chevy 400

[z2815]

does any body know what chevy 400's are external balance and witch are internal balance. also what cars came with 400's in then from 70-80. i have a 400 in my camaro and it has a baddddddd vibration i think it's the flexplate but i don't know if it's internal are externaly balanced. the problem is it's my driver in the winter and i don't feel like pulling the pan to see. any help would be very nice because this is driving me crazy.

[9secfirebird]

look at the flexplate, if it has weights on it, its external balance

[z2815]

the problem i'm having is the guy i bought the car from thought it was a 350 so he could have put the wrong parts on it thinking it was a 350. the car stock had a 305 so somebody put the 400 in it. so i can't go by the parts on it to tell. i looked up the block and heads casting #'s so i know it's a 400 but thats it.

[V]

catch me if im wrong but all 400s should be externally balanced. If its a 400 block then it should be externally balanced, with a specific harmonic balancer and weighted flywheel. certain 383 strokers require the ext. balanced setup when using a basic 400 crank and not a special stroker crank. i went through all that while doing my 383 build, i had to get an old impala 400 balancer and make a 153 tooth ext. balanced flywheel since i couldnt find one after a while of looking. however, it still could be a 400 block with an interanlly balanced setup(not stock) that would be if a 350 crank was installed to get a 377 destroker motor, known for high reving. These motors arent too common and i doubt thats whats in there, but just thought id mention it.

most likely i'd say the vibration is due to that the weights fell off or were never on the flexplate/flywheel. check that first, should be possible by just removing the dust cover/inspection plate behind the oil pan and looking at the front side of the flywheel/flexplate. crank the engine around with a wrench to check the whole flywheel/flexplate. if they are there, check to make sure it has the correct balancer. If you need to buy one, ask about an older Impala SS with a 400, that harmonic balancer will fit great with the serpintine belt drive on the 88-92 engines(what i used it on) and also the style from 82-87. hopefully this info helped some.

[The Fixer]

Originally Posted by z2815

the problem i'm having is the guy i bought the car from thought it was a 350 so he could have put the wrong parts on it thinking it was a 350. the car stock had a 305 so somebody put the 400 in it. so i can't go by the parts on it to tell. i looked up the block and heads casting #'s so i know it's a 400 but thats it.

Please tell me this is not under the hood of the car that's in your sig? 93-97 Z28s would have had an LT1 under the hood; a totally different animal. Hopefully you're working on someone else's car, or the year of the car in your sig is really wrong....

[z2815]

thanks that's what i wanted to hear i thought all stock 400 where externaly balanced but i wasn't sure it has a internal balance flexplate on it no weights so the guy put the wrong flex plate on it. also i own a ninty three but it's my baby it only has 80,000 miles on it andi've i bought it in ninty five with 15,000 miles that's my sig. but i don't drive it in the winter. i also own a seventy nine with creger ss rims, datona hood, all auto meter gadges, hurst quarter stick shifter, z28 rear spoiler, headers full length, tru duels and no cats, 400ci engine, pretty stock it has a edelbrock intake, holly carb i have heads and a 125 shot for it but i haven't put them on yet, th350 trans, and a ten bolt rear i have only owed the car a few weeks so this is all i have done so far. this is my bad weather car i can't bring my self to buy a import even for the snow i'd rather push my camaro then drive a import.

[Tru2Chevy]

A second gen with a 400 in it to use as a winter beater.....I like the way you think! 8)

- Justin

[DieselKickYoAss4Sure]

most likeley its the harmonic balancer on the front of the engine they go bad all the time. the flex plate prolly isnt weighted the torq converter is however but the weights never fall off.how long have you driven the car like this cause if it was for more than an hour plan on geting a new crank because they actually bend when you have this problem ive seen it many times. 99 % of vibration problems are because of the rubber in the harmonic balacer going bad though.

[z2815]

the first thing i did was pull off the balancer and look at it and there was nothing wrong with it but i changed it anyway with one off a 400. i called summit and they said all stock 400's are externaly balanced so i ordered a new flex plate. because i looked at the one on the car and it's for a internal 350 it never had a weight on it. i only drove the car about a block but i don't know how long or far the other guy drove it. i plain on rebuilding the engine soon anyway.

[9secfirebird]

bingo

[z2815]

installed new flexplate the other day and no more vibration ahhh.