Balancing question
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Joined: Jun 1999
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From: Dove Mountain Arizona
Balancing question
The 350 4 bolt block is at the machnine shop. I've got the forged (L2256F030) .030 pistons in my hand (they arrived last night). Something I never considered here. (BTW, I'm putting it together, the shop is just doing the machine work.) Do I HAVE to have the reciprocating assembly re-balanced? It had std cast pistons in it. This is getting expensive and some of the shops I talked to say it MUST be done, others say it might be Ok as is. :confused: They'll need the balancer and flywheel also and that stuff is still installed in a good running engine. Don't want to have parts scattered all over the garage while I wait for balancing. Advice?
Le Mans Master
Joined: Feb 1999
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From: Park Ridge IL
Re: Balancing question (MasterDave)
Definitely get it balanced. It might be 'close' as is, but a few grams of imbalance, multiplied by rpm, quickly adds up, and will affect bearing and journal wear, not to mention how smooth the engine runs.
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From: Dove Mountain Arizona
Re: Balancing question (gkull)
Yes they are, problem is they want the flywheel and harmonic balancer for some reason. Those are still on a good running 350 engine in the vette. I do have an old 327 flywheel and balancer, but the 327 balancer is probably twice as heavy as the 350 one on the running engine now. I thought the 327/350's were internally balanced and the flywheels were balanced on their own. Kinda wanted an assembled short block so when I change it out it could happen in a weekend, instead of removing the old bullet, taking the flywheel/balancer down, getting it balanced....you get the pic. I'll ask if the shop would just balance the crank/piston/rod assys. Dunno; well, just called my local 'Honest Performance' shop and they say it's just standard procedure to have the balancer and flywheel, but balancing just the crank & piston/rod/rings can be done and will work very well seeing as how it's an internally balanced engine anyway, not like a stroker or 400 block. This sound like a viable solution to you guys?
[Modified by MasterDave, 12:54 PM 3/20/2002]
[Modified by MasterDave, 12:54 PM 3/20/2002]
Team Owner
Joined: Apr 1999
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From: Reno Nevada
2024 C3 of the Year Finalist- Modified
Re: Balancing question (MasterDave)
I only build internally balanced motors - So I have never been ask to bring anything like the balancer or flex. They should also know that a balanced flywheel or damper has no effect in the whole scheme of balancing.
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From: Dove Mountain Arizona
Re: Balancing question (gkull)
Thank you, gonna let 'em balance it. Free Horsepower? (insert raised eyebrows). A balanced engine gives you how much, all things being equal? Hehe :chevy
Team Owner
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From: Reno Nevada
2024 C3 of the Year Finalist- Modified
Re: Balancing question (MasterDave)
As i understand it the more ci and the more rpm you turn the more losses to friction. I've never heard any outright quote. If it was just 10-15 in a small block and the longevity and smoothness makes it more than worthwhile.
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From: Dove Mountain Arizona
Re: Balancing question (gkull)
Thanks guys for all the info. They said to bring them the flywheel/clutch assy later and they will 'zero' balance it for no further cost. Brought the L2256F30 TRW forged pistons to them yesterday. From the factory they have some sort of coating on the skirts that allows for closer bore clearances. I've heard the 'old' forged needed like .005 but the inst's says minimum on these is .001 and the shop shoots for .015. Is this really right or should it be more like .025 or so? Would hate to have it lock up on me. Thanks for the info. :cheers:
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Drifting
Joined: Dec 1999
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From: Reno nevada
Re: Balancing question (mountainmotor)
It's called moly coated skirts. The coating is a few thousands thick. I have never seen a moly piston motor being torn down yet. So I have no idea how long the coating really lasts.
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From: Dove Mountain Arizona
Re: Balancing question (mountainmotor)
This is the 3rd time I've called the Summit tech line in the last two days. It's a good thing I get a different guy each time :D. This guy looked up the part # in the Fed Mogul book and for these pistons it says .0015 clearance. Oops, I see I've misplaced a 0/decimal point in my last post. :bb I hate when that happens. Anyway, the pistons & inst's are at the shop and the inst's were on the outside of the box flap. It stated min clearance at .001.
