FSJ_Moneypit

Hello! This is a cams, pistons/rods, converter thread. I'm building up a 6.0 for a stock looking '89 Jeep Grand Wagoneer. The block is torn down and out at the machine shop for cleaning/honing and other work, but I'll be assembling it. I use the vehicle for vacations, joy rides, tent camping, and general errands. No towing. Hoping to get some guidance from the community.

The Goals
-Engine that mostly fits the feel of the Jeep, not too rough at idle.
-Reliable enough to take the family on trips.
-Starts/runs fine in cold weather (below 0, I live in New Hampshire)
-At east 14 MPG
-Good response

Here's what I have so far
-LQ4 block
-pressed rods
-rebuilt 862 heads
-4L80E
-Jeep weighs 4500 lbs
-stock suspension and tires.
-93 octane

Cams: TSP suggested their stage 3 truck cam. I am torn between that and Summits 8720R1. Not sure which way to go or even if there's that much of a difference, other than the price. Should I go with one of the other? What's a good idle range for these cams?

Pistons/Rods: The plan is to reuse the pressed rods just to save on cost, but I don't believe upgrading would be worth it my situation. Could be wrong. I have to replace pistons and want to take advantage of 93 octane so was thinking of going flat tops. That would be SC at 11.5:1 vs 10.5:1 dished. The DC I got using flat tops on the gofastmath calculator was somewhere in the mid 9s depending on head gasket thickness. Lots of places I read said that's too high but other people seem to run high comp like this. I'm up for going with forged pistons if that's going to give a greater margin of safety and/or increase compression further. My only concern is piston slap in cold weather.

Converter: Should I go with a stall or would the high comp negate the need? I just want to avoid any stumbling off-idle.

Thanks!

G Atsma

Summit 8720R1 is 218/227, .600, 112+2
TSP Stg. 3 is 216/220, .600, 114,112, 110 (choice) no advance shown ground in.
Summit's cam is basically a modern high lift version of the old GM Hot Cam
TSP's cam has slightly more intake duration, 7 degrees more exhaust duration, and a choice of LSA.
Your best bet here is to call them both with your situation and discuss it with cam pros.

Jake Wade

I personally would go a notch smaller for a family rig and fuel mileage concerns.. Something along the lines of a 212/218 .550 lift deal.

G Atsma

I agree with this. You need a cam that will idle smooth for flexible off road driving also. The cams you listed sacrifice torque at the bottom end of the curve, which you do not want for relaxed off road driving.

FSJ_Moneypit

Thanks for the guidance on the cam!

Before making this thread, TSP recommended their stage 3 based on the compression, engine size, and the fact this is a street vehicle. But, MPG and smoothness for a family hauler is more what I'm going for. It's just tempting to go for more power.

Looks like a BTR stage 2 V2 (BTR31218110) falls in that duration range and so does the Comp cams 54-424-11. Which one of these do you think would best suit my goals? LSA looks to be the biggest difference.

Also, leaning heavily towards using hypereutectic dish pistons to keep compression at 10.5/1 and tighter tolerances compared to forged. It should be good enough for how I use the Jeep. I will be measuring the bores once the block is back from the shop so I buy the right sized pistons. Any recommendations on pistons?

G Atsma

The BTR cam would work well, especially since moving to an OEM Tier 1 supplier to grind their cams.

wretched73

I run this cam on a 112LSA in my 6.0 in my heavy Silverado 1500. I have no regrets. Drives great everywhere

FSJ_Moneypit

Thank you all for the input on the cam choice. It's much appreciated!

This is my first time rebuilding an engine at this level so hoping the more experienced guys out there can give some advice. I have re-ringed and honed and engine successfully before, but this time I 'm hoping to be more thorough and avoid learning the hard way... again!

Got the block back from the machine shop. They honed it with a torque plate and main caps. Also had new cam bearings installed. Looks liked hey nicked the back cam bearing. Catches a fingernail, not hard but definitely feel it. Someone suggested using emery cloth to clean it up. Good/bad idea? I reached out to the shop. Hopefully things work out.

Here's the clean block!


Here's the bad bearing at about 12 o'clock.






I measured the bore sizes just to check for piston size. I measured it with the main caps on but no torque plate. The bores are within spec for the most part (4.0009-4.0014) but the top inch of the bores are a bit big... around 4.0020 give or take a few .0001. Will bolting the heads down tighten the top of the bores .0006 or so to bring it within spec (4.0007-40014)? Also, there was some out-of-roundness on some cylinders on just the top 2 inches of the bore. Worst one was .001 off. Too much? Will bolting he cylinder head down fix that?