Carb'd 4.6 Questions

[Wombat Ranger]

Drill your yoke out and run U-bolts through it instead of straps. That will help. What size tire are you running? If I had stock sized tires I doubt this would have happened. My 33's and 3.07's means lots of leverage on the differential. Fresh torquey engine exaggerates that obviously. Thankfully my yoke failed, not the pinion or ring gear.

[Wombat Ranger]

Got exhaust on it. Full 2.5" with stock cat and turbo muffler. Sounds stock. Cat will be departing ASAP though. Finally got to drive it without it being embarrassingly loud, so I stomped on it a bit. It was impressive! I look forward to getting the MC2150 on it and tuning it in!

[Flabby]

I'm doing the same build on my 84 CJ. Just picked up the 92 4.0 HO that''s been stroked to a 4.7 to switch out the 258. Going with the MC2100 and HEI DUI. I'm looking at the Clifford intake, but some peeps on the other forums are complaining about the current quality and customer service. Any insight?

[Wombat Ranger]

Got your PM's, that's what brought me back to this website. Figured it would be better t answer the questions publicly so others can find the info if they need.

My engine runs awesome. I am more than pleased with it. With all the wrong gearing it is still a total hot rod now. I am having no problems running it on 87 octane gas as well. The only issue I have had with the entire thing is running the stock 4.2 intake on the 4.0 head. I have had to do quite a bit of "ball peen clearancing" to the header primaries (no big deal, not a crazy built motor) to get the intake to fit. My next problem is that the washers I have been using to spread the bolt surface area out enough to clamp on the intake and the header at the same time (anyone who had put a 4.2 intake on a 4.0 head knows what I am talking about) have been warping from the leverage of the weight of the horizontal intake and pulling the mounting surface away from the head, causing vacuum leaks to develop after a few miles of drive time. Been really frustrating, but I think I have it fixed now. Overall I am very happy with my new engine and the simple setup with HEI, MC2150, and 4.0 accessories/serpentine belt.

[Flabby]

I really appreciate the feedback. I'm ordering the Clifford intake and going with the MC2100. The serpentine setup is my target also. Since it's a 92 block from a 93 Wrangler, I'm assuming I have to pick up all the Wrangler brackets, alternator and PS pump to make it align properly. Are there any issues with the PS bracket aligning with clifford manifold?

[I6FAN]

I really appreciate the feedback. I'm ordering the Clifford intake and going with the MC2100. The serpentine setup is my target also. Since it's a 92 block from a 93 Wrangler, I'm assuming I have to pick up all the Wrangler brackets, alternator and PS pump to make it align properly. Are there any issues with the PS bracket aligning with clifford manifold?

At one time, they offered three different manifolds: 258, 4.0l 87-91, and 4.0l 1992 up. The brackets from those years should line up with the manifold.

[Wombat Ranger]

I am still having the same vacuum problems. Really frustrating. I want to just call up Clifford and buy their intake but I don't want to spend the dough. Might end up doing that though. Anyone else had these issues with the 4.2 intake on the 4.0 head?

Far as accessories I am running an HO XJ serp setup in mine, and there are no clearance issues with it by the frame or anything. These parts are much more common in my area since xj's are a dime a dozen. If that helps anyone.

[Flabby]

I really appreciate the feedback. I'm ordering the Clifford intake and going with the MC2100. The serpentine setup is my target also. Since it's a 92 block from a 93 Wrangler, I'm assuming I have to pick up all the Wrangler brackets, alternator and PS pump to make it align properly. Are there any issues with the PS bracket aligning with clifford manifold?

At one time, they offered three different manifolds: 258, 4.0l 87-91, and 4.0l 1992 up. The brackets from those years should line up with the manifold.

That's pretty close. The website says 91 and up, which is my current config for the 4.0. I appreciate it.

[Flabby]

I am still having the same vacuum problems. Really frustrating. I want to just call up Clifford and buy their intake but I don't want to spend the dough. Might end up doing that though. Anyone else had these issues with the 4.2 intake on the 4.0 head?

Far as accessories I am running an HO XJ serp setup in mine, and there are no clearance issues with it by the frame or anything. These parts are much more common in my area since xj's are a dime a dozen. If that helps anyone.

Looks like there are some pretty decent part yard finds for the XJ serpentine config here also, so I'll go forth and do great things based on your experience. I'll pick up the Clifford intake to keep the vacuum issue down. Going with a J10 power steering box from the 84 for the direct bolt on. Did you keep the CJ PS pump and alternator?

[Wombat Ranger]

Sorry to be so slow to respond, I am a busy mofo.

I used the xj pwr steering pump and ran the lines to my yj steering box. Also picked up an early HO efi intake manifold this week. Made plugs for the injector bosses and TIG'd them in, added material to the TB area, and made an adapter plate to put my MC2150 on it. It should be on this weekend. Hope my vacuum leaks stay gone.

I am running the 4.0 alternator, wired to run with no computor. Pretty easy to do and it works great. I wanted to run all the stock 4.0 style accessories for the sake of ease of replacement.


Question for you guys who know these engines real good. I am running a 1.08v MC2150 which is rated to flow 287cfm. The engine runs frickin awesome, pulls smooth through the rpm range all the way up to about 5000 if I feel so inclined. Been doing a lot of driving in a 93 HO 5spd yj and it feels like an absolute slug, even with much better gearing than my 88. But in a perfect world is 287cfm enough for this engine? Wondering if I would be better off with a 1.14 (300cfm) or 1.21 (356cfm) carb.

[sly-jeeper]

I would think that it would run best around 350 cfm if jetted properly, but I do not have any experience trying one

[Wombat Ranger]

Back for more.



Roughly 500 miles in to the new motor it started pressurizing the crank case. Dropped it at the machine shop for them to check it out.

What are the ideal specs I should have them work it over to? It is far from ideal at this point with too much quench and too much compression. I think this combined with the vacuum issues I was having with the old intake caused detonation and ring failure. I doubt it will need more than rings and a hone.


What do I want as far as piston-deck clearance? Am I okay running the stock type Sealed Power dish pistons that are in it? Head is stock 7120 fully rebuilt, RV regrind on HO cam, MC2150. I want low compression, and 87 octane if possible. At what point with deck height do I need shorter pushrods?



Thanks fellers.

[sly-jeeper]

Wow nobody has anything to say. What ended up happening?

[Wombat Ranger]

Bored from a .030 to a .040 over, all new bearings and rings, and left everything else alone. Builder tells me the deck clearance was .025" under, not what I had thought before. So it's safe as far as quench goes. Compression is higher that I wanted, but the mild RV cam helps (I think?). I don't have it completely back together yet. I'll report back when she's alive again. I am so sick of projects.

[sly-jeeper]

Your compression could be anywhere from 9.7 to 9.9 depending on different rod lengths and how big your head combustion chambers are. That's figured at sea level, I would strongly recommend premium and as far as pushrods go the only way to tell is assemble it and check the preloaded.