Thread: 383 build

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hey y'all I'm new to the forum and have some questions, I've read on here for the last 2 or so years, but never registered, anyhow, i have a 80's 350 thats been punched .040 over already that needs a rebuild, so I'm thinking .060 over, 3.75 crank, 5.7 rods, vortec 906 heads port and polished stock valve lift limit, with the block zero decked and a .043 head gasket, and a howards cam a 277/277 223@.050, .450 lift on a 108 lsa and 104 icl, after three different static and dynamic compression ratios the average is 9.72:1 static and 7.72:1 dynamic compression ratio, what are yalls opinions? i know its not a power monster with the cam specs but i want to it to last a good while, anything y'all would change? I'm also considering going retro-roller with springs retainers and locks to allow .550 lift in the vortices

Originally Posted by boxchevy84

hey y'all I'm new to the forum and have some questions, I've read on here for the last 2 or so years, but never registered, anyhow, i have a 80's 350 thats been punched .040 over already that needs a rebuild, so I'm thinking .060 over, 3.75 crank, 5.7 rods, vortec 906 heads port and polished stock valve lift limit, with the block zero decked and a .043 head gasket, and a howards cam a 277/277 223@.050, .450 lift on a 108 lsa and 104 icl, after three different static and dynamic compression ratios the average is 9.72:1 static and 7.72:1 dynamic compression ratio, what are yalls opinions? i know its not a power monster with the cam specs but i want to it to last a good while, anything y'all would change? I'm also considering going retro-roller with springs retainers and locks to allow .550 lift in the vortices

OK, first of all, current thinking by fellows who are smarter than I am places the static compression ratio limit for use with pump gas and iron heads at no more than 9.5:1. I personally would push that to 9.75:1 if I used a tight squish, like 0.039" to 0.041".

You reference to "ported and polished" is a term from the 60's and not used too much any more, because we have found that the intake ports can be as rough as a fingernail file or polished like a mirror and make no difference in the rate of flow. Exhaust ports can be polished to advantage, but not intake ports.

L31 Vortec heads will stop gaining flow at about 0.500", so there is no use in putting more valve lift in the heads than that. I would build a 355 with L31 heads, but if I were going to build a 383, I'd go with aftermarket aluminum heads. The L31 heads, with their little 170cc intake runners will not flow enough to feed a 383 at higher revs and you could waste up to $1000 trying to make them work, when you can buy aluminum heads for $1000 and be done with it. Here's a tutorial written by Cobalt327 and edited by a couple of us that may help you to understand the L31 heads a little better....
http://www.crankshaftcoalition.com/w..._cylinder_head


With the block bored to 4.060", a Scat 3.750" crank, Scat 5.7" rods, pistons with a minimum 1.425" compression height and 18cc dish, zero decked block, 64cc heads, 4.166" x 0.041 head gasket (Fel-Pro 1003), I find 9.72:1 static compression ratio. The KB pistons I'm showing below have a 1.433" compression height, so your stack of parts would be 9.008" and would sit at zero deck with the block decks cut to 9.008".

Scat Cast Crankshafts 9-103750 - Free Shipping on Orders Over $99 at Summit Racing
Scat Pro Stock I-Beam Connecting Rods 2-ICR5700P - Free Shipping on Orders Over $99 at Summit Racing
Keith Black KB Performance Pistons KB135-060 - Free Shipping on Orders Over $99 at Summit Racing

I won't recommend flat tappet cams any more, but if your budget can't handle a roller cam, then you are pretty close with your CL112431-06. Only thing is, you're after a lope at the expense of soft brakes and mid-range torque. If I were going to use a flat tappet cam, which I wouldn't, I would use the CL112431-12 grind. It'll be a lot more "power brake friendly" and have better mid-range than the cam you chose. Forget about that Mickey Mouse lope at idle and impressing the geeks down at the Sonic and build yourself a good-running motor that will support power brakes.

Howards CL112431-12
Advertised duration 277/277
0.050" duration 223/223
Valve lift 0.450"/0.450
Intake centerline 108
Exhaust centerline 116
Lobe Separation Angle 112
Operating range 2000-6200, Hot Street cam. Nice mid range torque. 4 barrel & headers recommended.
Intake valve closes 33.5 degrees ABDC.
Needs 10 inch, 2500 stall converter and 3.73 gears.

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80s 350? there were a lot of differant versions during the 80s-----------is it a one piece rear seal ? does it have factory roller lifters? if no rollers-does the lifter galley have the 3 bumps down the middle where the spider bolts down? are the top of the lifter holes machined flat for the dog bones? I would post some pics of what I'm talking about, but other people here have differant opinions about how it should be done----

Also, I would suggest using 6 inch rods as it allows crank conterweights that are better suited for balancing the strokers internally