1989-91 360 roller cam engine questions

-
J

Jerry Miller

Active Member
Joined
Jul 26, 2023
Messages
33
Reaction score
9
Location
Virginia
My son picked up a factory 360 LA roller cam engine. We're doing a full rebuild, swapping to a carb and putting it in an older W150 truck. He's planning on running a CompCams 210/220 Hyd Roller ram with the stock roller lifters (good shape and we have a budget) The truck is lifted on 35" tires, 4 speed manual (no OD) and has 4.56 gears. (A bit low for this swap but he was rocking a slant six before!) So this cam is good for 900-5200rpm which is about right and has advertised duration of 264/274 and lift of .48 with 1.5:1 rockers. 112 lobe seperation.
Now this question. I know these 308 heads use valve rotators on the exhaust valves and need to swap the springs and retainers. I think the valve spring seats need to be cut down as well to get the proper installed height. I think the stock exhaust valves have the lock groove further down on the stem than most 1.60 valves. Is this right? If so, can we swap to a standard exhaust valve and probably not have to cut the seats? This would also give more room for the valve stem seals.
Planning to run the SpeedPro H405CP30 hypereutectic pistons with moly rings. These are flat tops with valve reliefs, which if all my math is close should be a 9.0:1 CR, or there abouts.
So, aside from the valve question, do you think this cam, pistons selection, a Holley 650 carb and a dual plane manifold will yield a 320-350 HP motor?
Oh one more thing, The timing cover has half the provisions for a mech. fuel pump. The right bolt hole is there, but has a raised boss on it. The left hole does not exist and the hole for the arm is just a recess (not a hole) I plan to machine it open, remove the raised boss and drill and tap the missing hole. I assume this location is correct and that Chrysler just stop machining them all the way so they wouldn't have to use a plate.
Be easy on me, I'm an ex diesel guy...we just had to shove more air and fuel at a stock engine, LOL
Jerry
 
Last edited:
Man,
99 views and no opinions? Just kidding around, but I would appreciate any info. I'm hoping to get the block and heads dropped off at the machinist some time this week. If anyone has any input, I would greatly listen!
Jerry
 
Do Not. I repeat do Not sink the valves to get the spring height. Use different retainers or shims. They have plus and minus height retainers. And yes standard car exhaust valves would work perfect.
Get a different timing cover.
 
Your fine with the 405's but if you haven't bought the pistons, I would go with the h116p's get it closer to 9.5cr. 308's are nice, Check between the valve seats to ensure there not cracked though, most are. Throw the rotators in the trash. Go with regular spring retainers. 320-350hp with your above mentions is attainable.
 
Jadaharabi said:
Do Not. I repeat do Not sink the valves to get the spring height. Use different retainers or shims. They have plus and minus height retainers. And yes standard car exhaust valves would work perfect.
Get a different timing cover.
Click to expand...
What he said times a thousand ^^^^^^ Also, don't cut the spring seats deeper in the heads. A lot of them are really thin in that area and you'll hit water jacket REAL quick.
 
Awesome. I’ll look into those pistons. You think 89 octane would still be do-able with 9,5:1. He’s a high school kid and has to feed the fuel tank. We’ll get the replacement valves and go from there. I didn’t like the idea of cutting the seats either. I appreciate the feedback on the HP. I really hope we don’t have cracks. I didn’t see any but I haven’t cleaned the heads well yet and the valves are still in them so not sure if they are starting to crack or not….or do they just crack all the way all at once?
 
Use the 4 groove passenger car exhaust valve, and appropriate retainers/locks.
 
Well just came in from taking a closer look and using a brass wire brush on them. I can’t see any signs of cracking at least to the naked eye. Here’s hoping! The only head issue now is I have 3 exhaust manifold bolts that decided to become a two piece design during removal. Planning to just mig some nut on and hopefully back them out
 
Last edited:
The only thing I did find during the tear down this weekend was a very shallow pit mark on the crank mains 180 degrees from the oil passage. I’m not sweating this. I think we can run standard bearings and this mark is in line with the relief of the bearing. Hoping to just polish the journals but we’ll see.
 
Jadaharabi said:
Do Not. I repeat do Not sink the valves to get the spring height. Use different retainers or shims. They have plus and minus height retainers. And yes standard car exhaust valves would work perfect.
Get a different timing cover.
Click to expand...
Thank you. As for the timing cover, is this just because they are so readily available or is there a reason not to do the machining? I do have the proper tools and know-how (that sounds cocky, I don’t me it that way) and feel it’s a good learning experience to teach my son to work with what you have, etc. Though there is one on eBay right now for 65 bucks….
 
I should have paid attention to the name Miller. Of course you would want to machine it. LOL okay yeah go for it if you got the machines to do it do it. But I wouldn't pay $65 for a front cover I'd give $30-35 but that would be my top dollar.
 
Jadaharabi said:
I should have paid attention to the name Miller. Of course you would want to machine it. LOL okay yeah go for it if you got the machines to do it do it. But I wouldn't pay $65 for a front cover I'd give $30-35 but that would be my top dollar.
Click to expand...
Trust me, nothing special about Miller. No e relation to the welders or the beer. I wish LOL!
 
67/6barracuda said:
Your fine with the 405's but if you haven't bought the pistons, I would go with the h116p's get it closer to 9.5cr. 308's are nice, Check between the valve seats to ensure there not cracked though, most are. Throw the rotators in the trash. Go with regular spring retainers. 320-350hp with your above mentions is attainable.
Click to expand...
I looked these pistons up. Thank you, I think this is a better fit for sure. So at 9.5:1 and a mild cam, is 89 octane do-able? Really trying to keep him from having to run 91 or 93, just because of daily cost for him.
 
You must log in or register to reply here.
-

Back
Top