ok guys, after my car has been sitting on jackstand since april i finally got ready to fire the motor for the first time...put the carb on, primed the bowls since they were empty and cranked her over...BOOOOM...at first i thought a shotgun went off, but it was the loudest backfire i have ever heard...right out the open header...after my ears stopped ringing, we tried again..BOOOOOM another one...again after gettin my hearing back i took the distributor out and put it back in 180 degrees.....primied up the bowls and cranked again...a little cough, hickup and then it back fired slightly through the carb igniting the unburnt ful on the main body....so we played with time a little and no difference..still wont crank over..but it coughs and hicups....i pulled out the number one plug to find the compression stroke and i didnt feel anything..i mean nothing at all...so now im really starting to worry...
when i was building the motor i made sure before i dropped it in that it had compression...i didnt do a compression check then...when i manually turned the motor over i heard the compression blow out the exhaust ports.....

when i crank it over with the starter it doesnt sound like the motor is compressing...kinda like its just spinning it over ya know...
i had my buddy tw me home and when i was i put it in 3rd and let the clutch out...and when it was turning over you could feel the pulse in the exhaust form the compression......


im really very close to getting this POS going..and im getting a littel frustrated with this ****in bull ****...

does it sound like the compression is gone or the timing is out?.....but even with the timing out a little it should still fire...

im really stumped guys...


BTW..this is a 94 shortblock with LT4 heads

 

Sounds kinda advanced tech to me. Try posting it up there too and see what you find out. That sounds really Fd up to me, no matter what there should be compression in the cylinders unless the valves are staying open, maybe the cam is just degreed wayyyyyy off.

 

thats another thing...the cam never came out...so its set to whatever it was out of the factory... i pulled the timing chain, and im 100% positive it went back on the same way...

 

Weird. So what was off the motor, or out of the motor. Even though you cant feel compression, have you tried a compression tester. Seems to me with my knowledge, little as it may be that ignitino and timing have nothing to do with compression, and what causes a backfire is the gas not being burnt at the right time and detonating either in the exhaust or back up through the intake valve. So the causes of that would be a mis-degreed cam where the valves are opening at the total wrong times, which would explain the two different backfires, and how it is inconsistent with what it does. Id say when you put the chain on, it is on wrong, since if you had the crank say at piston 1 BDC when piston 1 exhaust valve is opening and the piston is going up, there would be no compression, all the air would go right out the exhaust and then be detonated. Might want to try putting the timing chain on again in my opinion, but wait for others to chime in cuz im no expert, just logically thinking.

 

what about the rockers being to tight, and the intake valves not fully seating...

cuz it would cough like it wants to start but its not gettin enough fuel...and since the intake isnt closing all the way when the piston comes up to squeez the mix it ignites and is forced out of the intake...how about that?...

i didnt roatate the motor when i took the chain off..so i know i got it back on the same way...

dot to dot with the dowel pin at 9 oclock


after i was complety done building it..i turned it over by hand and it blew my finger out...i cant rember if i lashed the valves after that or not...

i have another one started in advanced tech like you suggested

 

Now that you mention it it could be rockers adjusted too tight, but if you turned it when you put it back together and it had compression, did you readjust the rockers since then?

 

Check the rockers, then bring it around to #1 again and re-drop the distributor you make sure you have it in right.

 

ok i loosend the rockers and i could visably see the springs coming up...i got them all loosend up and took out the distributor out found #1 compression and put it back in...primed the carb and BOOOOOM she fired right up =)..but i have another problem...

when i key up the FP comes on and primes it up or whatever...when i crank it the the pump pumps a little and when it fires the pump doesnt pump anymore...so i have to run a wire from the 12v on/off to the fuel pump soleniod under that back seat right?....so that whenthe key is on the fuel pump will be on...and could i put a switch in-line so i can have the ignition on but flip the switch when im ready for fuel?...

thanks for the help guys

Rob

 

I don't know the history on your car, but I assume you have a hybrid with the carbed and normal distributored LT1 in it? What computer are you using? Please give some background so people don't have to guess what is going on.
Normally the pcm provides power to the fuel pump relay after it sees pulses from the optispark (which you don't have).

 

yes i should of stated that in the the beginning...

the car is a 91 tpi..i yanked the 305 and put in this LT1...i dont want to deal with optispark so i ran a rear mount distributor and carbed intake....(it looks bad *** with that red bowtie sitting were the thermostat should be )....
it will be FI again but i will run it batch fire instead of the optispark..


the ECM is the Speed density 730..

 

TTT

 

Is it the stock fuel pump? I dont know much about carbs but dont they require only like 12 or so psi of fuel pressure compared to out 42 I think? Wouldnt that cause some kind of a problem?

 

carbs 5-7psi
TBI 12-13psi
TPI, LT1, LS1 38-42psi

 

i have a 3 port regulator so the excess FP is sent back to the tank

i ran a wire from a 12v on/off in the fuse block to a switch then to the gray wire under the back seats...the FP will prime up as usual, but when i start the motor and flip the switch the FP comes on...so i got that goin...

guys youll will never guess whats goin on NOW!!

ok since im NOT using an oil/fuel pressure switch i plugged the hole on the block deck directly behind the intake on the drivers side...ok i started it and shes leakin oil like a sive...go back under there and notice a hole in the block right about the oil filter assmebly...ok so i plug that one.. and i still have a friggin oil leak...

when im layin under the car and i look up on the drivers side head i can see oil all over the side of the head..right at the rear most outer head bolt...i know i got them all tight so WTF is this oil coming from?...i cant really tell were its coming from because the whole driver side of the block is wet...its not a heavy leak...but its heavy enough..and it weird becaus4e it doesnt drop right down..it drips and runs down the bell houseing and aroun the tranny...