Iron Duke woes - S-10 Forum
 
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post #1 of 5 Old 06-09-2019, 04:04 AM Thread Starter
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Iron Duke woes

So I have a 1980 Jeep with and Iron Duke, and I figured this would be the best place to get answers.

So I just swapped in a roller cam from a 91ish Duke, what do those engines use for lifter guides? This is the most important question I have here and I canít seem to find any info on the internet.

Is is possible to make have adjustable valves? Iím used to dealing with a SBC so this torquing the rocker arm thing is just off the wall for me, and Iíve had issues with the rocker arm falling off. Even with literally new everything aside from cam (hence the roller cam swap) would it hurt anything to get slightly longer push rods or use a spacer with the rocker nut and locking nuts to make them adjustable? Or is it a nonissue on the roller cam models?

Iím carbureted, using a CA Rochester Varijet II, the computer carb. For one I was thinking of removing the EGR, would there be any negative effects? Also I considered swapping to a Holley 2300 350 CFM carb. Iím a machinist for work, So I was going to make an adapter, either to the Holley carb or deleting the EGR (taking place of the whole gizmo between the carb and intake) or both made of aluminum.

The engine is currently still in pieces and Iíd like the get it going soon. And I know with the 91 or so cam there is no fuel pump lobe so Iím looking into a electric pump and possibly using a Holley 2300 fuel injection throttle body and custom adapter but thatís $$$. Iím also thinking of throwing the long tube header on the engine while Iím at it

If anyone could shed any light on any of this that would be amazing, thank you!

And as a side note Iím pretty mechanically savvy, just unfamiliar with this engine. Iím used to small block chevys and diesels.


1980 Jeep CJ7 Iron Duke/T176/300 Dana 30/AMC 20
1971 GMC Jimmy 350/SM465/NP205 Dana 44/14BFF
1997 Dodge 3500 Cummins 5.9/NV4500/NP241HD 60/80
2019 Honda CRF250L (daily driver)
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post #2 of 5 Old 06-12-2019, 12:38 AM
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Re: Iron Duke woes

I am only vaguely familiar with these engines...


You can't use a roller cam in an early duke unless you buy "linked" roller lifters. The later roller cam engines had bosses cast into them in the lifter area for lifter retainers with a specific retaining bracket.

The after market Chevy roller cams had the these types of lifters. They were linked together with an arm so they could not turn in the bores.


You would also have to re-set your rocker arm geometry by using a pushrod that can be height adjusted to make the rocker perpendicular to the rocker bolt. Then you would have to buy a set of correct length pushrods.


I am running a set of Chevy big block rockers on one of my Dukes... I had to recalculate the rocker geometry and buy a set of Comp Cams special length pushrods.


The fuel pump part is easy. A Ford fuel pump block off plate works well on the Duke fuel pump boss.
Remember to install the fuel pump close to the tank, they push fuel better than they pull unless you have a British electric diaphragm pump.


As far as a carb... I have had no luck with a 2 SE Bogchester - particularly the electric version. If you run a header and big exhaust, you will never reach the full potential of your mods. Why do I know this?
I installed a header on a friends 82 CJ with a Duke. It ran so poorly, I had to install a Weber.


Which leads to the next issue - carb.
I am tired of recommending a Weber conversion, but it is the least expensive and best pop for you buck. They sell the complete kit at many sites including Ebay.


A Duke I built with all sorts of performance stuff...



I happen to have a header for the Jeep Duke. I sand blasted and painted it with high temp paint. I don't know if it fits an S10 - which is what I have, it looks close. I may part with it since I have a very expensive Clifford header.


I would recommend going with a flat tappet cam to avoid all of the possible problems that you will encounter trying to make the roller unit work correctly. They are inexpensive and you can find a Comp Cams 268 duration for under $150. BY the time you make the roller cam operate correctly, you will have way more than that into the build.


I am also running a Holley 390 CFM 4 barrel on an Offenhauser intake. I also have a Holley 350 CFM 2 barrel as an alternate.


I'll add more if you answer this post.

S10 addiction:
1)'82 S10, 383, 700R4, Shorty
2) '85 S10, 3.4, 700R4 4x4 stretch cab (Redneck)
3) '90 S10 2.5, 5 speed shorty
4) '91 S10, Built 3.4, 5 speed shorty (Voodoo)
5) '92 S10, 2.5, 5 speed shorty, (Barbie)
6) '92 S10, 2.5 5 speed, Shorty
7) 1979 LUV, Buick 3.8 V6, TH 350 Shorty.
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post #3 of 5 Old 06-12-2019, 12:44 AM
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Re: Iron Duke woes

I suggest reading this:
https://www.s10forum.com/forum/f104/...y-duke-637746/
I have developed more info since this was posted, but it's a good start.


Oh, you can install a flat tappet cam in a later Duke fairly easily, but a roller in an early, not so easy.

S10 addiction:
1)'82 S10, 383, 700R4, Shorty
2) '85 S10, 3.4, 700R4 4x4 stretch cab (Redneck)
3) '90 S10 2.5, 5 speed shorty
4) '91 S10, Built 3.4, 5 speed shorty (Voodoo)
5) '92 S10, 2.5, 5 speed shorty, (Barbie)
6) '92 S10, 2.5 5 speed, Shorty
7) 1979 LUV, Buick 3.8 V6, TH 350 Shorty.
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post #4 of 5 Old 06-12-2019, 12:47 AM
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Re: Iron Duke woes

This is a later roller cam Duke. You can see the brackets and retainers. The 2 brackets at either end of the engine hold the retainers on the lifters. I don't remember, but I think the earlier Dukes don't have 4 bosses on the block. They may only have 2.

S10 addiction:
1)'82 S10, 383, 700R4, Shorty
2) '85 S10, 3.4, 700R4 4x4 stretch cab (Redneck)
3) '90 S10 2.5, 5 speed shorty
4) '91 S10, Built 3.4, 5 speed shorty (Voodoo)
5) '92 S10, 2.5, 5 speed shorty, (Barbie)
6) '92 S10, 2.5 5 speed, Shorty
7) 1979 LUV, Buick 3.8 V6, TH 350 Shorty.
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post #5 of 5 Old 06-12-2019, 12:56 AM
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Re: Iron Duke woes

More detail:

S10 addiction:
1)'82 S10, 383, 700R4, Shorty
2) '85 S10, 3.4, 700R4 4x4 stretch cab (Redneck)
3) '90 S10 2.5, 5 speed shorty
4) '91 S10, Built 3.4, 5 speed shorty (Voodoo)
5) '92 S10, 2.5, 5 speed shorty, (Barbie)
6) '92 S10, 2.5 5 speed, Shorty
7) 1979 LUV, Buick 3.8 V6, TH 350 Shorty.
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