KSL '67 101234

During an upgrade from an automatic transmission to a Tremec 5-speed I had the service shop replace all the engine gaskets while the engine was out of the car. I'm glad I did. The outer ring on the harmonic balancer that contains the timing mark shifted counter clockwise resulting in a 12 degree difference. I don't think it would have been caught had the timing cover not been removed. With a new balancer and correct timing the engine has come to life. Of course, the manual transmission gets some of the credit. But so often we're concerned about "project creep" adding significantly to the original project costs that minor work is skipped. That would not have been found had I been solely focused on the tranny replacement and its cost. Second good find was the water pump had a minor leak and was replaced as well. Those two finds prompted a thorough inspection of the remaining drivetrain and suspension, and fortunately nothing else was found. I considered the extra work an early birthday present as my Vette is racing to 50 in September.

rtruman

MikeM

Maybe you had a later model balancer and an early timing cover?

Bluestripe67

Good catch. Adds peace of mind when you turn the key later. Hopefully the shop didn't over tighten the cover and pan bolts, thereby dimpling the rails and creating future leaks. After you get some 50-100 miles, check those bolts. I don't have the spec before me, but they only need a small torquing in inch pounds. Dennis

6T7L71CPE

Is your engine all original? You can also have a misaligned TDC if there is a mix of older/newer balancer and timing chain cover. I can't recall which way the mark goes though.


http://www.crankshaftcoalition.com/w..._TDC_lines_SBC

1snake

Good catch. I never take anything for granted. Every engine I build, before the heads go on, I use a dial indicator to find TDC. Then the balancer is checked against the timing tab to make sure everything is correct. Even using new balancers, I've seen a 2°-3° discrepancy between the tab and the balancer mark. It's an easy fix at that point.

tubman

I don't think this is a rare occurrence at all. I have a '67 coupe and a '68 convertible, both with 327's and both with over 70K miles. The dampers had shifted on both of them. The '68 went first, and I finally figured it out when I couldn't get it to run right with the timing set at factory specs. When I couldn't get the '67 to run right with factory timing, I pretty much knew what was going on. I sent them both out to be rebuilt. It was $110 each and no problems since.

buns

12 degrees is a lot of slippage. I'm guessing someone installed a later balancer.





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MikeM

Nah, can't be 'cause I brought this up early this morning and nobody biti on it. Just applause and admiration for finding a "defect".

larrywalk

I believe that the pre-69 balancers had the TDC mark aligned with the keyway. Later balancers had the TDC mark 10 degrees counterclockwise.
An easy check is to view with a mirror where the pulley bolt is relative to the TDC mark. Since one of the three struts to the outer ring is aligned with the keyway, it is a good proxy for locating the keyway.

rfn026

More Than you need to know about Harmonic Balancers.



Richard Newton

MikeM

I owned a crankshaft like that one once and I started studying about balancers.

As I recall, myself and four of my buddies all owned cranks like that. All of us had tri-five Chevys, all of us ran 4.56 gears, all of us did a lot of highway driving, all of us had just purchased a new SHP 327 shortblock and finally, all of us used the original 265/283 balancer.

Avispa

These things are just inertia rings bonded to the hub with rubber. It would be a rare high mileage damper that didn't have some ring movement relative to the hub

wraplock

I have a friend who had a similar problem with his 66 B/B. He complained of a sudden loss of power. I told him to verify his timing, he said he did with a timing light. He finally pulled the engine and sent it to a shop for rebuild against my advice as the compression test and leak down test showed excellent results. The engine shop called him the next morning and said they had found his problem when they pulled his oil pan. The damper's crank shaft end woodruff key was lying in the bottom of the pan. Seems that during the damper installation the key rotated out of the key way in the snout of the crank. The damper was free to rotate on the end of the crank with the result that his timing was WAY off. Just another thing to look at.

Don

JohnZ

I don't know where the thought originated that the timing index line on the pre-'69 balancers was indexed 2 degrees off of the TDC keyway slot. It wasn't - the timing index line on the pre-'69 inertia rings was aligned EXACTLY in line with the centerline of the keyway slot, and the balancer drawings all had a section of that area that showed the index line was to be centered on the keyway slot, +/- 1/4 of a degree.

buns

I got the thought from the 1991 GM Performance Parts Catalog. P/N 3817173.




.

Mossy66

Really? Think about that.

You could take the damper off the car and his timing wouldn't change.(it would leak some oil though)

Mossy66

John,
Why did they change it for the later years?

Gerry

wraplock

Perhaps I didn't state it correctly in my original post. The engine didn't begin to run poorly because the damper moved. It began running poorly when he tried to re-time the car after the damper had moved.

Mossy66

Got it.

The engine suddenly ran poorly, and he couldn't set the timing properly to fix it. So he probably had a loose distributor clamp bolt which caused the suddenly poorly running engine.

Sucks to have to pull the engine to find out though.


Gerry