Thread: bbc help badly needed

Tweet

okay, im near the end of my wits here. i have a bb 462 with holley 750, msd pro billet dist(no msd box), off the shelf cam(comp 468 i believe), holley dual plane manifold, and pete jackson gear drive. everything else is pretty standard.

complete rebuild, go to start it for the first time yesterday and have nothing but probs.

first off it backfires though the carbs violently(fireball etc). no big deal, i must have a sticking valve or radically advanced timing right? take all the plugs out, valve covers off and go through it. leakdown test(to make sure i didnt bend a valve), leakdown test is great, compression test is next. it comes out flawless, even good compression in every cylinder. okay on to timing. match up the damper notch with O on tab. check dist and rotor alignment. everythings is perfect. i even go the extra mile and seperate the wires as best i can. here we go, turn the key and.. boom, huge fireball, smoke the whole nine yards, it destroys my edelbrock proflow filter. i resign to the house.

today get a new air cleaner with paper element(to resist catching on fire) go through the whole tdc and dist to rotor thing. i go ahead and loosen all the rocker nuts just in case i have a lifter pumping up or something. same results. it must be some seriously f"d up timing so i crank the dist clockwise about an inch to "seriously" retard the timing. okay now it wont start at all and kicks the starter back. we'll try going the other way, crank it counter about an inch past my "0 degree" scribe marks and it starts right up but unless i keep my foot in it (3000 rpm or more) it wont stay running.

now for the reason i mentioned having a gear drive, ive never had one before so i dont know what to expect. but while i keep pedaling it to keep it running something is making the most horrendous whistling noise ive ever heard. its a constant high pitch whistle that is about three octaves higher than human ears were ever supposed to be subjucted to.

i continued to advance the dist another half inch or so with no real change, no favorable change anyway. but for gosh sakes dont start retarding it(clockwise) or it blows up through the carb and motor dies.

so to summarize, it seems ridiculously advanced but starts right up but immediately dies, it you make it stay running, its pretty rough and whistles something crazy.

please help!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

I don't really have the experience to help you but maybe you'll get something from what my experience was when i got my bb chevy running.
Before I had a timing light I set the timing as best I could, it was running well and it turned out to be almost 50 degrees advanced WITHOUT the vacuum advance. I rolled it back and it ran like crap and would barely keep running without my foot on the gas.
One time while I was trying to start it I was getting fireballs out the carb too (I didn't have the air cleaner on at this point though). I think the fireballs were because I flooded the hell out of the carb while I was setting up my gas pedal the night before (basically I emptied the floats while testing the linkage until I got it right).

At any rate, the engine was hard as hell to start and once it did it wouldn't idle until it was FULLY warmed up. I was getting real frustrated.

Long story short, after some tweaking of the carb and choke and timing it is working well now. My timing is set at 15 degrees static and with the vacuum hooked up it bumps it up to 25.
One thing for sure, it idled the best when it was way up before I got that timing light.

This probably doesn't really help you but there is hope.
I wish I got a picture of that fireball, that's for sure.

sounds to me timing way off or set cam in wrong

the whistling noise is the gears, and i guess the ? is do you have those gears timed right. it sounds like a timing problem. how are you finding #1? are you taking #1 plug out and letting the comp. blow your finger off the plug hole or just putting the timing marks togother. when you get it running where is the timing marks using the timing light?

I almost has to be something simple...dont get frazzled too much. Make sure your wires are in the right place, the right firing order. Make sure your plugs are good, you would be surprised how a good looking, fairly new plug will not fire after getting really wet. The gear drive, if installed correctly ( Big IF) will not do what you're describing. Are you sure you did the cam timing right? Did you degree it? Assuming so, let's move on. You say when you retard the timing a lot (turning clockwise), it kicks back....kicking back is a symptom of too much advance, not too little, so something aint right! Do the whole timing thing again. Are you absolutely sure that TDC on your marks is really TDC?? You have to be absolutely sure you're there before you set your distributor to #1 firing... Try it again from the top, and go from there. Is it a new carb? It might be a carb problem, but doesnt really sound like it. What type of cam are you using? It's brand new, I assume? If so, your wiping all the lube off of it with all the cranking, and needless to say, that's not good. Keep us posted on your progress. When you get aggrivated, just walk away for awhile, that's when mistakes happen. John

i find tdc(engine assembled) by taking off the the valve cover and spark plug(s), turn the crank by hand while watching the number one rockers. intake opens, closes then i watch the notch come around and line it up with the O on the tab. then (b/c i have no front end sheet metal on) i can look in the plug hole and see the top of the piston. then i postion the rotor in line with the number one plug terminal on dist.

