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Old 12-30-2007, 10:54 AM
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Help Me Out - SBC - Machine Shop Work

Ok, I "think" I am ready to have my 350 block taken to the machine shop to start having the work done to it. I had posted another thread (List your engine combinations) of which F-BIRD'88 listed the major assemblies that he suggested for a 500+HP race motor. Here is what I plan on having done to the block at the machine shop. This will have a Weiand 177 blower atop. If anyone can suggest something else that needs to be done, jump right in and help me please. The block I will be using is casting # 3970010.

Clean & Mag the block
Bored & Finish Honed to 4.030" (Using torque plates)
Decked to 0" for TRW-L2256F-30 forged FT pistons
Align Hone Mains (Using GM 350 Steel Crank)

I will be doing some work to the block myself like removing casting flash and smoothing out sharp edges, etc.

If I have this 0" decked, will I have problems finding a distributor to fit or will the Summit # SUM-850205 "ready to run distributor" fit without mods? Can I get by with just having the deck "cleaned up" so I don't have any problems fitting the intake and distributor and still expect the end result. How about taking half of the .025" off the deck and half off the heads?
I'm just asking because I don't know so please don't anyone get offended.

What type of rings should I use, Chrome, Moly or Cast?

For the Machine Shop guys here, what would all this cost if you were doing the work so I have a "ballpark" idea of $$$ I am looking at?

Thanks Bunches

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Old 12-30-2007, 11:50 AM
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Ayuh,........

I'd probably have the rotating assembley Fully Balanced while it's there......
Especially if you're shooting for 500hp.....
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Old 12-30-2007, 01:19 PM
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The L-2256F pistons are for stock or lightly modified engines. They will not hold up in your application. I would use an SRP or similar quality flat-top.

tom
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Old 12-30-2007, 05:42 PM
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The one problem I see is that with 0 deck and flat tops you're probably going to end up with too much compression for a blower.
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Old 12-31-2007, 12:06 AM
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Quote:
Originally Posted by engineczar
The one problem I see is that with 0 deck and flat tops you're probably going to end up with too much compression for a blower.
He plans on running strictly 114 octane racing fuel or methanol.

On The stock motor the stock piston is .025" below deck and a .015" head gasket is used. This results in a .040" detonation supressing piston/deck net quench clearance.
In order to use a .039" elpro gasket and maintain that .040" net quench clearance in the final assembly you need to cut approx .025" off the block.(measure yours twice, cut once) the intake manifold will end up very close to where it belongs. If slight distributor shimming is nessessary, thats what you want to do. Won't be a big deal.
Its all in the details. All part of making those $ affordable$ but not optimum L2256F (fits your budget) pistons, live a long life. You'll want the piston ring end gaps on the loose side. Other than that and proper carb and timing tuning there is not a lot of undue stress on the piston on this combo.
But.. if you can find the $$'s in your budget for a set of JE pistons, go for it.
Start getting too crazy with the nitrous either way and all bets are off....LOL
A little will go a long way. i think you'll be more than happy with this motor without needing nitrous.
Maybe some of the pro machinists can chin in here with some cool but affordable block, oiling system and crank tweeks and mods to help.

Last edited by F-BIRD'88; 12-31-2007 at 12:31 AM.
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Old 12-31-2007, 11:14 AM
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The L2256F pistons will break the skirts off. Period.

tom
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Old 12-31-2007, 11:57 AM
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Quote:
Originally Posted by F-BIRD'88
He plans on running strictly 114 octane racing fuel or methanol.

On The stock motor the stock piston is .025" below deck and a .015" head gasket is used. This results in a .040" detonation supressing piston/deck net quench clearance.
In order to use a .039" elpro gasket and maintain that .040" net quench clearance in the final assembly you need to cut approx .025" off the block.(measure yours twice, cut once) the intake manifold will end up very close to where it belongs. If slight distributor shimming is nessessary, thats what you want to do. Won't be a big deal.
Its all in the details. All part of making those $ affordable$ but not optimum L2256F (fits your budget) pistons, live a long life. You'll want the piston ring end gaps on the loose side. Other than that and proper carb and timing tuning there is not a lot of undue stress on the piston on this combo.
But.. if you can find the $$'s in your budget for a set of JE pistons, go for it.
Start getting too crazy with the nitrous either way and all bets are off....LOL
A little will go a long way. i think you'll be more than happy with this motor without needing nitrous.
Maybe some of the pro machinists can chin in here with some cool but affordable block, oiling system and crank tweeks and mods to help.
To each his own. 0 deck, flat tops, .039 gasket, and 73cc heads will yield about 9.5:1 compression which is just a tad too high for a blower IMO, add cheap pistons into the mix and I don't see it lasting as long as he probably wants it to. I would look at an SRP/JE inverted dome piston with a -24cc dish. This would allow him to use a 64cc head which would put his CR around 8.5:1 and would also unshroud the valves a little bit.
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Old 12-31-2007, 12:56 PM
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Just to throw my hat in the ring:

I don't like stock cranks for applications with 500+ horsepower. A 350 has to be pretty well tuned for that much power and with a blower the chances that everything will hold up and stay in spec is seriously reduced.

This is just my opinion but there are some rotating kits out there that will make you feel alot better about the strength of your bottom end. If your budget will not support it then you got to do what you got to do, but the piece of mind you will get with a set of rods and a crank that is made to handle that much power is almost priceless.

Say your distributor comes loose and advances the spark to a point that you have some detonation,with the compression above 9:1 and a blower the first time you put your foot in it you can say good bye to stock rods and then the crank.

It all comes down to what you are going to do with the motor as well. You mentioned race applications and if you are going to turn it above 6500 RPM the pistons will be moving like 3500+ feet per minute and then turn around and come back down that will put tremendous stress on the rods. If it is too advanced it would increase stress quite a bit (like throwing a two pound hammer at 40 MPH and trying to stop it by hitting it with an aluminum bat)

I am kind of a what if guy but I have yet to genade a motor, because I build them 30%-50% stronger than they are capable of running. This also means that you know your motor will handle HP upgrades or nitrous.
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Old 12-31-2007, 11:34 PM
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The 2256 is just a forged copy of the stock piston. To keep cost down why not use the TRW-2442P which is now sold under the Sealed Power/ Speed Pro name. It is made for blowers/turbo's and will do the job with the little blower you are going to use.
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