Change from 0331 head to 7120

[dwg86]

I was looking at the head on my 2003 wrangler and comparing it to the 7120 head that will be going on the stroker. I noticed that the earlier 7120 head doesn't have a hole in the front for the idler pulley. One can be drilled there, but would go into a water jacket. Has anybody dealt with this yet? If so what have you done to install an idler pulley?
I know on some head installs, you have to put silicone on some bolts because they go into a water jacket in the block. I thought I could do the same with the idler pulley.
Also what is being done to mount the coil pack? The 7120 head doesn't have the bosses to mount the coil pack. Maybe brackets bolted to the valve cover studs to hold the coil pack?

[SilverXJ]

I've put one on a 2000 XJ. It doesn't need the idler pulley bolt, so can't help you there. What I do for the coil rail is use some straps from the valve cover stud/bolts things to the coil pack. The bolts line up fine with the bolts on t he coil rail.

Where is this idler pulley bolt hole you speak of anyhow?

[dwg86]

Its on the front, left side of the head as you are looking at it (Right side as looking from the driver seat). The hole in the head is a little lower than the top, foward mount hole for the belt tensioner...if that makes sense.

[dwg86]

After looking at the 7120 head again, I found that it is not a water jacket but the area where the push rod goes thru the head. So I don't see a problem with drilling a hole in this area and sealing the bolt with RTV.

[Flash]

After looking at the 7120 head again, I found that it is not a water jacket but the area where the push rod goes thru the head. So I don't see a problem with drilling a hole in this area and sealing the bolt with RTV.

How about a blind hole and a stud. Would hate to see some one put to long of a bolt in down the road, and mess up a cam do to a bent push rod..................................




Flash

[dwg86]

The head thickness there is about 1/2 inch, but I do like the stud ideal....or making a bracket to hold the idler pulley. If I do drill a hole, do you think the head casting will be strong enough to support the tension from the belt without cracking?

[Shark]

why not use a XJ AC bracket with the idler pulley on it?

[dwg86]

Not sure what else I would have to swap, and I have all the brackets on my TJ. I am gathering and comparing parts as well as doing a lot of research. Got a couple of 12w cranks, 7120 heads, SBC 1.94 1.50 undercut swirl polished stainless valves, Mopar valve springs, 2 Moapr 30ab cams and lifters, a set of 258 and 4.0 rods, ARP rod bolts 2000 block and intake mopar performance head gasket, 11/32 viton valve seals to fit the SBC valves and the Jeep .531 valve guides. I am in no hurry as my 4.0 is running good, so if I need to fab a bracket...well that might be fun
I just noticed this problem when I got the 4.0 block to rebuild. It had the idler pulley on the 0331 head, so this drew my attention to it. When I popped the hood on my 2003 TJ, it was the same. My TJ is my DD so this will be a swap out when my stroker is done. Hopefully not too many problems. My backup vehicle is my toy...a 1979 fiberglass CJ-5 12 inches of lift and 400HP 401. At todays gas prices and 8MPG, I wouldn't want to drive the CJ too much. So I am learning alot from all you guys here on the stroker forum...I LOVE THIS PLACE!!!!!!!!

[Flash]

The head thickness there is about 1/2 inch, but I do like the stud ideal....or making a bracket to hold the idler pulley. If I do drill a hole, do you think the head casting will be strong enough to support the tension from the belt without cracking?

I guess I'm not familiar with this bracket. is there only 1 bolt holding this thing on



Flash

[dwg86]

The idler pulley has 1 bolt that holds it on. It goes through the middle of the pulley and has a spacer behind the pulley and bolts to the head. If I drill a hole in the the front left side of the head(left side looking from the diver seat), the thickness of the head in that area is only about 1/2 inch thick. Or I could make a bracket that attaches with the 2 upper bolts that hold the belt tensioner on, and turn 90 degrees in front of the head...kind of an "L" shape bracket. Maybe make it out of 1/2 inch thick cold rolled steel, 1 inch wide, and cut down the aluminum spacer behind the idler pulley 1/2 an inch.

[Flash]

The idler pulley has 1 bolt that holds it on. It goes through the middle of the pulley and has a spacer behind the pulley and bolts to the head. If I drill a hole in the the front left side of the head(left side looking from the diver seat), the thickness of the head in that area is only about 1/2 inch thick. Or I could make a bracket that attaches with the 2 upper bolts that hold the belt tensioner on, and turn 90 degrees in front of the head...kind of an "L" shape bracket. Maybe make it out of 1/2 inch thick cold rolled steel, 1 inch wide, and cut down the aluminum spacer behind the idler pulley 1/2 an inch.

I thing that would be the best plan if you don't want to up date all the brackets.

Flash