BBC problems. timing i think

[WS6]

ok i know very little about and have very little experience working on a BBC. i know they are very similar to a SBC, but i dont know their specifics. i think the problem may be BBC specific but i honestly dont know.



the engine is a 71 454. has a big cam headers and dual three inch exhaust. torker 2 intake i believe and a holley 750 at least on it. yes i know i dont know the specifics that well. this isnt my car. just one im playing with. heres the issue or issues. get the car cranked and warmed up. once it is warmed up it will start to pop in the exhaust as if the timing is way retarted and its exploding in the exhaust. to get it to stop, i advance the distibutor until it no longer does this popping. you can drive the car perfectly fine after that. no popping. no stumbling. i honestly dont nail it very hard since its a four speed and geared low. the neghborhood wouldnt like hearing this car opened up. shut it off and it does not diesel. check the plugs when its cold and they arent excessively rich or anything horrible. im sure it could use some tweaking to be right, but its not off by much.

this is the problem. go to crank it up after its cooled off and it wont. the combustion happens way too early and jams the starter. the reason it does this is because according to the timing light when its running fine and not popping or anything, timing is at about 30* BTC. in order to get it to crank the timing must be retarded back to about 16*, but like i said once its warmed up it will pop in the exhaust at 16*. i havent messed with this car any really and am just curious to know where to start. i know a BBC cant like that much timing, so im thinking maybe the distributor is off a tooth or something and im having to advance it way forward to make up for that. the distributor is an MSD peice and an MSD box is firing the dist. i did not install any of these parts. like i said im not sure if this is a BBC thing or not, but i thought i would ask since i have little experience with them and really wouldnt know if it was a BBC thing or not. i have checked firing order and its right. beyond that i really havent done anything other than ponder whats wrong. any ideas?

thanks

[WS6]

oh yeah supposedly the car and engine ran perfectly fine before a new remaned holley was put on. i never saw it run correctly though so i cant say for sure. the MSD system was on there before the carb swap too.

[dhardison]

Sounds like the distributor is off a tooth or two. Mine did the EXACT same thing after I changed my intake. Bring it up to TDC on #1 and install the distributor so the rotor is pointing at the #1 cylinder (just like w/a SBC).

Dan

[WS6]

resetting the timing to insure it is correct was my next step. ill let yall know how that goes since i should be able to try that today. thanks

[Zefhix]

Another possibility is there's a problem with the mechanical advance mechanism on the distributor. If you pop a spring off or the weights gets rusted open shut sometimes it's hell to trace down. So pop off the cap and rotor when you re-drop the dist and check

[yody]

all very good advise, if neither of those are it, you might be looking at the timing chain or cam, although if it was the cam, i doubt it would get better with advance, probably the dist. is 1 tooth off.

[WS6]

well i played with it friday before leaving town and this is what i have so far. my timing light is not working right. it no longer is advancing correctly or anything. i have no idea how long it has been doing this so i can not say what my timing was after all. right now with the timing light flashing hopefully at TDC on number 1, i was able to pull the timing back to 8 or 10 degrees at idle. in order to do this i had to open the idle curb screws a little. so that leads me to believe the popping in the exhaust i was hearing before was extreme detonation. ive never heard of someone having detonation problems at idle under zero load or advancing the timing to cure the problem. so im left still scratching my head a little bit right now. ive got another simple non advancing timing light that ill use on it tomorrow to get an accurate measurement. right now though the car is running fine and after a 4 hour cool down cranked back up on its own without having to pull timing back. this is a good thing so far. the car will have had two full days cool down come tomorrow so well see for sure in the morning when i try cranking it again.

thanks for the replies guys, i will let you know what i find tomorrow.

[WS6]

well it cranked right up this morning no problem. i need to get the timing set since i forgot to bring my timing light, but it cant be off by much. get the fast idle set and maybe see about getting the other fine tunning done and thats that. i dont get what was wrong i just know its right now i guess. thanks for the replies guys.