4.0L head w/ SBC SS valves

[75SV1]

I have my 4.0L head with Chevy SS big valves done. THe head has been ported and polished. Its been shaved 0.010. I used the stock springs and modified SBC spring retainers to work. I used Elgin valves I got off of E-Bay. I have pics, but can't post them. The valves were about $5.50 each. The springs I got in a deal with some roller rockers. The retainers were about $30 off of E-Bay. The head came off a '95 motor I bought for $100. I used the valve cover off that motor too. It will go on an '03 4.0L from a GC.
Tom

 

[Gil BullyKatz]

So... Is this an FYI or your version of a write-up?
Just wondering :dunno:

 

[75SV1]

New to the forum. Not sure what your expecting. Did you want more info? The hows and whys etc.? Let me know if people what more details and if there is a proper way to do a write-up? I still haven't put the head on the motor or installed into a vehicle. I do have a lot more to do on this project.
Tom

 

[mississippi_xj]

yeah.... hows and whys would be nice.....

scotty

 

[Ramsey]

i'd rather just hear the 5th step and half of a reason why your doing it

 

[75SV1]

OK, the whys was for a bit better flow. I had heard SBC valves would fit, but have a bigger stem diameter. I check spec lengths are they are the same (depending on brand). If you search around you can find some the exact length. I went with the Elgin from a guy off of E-Bay, Racer Outlet.. $5.50 each. These are swirl polished, cromed stems, under cut, and hard tipped. The main problem is finding springs to work. I retained the stock '03 cam. I have heard of other spring being able to work with some spring seat machining. I retained the stock springs and modified some SBC spring retainers. I had to turn down the OD which centers the spring about .025. I think Crane might carry a 10 degree spring retainer that might not need machining. I do have the head done. I put it one the engine and had to shorten some push rods, due to roller rockers. I put clay on the piston and rotated the engine a few times. No valve clearance issues. The machine work csot me $170/w oil seals and .010 shaved off. The guy just drilled out the guides and reamed them. No use of valee guides. The seats worked out OK. Hope this is enough info. It was hard to find a spring retainer to work with the larger diameter valve stems and the stock springs.
Tom

 

[5-90]

I can understand the idea of increasing airflow, but what else are you doing to offset this mod?

The basic airflow properties of the 4.0 head are not bad to begin with, and the limiting factor for you will end up being the throttle body. To take full advantage of the "big valve" head (I'm assuming you're trying 2.02/1.60 valves like Mike Parrish at Accurate Power uses) without using a blower or a turbo, you are going to need to replace the throttle body, or just have it bored out to begin with.

Also, if any work has been done to expand the port size of the head in conjunction with the valve work, you are going to move your power band up thru the RPM range and lose low-end power - which is the hallmark of the inline six engine! If you haven't increased port size, flow increases are still useful, but may not give you the results you are hoping for...

All else being equal, while I like the look of going to 2.02/1.60 valves for the head (and the concomitant increase in parts options,) I'd probably not go bigger on the valves without planning on forced induction as another mod.

I am sure I will hear from someone else saying that the "big valve" setup is not a bad thing, and I am always willing to be convinced, but that's my story and I'm stickin' to it!

All that being said, was the 2.02/1.60 setup an end in itself for you, or do you plan on doing anything else? At the very least, I'd toss on an aftermarket equal-length header, open up the rest of the exhaust, and bore out the throttle body. If you have the HO head, it would also be worth thinking of finding a 1999-2001 intake manifold, as it flows better and has been "tuned" to the power band of the 4.0 mill, saving you the need to build one of your own...

Lastly, it's your Jeep and you should enjoy it. However, there's nothing wrong with having your beliefs challenged - it will probably result in new ideas and a better end result...

5-90

 

[75SV1]

5-90,
Good points. I am already running a Pace Setter header. I plan to replace it with a Clifford set. I am putting the '95 head on a '03 block. I will be retaining the stock cam. The cam also influences were the torque band is. I'm sure you already knew this. I do have a 99+ manifold to go with this. I plan on boring out the TB to 60mm initially. I will also be running a K&N type air filter. Plans are to put on a hi-flow cat and exhaust. I am also planning on putting a Dana 300 with a passenger side drop. Then run the exhaust straight back. I do think I will loose a bit in torque with the big valves. I might be able to tune the exhaust with a bit smaller tail pipe like Go-Jeep speaks of. I will be running roller rocker too. Not much of a HP increase there, but suppose to make the engine run a bit smoother. This will be my daily driver. I will probably loose a bit of low end torque. Still, I hope to get a bit more MPG at highway speeds. Its going into an '88 Comanche.
Tom