Big Valve Head 1.60-2.02

[ripdawwg]

Hey all,
First time Post, but I have had a lot of dealings with Dino @ Yahoo strokers for almost 10 years now. (Hi Dino thanks for pointing me to this site!)
I have gone through the evolution of Cherokees/Comanches from my 88 that I swaped the crummy peugot BA-10 tranny for an AX-15, balanced an older 4.0 and threw in a 260/272 crane and swaped in a 93' HO head & intake. (it flew for a jeep before strokers were popular)
Fast forward a few years now I have a 99 xj that is in the works for a stroker.

I have a 91-95 HO head with the larger exhaust port. I want to install larger valves like what accurate power did a few years ago. I know a few other outfits have done this as well. I am going to go balanced 4.6 below with comp's 232 fuel injection cam. I know the Hesco aluminum head kinda stole the thunder from doing this, but I have the head in hand and I want a good challenge.

I have not be able to find any info on springs (my comp K kit has springs I hope I can use), installed height, keepers & locks to make the chevy valves fit. I know the stem guide will have to be opened up (some suggest using Mopar valves with the 8mm stems, chevy stuff is so inexpensive though damnit)

Help! Building the 5.0 in my mustang was so much easier ($700 for GT-40X Aluminum heads!!!) but slinging mud on the hill with a stout stroker will be so much more fun!!! (plus the F&R lockers, 32'' mudders, 12k warn winch, 5.5" Long arm suspension OUCH what a money pit......)

[Flash]

Hey all,
First time Post, but I have had a lot of dealings with Dino @ Yahoo strokers for almost 10 years now. (Hi Dino thanks for pointing me to this site!)
I have gone through the evolution of Cherokees/Comanches from my 88 that I swaped the crummy peugot BA-10 tranny for an AX-15, balanced an older 4.0 and threw in a 260/272 crane and swaped in a 93' HO head & intake. (it flew for a jeep before strokers were popular)
Fast forward a few years now I have a 99 xj that is in the works for a stroker.

I have a 91-95 HO head with the larger exhaust port. I want to install larger valves like what accurate power did a few years ago. I know a few other outfits have done this as well. I am going to go balanced 4.6 below with comp's 232 fuel injection cam. I know the Hesco aluminum head kinda stole the thunder from doing this, but I have the head in hand and I want a good challenge.

I have not be able to find any info on springs (my comp K kit has springs I hope I can use), installed height, keepers & locks to make the chevy valves fit. I know the stem guide will have to be opened up (some suggest using Mopar valves with the 8mm stems, chevy stuff is so inexpensive though damnit)

Help! Building the 5.0 in my mustang was so much easier ($700 for GT-40X Aluminum heads!!!) but slinging mud on the hill with a stout stroker will be so much more fun!!! (plus the F&R lockers, 32'' mudders, 12k warn winch, 5.5" Long arm suspension OUCH what a money pit......)

A statement that was told to me that stuck into my head, and is why i will be puting stock valve into my stroker when it built.

"If a HP alu casting, such as hesco's still uses stock valve......there has got to be a reason!!!!"

Sense that comment i have learned about unshrouding the valves and is beneficial with the stock exh valve.....................I'm not trying to rain on your plans. It can work but there is a lot more to consider on the larger valves, then just the seat and stem size/height, if they are to perform better then stock valves.

Flash

[seanyb505]

Over on NAXJA I was PMing Dino about info on how to accomplish the big valve head. Here's what he had to say,
"My advice would be to stick to the stock valves and the stock valve springs/retainers/locks. The ports in the heads aren't big enough to make the most of oversize valves. Just do a mild port job with a 3-angle valve grind."

Its a good enough reason to not throw more money into the engine for me.

[gradon]

I still want to hear from other people's experience with using different size valves. I'm gonna be using the stock valves(unless the machinist tells me otherwise). Tomorrow I'll be cleaning them and continuing the port and polish work on the head.

[John]

Haven't found the factory valve size a bottle neck for flow, You will find time spent on porting and un shrouding valves will yield improved performance. Here is a couple links from Hesco on this issue:

http://www.hesco.us/forum/forum_posts.a ... lve+shroud
http://www.hesco.us/forum/forum_posts.a ... lve+shroud

And a intelligent article on porting SBC heads, but the process is really the same, note the unshrouding of the valves.

http://www.chevyhiperformance.com/techa ... index.html

John

[tirod]

I just finished reading the Engine Masters magazine, a long thread elsewhere about a high compression stroker, and have put 2+2 together. Hope it actually = 4.

The current bane of the budget stroker is excessive compression, as I take it. Everything done to get a good quench also drives up the compression to unacceptable levels, especially with stock type cams.

So, aggressively unshroud the valves with a Dr. J type combustion chamber porting job. Normally this would be a no-no on a hi-perf V8 as too much compression would be lost - but on a 4.0, a whole point lost is the goal, not a goofup. Grinding back the chamber walls - appropriately - to unshroud the chamber wall (especially for bigger valves,) and opening up the cc's in the chamber sounds like a cure, not a problem.

The Dr. J method is to do a complementary "three angle valve job (my words)" on the combustion chamber side of the valve, to improve flow around it. That way at .100 lift, the chamber walls don't interfere or curtain off the air flow. He uses a set of dressed grinding stones that remove material in the "curtain zone" to improve air flow, and explains the profile was derived from his flow bench studies and dyno results. He only removes what is needed - but for the 4.0, I think we could approach this with freer hand.

I know the market probably won't support a lot of extensive testing and CNC setup for 7120 heads - but I think the concept is valid, and I'm currently confident it could do a lot to solve the problem. I would be interesting to see a template kit developed (not only for Jeeps) that would include profile sections for the home porter to grind match for a better performing head, not only for the interior of the ports, but also for the chamber. Right now the biggest problem may be the amount of cc's to remove not being safely available in the chamber, or inefficiently at best.

[ripdawwg]

Hi guys,

Thanx for all of the excellent info! I have been a bit hesitant on the porting because without a flow bench available, a lot of guess work is employed.

I was under the belief (from the guys @ Hesco) the reason the valve sizes were picked for the Aluminum head, was due in large part because they wanted the Head to work on older 232 & 258 AMC engines as well as the 4.0 Jeep engines. I believe that the Aluminum head uses the largest valves that will work in with the older engines smaller bore. Hesco offers the option of installing larger valves into the Head, and does this to quite a few from what I understand.

Just my two cents, thanks for all of the responses. I will let everyone know how it turns out. RIP

[jeep7081]

Its an old thread. But, someone may look at it.

Had my set up a year now. 2.02 and 1.60. Runs good!

[6TIME]

Curious, did you run stock valve sizes before changing? If the stem centers were a bit closer to each other I could see larger valves being a definite advantage by opening up the shrouded area at the chamber walls a bit.. With most aftermarket heads the valves are almost touching in the center. In our 4.0 heads they are spaced apart for some reason which reduces the advantage of making good gains with larger valves in a sub 4" bore.