Yet another engine rebuild / replacement thread v8 options

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NMEXPAT

Well-known member
I have a 1987 county with a 3.5 L V8 with LT85 transmission. I've had this vehicle for a few years now. I simply love it.

The odometer is showing 300k km. I'm confident this is the original engine but unsure of any prior major engine work, like head gaskets, cam etc. When I changed in the intake manifold a few years ago the cam was showing some wear. I've put lots of miles on it since.

Well, yesterday I was checking the oil and its milky. Looks like I've got a head gasket leak. My radiator is not a dual use version (it's only coolant).

At the minimum it appears I must perform a head gasket job. However given the age of the vehicle and unknown engine internals along with inherit lack luster performance of a stock 3.5L v8 I was thinking of the following 3 options:
  1. Option 1. full Rebuild of current 3.5L V8, upgrade camshaft to crower, isky or kent. interested only in modest torque / power increase.
  2. Option 2. Replace 3.5L v8 with 4.2 or 4.6L V8. NO EFI. Transfer all required components from 3.5L v8 to new engine to keep mechanical / distributor based.
  3. Option 3 Replace 3.5 L V8 with straight 6 Chevy 250 or Chevy 292. again no EFI. Also requires me to change transmission and tunnel.
I'm all ears for feedback on these options or others I might be overlooking. To be clear I don't want EFI or an LS swap. I want to keep it mechanical. I'm not overly concerned about fuel mileage as well. Thanks
 
erover82

erover82

Well-known member
#2. Power of 4.6 is better, but I don't like that the piston stroke travels below the water jacket. I'd stick with 4.2 if you can live with a more modest power increase.
 
B

bboretsky

Well-known member
I did #3. With EFI. Could not be happier. You do not have to change anything on the LT85. there is a bell housing adapter that worked with that Trans. Happy to talk about the experience as I did the work myself.
 
jymmiejamz

jymmiejamz

Founding Member
Callsign: KN4JHI
It probably is the timing cover gasket that has failed, not the head gasket. Or if someone did a water pump recently they may have not put sealant on the bolt that goes into the water passage on the block
 
evilfij

evilfij

Well-known member
Setting aside the EFI issue and fix what you have as @jymmiejamz says (14CUX is the finest system ever fitted to a rover and I will die on that hill — I know few people agree). IMHO the 4.6 is just not worth the extra power over a 3.9 or 4.2. The liner and block issues scare me. Since the truck is already running (she’ll run with milky oil for a long time IME) I’d find myself a v-belt 3.9 or 4.2, take it apart and built it how I wanted (mild not wild), do a reseal, and get it ready to go as much as I could, and then swap it in in a day or weekend. The 3.5 are very stout, but it seems most all of them have/had cam wear issues. Obviously you can get to the same place with a 3.5/3.9/4.2 v-belt and a 4.6 block, but the main point being to make sure you have something good before tearing the truck apart (if for no other reason that to be able to move her around).
 
jymmiejamz

jymmiejamz

Founding Member
Callsign: KN4JHI
evilfij said:
Setting aside the EFI issue and fix what you have as @jymmiejamz says (14CUX is the finest system ever fitted to a rover and I will die on that hill — I know few people agree). IMHO the 4.6 is just not worth the extra power over a 3.9 or 4.2. The liner and block issues scare me. Since the truck is already running (she’ll run with milky oil for a long time IME) I’d find myself a v-belt 3.9 or 4.2, take it apart and built it how I wanted (mild not wild), do a reseal, and get it ready to go as much as I could, and then swap it in in a day or weekend. The 3.5 are very stout, but it seems most all of them have/had cam wear issues. Obviously you can get to the same place with a 3.5/3.9/4.2 v-belt and a 4.6 block, but the main point being to make sure you have something good before tearing the truck apart (if for no other reason that to be able to move her around).
Click to expand...
14cux is great except that you can’t get quality replacement ignition components
 
L

LRover

Member
I did your #2 choice with a 4.6 short block, Crower Hi-torque cam, 4bbl carb, electronic ign., headers, etc. with my 110. Non-EFI allows you to run the engine a little cooler with a lower temp thermostat which I think helps eliminate some of the problems with the 4.6. I had it for over 10 years, loved the engine, and it never gave me any issues. If I were to do it again, I think I would consider going with a Holly Sniper set up instead of a carb though.
 
N

NMEXPAT

Well-known member
bboretsky said:
I did #3. With EFI. Could not be happier. You do not have to change anything on the LT85. there is a bell housing adapter that worked with that Trans. Happy to talk about the experience as I did the work myself.
Click to expand...
Which bell housing adapter? When discussing this option previously I understood the LT85 put the straight 6 to far forward into grill area. Perhaps my understanding was wrong.
 
N

NMEXPAT

Well-known member
jymmiejamz said:
It probably is the timing cover gasket that has failed, not the head gasket. Or if someone did a water pump recently they may have not put sealant on the bolt that goes into the water passage on the block
Click to expand...
Thanks for the advice. I will look into that in the mean time. I have not checked that out.
 
N

NMEXPAT

Well-known member
I will be proceeding with the 4.2. I think I sourced a used one for a reasonable price. Thanks everyone for your feedback! It is greatly appreciated.
 
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