the rating on the 4.3L is higher than the 5.3L which is what gm is concerned with. as to the real reason the 5.3L and 4.8L is so close to the 4.3L in milage, that's simple, technology. back in 99' when you could buy both trucks still in the same platform (K1500 extended cab for example) in the old and new body style, the L31/5.7L had a 2mpg lower rating than the LM7/5.3L. If they were to build a 6 cylinder version of the 5.3L it would considerably outperform the 4.3L as well as get better milage. another thing to consider is that if you're referring to your truck, you have a 5.3L. a 5.3L is far from a big v8. 325 cubes is by no means big. the 4.3L has a shorter stroke, but a much larger bore. cubic inches per cylinder are more for the 4.3L than the 5.3L. smaller cylinders are much more efficient and therefore much better milage.

 

So, 7krpm's is a no go? Damnit. Well the 4.3 vortec efi in my wt with the t56 i could crank it to 6krpm with underdrives air raid tune ignition and tb spacer. So I thought with a good bottom end and a lightweight valve train I could get 7k easy.

So what is required for a "dry sump"? Itd have to have a front sump to fit in my car and Im not much of a ford guy so I'd have to go chevy. I love all sbc bbc and lsx motors but the 4.3 Ive had most experience with and I think they are the lil motor that CAN. I figure with a nice t56 behind it in a car that weighs 2200+motor/trans/diff/me and a mild build up I could get some 13's on streets if it'd hook and I figure a big lift back on the rear wheels with factory 4link, it can hook.

What is it exactly that will hold me back from more than 6k? Is it cause it will be carbed? cam? What is it. I want 7krpm gauranteed (track days only) or I will keep the beater 42mpg 1.6L donut eater in there.

Guys I beg of you help me....

 

Just boost it. Besids i would not want to run the split pin crank to 7k and beyond. I would look into 18 degree stuff if you want to run up to 7k and have 500 na hp.

 

Ok ive torn down some 350's but ive never heard of a split pin crank. This is new term to me. I really don't want to boost the motor, and Im not looking for large hp numbers. I want a really high reving engine and I figured the 4.3 would be a perfect platform to work with because...

1. Ive had a few
2. everyone does v8's
3. its a nice torquey motor
4. whats less comon: 13sec v6 car or 13sec v8 car?

I'd love to boost this sucker but truth is I dont have that kind of cash. But Im really interested in that dry sump. Know where I can find out about it?
I started to tear down the motor today starting with oil pan. Man the pikcup tube had sludge on it where I dont know how this motor had oil pressure.
I've got front and rear seals and main caps off and the rod caps. Bearings look ok but Ive got a new set on order.

Ill get a lil further tomorrow and Ill let you guys know what kinda mess I find, it looks like theres a hole in number 5 piston but I can really tell till I get it out.

 

thank you for the info. zippy