Zandor7

What is the thread size and size on the Bolt that bolts to the bell housing??? trying to put my motor on the engine stand but not sure of the bolt and thread size??? Someone told me 3/8 with 16 threads per inch, but what is 16 threads per inch?? is that like 1.75 mm, or what???
thanks

JAMES POLEDNA

3/8"x16 is the SAE bolt size. 3/8" is the bolt dia. and 16 is the number of threads per inch. Anything )bolts) given in milimeters is metric and will not work for your app. Go to a good fastener store and purchase bolts rated for 180,000 psi. they should have 6 lines on the head denoting the strength.

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bought a wrecked(head on,bad)'84 Z28 rebuilt it in'92 parked it in
'93 and ordered a '93 Z28. Got tired of the 4th gen in '99 and sold it and begin swapping in '85 TPI converted to speed density. engine is all stock except for comp cam. body has '86 IROC nose peice,ground fx and IROC wheels/goodyear 245/50's. IMO this car looks and feels more "racey" than my '93 did. and I love driving it. BTW fuel injection is great I'll never go back to carbs.

[This message has been edited by JAMES POLEDNA (edited July 22, 2000).]

Zandor7

AHHH ok, i Know it is now metric but was using that as an example, thanks, I got some bolts that were wrong, so I am off to bet the right ones, the ones I have are red and have 8.8 (I guess MM) and also have 3F on is, what does that mean?? I see two lines on them also, cost 15.00 for four of them!!
thanks a bunch

D_Amlee

8.8 is not the size, that's more like a rating.

Our cars are sort of schizophrenic when it comes to metric/english bolts and screws. GM made the decision to make the whole car metric at one point in time, and everybody changed over EXCEPT the engine block guys. So if you look at all the fasteners on the sheet metal, body work, interior stuff, accessory drives on the motor etc., it's all metric threads. They are measured by the diameter of the bolt (6 mm, 8 mm, etc.) and by the distance between the thread peaks (1 mm, 1.4 mm, 1.8 mm, etc). The motor itself (primarily the block) still uses a lot of english fasteners, which measure the diameter in fractions (3/8, 5/16) and the thread pitch by the quantity of threads which are present in a one inch length of bolt. So a bolt which has 20 threads per inch will have .050 inches between threads.

Never use a metric bolt in an english hole or vice versa. That's a guaranteed way to destroy the threads.