Could use some help for those who know OEM Cranks & Dampers on BBC

[71CHEVYSHORTBED402]

71 402, replacement parts. The crank wasn't changed.

I'm mostly sure this harmonic balance is a direct replacement. It's bottomed out. Seems the front surface on both should be flush, because it takes a 2" washer.

Why wouldn't it be flush?

No problem pulling the damper to double check it's a direct replacement, but can a new seal take it? The bolts on the timing chain cover were loose when I lined up the damper, so the alignment is dead-on and wouldn't change.

Wish I had checked the original. Appreciate any input, thanks.

[weim55]

I've never seen a balancer flange that was flush with the crank snout, original or aftermarket. Rarely is that difference consistent either. If the differences were excessive I would sometimes machine the balancer flat washer to correct an excessive difference. Another thing I always checked once the balancer and heads were mocked up is to mock install the water pump, alternator and pulleys and check belt alinement with that new balancer.

Steve weim55 Colorado

[71CHEVYSHORTBED402]

Originally Posted by weim55

I've never seen a balancer flange that was flush with the crank snout, original or aftermarket. Rarely is that difference consistent either. If the differences were excessive I would sometimes machine the balancer flat washer to correct an excessive difference. Another thing I always checked once the balancer and heads were mocked up is to mock install the water pump, alternator and pulleys and check belt alinement with that new balancer.

Steve weim55 Colorado

Good to know, thank you. In your mind am I alright to go with what I got unaltered? The washer is fat and not going anywhere, so it's not going to contact the crank snout. Course I'll check the alignment when the pulleys are slapped on.

I couldn't leave well enough alone, so I backed the damper out a pinch and reset with same results. Was tempting to install the old one just to see

On a side, I don't know if this is a bad idea, I wouldn't think so. The threads in the snout could have looked better, so I cleaned the front end with a tap. Smooth as silk, the bolt screws in by hand and with good contact. The ARP bolt suggests using their high pressure grease only, no lock-tite.


Some links:
https://www.camaros.net/forums/18-en...-question.html

Guy says a 350 balancer extends past the snout, post 13. He's a good source of info. Course mine is a BBC, but from what I'm reading this and elsewhere, yeah, they don't line up. May imply there's supposed to be a gap between the crank snout and washer across many applications. https://www.jalopyjournal.com/forum/...seated.980215/

[Mike C]

IMO, the crank should always be below the balancer. The washer is so thick because it is clamping the balancer. If the crank stuck out further, the washer wouldn't clamp the balance but would tighten on the crank leaving the balancer to move out whatever the extra distance might be.

[68 TT]

Originally Posted by Mike C

IMO, the crank should always be below the balancer. The washer is so thick because it is clamping the balancer. If the crank stuck out further, the washer wouldn't clamp the balance but would tighten on the crank leaving the balancer to move out whatever the extra distance might be.

I agree. This way the machined inner surface of the balancer mounting surface is always torqued down against the crank gear and precision machined flange on the front of the crank snout below it and you are not relying upon a possibly hammered and unfinished surface like the snout of the crank.

[weim55]

Originally Posted by Mike C

IMO, the crank should always be below the balancer. The washer is so thick because it is clamping the balancer. If the crank stuck out further, the washer wouldn't clamp the balance but would tighten on the crank leaving the balancer to move out whatever the extra distance might be.

This is correct. If all the components are OEM and quality there are no issues. The problem I have run into is a soon as you start to mix and match and throw in the variables of the aftermarket problems with consistency of crank depth from the balancer flange occur.

Steve weim55 Colorado

[weim55]

[QUOTE=71CHEVYSHORTBED402;8350787]Good to know, thank you. In your mind am I alright to go with what I got unaltered? The washer is fat and not going anywhere, so it's not going to contact the crank snout. Course I'll check the alignment when the pulleys are slapped on.

From the picture that you show with the new balancer I would say yes you were good to go. Plus you answered my other question that you're using a proper ARP balancer bolt and washer.

What is actually more important for proper balancer retention on the crank is the interference fit between the balancer and the crank snout. A problem that people will run into are used balancers and cranks that I've had the balancer removed multiple times and the interference fit is now too loose and or the crankshaft or balancer keyway is not tight fit. Now you are trying to rely on the retainer bolt and washer to hold the balancer past the point it was designed for.

Steve weim55 Colorado

[71CHEVYSHORTBED402]

Thanks a bunch, I think it's good to go. I sent a note to Summit. See if they chime in, but I won't hold my breath.

I did a mock-up of the crank & cam pulleys as suggested. Looks real good. Ruler says it's right too, or the difference is so small I can't see it.

Should have mentioned, that's without gaskets. Torquing it down tomorrow. Currently juggling the rebuild with landscaping a new house. Too old for this, JK. Landscape is a passion, especially rock work. Go figure, this one is free, my ex-wife's place. Doing it for the dogs

On another note, sure glad I don't have an HOA, screw those guys "we'd like the front yard done in a few weeks." Kiss my what? I'll finish the back first thanks. On Friday a 1000 Sq. Ft. of 3x8" river rock is going to be dumped on "their" postage stamp of a front yard. Hope they like it.