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edizzle89 Dork
9/12/18 2:26 p.m.
Mustang50 said:

How much is this going to cost versus the cost of a rebuilt 4.2L truck engine?

I was going to suggest this as well, i dont know alot about 3.8 to 4.2 swaps but i know i've seen it done in mustangs and i'd imagine the 4.2 is probably cheap and a bump in displacement has never hurt anybody (besides at the pump).

KentF Reader
9/12/18 8:28 p.m.

Mustang50 and edizzle89 you are correct a rebuilt stock 4.2 would be a much lower cost option.

Some quick research on the interblag indicates that would cost roughly $2000. Further research indicates my existing 3.8 already has more power than a stock 4.2 (I estimate Mistress generates in the 230 to 240 HP range based on air flow measurements - although at the moment it makes zero power).

However, with the addition of my existing camshaft, ported intakes and replacing the damaged head with new ported one the 4.2 would absolutely make more. Extra cost about $1200 for head, gaskets, etc.

So - Total cost of a re-built stock 4.2 with the existing modifications transferred to it would come in somewhere about $3200. It might not even need a new tune ($150)! I could easily justify going this route. It makes a lot of sense!

However, one of the goals listed long ago was to move to a Pro-charger, probably of the 7 - 9# boost variety. For a robust build (I hate tow trucks) this should be combined with forged internals, low friction coatings on piston skirts and all that rot. That is part of the driver for going with a full hardened rebuild of the existing engine. The dropped valve has simply moved up the timeline (and cut my season in half). And if you are going to do all that work the data shows it should be a stroker. The stroker will put out something like 30 to 40 Ft-Lbs more torque depending on whose data you want to believe.

Cost for this rebuild - Forged parts, stroker crank, etc. about $5000. Gaskets, ARP Studs, replacement head, etc. another $2000. Machining $500. This build will cost $7500 or so. Lot of money, will require interest payments ( I hate that).

The resulting 3.8 ltr should have as much or more mid range torque as a GT of the same era (it already has about the same power) and it is lighter and better balanced. It will be fully hardened and prepared for the power adder if I ever really add that (another $6k someday).

When I write up the article on driving the friends GT with my tires it will show some interesting results with tire limited cars on an autocross course. There is a reason people are putting 13" wide rims on the back of these things.

The result is Mistress should be a robust build good for long trips in the moonlight and afternoon delights (also known as one minute arguments) on course.

That is "The Plan".  As I said many words ago - It takes a bit of madness...

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