New Guy Once Again Timing Sbc

[bigmeenchevy]

Alright here we go, i have a 355 carb. in a 93 pick up 4x4 the engine is a zz3 that was built little better than factory did being they left the rod cap loose anywho my problem is this when i park or neutral i can get the engine to rev relatively well but it has a hard sputter when you really stap the gas pedal if you ease on the pedal it cranks rpm's no problem it will almost die if you dont let up on the gas when you hit it hard. now when you put it in gear reverse or drive it will bust up really bad unless you very lightly increas the gas but if you dont it will back fire throught the intake. i have a brandnew procomp hei distributor and 8.5 accel wires plugs are new but the truck has been sitting for 2 yrs i have tried the timing all over the place 0 degrees all the way through to 30 degress did best around 16 degrees the carb i'm running is too big i think stock carb off a ZZ502 which is a 850cfm single pump duel inlet electric choke. initialy i was think the carb is to much which i still do so i disconected the vacum secondary and it improved tremendesly when in park or neutrual will rev hard no problem but in gear whole another ball game what am i doing wrong or over looking. park idle runs great in gear it's crap could my plugs be the problem along with way to much fuel.?

[Hemi31]

Before you do anything else get a smaller carb,then try 10-12 initial with 34 degrees totalas a starting point.You want to go with something in the 650-675 cfm for that motor.Most of your problems right now sound like the carb.

[bigmeenchevy]

that is what i did installed a 670 cfm 4 barrel holley runs 90% better but still has little hesitation on bottom end and mid range timing is 10 deg. at idle the gas in the truck is pretty old also so new gas and some new plugs should fix it all

[Hemi31]

Make sure you adjust your idle mixture to the highest amount of vacuum.That will help with the stumble as well.

[bigmeenchevy]

and that would be out on the screws on the metering blocks? i'm not a fine tunner

[Hemi31]

Yes,there may be two or four.Put a vacuum gauge on a manifold vacuum port.Turn one of the screws in a quarter turn while watching the gauge.If the vacuum drops stop and turn the screw the other way.Rotate around all the screws until the vacuum gauge is at the highest reading you can get.Then you can play with your timing again.You said you have 10 degrees now,try twelve.If it starts good and does not ping try a little more.Just don't go past 36 total.If you have an adjustable vacuum advance you can really play with it.

[bigmeenchevy]

well some progress went to the exhaust shop ran flow masters hooked up the lock up converter installed the proper ac delco plugs for this motor and gapped them to 45 thousands as specified drained the gas tank as much as possible and went and filled up on premium set the metering blocks the way you suggested and then went back to the timing it's sitting at roughly 14 degrees not a whole lot of change from 8 to 14 y is this and no ping what so ever. i know their is some bad gas still in the system i havent drove it enough to get the old crap out of the carb. but it still wants to pop back through the intake a little bit under a load while in gear do you think this will disipate when the old fuel gets out of the lines and carb. still have to mount and adj. the tv cable for the trans.

[Hemi31]

Make sure you have the good gas going in and also make sure your vacuum advance is working.You are timing this with the vacuum line off the advance and plugged for initial right.You should not be popping through the intake.Has it been doing that all along?Whats idle at?Any vacuum leaks?It sounds like the timing is still off.

[pelligrini]

The hesitation and popping might also be due to how you have your accelerator pump adjusted. There is a section on this pdf page from Holley that might help. It has some of the basics of Holleys spelled out pretty clearly and concisely.

I think Hemi31 has got you steered in the right direction.

[R Pope]

Popping out the carb usually means a lean mixture, try bigger jets.