To drill or not to drill
Doing a totally stock rebuild on a 300 HP C2 and looking for guidance and opinions on drilling the crank for harmonic balancer bolt. Been told that it should be a "no brainer" but I also hear it is a deduction in judging.
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Re: To drill or not to drill
I debated this myself but ended up having it drilled because I intend to drive it quite a bit and just didn't want to have to worry about it. -
Re: To drill or not to drill
Doug, that is correct what you have heard. Here is what page 116 of the 1965 JG has to say:
"Base Engine and L75 300 hp - The balancer is stepped in appearance with an outside diameter of 6 inches. The outer ring of Corvette balancers are without holes. Passenger cars['] balancers have a series of holes in the outer circumference of the outer ring. All base engine and L75 harmonic balancers are pressed on the crankshaft and do not have a bolt in the end of the crankshaft, nor is the crankshaft drilled to accept a bolt. Deduct for bolt."
Therefore, if you decide to drill the balancer for a securing bolt, it would not be correct for the 275 (base) & 300 hp engines. I do not know why you do not want to/cannot press-fit the balancer .
-ClarkComment
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Re: To drill or not to drill
I under the stand the reason to drill and tap for the bolt. but if it was going to come off it would have in the last 40 plus years of driving. i am sure now that it is restored it wont see the abuse it did when it was new. also being a low horse car the chances are slim. just my two centsComment
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Re: To drill or not to drill
Doug-----
The primary advantage of drilling and tapping the crankshaft for a balancer bolt is that it facilitates the balancer installation and avoids the need to use impactive force to install the balancer. By itself, this is a very good reason to drill and tap it and, to me, far outweighs any minor point loss.In Appreciation of John HinckleyComment
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Re: To drill or not to drill
Totally agree with Joe and do not agree with the judging manual. This is a safety issue as far as I am concerned. The facts are that the 40 year old balancer was pressed on when it was NEW. Now at age 40 plus it may have some stress cracks and the outer ring may not accept the pounding that will be necessary to install it again. I use the word (pounding) because you don't have the tools necessary to press the dampner on the crankshaft that Flint used.
Drilling and tapping the crankshaft will allow you to gently pull the dampner on the crankshaft.
If this point has not been made, go ahead and drive that dampner home! It will be the front of your engine destroyed and not mine.
JRComment
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Re: To drill or not to drill
To all, thanks much for your input. I respect both points of view although I really can't bring myself to beat on a crank and thrust bearing to satisfy what was an engineering oversight to start with. Drill it!
Comment
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Re: To drill or not to drill
So... drill the hole and install the bolt/washer for driving. Remove the bolt and washer for judging. I don't think the snout of the crankshaft is judged so the hole without a bolt shouldn't be a deduction.
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Re: To drill or not to drill
Mine fell off on my '66. Happened when the car was 17 years old albiet high mileage. Who knows why. Maybe those bolts back out and they fall off anyway, I don't have all the service data to know what failure modes and frequencies are out there.
I had it drilled and added a bolt for the insurance. Who says lighting does not strike twice or why the engineers decided to add the bolt. I was not going to risk another tow home for that boltTom BradyComment
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Re: To drill or not to drill
All------
Starting in 1969 all small blocks got the balancer bolt. So, I expect the GM engineers finally saw the error of their old ways.In Appreciation of John HinckleyComment
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Re: To drill or not to drill
I am havving my 1960 283/230 rebuilt and that is one thing that was first on the list. Somewhere I saw a picture of one that came off and the $50 that is cost to have done appears to be a lot less than the damage that it can cause.
PhilComment
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Re: To drill or not to drill
There are a lot of judges who consider that bolt a safety item and will not deduct points for it.
DennisComment
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