Intake/ head question

[1970 beepbeep]

Couple of questions. Friend has an 80 CJ7 and has a AMC 258 i6 / 4.2l block with newer F.I.head (4.0?) Wants to return back to stock and go with carburator.
1. Can he use newer style head with the F.I. intake and remove the throttle body and swap on a Weber?

2. If he cant use the newer F.I. intake to adapt a carb., can he use an period correct intake and bolt it to the newer head? Wondering if the intake ports are different.


Thanks in advance, Rick

 

[Cheepjeep85]

Can't use the mpfi intake for a carb. But he can use a AMC 258 i6 / 4.2l carb intake on the 4.0 head.

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[IOPort51]

just find an 80 something aluminum manifold to replace the FI manifold.

 

[Torxhead]

This is interesting, I don't see why the Weber, if you can find an adapter, won't work on the 4.0 intake manifold? I have a tbi mounted on a carb manifold and am satisfied with the results.

 

[1970 beepbeep]

Thanks brothers! My friend and I thank you both! He still likes carbs, thats why the swap,plus I have a fresh weber to donate to his project. So he will gain some performance with the newer head? I thought maybe the ports wouldn't match up ,hence the question Can he use a AMC 258 i6 / 4.2l valve cover?( wants to dress it up) thanks again!


Rick

 

[IOPort51]

I don't think the cover will work but 4.0s came stock with cast aluminim covers.

 

[1970 beepbeep]

Thaks again IO

 

[Cheepjeep85]

This is interesting, I don't see why the Weber, if you can find an adapter, won't work on the 4.0 intake manifold? I have a tbi mounted on a carb manifold and am satisfied with the results.

Well its a common thing for carb to tbi swaps. Its not a common thing for swaps from chrysler mpfi to any type of carb I don't think anybody makes an adapter for that. Although I suppose it could be done if you had the right tools to machine an adapter. You'd probably run into several other problems too. Not worth the investment most likely

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[yellow85cj]

Don't think an 80 cast iron intake would work as the heat riser may not fit with the 4.0 exhaust manifold.

Think the problem with using a carb on a MPFI intake (other than the adapter) would be that they are designed to handle air only. The fuel is introduced at the head intake port. A TBI swap to a carb intake still mixes fuel and air at the beginning of the process.

Most I have seen use the aluminium intake (84 to 86). It needs a few minor mods to fit. Here are some "how to" pics of the mod - https://picasaweb.google.com/85YellowCJ7/40HeadSwap#

Need to make a couple of larger washers to bridge a larger gap between the 4.0 exhaust and the AMC 258 i6 / 4.2l intake.

I used studs instead of bolts and some larger washers that I got form Mcmaster carr and some home made large washers.

You can get an aluminium valve cover from a 4.0. 4.0 and 4.2 are not interchangable. They came with steel and aluminium. Check XJ 4.0's for them at the junk yard. Paid $15 for mine at the pick n pull. A little time with a wire wheel and some clear coat and it will look "pretty". Have read that the aluminium covers were more prone to leaks. I did use the Felpro silicon (??) gasket. No RTV necessary. And I did use headless bolts to make sure nothing moved when putting the cover on. When everything is lined up, swap headless for final bolt one at a time.

 

[IOPort51]

did the 4.0 exhaust have the EGR bung or did you have to do that yourself?? I kind of miss the EGR, I think I would idle a bit smoother with it.

Don't think an 80 cast iron intake would work as the heat riser may not fit with the 4.0 exhaust manifold.

Think the problem with using a carb on a MPFI intake (other than the adapter) would be that they are designed to handle air only. The fuel is introduced at the head intake port. A TBI swap to a carb intake still mixes fuel and air at the beginning of the process.

Most I have seen use the aluminium intake (84 to 86). It needs a few minor mods to fit. Here are some "how to" pics of the mod - https://picasaweb.google.com/85YellowCJ7/40HeadSwap#

Need to make a couple of larger washers to bridge a larger gap between the 4.0 exhaust and the 258 intake.

I used studs instead of bolts and some larger washers that I got form Mcmaster carr and some home made large washers.

You can get an aluminium valve cover from a 4.0. 4.0 and 4.2 are not interchangable. They came with steel and aluminium. Check XJ 4.0's for them at the junk yard. Paid $15 for mine at the pick n pull. A little time with a wire wheel and some clear coat and it will look "pretty". Have read that the aluminium covers were more prone to leaks. I did use the Felpro silicon (??) gasket. No RTV necessary. And I did use headless bolts to make sure nothing moved when putting the cover on. When everything is lined up, swap headless for final bolt one at a time.

 

[yellow85cj]

IO - bought the bung and had it welded on, used a couple of tubes from an early 4.0 (pre H.O. IIRC) did a cut and paste, well the shop did it. It is pictured in the link to mounting the AMC 258 i6 / 4.2l intake to a 4.0 head in the above post.

 

[IOPort51]

I have a header and just plugged the EGR. If I have the need to pull the head again I will more than likely do what you did. good job.

when I read your post about the studs from McMaster and the over size washers I thought you had copied one of my posts. Great minds and all.

the other thing I did was mark the gasket with the intake outline to aid in the alignment grinding. It is very easy to have the ports overlap and partially block them.

square washers? why didn't I think of square washers?

IO - bought the bung and had it welded on, used a couple of tubes from an early 4.0 (pre H.O. IIRC) did a cut and paste, well the shop did it. It is pictured in the link to mounting the 4.2 intake to a 4.0 head in the above post.

 

[yellow85cj]

I did the reverse on the marking.

Using the studs made things a lot easier for mounting. The studs that I have used an allen key in the end to tighten them with. No double nutting to install.

The squares ended up more big rounded triangle shaped after grinding them to fit the space.

 

[thiswontbetooexpensive]

I am going to have to see some pics of this build with some mud and dirt on it! I hope my engine doesn't look this nice when its done, I might have to just stare at it for at least a 12 pack!