Question about intake/exhaust manfiold mockup (1 Viewer)

[Will Van]

I have a 1977 FJ40 series with the original OEM 2F engine. I am installing a JT Outfitters exhaust header. Before I install it, I'm having the intake manifold and exhaust header machined to match flange thickness and ensure they're flat.

My question is, if I buy a used 1973-1974 2F head, can I use it to mockup the intake and exhaust manifolds so my machinist can machine the flanges? Are all 2F head fastener's laid out the same?

Thanks!

 

[Dizzy]

The used head should be the same as your '77 head, flat(ish). There was no '73 to '74 2F, btw. On a header like this, flatness is going to be temperature dependent. The hot-rolled-steel has many stresses, and engine temperature is going to affect it. Milling one side will also result in a bit of stress relief, making it kinda potato-chipped. I have an intake manifold from a '72, and there was a bit of galling under the washer, or nut, which has made it hard to measure. Counter-boring / spot-facing, for a bolt head, is common practice in machine shops. If your intake manifold isn't flat, then have them restore the surface opposite the manifolds' gasket, and match it to the surface on the header. But, if the intake manifold's bolt-surface is good (I have two 2F intakes that are almost exactly 10mm) then have them simply create stepped washers (the side on the intake is thicker to match the thicker header), use plenty of anti-seize to keep the nuts from turning the stepped washer during assembly. Or, just have them adjust the header's thickness to match the intake manifold. As a former machinist, I would cringe at having to bolt a header to a milling table to mill the surface on the gasket side, or even to machine thru ceramic coating to create the spot-face / counter-bore, particularly while maintaining vertical clearance from the exhaust tubes, plus it would take me hours to do, rather than minutes to create a few washers from easier to machine materials.

I'm assuming that the JTO header flange is 7/16" thick. Am I wrong? My Aussie Performance header is 10mm, but it tucks the exhaust down under the skid plate, so I skipped the post-purchase manufacturing.

 

[Dizzy]

A 2F intake uses larger head studs than an F intake.

 

[Splangy]

Why would a machinist need the head to make the flanges the same height?

 

[Will Van]

Why would a machinist need the head to make the flanges the same height?

He doesn’t need them for the flange thickness.

But I need to use oversized washers to get enough “bite” on both the exhaust and intake. He needs the head to mock-up how much machining to do to get the oversized washers to work.

 

[Dizzy]

So the '77 OEM washers were too small in diameter to support the header?

 

[Will Van]

So the '77 OEM washers were too small in diameter to support the header?

Correct. The OEM washers are too small to fully bite both the header and the intake manifold flanges. They’re just barely touching if you center the intake and header.

 

[Jdc1]

Here’s what the machinist did to mine to accept the Belleville washers.

 

[Will Van]

A 2F intake uses larger head studs than an F intake.

Larger head studs = Studs from head to block, correct?

What about exhaust/intake studs and bolts? Same between 1F and 2F?

 

[Dizzy]

Then, in directly answering your initial question, yes, the bolt patterns are the same from F to 2F. But, no the 2F exhaust and intake studs are different; the F being smaller in diameter.

Your photograph makes me wonder if the gasket sits properly on the header flange, seeing as it doesn't fasten properly to the locations on the studs. Would it be prone to an exhaust leak? If you have a good intake manifold, I'd seriously consider not modifying it to meet the header, as its value is much greater than a header that you can buy, which might actually fit better.

 

[Steamer]

Is that a new header? Is it out of shape a bit? Do the other bolt holes fit like that? Is the header just slipping down on bolt hole slop and can it be pushed up? Kind of looks like the header is warped some either from use (if it's used) or from the stress of welding during fab.

From the design of most headers I've seen for these engines I've always felt they'd be prone to warping. I sure hope my NLA cast manifold lasts a lot longer.

 

[Will Van]

Then, in directly answering your initial question, yes, the bolt patterns are the same from F to 2F. But, no the 2F exhaust and intake studs are different; the F being smaller in diameter.

Your photograph makes me wonder if the gasket sits properly on the header flange, seeing as it doesn't fasten properly to the locations on the studs. Would it be prone to an exhaust leak? If you have a good intake manifold, I'd seriously consider not modifying it to meet the header, as its value is much greater than a header that you can buy, which might actually fit better.

Is that a new header? Is it out of shape a bit? Do the other bolt holes fit like that? Is the header just slipping down on bolt hole slop and can it be pushed up? Kind of looks like the header is warped some either from use (if it's used) or from the stress of welding during fab.

From the design of most headers I've seen for these engines I've always felt they'd be prone to warping. I sure hope my NLA cast manifold lasts a lot longer.

Yes, it is a new header. The header and intake manifold are not torqued down in the photo. I was just using it for illustration and mock-up purposes. Yes, the header can be adjusted (moved up) and get it slightly better centered. But I was just trying to illustrate that the OEM washers are way too small.

 

[Steamer]

Ah! Got it. You just need some big thick washers.
McMaster Carr is a good source for unusual hardware and they're very good about giving all and exact dimensions. I'll bet you could find the washers you need there. Check the SAE sizes also. I just put my manifolds back on and I had some 5/16 washers that fit my M10 studs just fine. I also had some 5/16" that wouldn't fit. I just checked and see that 7/16 washers fit your M12 studs/bolts as well.
Happy hunting.