4.2

MikeB · #1 (**permalink**) 09-23-2005, 09:57 AM

ive done a little bit research on how to get a little more power out of my 4.2, turns out there are quite a few things you can do.....
the first thing i did was go to a junk yard and found a dodge 318 carb, it made a big difference in power. with this carb i dont have to downshift nearly as much as i did before.
After that i decided to put a riser on the carb, i took 2 stock carb plates and put them together so now the carb sits 1" off the intake instead of the stock 1/2", the only thing i had to do to make this work was get longer studs to bolt the carb down.
i also moved the coil off of the engine, i made a bracket and mounted it onto the fender. the reason i did this was because i heard that when those coils get hot, they throw a weaker spark.
I bypassed all my pollution control, but depending on where you live that might not be a very good idea. Where i live it isnt enforced at all, if it isnt where you live i suggest you do this too.
The best part about doing all this is it barely cost me anything to do and there is a signifant differance in power.

Junkpile · #2 (**permalink**) 09-24-2005, 08:56 AM

Quote:

The best part about doing all this is it barely cost me anything to do and there is a signifant differance in power.

It's a very rewarding engine to tinker with for that very reason. The factory sent them out in such a sorry state of tune that there's a ton of room for improvement on all levels.

I'd splurge for a header next, and then a good ignition.

MikeB · #3 (**permalink**) 09-26-2005, 10:04 AM

its pointless for me to run a header where i live, i would only be able to get any use out of it for 3-4 months. the winters are harsh, headers just rot out because of the extreme temperature changes from when it is running and parked. all the salt that they put on the roads doesent help either.
the next mod im going to do to that motor is going to be a head conversion, hopefully i'll get better fuel milage because that 318 carb really hurts the fuel economy, but the power is definitly worth it

Snitty · #4 (**permalink**) 09-30-2005, 02:48 AM

If you do a head conversion, use the stock manifold (actually a header) from the 4.0. Before installing that, I suggest using two pieces of 3/16" steel, 1"x3" or 1"x4" to weld up between the pipes right before the collector. This helps strengthen it to avoid the very common crack that they are known for

Junkpile · #5 (**permalink**) 09-30-2005, 10:12 AM

Quote:

its pointless for me to run a header where i live, i would only be able to get any use out of it for 3-4 months. the winters are harsh, headers just rot out because of the extreme temperature changes from when it is running and parked. all the salt that they put on the roads doesent help either.

T-304 stainless steel. I'd second Snitty on a factory older XJ manifold for a lowbuck solution, but if a header won't last, that won't either.

When you do the head conversion you will see an increase in power, but it will be much more impressive with a proper camshaft, intake manifold/carb, and header on it to make that head work up to it's potential.

judge09 · #6 (**permalink**) 10-08-2005, 04:02 PM

wont powder coated headers resist the rust?

Brad_Shep · #7 (**permalink**) 10-10-2005, 08:33 AM

i have a 4.2L i am going to be building up and what i am going to be doing is changing to 4.0L fuel injected w/a larger cam, Borla Header, and better throttle body. Any suggestions on a Cam? might sound stupid, but i love the lump of my mustang(E303 cam) so what type of cam would give me that for my 4.0L?

Junkpile · #8 (**permalink**) 10-10-2005, 12:42 PM

The factory computer is going to go nuts if you install too big of a cam. Comp makes a decent cam for the FI six bangers, but it doesn't really have that radical lope that you're looking for. It's close to the factory duration but has alot more lift. The long duration and big valve overlap of a monster camshaft isn't something that the factory setup is made to deal with.