want to make my 3.8 into 4.2?

Topic: want to make my 3.8 into 4.2? (Read 1377 times) previous topic - next topic

want to make my 3.8 into 4.2?

August 01, 2008, 12:35:04 AM

i have 1986 3.8TBI .the crank went out ,just wasn't holding the oil pressure any more. the car ran great, started find but when i took the crank in to have it turned. the machine shop say the crank non-turnable. so i want to make it into 4.2 but still use my top end with intake/stuff. so my questions are;
1- from what parts 4.2 do i need and of what years?
2-can i reuse my block ?
3- what year 4.2 short block can i use with my heads and intake?

from what i can find out, the 4.2 is a stroked 3.8 . kinda like the 302 is of the 289V8 but im not sure because the years are different from the two.
i want to keep the car as V6 because in the next year or so ,i will be giving the car to my youngist when he completes high school. i figure the 4.2 would make more low end power to help in the city driving but still keep the gas milage up because my son allready has 2-V8 cars (1987lincoln VII LSC 5.0H.O and a 1979 T-bird with a400c) to get the low gas mileage with.

want to make my 3.8 into 4.2?

Reply #1 – August 01, 2008, 03:12:29 AM

well you will need the crank/rod/piston combo for sure. and yes you can use your existing block im about 90% sure on that and if you want a short block allt he 4.2's are gonna have a newer type head... which you can use yours on they mostly interchange. Here are some sites that may help you out
http://www.babpen 15s.com/editorial/ar/ar90134.htm
also talk with Supersix motorsports
http://www.supersixmotorsports.com/
I have talked with supersix and they are very helpful

this is another one Tom Morana V6 Racing
http://www.moranav6racing.com/category.html?CategoryID=32
I havnt really talked with these guys much mainly cause they are not in the united states and i dont want a big phone bill lol

Hope you can gather the necessary information thru these guys

want to make my 3.8 into 4.2?

Reply #2 – August 01, 2008, 09:23:15 AM

Have you considered a split port swap for the 4.2?

want to make my 3.8 into 4.2?

Reply #3 – August 01, 2008, 10:12:30 AM

NO, you can not use your block with that crank. point blank no if's ands or buts wihtout balance problems.

However,,, all bottom end parts fit like a glove (crank / rods / pistons).

the only 3.8 fox engine that would qualify for the 4.2 stroker option would be the 1988 motor.

want to make my 3.8 into 4.2?

Reply #4 – August 01, 2008, 11:06:29 AM

hmm my bad the crank front main journal difference. forgot about that lol

want to make my 3.8 into 4.2?

Reply #5 – August 01, 2008, 03:26:27 PM

someone over at FEP(plskjnkr or something like that) has done this with a pre-88 block, his was an '85 if i remember correctly.
there are probly others.
your right about the balanceing but I don't recall him complaining about the balance issues.
i think its safe to assume the 83-4 blocks wouldnt work with it though.

want to make my 3.8 into 4.2?

Reply #6 – August 02, 2008, 02:23:41 PM

Quote from: Ductape91;230175

someone over at FEP(plskjnkr or something like that) has done this with a pre-88 block, his was an '85 if i remember correctly.
there are probly others.
your right about the balanceing but I don't recall him complaining about the balance issues.
i think its safe to assume the 83-4 blocks wouldnt work with it though.

this is where i ran into a show stopper.

I had no idea what to do beyond researching. The crank was totally different meaning the leack of a balancer. The 4.2 is internal balanced like the 88 3.8 which makes is farily a direct swap.

since i did not do the conversion, maybe i should not talk but from all the reasearch and questions i asked, i didnt want to put all the work into it not knowing the dynamics or the consequences of all my work.

The 4.2 crank is steel , the rods are broken caps. Broaching the 4.2 rods means you can only go oversize vs a rod you find typically in the traditional index (if thats what you call it) caps.

want to make my 3.8 into 4.2?

Reply #7 – August 02, 2008, 03:57:51 PM

the_intimidator03:
thanks for the enfo. it looks like i need a 1989 to 95 short block but what years 4.2 crank and rods do i need?
on the secound site:boy ,8 grand for long block 3.8 ?why would we spend that kind money on just a v-6?

V8Demon; no change style of heads. want to keep the style i have. I need to replace my current 3.8 crank. so i'm just looking to do a stroker of some kind at this time.
before i would go through all the work split port swap , i would put a V-8 IN HER.

if you have to replace the crank. i allwise look for the easyier way to make more cubic inches! like
making a 289 into a 302,
making a 351M into 400,
making a 429 into a 460,
i see a 3.8 is a same bore as the 4.2. so i'm just looking to make it into 4.2... any help i would enjoy.