Drifting
Joined: Aug 2000
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From: Annapolis MD
Re: Balancing question (MasterDave)
I've never heard of forged pistons running that close. Cast and hyperutectic yes, but not forged. The clearance required is due to the metals expansion coefficient (related to it's density), so I would not think a coating would affect it. The boat's motors (which are run hard all the time) were set up to .0065 for forged pistons.
-Greg
-Greg
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From: Dove Mountain Arizona
Re: Balancing question (GregP)
I just called our PED shop (Performance Engine Development). They build most of the racing stuff around here. Talked to the engine builder, he is about my age :cool: He builds all his engines (when using this same piston) with .0015 clearance. The drag racers use these engines all season and then at the end of the year all they need is a simple hone and rings. Says they go 2 maybe 3 seasons like this before they need an overbore. :D New tech in piston development has allowed the closer tolerances. Talked about 15 mins with him, nice guy. I'm taking his sage advice and letting this go off my chest. :cheers: Thanks for all of your comments. Will get the parts back next week.
Safety Car
Joined: Apr 1999
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From: Ohio
Re: Balancing question (MasterDave)
I feel the flames getting closer :) ...
SOME Drag race motor builders have a one track mind. ;) Is that ALL that you are going to do with the car? Will it ever be "exercised" for any extended period of time? If it's just a point and shoot WOT machine, I wouldn't even raise the question. I run on road courses, and .0015" for that piston might be a bit tight after a half hour of whaling on it throughout the rev range of the motor. Also, what's he recommending for valve guide clearances? I've had two friends that had their heads done by drag motor builders, and had the exhaust valves hang up after the motor got good and warm.
Don't be afraid to ask questions...it's YOUR money!
SOME Drag race motor builders have a one track mind. ;) Is that ALL that you are going to do with the car? Will it ever be "exercised" for any extended period of time? If it's just a point and shoot WOT machine, I wouldn't even raise the question. I run on road courses, and .0015" for that piston might be a bit tight after a half hour of whaling on it throughout the rev range of the motor. Also, what's he recommending for valve guide clearances? I've had two friends that had their heads done by drag motor builders, and had the exhaust valves hang up after the motor got good and warm.
Don't be afraid to ask questions...it's YOUR money!
Drifting
Joined: Jul 2001
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Re: Balancing question (MasterDave)
It looks as if they do make this new piston.Do I live in a cave I must ask? He He. I knew about the knew KB Hypo 18 Forged piston but not these.
I went to the Website and read about them.Still cannot find all the application part numbers.Even local new Speed Pro Catalog does not have them listed.Any links to these?
I went to the Website and read about them.Still cannot find all the application part numbers.Even local new Speed Pro Catalog does not have them listed.Any links to these?
Instructor
Joined: Nov 2000
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From: Ballston Spa NY
Re: Balancing question (MasterDave)
Federal Mogul classifies these pistons as street forged pistons. They are made of VMS 75 a high silicon alloy. Their race forged pistons are made of VMS 95 alloy which does not have the same silicone content as the VMS 75, but it is stronger especially in high temperatures. Because of the silicon make up and the skirt coating FM lists the skirt clearance at .0015 for part # L2256F. Depending on the application FM recommneds running the VMS 95 alloy pistons with .0040 or .0050 clearance (for 350 ci based chevy engines).
John.
John.
Thread Starter
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From: Dove Mountain Arizona
Re: Balancing question (MasterDave)
h rocks; This is a weekend cruiser w/one or two trips to the drags for T&T only. 100 horse shot.
mountainmotor; I've not seen/heard of these slugs either. Got a flashlight? :lol:
69bblock3x2; Thx, great info. Getting the block back Wednesday.
mountainmotor; I've not seen/heard of these slugs either. Got a flashlight? :lol:
69bblock3x2; Thx, great info. Getting the block back Wednesday.
Thread Starter
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Joined: Jun 1999
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From: Dove Mountain Arizona
Re: Balancing question (MasterDave)
Hehe, got my block and associated parts back from the machine shop last night. :D All cut, balanced and clean as a whistle. Almost seems a shame to put them purty pistons in. :lol: Shoulda bought 9 so's I could hang one on the wall in the garage. This is a proven dyno'd combo from WP's website that says 430 hp. With a 100 shot it oughta be fun.
