Thread types and sizes

[MilesnMiles]

Does anyone have a link or fact sheet? I'm pulling the motor and want to replace some of the hardware, especially exhaust manifold bolts/studs.

[mad machs]

Mainly UNC With a smattering of UNF, plus a spot of NPT to add to the confusion

Proceed with caution with replacing fastenings though Miles, put an ordinary bolt in a hole where a hi-tensile effort should go & there be some unpleasantness

[Dave-R]

Get yourself down to Machine Mart (or online) and buy one of their cheap (but extremely handy) tap and die sets in UNC and UNF sizes.

Not only will you be able to clean up all the threads on your engine with this but you can also use it to quickly see exactly what size each bolt is.

[TrevD]

you will find most if the threads to be UNC, but as mad machs pointed out all bolts are not created equal. i have some charts on my pc at work showing all the UNC / UNF and metric thread sizes, i will send you a coppy if it helps. i agree with dave a cheap set of taps will help to :-
A: identify threads
B: you can clean out all the old holes to ensure correct torque settings are achieved.
i will also see if i can find any info on how to identify the different grades of bolt (i have it on a powerpoint presentation and possibly on one of the handouts i use) so you can determine exactly what you should be using.

[MilesnMiles]

Thanks chaps, ask an easy question, I thought!! Already have a snapped manifold bolt that i have to remove. All info/spec appreciated.
Also, can I reuse existing head bolts, or do they stretch after a while causing reliability/torque issues?

[MrNorm]

There are a bunch of online sources (e.g. http://www.sizes.com/tools/thread_american.htm) I have some others at home, all the info you need