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302 problems
I've only got 300 miles on my rebuilt (by myself) 302 and I've just noticed a knocking from the engine when starting from cold. It's coming from inside the centre of the engine somewhere but it's difficult to know where. When it's warm it's quiet but something needs sorting. Whats the best way to diagnose the knock?
It's been rebuilt with reground crank, 30thou rebore, performer plus cam and standard (but ported) heads. I would guess that I may have a Camshaft problem but is there some way to tell withoout pulling the whole motor? Any advice greatly appreciated. Simon |
Engine noises (knocks and such) is one of the most difficult areas to diagnose.
A big clue here is: The noise goes away when the engine is warm. That could apply to piston slap. As the skirt expands it fits tighter, ie, to specs when warm. SOME, 350 Chevy engines have this "problem" as the engine was DESIGNED that way, it's not in itself "bad". I am not aware that any standard Ford 302's had "designed" in piston slap. Race engines are often built "loose" and have it. Main bearing(s) can also give this symptom, but less likely and a different (more "thud" to it) sound than a piston(s). I'm not sure how the "cam" would exhibit these symptoms except for possible "lifter" noise, which is generally easy to diagnose as it has a distinct sound (assumes hydraulic lifters). Ernie |
I used to have a Thunderbird Super Coupe that made quite a loud knocking sound when cold, especially when accelerating. It would disappear as soon as the engine warmed up. It was caused by a piston that had a bit too much (.001" over the max.) clearance on the skirt. Changed the one piston and it was perfect after that.
Wayne |
If it's a deep knocking that goes away: piston slap, no biggie if they are forged
If it's more like a tick, it may be a lifter that is taking a while to pump up. If it doesn't go away, you have a more serious problem |
302 knocking
Thanks guys,
Ive found out that the knocking is in time with the crankshaft NOT the camshaft, so presume it's a big end/main bearing problem. Is it possible to renew both just by dropping the sump? Thanks |
Don't rule out piston slap. The T-Bird would make more noise while accelerating, that is with the engine under load. It was an automatic, so putting it in drive, and pressing on the gas while holding the other foot firmly on the brake would really make it knock.
Does the engine make the noise all the time while cold or does it change if you rev the engine, load the engine, etc.? Wayne |
Yeah, with luck you can change the mains by just dropping the pan. Not an easy job, but could be worse. Hmmmm,,,main bearing, I'm not surprised!
Ernie |
The Ford 302 was designed with off center wrist pins. This (I think) was done to reduce piston slap at the expence of horsepower. It has something to do with the geometry of the bore, piston, con rod, and crank. In fact, a little trick to gain power is to put all the pistons in backwords (left bank pistons on the right etc..). The result is the engine will act like it has a longer con rod and provide more leverage on the power stroke but the engine will knock. I read about this ( CAR CRAFT ??HOT ROD ??)when I was building my engine 2 years ago but decided I couldn't put up with the noise. The net result was something like 400+ hp at a cost of $1100. Please don't anyone crucify me on this, I'm just trying to relate something I read some time ago.
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Backwards?
Quick,,,,,shoot the messenger! The relationship of the wrist pin and positioning of the pistons in any particular engine is often a well gaurded secret by top engine builders! There IS horse power to find in this area for sure!
Ernie:D :D |
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