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Author Topic:   balance engine
brdhil
Member
posted December 22, 2003 09:04 PM
anyone ever had any luck racing an engine without balancing it?? 383cu.


outlawstock17
Member
posted December 22, 2003 09:44 PM
sort of....i had an engine that was balanced and i changed the pistons to heavier ones. it ran good but it had a slight vibration around 7200 rpm. i didn't twist it any higher than that. it ran all year but i was lucky. i wouldn't recommend it, especially with a stroker combination.


dirtrace
unregistered
posted December 23, 2003 06:37 PM           
Ive had 13 race motors all balanced.

I now will be racing in a claimer class.

The 14th engine I have sitting here is a unbalanced 406,5.7 rod.

Well see how it goes, but Im not thinking too well myself, its surely not going to idle smooth like Im used to, so I cant imagine at 6000 rpm.

chapa73
Member
posted December 23, 2003 09:17 PM
I know around here its $125,and I wouldnt even think about putting an engine together with out doing it.

My personal thoery is if a guy is gonna spend the money on pistons and block work,just go ahead and have it balanced.

ford5
Member
posted December 24, 2003 06:24 AM
if you ever have balanced an engine personally, by that i mean spun up a crankshaft assembly in a balancer, you would soon know the importance of a good balance job. i have been amazed at far off a standard rebuilt engine sometimes is. let alone trying to race it LOL.......its worth the extra money.


wrenchturner10
Member
posted December 24, 2003 08:39 AM
quote:
Originally posted by wrenchturner10:
If you balanced your assembly and changed rods & pistons that are balanced to +/- 1 gram, should you have it balanced again?


Yes!!!

When the balance job is done, the crank is spun with the new bob weight (piston, rod, rings bearings etc) attached to all the journals. Then, the counterweights are drilled or filled with mallory metal to make it dynamically balanced, not just static (the parts are static balanced).

I had a 3.8 Ford V6 balanced and then changed to Total Seal rings and 40 gr lighter wrist pins. Those small changes required to mallory metal slugs to be added to the crank counterweights.

So yes, ANY change in rotating weight should be cause for a rebalance.


squid
Member
posted December 25, 2003 12:25 AM
nothing against having it done. i think you should. But i have raced motors without and won races and had them run for a long time 30-40 shows. had a cast motor stock rod go 35 nites and broke a valve gernaded the motor. pulled it apart saved 6 rods and pistons and the crank, replaced the 2 and put it back together no machine work, and still runs 25 shows and counting. couldn't believe it crank should of been bent atleast, bearings all looked perfect.

Have seen others take 3 months to build and 5 laps to blow up. If your gonna have it balanced make sure the press the mallory in from the side and not the ends. force pulls and welds dont hold. watched $6000 blow out the bottom of the pan after 10 laps...

zeroracing
Member
posted December 25, 2003 02:40 PM
mine is unbalanced, and it has little to no wear and last 3 years between rebuilds, i have friends that spend a ton of money on motors and claim they must be balanced and can not get one to run longer than 20 races without bloweing them up.
if it is built good it does not have to be balanced.
if i was using an expensive aftermarket crank i probally would balance it, but for now i dont see the need in spending extra money.


sjakes8
Member
posted December 26, 2003 06:29 AM
Whew..... I was starting to think I was the only one not running a balanced one.

Well I run a heavily claimed track on a normal year so that may keep people from sticking extra money in the motors. For the most part. I haven't had one balanced yet, and my luck, knock on wood is pretty good. 30 nights on one of my motors that was built with cast factory parts w/exceptions of pistons. Still together with only freshening.

If I ran a non-claiming track, I probably would spend the money.

------------------
visit us at: www.geocities.com/sjrracing


24s52
Member
posted December 26, 2003 07:57 AM
What is balanced?? lol. We put together an Olds 350. Honed block, decked heads, old crank, new cam, old rods, new pistons, blah blah blah. Had all the parts together one night and threw it together in about 4 hours. Ran all season until we got a little roughed up. Sold the car, they put it together (mostly body and radiator and such) and blew it on their first race. I guess we were lucky and they weren't.


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