Originally Posted by CadCaman
Twin stick, thanks for the reply. Any chance I can get your opinion on TBI vs. MPFI?
1. What is the best kit to buy?
2. What kind of performance improvement can I expect?
3. Do the kits come with a cam position sensor?
4. Does the fact that I have a 4.0 head on my 4.2 block mess anything up?
5. Do I have to weld on an oxygen sensor?
6. Does the fact that I have no smog stuff left complicate things.
7. Does the HEI have to go away?
Just to give a little different slant on your fuel injection questions.
1. It depends on what you want. If you want to be able to tune/tweek the fuel injection system on your laptop, then you may want to look into an Accel DFI - http://www.hesco.us/shop.asp?action=...99&catId=21873
. The MOPAR kit isn't adjustable, so if you want to mod your engine (bigger cam, exhaust, etc.) you may have problems - http://www.hesco.us/shop.asp?action=...116&catId=7577
. Call the people at HESCO, they sell both kits and are very knowledgeable.
I would seriously consider a TBI injection kit such as HOWELL or AFFORDABLE FI. You keep your HEI, Clifford manifold, no crank position sensor (one less sensor) and save better than half the cost of an MPFI kit. Also, the GM sensors are cheap and readily available. The 4.0L and 258 are not high performance engines. So for that $2300 to $3000 MPFI kit you get, maybe 5 HP? It always struck me as funny that AMC/Renault (later MOPAR) slapped a sophisticated multi-port, sequential fuel injection system on a "pig".
2. Fuel injecting a properly tuned carbed engine will not necessarily increase (minimally at best) increase horsepower/torque. With a MPFI you may get a slight increase (doubtful). Actually, factory FI systems are tuned as a compromise between fuel efficiency and emissions control. Performance is not the top priority. If the FI kits increased power by 20 to 40 horsies, wouldn't they advertise that in great big RED letters? The beauty of fuel injection is the reliability and efficiency over a large range of conditions.
3. Yes and no.
4. Don't believe so.
5. You will need to weld an O2 sensor bung to the down tube. Any muffler shop should be able to do this. http://www.summitracing.com/parts/SUM-G2990/
6. Don't believe so.
7. Maybe yes, maybe no. Depends on which FI system you go with.