help with sbc 350

[black86442]

I hate to admit it but i need some advice or input lol i have a 350 9.5:1 with L98 steel heads comp 270/278 cam.torker intake holley 750 carb hei dist. It runs great at idle or 1/8 throtle but after that it spits and backfires and has noooo power at all. Ive tryed a smaller carb aslo and no diffrence ive adjusted the timing a million times in diffrent ways changed spark plug gaps. Checked vacume at idle it was 12.5psi vac checked the valves to see if there too tight and checked fireing order. The throtle responce is terrible and the motor will hardly spin past 4 grand free reving it. Any suggestions would be helpful

 

[86-blk442]

It kind of sounds like the valve springs are incorrect for your application, they'll cause a motor to not rev. Either that or the timing but you said you have checked that already. I'm no expert though.

 

[black86442]

The springs i have are 1 pound lighter with valve closed and 2 pounds lighter with valve open and same coil bind. I should aslo say that if i easly bring the rpm up it wont miss and back fire. but if i stab it thats when it hapens

 

[richp85elco]

i would pull the distributor out and reinstall it to make sure your not a tooth or 180 degrees off. It really sounds like plugs are mixed up but since you said you checked them, the next most likely things would be what I said above.

 

[84cutspreme]

I agree sounds like a timing issue. Either the distributor is 180 out or only other thing I could think of is the cam is off a tooth on chain (retarded or advanced a tooth), I doubt that's it though...because they are usually clearly marked to align the cam and crank

 

[black86442]

I agree sounds like a timing issue. Either the distributor is 180 out or only other thing I could think of is the cam is off a tooth on chain (retarded or advanced a tooth), I doubt that's it though...because they are usually clearly marked to align the cam and crank

Yeah i put the cam marks dot to dot. If it was off a tooth would it still show that it is in time or would that matter? Because it shows its in time... but that being said it will not idle at 2° advanced or anymore retarted than that. It will only way it will idle is around 8°-12°deg advanced.

 

[richp85elco]

did you put the distributor in when the cam and crank sprocket were at dot to dot? because that would put you 180 out, they both dots should be facing down (compression stroke) when you put in the distributor

 

[black86442]

Yeah i might of put the dist in when it was dot to dot. Will it will it run 180° out

 

[jrm81bu]

It won't run if it's 180* out. I wouldn't reall go by a number for the timing, just give it what it wants, may need to advance it more.

 

[CHRIS.O]

You can put it dot to dot your just supposed to roll it over 180 before you stab the distributor in.