F-134 Performance Report

I admire the folks that put these back to factory stock. That said, I know I would never ever be happy again with either 134's in a Jeep I actually want to use. BTDT. I still think building a stocker is way less difficult than a properly built restomod where you have to actually engineer everything. The "anyone throwing in a crate motor" thing usually doesn't end well. And I'm another big believer in "light", especially aluminum blocks/heads/wheels. The SBC in my 3B weighs about 40 lbs less than the F head, for almost 3.5 times the displacement.

And unless you are opting for the 3.0 or 392, you don't gain all that much usable power wise in a new Wrangler. The 3.6, IMO, is an absolute certified dog in that platform.

 

And the SBC has long been stuffed into our rigs, I would definitely consider that period modification. Where I personally get a little shrugged is sticking a Japanese engine into an American vehicle. That's just my personal feelings, doesn't make them right or wrong. I just stay in my own lane. I've liked some of the Jeep built resto mod Easter Eggs, but sticking every whizz bang one can, to me, it's no longer the original, it's what's underneath wearing a mask. I love Stan Fuller/Flatfendering Aficionado and all those guys out west wheeling in the flatties, living life, enjoying the outdoors. And then here in North Alabama I see all the mall crawlers, local FB Groups asking which accessories are the best...... But hey, 'Murica, land of the free!

 

That's a stock cj10.

 

I can handle that ugly duckling as it was designed from the get go with that Nissan diesel. Man that thing is ugly, but still neat. IH also went the Nissan diesel route.
I would love a CERLIST 3 cylinder with a turbo if I had the time and money.

 

Only some of them---

 

http://www.earlycj5.com/xf_cj5/index.php?threads/156341/
Spence, if you haven't looked at this thread... It starts with "F head"

I resemble that remark. And no apologies either. Having driven a couple of F heads into the ground I'm OK with a "period modification" . But I do have respect for those intent on looking for the best out of the originals, including all the "stocker lockers" that gather in Moab for "Flat fender Fridays" .
Good luck on your quest!

 

I like the Weber 38 on my F head, even just that alone seems like an overall improvement.

 

I have a Weber 38 I got from Spence and have been debating whether to install it on the F-Head in my CJ5, or the L-Head in my CJ2A. Leaning toward the CJ5, but it already runs great with the YF on it now.

 

32/36 progressive Andy. Perfect for a stock Jeep and more umph

 

So there is someone else! What's your jetting and location?

 

You are right, I had a senior moment and was dreaming.

 

Your knee still on the fast mend? Get your knuckle stud upgrade done?

 

Knee is doing okay, it hurts a little today probably because I overdid it yesterday I think.

Haven't done the knuckle stud upgrade yet, have been working on a windshield for my CJ5 instead, but will be getting to that soon.

 

I did not mess with the jetting, I'm located basically at sea level, like 200 feet or so.

I ended up having to make my own adapter for the adapter (double stacked, haha!) but it works good. and I can still access the factory oil dipstick because of the added height of the 2nd adapter.

Oh, actually nevermind, mine might not be the 38, mine has one larger butterfly and one smaller one.

 

I'm running a phenolic spacer from Fastman, SVTEK airhorn and itb "sausage" air filter.

 

Good to hear you've had some success with waking up your fhead.
They really are a hoot when compared to stock after some tinkering.

 

I was incorrect about my mains, 145 are what they ship with. I changed the air correctors from 170’s to 200, same bin as the 160 mains. I looked at the diagram wrong confusing air correctors and main jets. Now I am clear about thr various circuits, will install wideband to be certain where I am and go from there. The Weber is said to be very sensitive to changes with the idle circuit which is what one spends the most time on.

the change in air correctors gave me the 2500-3k rpm punch I was experiencing in 2nd . But one must take the time to balance it for all rpm ranges, unless a specific range is desired depending on use. I’m ok with loosing some top end with an emphasis on the low and mid rpm ranges.

as Gene Winfield says “everyday’s a school day.”

