Today I have been working on my front locker install and while under the truck seen both headgaskets are leaking coolant down my block.Must have just started cuz no coolant has made it to the ground yet, just some damp green areas on the block. So it looks like after the front end is back together I will be replacing the headgaskets.

So here is my question. What are the best gaskets out there for a 4.0? This will be my first time in a 4.0 so I wanna make sure I get the best parts possible so I aint doing it again next year,or sooner. I know in my 2.3's I only use Felpro 1035 headgaskets cuz they are proven to be the best out there. I dont wanna just get some 10.00 parts store replacement if there is something else out there that is proven to be the best.

I also am one of those guys who can not just complete a major repair without looking for ways to improve something. That being said I will have the heads milled,ported,new springs and valves installed.My good friend has his own machine shop and will do all this for me for pennies on the dollar.

Are there any good aftermarket springs for these motors or will a spring from another app fit these heads as a upgrade?

Also By milling the heads and bringing up the compression a tad along with the head porting does anyone see a problem with the stock injectors,ecm and maf making the nessesary adjustments to keep it from going too lean? These mods alone would prolly be the same as swapping in a hot cam{which I will not do}. With a cam swap do people have issues with lean conditions or the ecm not adjusting nicely?

 

how many miles are on your truck?

 

118k.

It still runs perfect and hasnt burned a drop of oil in the two years I have had it.

 

since your going to be tearing it down i would suggest a new timing chain and water pump

 

If your not changing the cam your TQ curve is going to be pretty much the same after porting. Maybe in the 5200-5800 rpm area you'll gain a little. But not to awful much.

What I'd suggest is just removing about 1mm of material on the intake side and then porting the exhaust side to have a constantly growing crossectional area. Take about 1mm off the ID of the seat and then continuously grow the port from there.. and matched to a set of headers. Prefeably stepped headers.

That way you'll reduce the delta P accross the head and maximize available TQ in the midrange.

Also, since your not boosting the motor and won't really spin it higher than 6k I'd just use OEM stock valve springs and OEM stock valves. They are about the lightest components you'll find. And they'll work fine with a 1mm ID cut. Maybe give the valve a 3 angle job if you'd like.

Besides.. if you want to spin past 5800-6000 your going to need to balance the bottom end. So you might as well just maximize the stock setup for mid range TQ.


But hey.. what do I know?
Rich

 

Rich,I wont be doing any of the head work myself. My good friend will do them ,he has done all my 2.3t heads and he builds motors for about 1/4 of the guys that run at Milan and even has a Pro 5.0 team as a customer.Once he gets the head it most likely end up with a 5 angle valve job cause I have never seen him do anything different for my heads and I know he wont be putting stock springs in them either.Like he always does,if there aint a aftermarket spring made for a 4.0 he will find one that will work.You wont find any NAPA boxes in his shop! The lower intake will get matched and I might look into a set of JBA's for it as well.I will prolly do the timing set also because I just seen on line how they are setup with the guides and tensioners and I am sure mine are wore by now.

 

Most SS valves are heavier than OEM sodium filled ones. And if your not going to spin it higher than 5500-5800 a stiffer spring and heavier valve will only cost you power. Not increase it.

I'm sure your friend is good at what he does. But science is science. Added mass and resistance to a engine that will only operate in stock rpm ranges.. is throwing TQ out the window w/no other benfiets. Now if you are going to boost the motor that's a different story. But not NA motors limited to stock rpms.

These are just my opinions for a stock 4.0L short block, stock cams, and ported heads.

btw, D said that up around 5800 you run against the limit of the stock bottom ends balancing. I've spun mine to 6500 and I agree. 5800 is where it starts to get "noisy". (Even with a ASP damper)


Rich

 

As for the valves that will be his call.If mine are looking wore he will replace them with whatever he feels will be best for my motor. As for the springs,I am not tryin to increase the spring rates,I just want a better quality spring.I have used parts store valve springs in some 302's I have done in the past and they were garbage before I knew it.I have no idea where these over the counter springs are made or who is making them but I have never seen any last more than a year when I have used them. Since then I have only used Crane,Comp and K-Motion springs in every motor I have had.

And I prolly will never even spin my motor past 5000rpm anyway so I aint lookin to make big power up top. Matter of fact the heads prolly wont even get much metal removed from the runners,I dont wanna make these lazy down low for a small gain up top.Most work will be in the bowls and the chambers and the valve seat angles so we can increase the flow numbers between .200-.300 lift where it would do the most good for a low rpm motor.