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4.2 motor build

4.2 motor build
^^^^^^^ I agree with tarry on this.
 
tarry99 said:
:)That might be a great Cam and roller setup if you operate your engine in that RPM range and have the induction & Ignition system to go along with it....... ..................1500-5500 RPM's so and average of 3000 RPM's to see any gain???
:D:D:D:D
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I'm inclined to agree with you Tarry. What's the point in forking over major bucks for a roller setup in a motor that spends most of its life between 800 and 3000 rpms?
As far as reliability, a properly set up flat tapet hydraulic cam will easily last hundreds of thousands of miles. How much more would someone want??? :rolleyes:
 
Rescue Diver said:
What Comp cam grind number did you go with? Or did I miss that in one of your posts? I decided on the 252h for the stoker I'm building because it only increases the valve lift to .433" from the stock 95 H.O. 4.0 cam's .424", so my stock 95 springs should be fine. Which 4.0 head casting number are you running again?
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Sorry I missed this A6 X4 250H-13 is the grind number on my cam. Mine has .460 lift on intake and .476 on exhaust. Ive heard people run stock springs with this cam but they don't have enough spring rate.
 
Rescue Diver said:
I'm inclined to agree with you Tarry. What's the point in forking over major bucks for a roller setup in a motor that spends most of its life between 800 and 3000 rpms?
As far as reliability, a properly set up flat tapet hydraulic cam will easily last hundreds of thousands of miles. How much more would someone want??? :rolleyes:
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These arent race motors more like tractor motors lol :D
 
coldair said:
These arent race motors more like tractor motors lol :D
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Yep!

I've built more than a few race motors, and I've been known to fork over the bucks for roller cams and lifters, but I just don't see the point in using one in a CJ motor. The reason I went with a roller cam in my 69 Vette 383 Stroker was because I was shooting for serious hp at 8000 rpms, and I wanted to have some semblance of vacuum off idle. Flat tappet cams come stock in 4.0's, and 4.0's easily last 200k plus miles, so reliability isn't a good reason to shell out major bucks for a roller setup. And honestly, for a stump pulling rock crawler motor that isn't going to see much above 4000 rpms, there really isn't a good reason to go with roller rockers either. Of all the old stock motors I've torn down, I've never found a failed stamped steel rocker. In fact, the only time I've ever seen a failed stamped steel rocker, or for that matter even a failed stock pushrod is when they were being used on a high lift aftermarket cam. I consider above .480" valve lift to be a good low end threshold to start thinking about stronger pushrods and roller rockers, and .500" to .550" the low end threshold for thinking about a roller cam and lifters. Some people think they have to buy the best of everything, but the gains they get from them aren't even noticable.

I'm sticking with stock pushrods, stock rockers, and I'm running a cam that doesn't have much more lift than stock. Cheap reliable and strong low end torque is easy to achieve with these motors, without the need to fork out all kinds of cash for fancy expensive performance parts. :D
 
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i would have to agree as well. sorry, i have to remember we're not talking about 7500 rpm V8's with .600+ lift. yall are very right in saying that the necessity of a roller setup in the straight 6 is slim to none as they rarely rev past 4500, normal operation of 1000-2500, and we're no where near a radical cam grind that would warrant a roller setup. this whole conversation is fueling my desire to put a cam in when i do the head swap. :drool:.
 
That is :drool: ! Thats gonna kill the factory numbers. 80s era 258s were rated at 115 hp and 210 torque at 2000 rpms. Thats fresh from the factory , not with 32 years worth of wear and tear. :notworthy: That new motor is gonna "feel" good. :)

coldair said:
Pete I was messing around on Comp Cams Camquest selector I put in all the values for my motor this is what they say it should make. ( really hoping for this!!! ) 225 max HP 289.9 Torque :chug:
CamQuest – Select The Perfect Camshaft & Valve Train Components
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going to ask the questions in this thread since you did the 4.0 head swap.

will the AMC 258 i6 / 4.2l intake manifold work on the 4.0 head?

are the AMC 258 i6 / 4.2l and 4.0 valve covers interchangeable?

i have a clifford 4bbl intake and clifford aluminum valve cover on my AMC 258 i6 / 4.2l that i would really like to keep when i do the 4.0 head swap. i keep coming across mixed information on this topic, some say you can, some say you cant. my biggest concern is that clifford makes the intake that i have and another that is specific for the 4.0 head swap. thanks guys
 
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On the stock intake manifold you can use it with a little modification. No sure about the the clifford one. I know they will tell you the stock AMC 258 i6 / 4.2l won't work but I know of a ton of people that run them.
 
