71scamp78
Well-Known Member
Throwing a set of speed pro 405 pistons into a 360 would the engine have to be rebalanced. If so is there anyway to know if it has been since they are external balance.
Engine balancing
- Thread starter 71scamp78
- Start date
-
1- yes, you'll need to rebalance. anytime you change a component of the reciprocating assembly you need to rebalance.
2- why are the 405's your choice?
2- why are the 405's your choice?
71scamp78
Well-Known Member
They actually arent
71scamp78
Well-Known Member
They are already in the engine that was in a car i bought. Don't know anything about the build. Was curious if it should have been balanced or not.
i see.
to answer the last part of your question and this latest one: yes, it should have been balanced. no you generally can't tell if a motor has been balanced based solely on outside appearances.
to answer the last part of your question and this latest one: yes, it should have been balanced. no you generally can't tell if a motor has been balanced based solely on outside appearances.
71scamp78
Well-Known Member
Looks like these pistons sit down a bit in the hole. Had the heads off and they are around .040 down. With the open chamber j heads and 2.02 valves compression can't even be but somewhere in the 8.5 to range.
i'd bet good money it's likely lower than that even.
those pistons are notorious for being way down in the hole due to their crappy compression height.
71scamp78
Well-Known Member
Lovely
aaronk785
Well-Known Member
They are duplicate weight. So balance should be as good as factory. Check the weight to be sure. Mine were within 5 grams heavier.
Last edited:
aaronk785
Well-Known Member
How much compression do you want? Shave the heads .030 and use a .028 gastket and you’ll be about 9.0 to 9.25 depending on head cc.
I wouldn't think it would need rebalancing. They are either same weight as factory (likely) or lighter. in either event, balancing is not critical. Nor would I worry about where the compression is. Measure it, of course and cam it accordingly. Install the cam where the card says, unless you choose one a little big, then advance it maybe 2 degrees more than the card says. do that and with a good loose ignition curve, it'll run quite well and run on 87 octane.
PRH
Well-Known Member
I’m pretty sure the OP’s balance inquiries are rooted in the fact that the engine in question is a “shaker”.
Needs to be balanced when ever you change the reciprocating weight. When determining the bob weight you must have the total weight of the. Rods with bolts ,nuts , bearings and the piston with rings. That will determine the weight of the counter weight on the crank. Example of weights>
aaronk785
Well-Known Member
He has the h405pc pistons I believe. He said they have valve reliefs. Didn’t know the engine was a shaker. Definitely balance.
middleagecrisis
Well-Known Member
Unless you read this in another post, I didn’t see anywhere where he said that the motor was shaking.
OP did put this up previously
Harmonic balancer and torque converter ?
Recently got a car with a 360 la engine with J heads and some sort of cam nothing radical. Has Turbo Action manual valve body trans. I have a pretty good vibration if I rev it sitting at idle. Just thinking maybe engine could have wrong balancer or torque converter. The balancer on front is a...
www.forabodiesonly.com
however, sean may have just taken a SWAG on it...
I knew a dude that bought a 340 and a 4.0 crank rotating assembly at a swap meet.
Oh yeah, it is balanced. (It was not balanced)
I'll throw in this new cam and lifter set. (Solid lifter flat tappet cam with hydraulic lifters)
He never had anything checked at a shop. He just cleaned stuff up and assembled it.
Yeah....it shook like a diesel but he thought it did because of that HUGE cam !
No, sir...it shook because it was not properly balanced. The whole car vibrated to the point where on the freeway, it tossed the crankshaft pulley, it broke a power steering hose and shook loose the floor shifter brackets.
Oh yeah, it is balanced. (It was not balanced)
I'll throw in this new cam and lifter set. (Solid lifter flat tappet cam with hydraulic lifters)
He never had anything checked at a shop. He just cleaned stuff up and assembled it.
Yeah....it shook like a diesel but he thought it did because of that HUGE cam !
No, sir...it shook because it was not properly balanced. The whole car vibrated to the point where on the freeway, it tossed the crankshaft pulley, it broke a power steering hose and shook loose the floor shifter brackets.
71scamp78
Well-Known Member
It did have a vibration in neutral when I would rev it. I think it may be bad torque converter. Pulled trans and the splines on trans pump shaft were cheered off a little on the end.. never seen that before
71scamp78
Well-Known Member
Pic of it
I think that's normal...
71scamp78
Well-Known Member
My pan was full of metal
Well, that's NOT normal. lol
if your pan was full of metal it *likely* didn't come from the input there.
-
Similar threads
