F-134, Chevrolet Valves Modification?

Preface: I know the limitations of the venerable F head, these are modest upgrades to maximize the performance within reason, the focus on torque and NOT top end.

I seem to recall seeing something on the web with regards to increasing the F-134 valve size slightly to Chevrolet units. Does this jog anyone's memory?

I rebuilt my engine, the PO had .060 shaved between block and head, bored .060 so I stayed with that, NOS crankshaft at STD, sent a NOS camshaft to Isky for their mild grind, running a Weber 38 with an Advanced Distributors recurved IAY-4401 and it's running well, just completed a 900 mile round trip and it ticked like a clock. The Husky OD I had Herm rebuild really gave me the 55-60 MPH at 2500 RPM I was looking for to comfortably cruise the back roads to my adventures and not beat the long stroke F head to death.

Advanced sent the distributor back with instructions for 12-16 degrees of base timing, I am physically maxed at 12 as is, I need to adjust the lock plate mount to gain more adjustment but waiting until I have the local performance exhaust shop mandrel bend new up-sized pipe to a Flowmaster absorption muffler to uncork the exhaust as it's noticeably "stuffed up" with the intake side now more opened. Will have bung installed to connect my Auto Meter wideband unit to assist with further tuning.

If I can confirm the Chevrolet valve mod, I will engage Isky to inquire if they have a roller rocker with matching cam option for the F head.

And lastly, I found a custom header manufacturer and will have them design a Tri Y similar to Mark W's nice unit.

 

I thought it was a dodge stem. Are you looking at intake? The intake valves are already really big and shroud the bore. The exhaust already risks heat cracks between the number 2 and 3 exhaust valves.

I would focus on the exhaust header and mild cam, bigger valves will bring new issues like float and fitment. Your at the point of diminishing returns and not enjoying the drive because the motor has a big "personality".

 

Very good points you bring up. Hence why I asked this in a public forum where knowledge abounds. Thanks for the feedback.

Side note, I am curious if a roller rocker setup, if available as an option, would enhance the current duration of intake/exhaust to a worthwhile point? Or more beneficial to a mid-top performance engine moving much more air than the F head currently is or should?

Luckily I have a Buick 215 w/T-90 bellhousing in the garage to build if I start feeling the need.

 

I’ve personally found that any mods *short of a blower* only give a noticeable power boost in the range of rpm that is out of the f-head’s happy place. Yes, a 10 hp gain is like a 14% power boost, which sounds great on paper, but you’re still well down in the 2-digit numbers at peak, and spinning things faster than they were designed to spin to get it. Fine for a race, not great for every day practicality and reliability.

It’s taken me many years of denial and many experimental dollars donated to admit that the best way to increase the power of an f-head is to swap it out. I’m currently running a 4-cyl that has double the power of an f-head and am just barely in the happy range.

 

I am overall happy with it. I was seeing how far I can tow the line before getting too dangerous or sacrifice performance elsewhere. Sounds like I need to get the custom header and call it done.

 

Yes. My opinion is that "tuning" an F-head is a misunderstanding of the 4-cylinder Jeep heritage.

If you need more power, look for a V6 jeep.

 

I think you have squeezed about as much as is reasonable to get out of an F-head, so X3 on the idea that if you want more power swap in a V6, though I would go with a GM 4.3L V6, which is IMHO the best choice for a compact and powerful engine which is easily adapted to a Jeep.

 

I looked into it and you could stick some sbc 2.02 valves in the head but there's no gain. The 2" intake is plenty enough.
@ITLKSEZ really said it best.
I know my fhead rips but at the end of the day, it isn't practical for trail rides or street driving. It makes power from ~2500-7000 rpm. I know its lifespan is cut in half at best.

 

If needed, I have a Buick 215 all aluminum which weighs a whole 317lbs. With Egge pistons, warmer camshaft all from D&D, I can get about 200+ hp/torque in a reliable "stockish" form. The 215 3.5 being the granddaddy of the Dauntless and used in Rover Disco's until 2006 all the way to a 4.6L in the HSE's.

But for now, the F head is plenty. Being a guy, of course I'm always on the quest for taking anything, and everything, to the limit! Thanks for all the valuable feedback. Good to have wisdom shared to help me decide wisely.

 

I have two F-head cylinder heads that have Chevy 2.02 intake valves installed. They require the spring pockets be cut a little, and the seats reshaped. These heads also have alloy roller rockers and custom longer pushrods. Even the rocker cover needs to be extended taller. Larger Chevy(?) exhaust valves (don’t remember size, 1.60?) are also in the block.
Crane used to have a special F-134 cams that make power up to 7,000 rpm. I don’t know if I have the cam specs anymore, but still have the cams. The heads and blocks get serious milling to raise the compression ratio. The pistons stick up above the deck height by more than 1/8”, and the crowns are milled leaving only the combustion chamber the original height.
Theses parts are out of Naples (FL) swamp buggy racers.
The Buick/Rover 215 is a much better alternative. I ran a ‘63 4300 series 215 (factory 200hp high compression 4 bbl) in my Tux for over 20 years.
-Donny

 

Yep, but when I burned #2/#3 exhaust valves trying to pull a SMALL U-Haul 600 miles, I was completely over 134's of either variety. That was 1972-------

As I said to this at the other site, lipstick on a pig. Yes you can make some power but only if you are willing to tear things down on a regular basis. Without addressing the intake side of the head, the marginally larger valves aren't going to much of anything anyway. Time and money for something dependable off road with enhanced performance is much better spent on just about any other engine platform.

 

Could always put a turbo on it!
Thanksgiving is still 6 months away

 

lol, is that in reference to the older thread the guy has yet to update?

the Nicholas guy doing the Sniper kits mentioned something about in his research that balancing the rotating mass helped in boosted applications. No hard data provided, just a blurb. I had my eye on a McCulloch VS57 blower only on FB MP that sold. I see complete kits for around $2-3K on eBay, too much $ to play around with and quite possibly find heartache at this point in my life. Nicholas was touting an older Toyota blower unit that was around $500.

If anything, since I am happy with the F head as is, add a custom header, call it done, but with the 215, if I build it, I could go with an older blower/low boost for an extra kick. I have a 71' T120 scrambler to finish and just inherited the family 70' Airstream so my hands are full at the moment, taking on only the low hanging fruit in life for a while.

 

Yep, it's like a decade old now LOL

 

There is a guy still running a Saab turbo. He has a youtube channel for other stuff but the jeep gets driven here and there.

I used a td04 from a 1.6l colt.