i did degree the cam even though i installed it straight up. and the cam did degree to the cam card. i installed the gear drive per the manufactures instructions and didnt have any problems when i did it. is there something that i could of still did wrong with the gear drive that maybe wasnt covered in the insructions.

searching through other websites, manuals etc, i am finding one common statement. and that is vacuum leak at carb or manifold. could this be causing a backfire? and if so, how. rationally thinking i cant imagine how it could(if no spark is available to fire the mixture because the valve is closed then how can you backfire) and could a vacuum leak be making the noise i described.

i belive if you had a vac. leak as bad as that you would know it. you are out of time. take the #1 plug out put your finger over the hole turn the motor until it blows you finger off, this is #1 TDC put the timing on the HB on 0 now the rotor should be on #1 in the cap. is it?

yep all lined up. (still puzzled)Hmmm

by the way i appreciate all the help
please dont give up on me yet

put the timing light on #1 plug wire and try to crank it where is the mark on the HB?

The loud whistling could def. be a vacuum leak, and that would cause a lean condition, which could cause the backfire. Check carefully around the intake gaskets, carb base gasket, etc. You sound like you're OK with the TDC issue, and the gear drive install. Keep at it.

got your replies here at work ill let ya know tonight what i find

When I changed cams, I put my cam in 180* off. The symptoms were what you described. It was a pain, but, I had to pull the timing cover and retime the cam. I also had a gear drive, which I later got rid of.
My reccomendation, is to make certain the *1 piston is timed with the cam. It is fairly easy to mistake. Lining up the marks on the crank and cam, it is either on, or off.
I had changed so many cams, making that mistake, it was the absolute thing I thought I could have don. Sounds like the same with your machine.

okay good thought, ill check that out too. but just so i know, you are saying that by installing the cam straight up with the two dots lining up, it can still be 180* out?

ill let ya know

Hi , Ive been down this road before. Your starter kicking back means your ignition timing is too far advanced. You did not say if you used the stock Damper with your motor. If you did not your timing marks could be off. I would , ensure that my cam was installed with the marks facing. one tooth off can cause all kinds of trouble. Ensure that when your piston is at TDC you are at "0" degrees at the crank damper. Make sure that when you are at "0" at tdc on compression stroke your distributor rotor is pointed at your # 1 wire post on the cap.If it isn't the motor will still run but you will be trying to time it on the #6 cylinder which will mess up everything.(180 degrees out) Number one cyl is the driver side front of car. Firing order is 18436572 cylinders are numbered driver side 1-3-5-7- pass 2-4-6-8. Start with your idle mix screws about 1 1/2 turns out.If its a holley you generally adjust the floats ,engine running until gas just begins to come out of the sight screw on the side of the carb.The adjustment is a screw/nutcombination on top of the carb. My guess is that you are 180 out(ignition) or that your cam is out of time.You did not mention if your running solids or hyd cam and what its specs are( did adjust your lifters correctly, none too tight?). You did not say if you are using vacuum or full centrifugal advance. Good luck ,Its probley something minor like this. Don't panic , just systematically check each item and write down what you know to be true so that you don't get lost. The problem with any new engine is that it can be any problem , confusion comes easy. Good luck

my buddy, a drag racer of 12 years, came over to lend a hand. now i have enough hands to keep it running and check things out. we go through everything and it all checks out. we go to start it and sure enough, instand replay of yesterday. he takes the air cleaner off and tells me to start it up. i do and he keeps it running manually with the throttle lever on the carb. he grabs a flashlight and inspects the inside while its running. gives me the shutdown signal. he then tells me that there is no fuel flowing with the plates closed, he says we are keeping it running with the squirters. we go through the carb real quick. plenty of fuel in the bowls, squirters work fine, fuel pump works. but after another start, same thing. with the plates closed, no fuel. he said the everything cam and dist related is installed correctly but since i dont have enough fuel to sustain idle i dont have the time to keep it running and set the timing, let alone check anything else. a spark boot burned on a header and arced out which ended our testing for the day, but he claims he is not very good with carbs in general, and not at all familar with holleys. hes always ran carters, and for the last seven years has had mechanical methanol injection. so here i am with a brand new(which is why i never even looked twice at it) holley 750 vacuum secondary carb that i have no idea on how to fix it, and wont get much help from him either

what do you all think???????????