454 bbc valvetrain wear. what is too much? - Hot Rod Forum : Hotrodders Bulletin Board
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Old 09-10-2004, 03:19 PM
MuscleBlock81's Avatar
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454 bbc valvetrain wear. what is too much?

I have a '74 454 BBC that back fires all over the place and runs like junk. i replaced the streched put timing gears and chain, only for it to coninue runing like junk. So i have taken the cam out along with the lifters, push rods, and rockers.

CAM: it looks to be only a little worn at the peak of the lobes (stock gm cam) but nothing drasctic.

PushRods: they seem to be straight; however, the ends of ome of them are worn to the point that the hole in the end of the rod is bigger. some also have little chips taken out of the ends of them.

I haven't look at the rockers yet. I ran a compression test before taking the cam and everything out, but after i replaced the timing chain, i had 150 PSI in every cylinder.

If i have even 150psi compression, my valves are good and my crank, connecting rods, and pistons are all good right?

ALSO... froim my description of everything, what seems to be the cause for it to backfire all over and not be able to time it?
Whick only leaves: ignition and carboration to be my problems right?

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Old 09-11-2004, 03:22 AM
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w/o knowing how many miles are on the engine, the wear on the mentioned pieces sounds acceptable

for the cam, tell tale damage would be a lobe w/ a noticably different finish in the wear patern, and the lifters should show a circular pattern on the cam side, showing that they are rotating properly,

but as for the compression test, it doesnt tell the whole story, the other 1/2 of that job is the leakdown test, which will show you how well the cylinders HOLD pressure,

the better the leak down results, the better job your engnine will do holding back that TWO THOUSAND pounds of pressure the cylinder sees after the spark ignites the fuel

if i remember correctly, leak down tests are best done w/ the cylinder at TOP dead center and w/ a few drops of oil in the cylinder to simulate the oil the rings would get while the engine is running

now onto the erratic ignition ... this can be caused by a number of things

1) worn cam-to-distributer gears.... slide the cam back in, drop in the dist just whereever it wants to go ... and lightly twist the rotor side to side ... ir realy shouldnt have more then a degree or two of slack. if it has more slack then that, make sure the gear is tightly pinned to the dist shaft. if thats not the prob, the cam and dist gear might both need to be replaced

2) clean the points w/ fine sand paper - dirty points screw up attemps to time the car ... for electronic ignition, make sure all the wires are making proper connection and none are damaged

3) cap / rotor - remove any carbon tracking on the points or replace accordingly

4)vacuum advance ..... make sure its bolted in tight and doesnt leak

5) coil - some coils w/ bad connections will fire at the wrong time, or will skip a cylinder

hope one of these helps ya out
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Old 09-11-2004, 09:55 AM
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I vote for the ignition as well.
did you replace the cap and are you 100% the plug wires are on right.? also if you are running points the coil could have carbon tracked between the high voltage and low voltage terminals. I had that happen to me before. Carbon tracking inside the distributor cap could also be a problem. cleaning it does not work as the distributor we retrack in no time.
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Old 09-11-2004, 11:05 AM
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i run an HEI distributor. the distributor was running fine in my other motor. And i've tried two different distributors in this engine. I'm also 100% sure the firing order is right. Anyone how says "i could be off a tooth on the distributor" is frustraighting me b/c if you get the motor to tdc and start the fireing order on your distrbutor cap with 1 where the rotor is pointing, teeth don't matter as long as they are engaged.

Also, i could feel vacuum with my fingers but there most not have been enough or somehting b/c i couldn't adjust the rich to lean on the carburator and i couldn't get the distributor to make the motor settle down in any degree. It ran the best 55degrees off... I have a new cam and lifters in it now and i'm waiting on a new carb, pushrods, rockers, intake manifold, plugs, wires, and a distributor... I'm so extremely frustraighted b/c non of this is making any sence.

I could understand why the broken teeth and the stretched out chain on the old timing gears and chain were a major problem, and after replacing that and not fixing the problem i was really hoping to take the valve train apart and find more broken parts... but all i have are just worn pushrods, rockers, lifters, and i can see theres wear on the cam lobes and distributor gear, but i don't THINK its enough to cause this much trouble.

ALSO VERY IMPORTANT!!! The fuel pump i have on there has three nipples, the inlet, the outlet, and the return. My el camino doesn't have a return line so i just pluged the return nipple coming out of the feul pump, Could that have caused any of this trouble? Let me know THANKS SO MUCH!!!!
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Old 09-11-2004, 01:49 PM
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Resistance test your plug wires.
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Old 09-11-2004, 02:15 PM
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Quote:
Originally posted by MuscleBlock81

ALSO VERY IMPORTANT!!! The fuel pump i have on there has three nipples, the inlet, the outlet, and the return. My el camino doesn't have a return line so i just pluged the return nipple coming out of the feul pump, Could that have caused any of this trouble? Let me know THANKS SO MUCH!!!!
get some extra fuel line and a metal one gallon can with a tight fitting lid , tie the can SECURLY to the frame near the fuelpump ... puch a hole in the top of the lid just big enough to fit the hose thru, and use that as a temporary "return" off the fuel pump ...

take it for a pass up and down the street and see if if it stops back firing so bad

id be willing to bet that w/o the ruturn, your force feeding fuel to the carb and therefor running WAY rich - which would be a good reason you couldnt FORCE it to run lean / rich off the carb adjustment

if this fixes the backfiring, go pick yourself up a 2 nipple pump, then come back and make a new attemp at your timing
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Old 09-11-2004, 05:02 PM
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I don't think so... maybe try it just for the process of elimination.
I am running a 3 nipple with the 3rd blocked off on mine, it's the stock 74 454 pump, and it seems to be fine. I have been a half a tooth out before. I know, I thought it was rubbish too, but i was firing up a freshly rebuilt 350 of a friends. Did not have the dist bolted down tight, flashed it up for a second just to see if everything was set up. It started immeadiately. shut it off to fill up the tranny. went to start it again, it would not start. was all over the place backfiring. it was weird because I already had it running.(must have jumped a tooth) any way, sometimes the magnetic pickup will not line up at the same time as the rotor. Move it a tooth over and rotate the plugs on the cap if necessary. this may solve it. even though the rotor is pointing at number one, the stator may not be lining up with the pickup when it is supposed to. you may move the wrong way the first time, so don't be afraid to perservere and move it one tooth either way if you do not succed at first.
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Old 09-11-2004, 11:22 PM
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well... as of right now, i can't do anything with it b/c i replaced the cam and am waiting on rockers, pushrods and an intake before i put it all back together, i might also spring for a new distributor. I have a new holley 700 dp i'm going to put on it and i'm just going to pick up a regular two nipple fuel pump.... New wires and plugs.... i didn't do a leak down test before i pulled everything apart but i did do the compression test. anymore ideas from anyone?

ratlover, was that a new distributor on that motor you were talking about of an old used one?

Thanks Much
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Old 09-12-2004, 12:50 PM
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just your run o the mill HEI with a new cap. it took over 4 hours to finally give up and resort to pulling the distributer and moving it a tooth. It was weird because it started fine the first time. anyway, good luck keep us posted.
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