Hot Rods sbc stumble that won't go away

More specifically, direct manifold vacuum varies with changes in engine load. Increasing load will decrease the vacuum. Decreasing the load will increase the vacuum. It's not so much directly related to just engine RPM. This is why it works so well to control power valves, vacuum advance and transmission vacuum modulators.

 

roger that

 

Any updates ??
dave

 

its been raining like crazy the last two days. i did change the red bushing to the blue one. reset initial timing to 16 total 36. runs much better on the freeway now i still have the light springs in the dist. with these changes it still starts fine hot. i took off the holley elect. pump it was driving me crazy with all the noise. i put on a holley 110gph mechanical with a new comp cams rod. i ran the valves and found one a little tight. with all the rain i spent a lot of time cleaning the whole car and fixing little things on it. as far as the slight stumble now that the timing is where it needs to be I'm going to richen it up a little on the primary side. i will be able to do that on sunday. i got it registered also and put the insurance back on. dave i see you are from illinois. drag week is going from st. louis to indy to great lakes so far. maybe you are close to one of those tracks and can take in some crazy action. i compete on drag week with the hemi coupe.

 

Absolutely!!

 

good news the stumble is all but gone. i could actually live with what little i have. i tried bigger and smaller squirters and differant pump cams today. i was thinking i needed more fuel. usually a stumble just off idle is lean. wrong! sometimes less is more. on a new carb i usually jet it up a little due to the alch in our fuel around here. when i was first attempting to cure the car i jetted it up from 73 up to 77. i never had black smoke or fouled plugs. today i put in some 80s. it got way worse. so i figured i was on to something. at 2000 rpm with a light load it bucked and stumbled worse than before. i pulled it back into the shop dropped it down to 73s took it for a ride and its barely there hardly noticeable. with the timing off as much as it was at the start of all this the jet changes didn't seem to make much difference then. it was well worth the effort today. i will drop back to the stock 71s and see what happens. i think i screwed up putting a 750 on this 327. i have never owned a engine that small. i thought it could handle the 750. its been a long road. all the things that worked on past cars did not work on this one. with the timing and now fuel figured out the car is fast and crisp. i have a af gauge on the hemi coupe. i think i will be putting one on the chevelle. thanks to all who offered input. while this has been frustrating at times it has also been fun. its been a challenge to figure it all out. my old high school hot rod is faster than ever. i will post some track numbers soon.

 

ALL IN TINKERING........ GLAD YOUR GETTING THERE......

 

i will change the jets tomorrow. that should do it. it is all in the tinkering. thats the fun part some times. i thought putting 8-97s on my blown hemi coupe and making the car go in the nines at the track while staying street able was tinkering. that was until i converted it to efi. i put on a hilborn four port upright with a fast efi-x2 controller. that mess took some time to figure out. i started in april and got it all working right just in time for drag week. i got so frustrated i almost took it all off. that was some serious head scratching b.s. I'm glad i didn't it was all worth it. now the nitro car in the avatar was a crazy thing to sort out. i was hung up on many times calling shops saying i had a 65 dodge awb car with a straight axle that i want to go sevens in while burning nitro weighing 3000 lbs. i got it figured out to a best of 7.47/ 189.9 with out their help. trial and error with a big load of determination. I've been down this road many times,

 

Jets returned to stock. Demons be gone its cured. Runs like a dream. Now that the chevelle nightmare is over its time to put the hemi back together for the coupe.