to about 3500 then to idol then back up is this what a bad seal, open port etc would do ? if i remove an intake manifold plug & applied an air pressure nozel with 50lbs????? 100lbs????how much pressure????? duct tape off the top of carb i guess will this work????? thanks for the response's folks

[68gmsee]

The air pressure in the intake probably wouldn't tell you much since you would have to have the valves closed also. Only way you can do that is to loosen all the rockers.

A vacuum "leak" (sorry c.l. ) may be the intake manifold gasket, p.b. booster or automatic tranny modulator if you have one. First thing I would do is to plug all ports on the carb even the vacuum advance and plug the p.b booster and tranny on the intake and see if it changes anything.

[peglegs]

parts house where i got my electric fuel pump suggested i needed a pressure regulator even though the write up states one is not needed.......installed one today.....nothing changed still races. yes i did find a port open on the back of the manifold carb risor & plugged it.....nothing changed WTH (what the hell) it still races.

trans is a 7004r .......no modulator????? is there some sort of vacuum line to it.

folks im an amateur at this & know a little about alot & enough to make me dangerous im at wits end here why does this engine race???????

68gmsee, i will plug all the ports tomorrow & if no change then may remove & reseal intake.......i did look at the front & rear intake seal areas with a mirror & most all sealant squirted out with very small areas that did not....those rails are pretty skinny to make a seal on the 4.3

[GASoline71]

This thing have a carb on it now? Or factory FI?

Gary

[peglegs]

Originally Posted by 68gmsee

The air pressure in the intake probably wouldn't tell you much since you would have to have the valves closed also. Only way you can do that is to loosen all the rockers.

A vacuum "leak" (sorry c.l. ) may be the intake manifold gasket, p.b. booster or automatic tranny modulator if you have one. First thing I would do is to plug all ports on the carb even the vacuum advance and plug the p.b booster and tranny on the intake and see if it changes anything.

68gmsee tried blocking off all carb ports......no change still race

taking off the intake this afternoon to reseal

GASoline71 new edlebrock 500cfm readjusted the floats 1 was off 1/4" no
change
cableguy used a remote starter to start linkage free.......accelerator pump free

[peglegs]

ok ok now im really lost at wits end i started it after resealing the intake it was barely running.... hopped out of the cab to turn the distributor as soon as i budged it the rpm's soared.......coincedence or ????? something with the distributor?

[crazy longhorn]

I have to ask? I see that you are running a carb on that "mill"....did you also opt for the old school HEI? Longhorn

[peglegs]

Originally Posted by crazy longhorn

I have to ask? I see that you are running a carb on that "mill"....did you also opt for the old school HEI? Longhorn

long horn i bought it online from Skip White

[crazy longhorn]

It still sounds to me that you have a big air leak somewhere....brake clean, or starting fluid (carefully), will find it? longhorn

[peglegs]

longhorn thats where im really concerned i would have done that way back but on a new rebuild not broken in & letting it race 3500 rpm up ? given its a roller cam but im concerned if i have done damage this far

[peglegs]

it was suggested that if the centrifugal advance springs were to light it would cause my problem with racing ????

[cableguy0]

theres nothing to damage by the engine turning 3500rpm. There really is no break in and you cant hurt anything as long as it has oil pressure. Let it run so you can figure out whats going on. Make sure the choke is working and releasing like it should. Get a timing light on it and make sure it isn't just advancing a large amount. You have the cheapest lowest quality Chinese distributor money can buy. It wouldn't remotely surprise me if its not working properly.

[peglegs]

cableguy ty i suspected something with the distributor since i resealed the intake . b-4 i removed the intake i again rechecked top dead center, rotor position etc. & it was right on im so paranoid about this extreme racing im contemplating a new distributor b-4 i try your suggestion. this engine, being rebuilt, was down to the bare block i had a lot suggesting massive leak & cant find anything that may be missing ie: a plug, old sensor etc. but im going to look again with a mirror.

cableguy i see your looking for a project to bad you dont live out this way you could almost choose your year, color & engine within a few short weeks. any trip into town, im out in the country, i will see a dozen or more 60's & 70's pick ups

[cableguy0]

Are you sure it isn't up on high idle from the choke? If you hit the throttle does the speed come down. Is the choke opening?

No funding right now for a project even if I could find something. Problem around here is cheap trucks are completely rotted. Snow and salt take their toll on metal over 40-50yrs.

[peglegs]

i held the choke open with a screw driver wouldnt that eliminate the high idol ?

[cableguy0]

Originally Posted by peglegs

i held the choke open with a screw driver wouldnt that eliminate the high idol ?

No definitely not. the high idle is done through the carb linkage. you have to hit the throttle to kick it down from high idle. There is a separate high idle adjustment. It could be way too high but still should come down once you kick it off high idle by opening the throttle.

[peglegs]

i backed off the fast idol & throttle linkage once to eliminate that & it still raced was i on the right track ?

by backing off was wrong should i have turned in to contact the cam?

[cableguy0]

Did it actually kick down though? On a vehicle with electric choke. pump the gas to set the choke. Start the truck. Once the idle speed starts rising hit the gas again and speed should fall.

[peglegs]

tried it twice no luck thanks again

[peglegs]

reset all the carb linkage according to Edleberocks rebuild instructions sheet most all were off considerably, reinstalled RPM'S spiked again

[77 350 Shorty Wide]

This may be a silly question. Is the intake for a square bore carb or spread bore?

God Bless, Terry

P.S. have been watching this thread from the beginning.

[peglegs]

Originally Posted by 77 350 Shorty Wide

This may be a silly question. Is the intake for a square bore carb or spread bore?

God Bless, Terry

P.S. have been watching this thread from the beginning.

ty for the reply terry its not .