Posted By: rickb67
Problem at the machine shop - 12/20/14 06:43 AM
Had a 73 340 sitting in corner of garage and picked up a 80 step side 2wd. Tore down the engine 2 cylinders bad . Took everything to machine shop.Needs bored crank turned rods balanced.So I order .060 over pistons and get a call the pistons are out of the block .100. well that won't work.I ordered Kieth Black pistons. Deck height is 9.538. need ideas. this was to be a cheep build ha ha.
Posted By: Twostick
Re: Problem at the machine shop - 12/20/14 07:23 AM
Are you sure they shipped you the correct CH piston?
If the deck was stock at 9.60 you would still be .038" positive.
Kevin
Posted By: 70AARcuda
Re: Problem at the machine shop - 12/20/14 09:00 AM
buy 72-73 340 pistons, there compression height is .100 less then the 68-71 340 piston.
Posted By: Leon441
Re: Problem at the machine shop - 12/20/14 01:29 PM
Sounds like you have a 360 stroke crank with a 340 compression height piston.
A 340 with standard ch pistons should not stick out .100 on a 9.53 block. That is only .050" shorter than stock.
What is the CH on the new pistons? 3.31 stroke divide by 2, 1.655". Add that to your rod length, should be 6.123", 7.778". Subtract this number from you deck height. That will be the tallest ch you can use.
Posted By: JohnRR
Re: Problem at the machine shop - 12/20/14 05:11 PM
I don't know what the deck height on a 340 block is supposed to be but you better step back for a moment and think. If the block has been decked a lot how is an intake going to fit ?
Posted By: mike s
Re: Problem at the machine shop - 12/20/14 06:28 PM
Weren't the stock 68-71 pistons positive deck? +.020 or so IIRC
Posted By: Tom Fox
Re: Problem at the machine shop - 12/20/14 10:36 PM
Most recent 340 I've built,(last week)the KB 243 pistons were out of the hole .024. the block was parralel decked, & I beleive my machinest said about .006 ?
Posted By: cudadoug
Re: Problem at the machine shop - 12/21/14 04:40 AM
Just did a 340. Slight clean up of decks resulted in Speed Pro hyper pistons being .050 out of the deck.
Since the heads are RHS with a 62 chamber, we sliced .050 off to get to zero deck. This way owner can run a standard Fel Pro head gasket and have .038 piston to head clearence vs. a MLS type gasket.
Posted By: sr4440
Re: Problem at the machine shop - 12/21/14 05:56 AM
What was the compression height of the old pistons?
Posted By: cudaman1969
Re: Problem at the machine shop - 12/21/14 06:12 PM
just use a thicker head gasket(multiple layer gaskets can go up to 1/4 inch) deck height will be back where the intake fits.
Posted By: rickb67
Re: Problem at the machine shop - 12/22/14 12:10 AM
We had run the engine a few years back in sons Duster. He got a 360 for the Duster and the 340 sat in the corner. Pistons were the 8.5 73 pistons i think they were .020 down the whole. I guess I need 73 style .060 pistons.
Posted By: TRENDZ
Re: Problem at the machine shop - 12/22/14 12:50 AM
Pistons + lathe + 1 hour = fixed
Posted By: rickb67
Re: Problem at the machine shop - 12/24/14 05:36 AM
Sounds like I can solve my problem with 72-73 pistons like the L2385 pistons but i need .060 over and am not having any luck. Anybody have an idea on where to get them.