The other day bolted the valve cover on the head found out I have clearance issues with the mopar valve springs :censored: (springs are bigger around then stock ones) Tonight I ran across a great deal on a aluminum valve cover went picked it up and couldn't be happier :D payed $5 for it
 
justinfonder said:
going to ask the questions in this thread since you did the 4.0 head swap.

will the AMC 258 i6 / 4.2l intake manifold work on the 4.0 head?

are the AMC 258 i6 / 4.2l and 4.0 valve covers interchangeable?

i have a clifford 4bbl intake and clifford aluminum valve cover on my AMC 258 i6 / 4.2l that i would really like to keep when i do the 4.0 head swap. i keep coming across mixed information on this topic, some say you can, some say you cant. my biggest concern is that clifford makes the intake that i have and another that is specific for the 4.0 head swap. thanks guys
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Intake yes, valve cover no.

I'm running a stock early 80's intake on my 1995 #7120 4.0 head and it works fine. I just had to grind a tiny notch under the dowel pin hole and position the intake above the dowel instead of the dowel sticking through the hole. This is needed because the intake ports on the 4.0 are a lot higher than the ports on the AMC 258 i6 / 4.2l .

I wouldn't be surprised if your clifford intake is factory made to work on either head without any modification, but that's just a guess.
 
coldair said:
The other day bolted the valve cover on the head found out I have clearance issues with the mopar valve springs :censored: (springs are bigger around then stock ones) Tonight I ran across a great deal on a aluminum valve cover went picked it up and couldn't be happier :D payed $5 for it
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That makes me glad that I went with a cam that will work with my stock 4.0 springs. I kind of like my 4.0 aluminum valve cover. :)
 
Rescue Diver said:
That makes me glad that I went with a cam that will work with my stock 4.0 springs. I kind of like my 4.0 aluminum valve cover. :)
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Rescue I am using a stock aluminum valve cover off a 93 which is a 7120 head. Im betting its the same valve cover as what you have. I had to do some custom "machine" work to make that valve cover fit my 0630 head. As for the stock valve cover for the year of head I'm running it has the stamped steel cover which doesn't have as much clearance as the older aluminum ones.
 
coldair said:
Rescue I am using a stock aluminum valve cover off a 93 which is a 7120 head. Im betting its the same valve cover as what you have. I had to do some custom "machine" work to make that valve cover fit my 0630 head. As for the stock valve cover for the year of head I'm running it has the stamped steel cover which doesn't have as much clearance as the older aluminum ones.
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Really? I've always heard that the 91-95 aluminum valve cover from a 7120 head will bolt right in place of the cheaper looking stamped steel valve cover from a 96-99 0630 head? I'm glad you set that straight for me. I'm about to advertise my spare 7120 head on Criagslist, and I'd feel bad telling someone with a 96 or newer 4.0 that the head will be a clean swap with all of their parts. What machine work was needed to make the valve cover fit?
 
There is a lip that sticks down that needs to be taken off so the surface is flat. Wish I would have taken pictures before I took it off. I was excited that I didn't have to spend $100 on an aluminum valve cover. As this motor has cost me more then planned.
 
coldair said:
There is a lip that sticks down that needs to be taken off so the surface is flat. Wish I would have taken pictures before I took it off. I was excited that I didn't have to spend $100 on an aluminum valve cover. As this motor has cost me more then planned.
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Where is the lip located? Is it part of the wall that holds the gasket in place?
 
I beleave it does hold the gasket in place on the aluminum head. The stamped steel has a diffrent gasket made of steel and rubber.
 
Here's the lip I think Coldair is speaking of.

valve%2520cover%2520003.jpg


valve%2520cover%2520002.jpg
 
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