[troy-curt]

I would say the valve train is worn out. The weak part of an org. big block. ( cam, lifters, push rods, valve springs, rockers and guides )

If it hasn't been firing right, you will not get a good compression check.

Troy

[williambartram]

I have seen engines with the symtoms you describe that had a too tight valve adjustment. Too tight means the valve is open all the time slightly. An intake will make fire come out the carb, An exhaust will make a backfire out the exhaust. Vacuum will be low and pulsing. Compression would be low or 0 in some cylinders also. I have been a ASE master mechanic for 18 years and I still make firing order mistakes once in a while CHECK IT AGAIN! If you find a low cylinder in a compression test, you can make a primative leak down tester by plumping compressed air into your comprssion tester. It dosnt matter what the preasure is, just bring that cylinder to TDC comprssion and put air into it a listen to where the air is comming out. If compression is good and even in all cylinders I would suspect a pickup coil or module problem. YOU CANT ASSUME YOU HAVE ELIMATED A POSSIBLE BAD PART BY INSTALLING UNTESTED USED PARTS. Good test parts come from engines that ran just before you removed them Good luck!!

[fastech27]

What would a timing mark at 12 oclock mean and what would you have to do to make that happen, My bbc I put a cam in after the old one burned off a lobe. It runs like **** now.

[cdminter59]

Here is an article to read to help check your balancer and find TDC. http://www.crankshaftcoalition.com/w...op_dead_center Another article on how to install a HEI distributor, http://www.crankshaftcoalition.com/w..._a_distributor pay attention to another method for setting timing for start up. I would pull the timing cover back off. Turn the motor over until the dot on the crank gear is at 12:00 and the camshaft gear is at 6:00. Pop the distributor cap and the rotor should be pointed at #6 plug wire on the cap. If you turn the motor over until both dots are at 12:00 the rotor will be pointing at #1 spark plug wire. If not pull the distributor and install it correctly. Check all the spark plug wires for the correct firing order. Clockwise 1-8-4-3-6-5-7-2. When putting everything back together do not turn the crank. When you install the balancer the line should be on zero on the scale. If not replace it with a new one. The engine should start now, adjust the timing to 10*-12* BTDC with your timing light. If you have noisy lifters here is an article on adjusting valve lash. Engine Valve Adjustment Procedure - The Right Way Hope this helps.

[fastech27]

Maybe will line up dist at cylinder 1 and move it to 6 just to see many people keep saying that,

[cdminter59]

Originally Posted by fastech27

Maybe will line up dist at cylinder 1 and move it to 6 just to see many people keep saying that,

Try pulling #1 spark plug and have some one bump the engine over while you have a finger over the hole. Stop when air blows your finger away from the hole. Now check the line on the balancer to see where it is on the scale. It should be close, Turn it to 12* BTDC using a socket and breaker bar and check the distributor to see where your rotor is pointing. If not pointing to #1 spark plug wire on cap reinstall distributor pointing to #1 spark plug wire. It will make the motor easier to turn over if you remove all the spark plugs.

[E.Furgal]

I'll throw this one out there.. the big block , cam makers did switch the firing order as did g.m. later in life..
could the p/o(s) installed a new cam with the other fire order and used a new nylon gear set..stranger things have happened.. and the backfiring brock the gear you replaced?
it's a wild guess.. but.. worth a look..
I'd start by bringing the engine to tdc of cyl#1 and pull the timing cover and make sure you have the gear marks correct.. it's real easy to think your on cyl#1 compression tdc and be on the exhaust stroke tdc and be 180* out of time

[fastech27]

fixed .....bad rotor thats why timing mark was off rotor not facing correctly