Jeep Strokers

I have a 4.6 stroker and twice now the center two cam bearings have failed, bearing 2 an 3 have been squished out from the cam journal like play dough in-between you fingers, 1 and 4 have wear, I thought maybe the cam was too big or to high spring pressure, low quality bearings, or cam walk, if it was cam walk would my distributor gear be trashed? Its fine but I have about 3/16" of lateral movement with the camshaft, it has the spring bolt I'm going to use a solid pin this time to make sure it has the proper thrust clearance, I talked to a lot of shops and most of them said I should polish the cam and increase clearance to allow more oil cushion, I've heard .002-.0025 and also .004-.005, everyone has their opinion, this time I'm using ACL cam bearings and a solid pin, the first cam I used was a bullet racing cams stage 3 217/223 .484/.494 with spring rate of 110 318 and going to try to use it again because it's what I have on hand, I don't want to put a stock cam back in because it has a lot of nice stuff in it, I'm trying to find a stage 1 cam but I don't know anymore what's good quality and if it will run ok, the second cam I had draw to low of a vacuum at idle and messed with the computer, don't k ow what brand or specs, a shop built the engine the second time, I would appreciate and advice info or other things to try and consider, thank you so far for all your help with this, it's been a huge stress and struggle, I just want that old jeep reliability back

Jeepking1995 wrote: ↑September 11th, 2024, 8:18 am twice now the center two cam bearings have failed, bearing 2 an 3 have been squished out from the cam journal like play dough in-between you fingers, 1 and 4 have wear

All Jeep straight 6 cam tunnels were line bored during OE assembly with the cam bearings installed. That procedure almost always resulted in material being removed from each bearing between the 8 and 4 o'clock position. Folks often mistake this machining as bearing wear during disassembly.

Maybe it's time to get out the bore gauge and measure the cam journal oil clearance. I would guess that the vertical clearance is very tight, less than .001".

318 open spring pressure? Good gosh, I’d find some different springs. Maybe something a little more livable for a flat tappet cam. It’s not a race engine, I’d look for something 90-100 seat and 250-260 open pressure. I’m no expert engine builder. Maybe Russ can chime in. If it’s a Bullet cam, call to see what they recommend.
I’d definitely use a solid pin to control cam walk.

dwg86 wrote: ↑September 12th, 2024, 9:14 pm 318 open spring pressure? Good gosh, I’d find some different springs. Maybe something a little more livable for a flat tappet cam. It’s not a race engine, I’d look for something 90-100 seat and 250-260 open pressure. I’m no expert engine builder. Maybe Russ can chime in. If it’s a Bullet cam, call to see what they recommend.
I’d definitely use a solid pin to control cam walk.

In total agreement. Not much to add other than from my experiences I generally don’t feel the need to go above 275 to 280 on the nose even from the most aggressive flat tappet cams that I’ve run.

This doesn’t necessarily pertain to you, but for some general information to put out there I found when you start getting up to 310 to 320 and depending how aggressive your cam is that 6k and above we start seeing pushrod deflection with a stock diameter 11/32 Chrome Molly pushrod so therefore you should consider stepping up to a 3/8 pushrod.

Keep in mind our Jeep pushrods are about a full inch longer than your typical small block Chevrolet.

Russ,
You sell drop in LS springs, as I remember. What are the specs on them? My info here is coming from looking at LS specs (Roller Cam) and 4.0L cam, and David Vizard books. Also, I do have a mini- stroker running with .450 lift. With LS springs vs lift, 90-95 lbs is about .550 lift. That is a behive spring. The 4.0L spring is a conical. So, both types do self dampen. Also, the retainers are lighter. I do have Melling 95 HO springs on a 4.0L head. They rate from 81-89 lbs at 1.640. I am using a Ford Modualr spring from PAC on the mini-stroker. 90 lbs at 1.640. Machining had to be done. I haven't run the other head.

man, that's a tough situation. really sounds like youre doing everything right, though. id say take a step back and maybe recheck your installation process if things are getting kinda squished. constant wear and tear seems normal, but it might also be worth looking at if youre using low-quality parts. weve all been there with the trial and error, but making sure everything is at its best quality can honestly save you a whole lot of stress. dont lose hope and keep on truckin!

I'm running 150 seat and 360 open. I did have the same issue you are experiencing but now I only use the ACL bearing and have not had an issue...yet. I was using a melling high volume pump. All spring/retainer clearances were checked and found to be good when they failed.

75SV! wrote: ↑September 16th, 2024, 4:34 am Russ,
You sell drop in LS springs, as I remember. What are the specs on them? My info here is coming from looking at LS specs (Roller Cam) and 4.0L cam, and David Vizard books. Also, I do have a mini- stroker running with .450 lift. With LS springs vs lift, 90-95 lbs is about .550 lift. That is a behive spring. The 4.0L spring is a conical. So, both types do self dampen. Also, the retainers are lighter. I do have Melling 95 HO springs on a 4.0L head. They rate from 81-89 lbs at 1.640. I am using a Ford Modualr spring from PAC on the mini-stroker. 90 lbs at 1.640. Machining had to be done. I haven't run the other head.

My drop in LS valve spring at 1.650 is 100 lbs at a spring rate of 34 lbs putting it around 285 lbs at a gross lift if .500