400 sb balancer timing marks

[gkvette]

Having changed my stock 270hp to a 383 stroker using the stock 8" 400 external balancer, I now wonder if the timing marks on the balancer may be located different than the stock 71 balancer.
My understanding is that the bolt on timing indicator I am using is for a stock 350. Maybe some one can shed some light on this. One other detail, I am really having to back off on the timing(4 to 6 degrees) to keep the pinging down(I have a little over 9:1 comp. ratio)

 

[john wilson]

I have done the same thing to my 80 the best thing you can do is throw out that stock balancer and buy a GOOD fluid dampner for a 400 this should be degreed all the way around if it is not buy some timing mark tape. to find top dead center with the head still on remove the #1 plug and have someone bump the starter while you hold your finger lightly over the plug hole when you do not feel any more air come out that should be T.D.C. put a mark on your balancer that can be removed do this several times to make sure that you are coming to the same mark every time. once you have established t.d.c. the rest is easy. most people do not use those timing tabs they bend a dhort wire and line that up at t.d.c. and use timing tape to advance their timing. GOOD LUCK
JOHN :s

 

[Jack]

timing marks 400 vs 350

I'd like to think the marks are in same place ... BUT I DON'T KNOW ... I don't have both here to compare. I've emailed BJH(damper manufacturer)
http://www.bhjinc.com/dampers/ep_damper.html

for an answer ... no time yet for a reply. I'll post answer here when they do.

I respect JW's suggestion and agree with him for the most part ... However, unless you're an all-out racer, you might consider staying with a rubber-elastomer type damper (that's what your's came with) ... GM likes rubber hb's and uses them in everything I know of (except possibly some commercial diesel & off-road diesel motors). There are excellent rubber hb's available that are race approved (BJH & others) ... some special light ones with aluminum hubs and steel outer rings. Here's a link to a related CACC thread.

http://corvetteactioncenter.com/forums/showthread.php?s=&threadid=4504vette:

Hope this helps. JACK:gap

 

[rL82s]

TDC

Let me toss this one out, it is possible that the outer ring of your harmonic balancer has been spun slightly, causing the timing marks to be off. I have not ever seen this phenomenon but I have heard of it happening. My dad did own a '58 Pontiac that came from the factory with the balancer pressed together 180 degrees off. Either scenario is possible. The distributor may be a tooth off TDC and cause the timing to act as you described.

 

[Jack]

400 & 350 tm indexed same

The zero timing mark location in relation to the keyway on a 350 vs. a 400 are the same. Only the earlier 283 and 327 chevs. were different by 10 degrees.

/Mickey Foster of BJH Dynamics (hb manufacturer)

Also, RLS82s is right ... and I have had slippage happen to me (on a low-power stock straight six motor)... the outer ring can slip and cause timing mark to migrate. Chances are, when it does slip ... it would cause the outer ring to slip behind the inner hub ... incorrectly placing the mark in a retarded location ... causing the "true" timing to be too advanced when you set it on the mark. This slippage usually occurs when very old hb's rubber is weakened by some combination of oil, heat, age, torque, improper remove/install. Possibly even gross belt mis-alignment might factor in. So ... your 71's rubber hb's had 30 years of heat, oil & stress ... try a NEW hb; either rubber or fluid ... I like 8" rubber-elastomer type for all but a true racer. You won't go wrong with either choice. Let us know what you do & how it works out?
JACK:gap