Engine rebuild

kellymoe

Expedition Leader
OK, I have a 3.9 sittin in my garage that I have been putting off rebuilding. My 3.5 works fine but as you all know is guttless, even more so than the 3.9 If you were rebuilding the 3.9 what would you do? What cam, what carb, yes carb, I am running an edelbrock now. Headers or ceramic coated manifolds? The list goes on. What would be priority? I am not going to get a 4.0 4.2 or 4.6. I just want to build a nuce reliable field servicable engine. Thanks in advance.

Kevin
 

ntsqd

Heretic Car Camper
I've been around a couple 215's, but never have seen the metric model opened up so I can't claim any intimate knowledge of them. Forgive if my thoughts are redundant.

I'd go for low speed torque oriented mods as most of those also pay off in the higher RPM's.

Hard valve seats. Intakes too if the heads are known for being soft. Won't be cheap, but also will last if done right.

A little gasket matching & bowl work on the ports, nothing large or such. Just improve the low valve lift flow. That is the key ingredient to a port that works. Leave a step in the floor of the intake ports at the intake gasket so that any liquid fuel running down the port floor gets tossed back into the airflow. A good set of properly re-worked cylinder heads is worth every penny and can cost as much or more than the short block.

Balance it. Build it to rev to 8k even if it only ever will see 5.5k once in a great while. The subtle joy of a smooth running engine must be experienced to understand.

Look into crank journal treatments like "Cool-Case" hard nitriding.

Blueprint the oil pump and blend oil ports. Smooth transitions everywhere.

Baffle the oil sump if not already done. Don't need exotic hinged gates, just some baffles to keep the oil around the pick-up.

Look into windage solutions. Windage (oil whipped around & aerated by the crank) costs both HP and efficiency and is invisible. Be it a custom fab'd windage tray bolted to the mains or attached to the oil pan, or something off the shelf. Have a look at the "Diamond Stripper" from Moroso for a simple and very effective tray idea.
Control lifter valley return oil so that it does not drip onto the spinning crank on it's way back to the pan.
 

Yorker

Adventurer
kellymoe said:
OK, I have a 3.9 sittin in my garage that I have been putting off rebuilding. My 3.5 works fine but as you all know is guttless, even more so than the 3.9 If you were rebuilding the 3.9 what would you do? What cam, what carb, yes carb, I am running an edelbrock now. Headers or ceramic coated manifolds? The list goes on. What would be priority? I am not going to get a 4.0 4.2 or 4.6. I just want to build a nuce reliable field servicable engine. Thanks in advance.

Kevin

Email these guys they'll steer you in the right direction:
http://aluminumv8.com/
 

revor

Explorer
Crower 50227 Nice torque cam.

The 3.9 is basically a 215 with a bigger bore. Rings can be had reasonable Chris Davis posted the info on D-90 a while back I'm sure a search would yeild good info or call Chris.

Then just do all the stuff mentioned above. The 3.9 has hardened valve seats (Aluminum head) so no worries there, a three angle valve job really seems to help these motors.

While 3.9's don't seem to have a liner slippage problem you can bolt the liners to the block by drilling a 3/8 fine thread through the liner and the block down by the skirt then boring and honing, silly if the motor isn't going to see over 4500 RPM much.

Hone it, port match it, chamfer oil ports, nice RV cam. Ceramic coated manifolds (just say no to headers) Rhoads lifters work nice for the low end, GM TB injection off a 4.3. I'm an EFI snob sorry :) Done. You can reuse the stretch head bolts.

It's all SAE threads.
 

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