Harmonic balancer bolt, on a 307???

[71chevelle]

help me somebody, i have a 71 chevelle i pulled the motor and when i stripped it there was no balancer bolt that goes into the crankshaft? i built the motor up and before i put the belts back on i want to know "what the hell should i do" the balancer is pressed on so could i take my chances? i bought it a year ago and drove it and never had a problem, i put a flashlight down there and looked, i really did not even see thread marks! its a original 307. i need an answer from someone please!!!!

[MagicRat]

The balancer does have an 'interference fit' on the crankshaft so it's like being pressed-on. However, that tight fit is there to prevent harmful vibration and looseness. The tight fit is not intended to hold the balancer on all by itself.

The bolt is necessary. Without it, you could break a crankshaft. IMHO you have been lucky so far.

If you cannot see the threads or see a hole in the front of the crank it's possible the bolt head has snapped off, leaving the shaft plugging the hole.

Get a balancer puller and remove the balancer. If the bolt-gods are smiling, there may be some protruding bolt left. If so, you can get a good grip on it with vice grips or use a stud extractor, or weld a nut to the end of the broken bolt to turn it.

Then get a new bolt and install it. Go to an auto parts place to source the correct bolt for the application. Don't use a cheapie hardware store bolt.

If it has snapped off flush with the crankshaft itself, you could try drilling a hole in the broken bolt piece and using an extractor to get it out. However, if you have never done this before, it may be better to take the whole engine or car to a machine shop and let them extract it for you and fit a new one. Often, efforts to extract bolts by people unfamiliar withthe process only makes matters worse.

[MrPbody]

Virtually ALL of the small-journal small blocks had no provision for a bolt. We make it a practice to drill and tap the cranks. The "001" 307 crank may not have the hole drilled. It's also the crank used for non-performance large journal 327s, which had no bolt. 7/16-20 is the correct thread if you choose to drill and tap. It must be done with the crank in a drill press or lathe, though. Don't try to do it "in the car", as keeping the hole perfectly straight is paramount.

You must use a "balancer installer" to put it back on. DO NOT beat it on with a hammer. The installer is a sort of "reverse" puller. It PUSHES instead, attaching to the block at the front motor mount holes.

Jim

[MagicRat]

Originally Posted by MrPbody

Virtually ALL of the small-journal small blocks had no provision for a bolt.

%&$#@*(&^)%$#
Whoops. I forgot about that. I have been working on too many 305/350 engines.

[MrPbody]

Mr,

No sweat, dude... That's why we're ALL here! Nobody can be expected to remember ALL of this stuff... I just "did" a 327 for a boat last month, so it was fresh in my mind! We "stroked" it (ground the mains down on a 350 crank). Had to scare up a bolt because the original didn't have one. The customer is exremely happy with the results. A wierd one, too! (the engine, not the customer) Reverse rotation, reverse-ground camshaft.... Found a performance cam for it in Seattle, of all places...

Jim

[MagicRat]

Originally Posted by MrPbody

Mr,

No sweat, dude... That's why we're ALL here! Nobody can be expected to remember ALL of this stuff... I just "did" a 327 for a boat last month, so it was fresh in my mind! We "stroked" it (ground the mains down on a 350 crank). Had to scare up a bolt because the original didn't have one. The customer is exremely happy with the results. A wierd one, too! (the engine, not the customer) Reverse rotation, reverse-ground camshaft.... Found a performance cam for it in Seattle, of all places...

Jim

I hang around on a boat forum, too, so I am familiar with lots of those dual engine inboard set-ups have one engine turning 'backwards' to cancel prop torque.

I still think one of those engines would make a great 'exhibition' vehicle. You could have your 4 spd Camaro go full-tilt down the strip backwards.