 

Weber 38 DGAS/F 134 update: I finally installed the wideband, it was 15+ running the base/shipped 55 idle jets. I tried 50 thru 40 idle jets before settling at 40, 1 turn. Very close to 14.7 at idle. Noticeable improvement in off idle and gas smell gone. The air correctors are the progression circuit between idle/mains, mine (K380 kit from Redline) came with 170's (rich), most other 38's seem to ship with 185's (leaner), I have 180's/190's on hand. The 180's are a definite improvement, and will try the 190's, hit the road to see how much closer to 12 it reads, ordering 185's to have on hand.

NOTE: this is a mild F head engine build, .060 shaved between block/head, .060 bore, Isky 240/238 camshaft grind, 2" free flow exhaust. For a stock engine, it's recommend to run the Weber 32/36 which Sal/Vintage Jeeper can set you up with a ready to run unit.

If you followed my last thread, I was confused on the jet locations and had swapped out the air correctors thinking they were the mains not fully understanding the circuits and their performance throughout the ranges. I ran 200 air correctors, running the trails 2K-3K in 2nd which it really seemed to like, but without the wideband I was flying blind. Now I have a point of reference, not definitive, but a wideband AFR meter is a helper tool/point of reference. For those not familiar with tuning by AFR, it assist visually in getting very close to the ideal idle air to fuel ratio 14.7.1, tuning further by ear/sound/butt dyno. I run non ethanol, this AFR measurement changes with E10 and other blends, but this is where I am starting. 12 AFR is the desired WOT/main jet circuit for maximum power.

D3Sshooter has the best Weber 38 videos I have found, a wealth of knowledge: https://www.youtube.com/@D3Sshooter/search?query=Weber%2038

 

I was initially talked out of the 32/36 by Redline since my engine is mildly overbuilt, flows more air than a stock unit. I came across this chap in South Africa that does Weber rebuilds, he modified a 38 DGAS into a progressive unit on his Nissan A14 1400, and boy does it perform! I just sourced a genuine Weber 32/36 for parts to cannibalize to build my own 38 DGAS Progressive, gaining the best of both worlds. Of course adding a little more complexity to the tuning but should be similar to tuning the 32/36 and of course the wideband will be a godsend.

Addendum: Sal/Vintage Jeeper brings up a good point, tuning equal barrels vs a true 32/36 will be challenging. The SA lad seems to know his stuff, contactable via WhatsApp, I may be buying him beer or whatever he wants for guidance.

Update: the gent out of SA that performed this mod advised how to tune each barrel, luckily I had bought the rubber adapter for the bores and have two German made air meters to assist, but this will be a mod for later. Continuing with tuning stock setup

 

Preface: obviously this is a learning process, there are variables, and there is arriving at a conclusion from logical deduction.

Very informative and concise book, worth its weight in tuning gold. Now, to figure out Redline’s reasoning behind a 170 air corrector and 145 main. A long time tuner in the manual uses a formula of main jet size plus 60 for air corrector size. Stock Weber 38 DGAS on a 2500cc engine is listed from Weber as 142 main, 185 air corrector, 45 idle jet, mine shipped with 145,170 and 55, rich out of the box. Perhaps for E10? I run 90 non ethanol. Redline did mention “proprietary” tuning in their listing for the K380 kit they sell…. The main, air corrector, idle all interact in the transition, main size affects backwards.

I am currently at 145 mains as shipped (still rich up top) 180 air corrector (definitely improved) and 40 idle, again definitely improved.

I’ll try a 140\135 main, 200/190 (I don’t think I have a 195) air corrector and test from there. But definitely heading in the right direction.

Side note, according to Weber chart, the 32/36 is commonly used on a 1500cc engine, seems a bit too small for a 2.3 F head on paper…I mean for fuel economy and drive ability it makes sense, but for optimization, it seemingly leaves a lot on the table but is a proven model for good fuel economy and performance for a stock engine. I guess it depends on how you use your rig, but then again a better sized venturi for the application tuned correctly would also give good fuel economy. Which has me curious if a F head were modified for a sidedraft, it would flow atomized air/fuel horizontally vs downdraft which has a "bend" due to the position of the OEM intake hole and the intake chambers into the combustion chambers, which on a low revving F head may not even be worth the effort, but fun to think about.

If you‘re curious about Weber’s, this is the book to get, about $23 on Amazon