Drumfreak77

Does any one know what size, length and pitch the intake and exhaust manifold bolts are on a 1997 4.0 in my cherokee se. None of the auto parts stores in my area have a listing for them and I want to replace them having them in hand first.

5-90

They should be 3/8"-16x-1.25".

Notes:
- Do not use SAE8 - it's more sensitive to heat-cycling! SAE8 will lose strength very quickly.
- Use SAE5, if you have to use steel. This is also in preference over CRES alloys (which are usually 304 or 316.)
- If you can get them, use brass or bronze screws. Check a local marine supply house, or find your local Fastenal branch.
- Reuse the little bowl-shaped washers - they're there for a very good reason! They may be replaced using 3/8" Belleville spring washers, Fastenal has them.
- If you need new studs, they may be cut from 3/8" threaded rod, I use brass and cut them 2.25" long. Dress the ends after cutting. You'll need no more than three - extreme ends and top centre to hang the exhaust on so you can work.

EDIT - In reference to the first note, I have experimentally verified this. It was a project for Manufacturing Materials & Processes last time I was in college - I subjected an SAE5 and SAE8 screw, as well as a brass screw and two bronze screws (Si-bronze and Al-bronze) to estimated heat cycles similar to the service for exhaust work. Tied up a heat-treat oven for a month! The SAE8 had about half of the strength of the SAE5 at the end of the month - which I didn't expect - the brass screw had gotten something like 20% stronger, and both of the bronze screws were stronger than the SAE8 and slightly stronger than the SAE5 - which I'd expected, but not that much.)

onlyinajeep726

Sorry to rehash an old thread, but I'm in need of the same things as the OP...

So when you say SAE8 or SAE5, is that the same thing as Grade 8 or Grade 5, respectively?

Also, would these suffice for the manifolds? http://www.fastenal.com/web/products...ex?sku=0172936

Or these? http://www.grainger.com/Grainger/Hex...ap-Screw-1YB47

salad

Yes, "Grade 5" and "Grade 8" refer to SAE Grade 5 and SAE Grade 8.

He's referring screws more like these:

http://www.fastenal.com/web/products...l.ex?sku=74936
http://www.fastenal.com/web/products...l.ex?sku=75021

5-90

SAE5 = SAE Grade 5
SAE8 = SAE Grade 8.
SAE refers to "inch" screws - when I'm talking about metric, I'll use ISO ("ISO PC" refers to "ISO Property Class," which is the equivalent strength markings.

onlyinajeep726

Ok, thanks man. You're very knowledgeable.

5-90

Thanks.

And I forgot to check the links last time:

- The CRES (Corrosion RESistant, "Stainless") parts should work, but you are still likely to have the problem of "iron-iron seizing" from elevated operating temperatures on the exhaust.

- The brass is a bit soft, and some people have had them strip out. I'd probably look for something more like silicon bronze or aluminum bronze - bronze is stronger than brass, and the Si-bronze or Al-bronze will be stronger than conventional bronze. Also, the bronze will NOT seize against iron, which is why I like to use it.

onlyinajeep726

I didn't even see your reply until just now. Thank you also Salad for providing links.

onlyinajeep726

Oh, one more thing I forgot to ask... Where can I purchase those bowl washers or is it fine to re-use the stock ones?

jeep3200

There is a Help kit for the 4 cylinder that also works for the 6 cylinder. This is what APN sells when you get the replacement hardware. I do not remember the part number. It does not include the domed washers. It does include the studs and new nuts with washers making them much easier to get.

The bolts are SAE thread even though the OEM ones have metric heads.

When I did my APN manifold I reused the domed washers, repainting them with high temp paint

onlyinajeep726

That's likely what I'll do. The reason I was searching for new is because I am building up a stroker on an engine stand before I swap out the old motor. I will have to make a junkyard run, I suppose lol.

5-90

Although I have yet to work out particulars, the domed washers can & should be reused.

If they have been mislaid, they can and should be replaced - Belleville spring washers are easier to find. I'm thinking that two of them could be nested to get enough flex & clamping force, but (as I said,) I haven't worked out the details yet.

This is particularly important with the AMC six, since it is a side-draught head with an iron exhaust and an aluminum intake (which complicates things all over the place.)