Whats the Header Bolt thread size at the cylinder head? And whats a good rule of thumb for determining the length needed?

 

19z28camaro02:
I assume this is for after market headers.
3/8" x 1" x 16 tpi. 3/4" is the common length but 1" works and is less likely to loosen and cause leaks later.

 

Go with a 1" bolt, as long as you have the clearance to get them in.

What headers are you going with?

 

Another vote for 1". 3/4" tends to only grab the last few threads, then you run the risk of the bolt coming loose and falling out, or stripping or pulling the threads in the head to get them to spec.

I prefer header studs myself.

 

Yeah but are those a possibility with LT1 engine bay?

 

I don't like Stage 8s and I've decided i'm gunna go with the 1" because I'll have clearance and I don't want to have to mess with them. I' also have a decent flange size on the LPP headers.

 

The diameters and threads are based on the heads being used. The length, however, is just a matter of measuring because the thickness of the header flanges and the gaskets can differ from header to header and gasket to gasket.

Easiest way I've found is to stick something straight into all the head exhaust bolt holes, then measure how far it went in. Write down the results. I say "all" because it's possible that the depths of the holes are different due to head design and manufacturing tolerances/differences.

To that number you would add the thickness of the header flange and the gaskets.

Now you'll have the over-all distance number to work with.

From that you must subtract the clearance amount you'll need to keep the bolt(s) from bottoming out in the head. I'd give myself a 1/8"-1/4", but no more, in order to maximize the amount of thread engagement. Going less than 1/8" would depend on the accuracy of your measurements, so I'd play it safe and stay at or just above 1/8".

Just how I'd do it.

Jake

West Point ROCKS! Nation's TOP COLLEGE per Forbes Magazine!! Graduation Day Parade 20 May 2010!!!