ls/carb-i just cant get it to run right
05-06-2008, 03:53 PM
#1
ls/carb-i just cant get it to run right i have a 6.0, z06 cam, 317 heads, 850 carb and d1sc procharger-i am using the msd 6010 box-it fires right up, idles good-it is just rough when you give ie gas, no power-i pulled the carb hat off, but same symptoms with or w/o the supercharger-i spent an hour on the phone with msd, he walked me thru setting it up, doing changes, no diff, so i have ruled out ign timing
the carb i have worked great on a previous procharged car, so i have to assume its ok also-when i built the engine, i had about 1 1/2 turns preload on the valves, which was ok-i am sure i put the timing chain in correctly, i always recheck it anyway-i pulled a comp. test on the motor, all cyls had 150 lbs, give or take a couple pounds, so that seems to be ok-could there be some kind of phasing problem between the cam and crank sensors? i have tried a couple diff plugs, no diff
the motor just wont rev clean, kind of a shake like a fouled plug-i am totally out of ideas-all ideas accepted, cause i am out of them
the carb i have worked great on a previous procharged car, so i have to assume its ok also-when i built the engine, i had about 1 1/2 turns preload on the valves, which was ok-i am sure i put the timing chain in correctly, i always recheck it anyway-i pulled a comp. test on the motor, all cyls had 150 lbs, give or take a couple pounds, so that seems to be ok-could there be some kind of phasing problem between the cam and crank sensors? i have tried a couple diff plugs, no diff
the motor just wont rev clean, kind of a shake like a fouled plug-i am totally out of ideas-all ideas accepted, cause i am out of them
05-06-2008, 04:59 PM
#3
i didnt think about replacing the sensors, not sure if they either worked or dont work, but i would replace them if they can be bad
i took the carb off my other car a couple months ago, it was running perfect, should have only needed minor jetting-trying to borrow another one now, although it doesnt feel like a carb problem
i wondered if a couple coils could be wired wrong in the msd box
i took the carb off my other car a couple months ago, it was running perfect, should have only needed minor jetting-trying to borrow another one now, although it doesnt feel like a carb problem
i wondered if a couple coils could be wired wrong in the msd box
05-06-2008, 08:19 PM
#7
On The Tree
For nitrous I know guys that usually use tr6's. The tr5's are a hotter plug than the tr6's or tr55's. That might be a problem, but if you took the blower hat off and it was still giving you problems that might not be the problem. I know a temp gun works , but we test to make sure all the cylinders are firing with a little spit on the tip of the finger( wipe it across each of the exhaust primaries ) if it instantly drys off it is firing.
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05-06-2008, 08:20 PM
#8
Take a digital voltage meter and put it on the OHMs setting. Read the resistance in all the spark plugs, and wires. More then once ive bought new plugs and they read way too high in resistance. They should read less then 5000 ohms anything more and id get new ones.
05-07-2008, 06:47 AM
#9
On The Tree
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You didn't mention what size motor that 850 was on, personally the 850 for 368 cube is way to big and will require massive tuning changes to get things right especially in the lowerend. Bigger CFM carbs are needed for duel plane intakes vs a single plane because of the longer runners. I run a 750 mighty demon on a 427sbc pushing close to 550hp and no issues, I also ran a 650 on a 413sbc and produced over 500hp on that as well. Carburators can create issues very simular to ignition problems.
05-08-2008, 11:40 AM
#12
850 Does seem kind of big. I ran a 750 mighty turd on my brothers lq9 s10 and it was pretty fast but had erratic air fuel readings on the wideband that I could not remedy. Added an out of the box stock holley 650 dp and picked up .30 in the 1/4 with a 12.2 wot afr. In my experience these motors like smaller carbs. HTH
05-08-2008, 06:13 PM
#14
i put out another post, found the trouble, cam/intake seemed to want a real aggresive squiter cam, never would have belived with its sym. that that was it, but runs super now-i think programing the box and taking out the map now lowered the vacume, as i notice it in the brakes
05-08-2008, 11:20 PM
#15
Added an out of the box stock holley 650 dp and picked up .30 in the 1/4 with a 12.2 wot afr. In my experience these motors like smaller carbs
