Hey guys,

Well I am thinking of building a high compression N/A (for now) 408 for my 2500HD but I have a few questions.

I am looking for a good mild, very high torque, drivable set up.

How is the durability on a moderately driven 408? I plan on using the Texas speed kit with Callies crank and rods with the weisco flat tops. And it’s all going in a LQ4.

I have been looking around and I am a bit confused about the highest compression ratio I can run safely on 93 pump gas, I would like to run 11-11.5:1 if possible.

I am trying to figure out what heads to run. Could I get to my CR goals with flat tops and slightly milled 317’s or should I go with 243’s? I will more than likely have the heads no matter what casting numbers ported.

Injectors… What would I need?

I think those are the only real big questions I have right now, but I know there will be more.

Thanks
kody

 

The only difference between 317s and 243s is the chamber size and the valves if the 243s cam from a Z06 instead of an LS2. In either case, you probably want a set of worked heads for flow.

Flat tops and 317s will get you around 10:1 CR using the GM MLS gasket.

408s are torque-monsters, so you should be set there.

11:1 is probably a good target for a street driven monster.

Injectors will depend on the H/C combo, as well as the intake manifold and TB option you choose.

How much power do you want to make? How much lope do want? How smooth do you want your DD?

 

Could I mill 317's to 11:1?

The only reason I ask about the heads is I can get my 317's milled for 100-150$ and if I can save there I will put that money somewhere else, like getting them ported.

If I could make 425-450 to the wheels I would be beyond happy.

As far as lope I want a pretty good chop to it. I just don’t want something that is going to be unbearable to drive.

Thanks
Kody

 

Hey guys,

I will be ordering my stroker kit either by the end of this week or next week!

Next thing on my list is heads then I can send my specs to pat-g and start working towards a cam.


Should have my 317's milled, ported and polished? or should look into some aftermarket heads?


Thanks
Kody

 

whats your plan for an intake?

 

Probably a TBSS.

Or would it be worth it to spend the money on a fast LSXrt?



Thanks
Kody

 

definately go with the fast lsxrt if you have the coin laying around. 11.3-11.5 is good for pump 93. some go higher without any issues. drivability is a personal opinion. i drive a 11.2:1 408 with a 247/255 .632/.632 112+4 cam, 4.30 gears and 4400 converter and it cruises through stop and go traffic like a prius (a loud prius lol)

 

I am really thinking about doing the LSXrt but the price really puts a damper on those plans.

I am thinking around 11.2-11.3 CR wise.


I know drivability is personal, and I have a high tolerence when it comes to that, but.... I am not the only one that uses it is where the problem is. So I have to keep that in mind.

How would a 3000-3200 stall multi disc circle D drive with 33's on a 4:10 rear gear?


Thanks
Kody

 

Hey guys,

Well I got my stroker kit ordered and I am saving for all my other parts.

I am thinking a 408 would do better with a 3000-3200 stall converter, the only thing is I do tow from time to time, and it is typically a pretty load. I know I would need a better trans cooler, but how would towing with a 3000-3200 stall go? and also how would it work with the stock LQ4 cam?

Thanks
Kody

 

So I just had my 6.0 stroked bored to 408 with eagle crank comp cam porter polished heads new valve size new rockers arp fasteners. Put the motor in first start got a horrible grinding noise sounded like flexplate or starter got stuck. So I started truck in nuetral and noise went away. Should I drive it? Or can you misalign something during reinstall?