Thread: engine stumble

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ok no more shocks, no more water in the fuel and a very strong idle at 750 rpms. but the problem im still having is a very bad stumble if I get on the accelerator from anything after idle. sitting at a stop sign and then punching it there is no problem, but say im doing 15 to 20 miles per hour and then punch it it falls on its face. after a few seconds of very bad stumble it clears up and goes down the road like nothing was ever wrong. I've got a brand new holley 650 double pumper on it and the truck is timed at 14 degrees advance initial. the pump shot is set where it was when the carb left the factory. I'm thinking that when I open it up it is either running too rich or too lean. anybody have any suggestions??

thanks in advance.

hey sorry for the lack of info: the engine is a newly rebuilt 355 with an Edlebrock dual plane performer intake, L82 cam, 195/160 heads with shorty headers. The transmission is a new turbo 350 with a norm. torque converter. All of this has been placed into a 94 s10 that was originally equipped with the 4.3 vortec and 5spd manual transmission.

goes down the road just fine, and from a dead stop it will burn the tires for as long as you want, but punching it from 15 or 20mph and it stumbles spits and sputters.

thanks for any help

check your vaccum advance can on the dist.
check your vaccum line to the tranny

denny,

could you explain the 1" spacer for the cam? this is my first build of any sort so Im a little slow.

Also I failed to mention that the carb has #68 jets in it from the factory. the engine is suppose to be good for around 315 hp but who knows, does the jet size seem right to you guys for the engine???

thanks for any further advice.

ok just checked the bowl levels, both are good. A little bit of fuel dribbles out when I shake the truck. I readjusted my idle screws from 2 1/4 out to 1 1/4 out - the stumble now has gone away during hard acceleration and now happens just driving down the road when the engine is under no load. I'm hoping this means I can just find a happy medium and adjust the problem out.

IN GENERAL : stumble under load = too rich and stumble under no load = too lean --- is this correct? if not, are there any generalities dealing with this stumble that I might could use to help diagnose this problem?

thanks for all the info Denny

ok the squirters are squirting exactly when the accelerator is pushed. I readjusted my screws to 1 3/4 out and drove it a little down the road: good acceleration from dead stop, good acceleration from roll on, and no stumble while crusing. Seems to be running better now than it has since ive had it running. Im going to run it a little harder later on this evening and see if it is still doing good.

thanks for all the help til now, I'll let you know how she does when I really get on it.