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Old 03-19-2017, 09:11 PM   #21
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Originally Posted by yellowxj View Post
My cruising rpm is in the 2500-3000 range. I think 2700 is about 60. Rear is 4.10 gears. Th400 is 1:1 tires are 215/85r16.

One of my cyl isnt firing. Rocker arm is barely moving. Compression is great across all the cyl. Holds pressure too.

Jeep, bus, repeat.
Make sure it isn't something silly like a collapsed lifter or loose nut on the rocker arm first. GM hasn't had many cam failures since the 305's in the 1980's. Depending on actual cam setup, you can seriously improve on the power. Any RV cam upgrade combined with free flowing exhaust and air filter will help. If you have throttle body injection, adding a spacer to it will help move the power band into a higher rpm for better highway cruising. If you have a Central Port injection, you can use a cold air intake to add a little more power as well.
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Old 03-20-2017, 10:35 AM   #22
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Thanks Hops. Ive got big dual factory exhaust and a good cam now. Still wondering if i should keep the factory 4.10 gears or go to 3.73 or 3.21...both options i can find in the junk yard i think.

Jeep, bus, repeat.
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Old 03-20-2017, 12:05 PM   #23
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whats in that van an 8.5 or the 12 bolt ?

in my opinion a 3.73 gear is about the perfect mix of both worlds.. ive run a lkot of gesrts over the years and except for all-out race cars ive liked 3.73's..

if you had a 4 speed OD trans then id say the 4.10's would be great...

3.21's will definitely give you better highway, but in the hills you may end up a little underpowered.. but on flat ground 3.21's would give a very low cruise RPM..

if you have an 8.5, a lot of the caprices that were built in the 80s / 90s had 3.2x.. gears..
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Old 03-20-2017, 01:00 PM   #24
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Pretty sure its a 14 bolt rear. Theres a newer single rear wheel cutaway at the salvage yard with 3.21's i think. Pretty sure i just would have to swap hubs and brakes. Just not sure if the work is worth it. 2500 rpm @55 with 4.10 2300 rpm @ 55 with 3.73 or 2000rpm with 3.21

The big question is, pushing my box along the road at 55. Would the fuel economy change be noticable? Feeling like it might be. With 3.21's i could pull it to second gear and turn 2700 rpms at 55 for steeper hills?

Jeep, bus, repeat.
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Old 03-20-2017, 01:04 PM   #25
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Lemme know if you see any buses at the junkyard!
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Old 03-20-2017, 02:14 PM   #26
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Pretty sure its a 14 bolt rear. Theres a newer single rear wheel cutaway at the salvage yard with 3.21's i think. Pretty sure i just would have to swap hubs and brakes. Just not sure if the work is worth it. 2500 rpm @55 with 4.10 2300 rpm @ 55 with 3.73 or 2000rpm with 3.21

The big question is, pushing my box along the road at 55. Would the fuel economy change be noticable? Feeling like it might be. With 3.21's i could pull it to second gear and turn 2700 rpms at 55 for steeper hills?

Jeep, bus, repeat.
Before you take the time and $$$ to do any swaps I would install a manifold vacuum gauge. With the vacuum gauge you can determine how hard the engine is working.

If you are pulling above 12" @ 2500 RPM's then you should be able to step down a gear set or two. But if you are only pulling 10" I doubt you would be able to run gears any faster and see an improvement in anything. In fact, you might actually end up using more fuel in order to do the same work.
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Old 03-20-2017, 04:40 PM   #27
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Originally Posted by cadillackid View Post
ive run 15W40 in small blocks without issues.. though im sure theres some nay sayer that will tell me I shoulda never done that... but I was HARD on engines... ran em like I stole em.. Lots of tire smoke!... and wanted good heavy oil to handle the way I drove...
I and alot of other old Kawasaki enthusiasts run rotella 15w40 in our KZ engines believe it or not... I put over 200k on my 1100 and she still purred like a kitten... Shell must be doing something right...
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