Front cover and Oil pan bolt sizes

[2toneNV]

I have seen different sizes mentioned for the front cover. I have found 5/16-18 and M8x1.25, which one is correct?
Also what is the size and length needed for the 20 bolt 109 Oil pan? I had my Oil pan bolts soaking in Varsol and added Jasco prep and primer. Don't mix those! They destroyed my oil pan bolts to where they are not usable.

Thanks is very much appreciated.

 

[earlbrown]

The timing cover have both metric and SAE 5/16, 1/4 asnd M8.. along with the studded fasteners on the bottom if you have an 86/87.

The 20 bolt pan is all SAE but two different sizes. If you want to keep that PIA line holder you'll also need a studded fastener and a nut.

 

[2toneNV]

Thanks Earl, where does the M8 get used? Also any idea of length on the fuel rail M8 bolts?

 

[earlbrown]

The M8 is that goofy large studded (for no reason) fastner on the water pump-to-timing cover connection. Very top of the pic with the large washer...
http://www.turbobuick.com/attachments/timing-cover-jpg.197352/

On the fuel rail, you have two short bolts on the front, the rears are studded to clamp down the rail and allow fastining the coil pack bracket. There's also the small units that hold the regulator to the rail. Upper right on this pic....

http://www.turbobuick.com/attachments/intake-manifold-69pc-8000-jpg.197353/


Granted these are non stock fasteners but the scale still works. I don't have any pics of stock bolts laid out in a pattern.

 

[2toneNV]

The length on the fuel rail bolts look to be around 3/4" is that about right? How about the EGR bolt, throttle bracket and thermostat housing bolts?
Why the threaded stud for the Drivers side rear of the plenum?

 

[earlbrown]

3/4's sounds way long (I'm going by memory here the lenth is actuall in mm's, but I know they are shorter than 20) Those fasteners only have to get through sheet metal to get to meat and can't be allowed to bottom out before they pull down tight.

On my SS bolt kits I use the same length for the EGT and the thermostat. In real life the thermostat is shorter but it turns out GM drilled and tapped that hole much deeper. I learned that the hard way then my thermostat stripped out and i used a longer bolt to fix it. It was pretty sweet as the stripped section works as a 'line up dowel' to run the bolt in straight.

The threaded stud on the DS plenum is where the throttle cable bracket drops down and you have to tie it down with a nut.