what is the big end, i am sure i could shim my 4k kit and pick up some more rpm's. but what valve springs would be need to hold a 5k cummin's. i have the one's that came with my 4k kit how far are they safe to? just doing some research for the new toy. mike

 

rumor is the bottom end has a bit to much mass to keep spinning it safely. I ve heard that 4500-4800 rpm could produce large holes in the bottom, ie rod bolts probably strecth and break.

Since I did the 60 lb vlve springs its real nice to 4000 though.

 

New toy????
Scott

 

4,200RPM sustained will snap anything but a true billet cam.

If you get past 4,200RPM, a balanced botom end will run to 5,300RPM and then the Rods decide they'd like to re-locate.

Depending on boost, the valves will float anywhere from 3,500RPM to 5,000RPM.

My truck will have ~300Lb Valve Springs, and a balanced bottom end. I plan to buzz the motor quickly past 4,200 and keep it in the 4,300-5,200RPM band. That's where the power is planned to be on my truck. It's going to depend on your turbo if you can get it to flow that air....

Merrick

 

I buz mine to 4500 every time I drive it. Piece of cake. It purrs at 4500. Its been higher. 5000 plus with ease. My brother in law drove it last Christmas. He had never driven a 12 valve before. He wrapped it to 5000 rpm and held it there, in third gear for a long time.

No pieces have flown out of it yet.

60 lb springs, a few secret valve train tweaks, and a gov that will allow it....4500 is a few seconds away.

BTW, 60 lb springs are not 60 lbs. They are over 140 lbs of seat pressure.

Don~

 

ok then i will keep this info on the back burner, looks like i might be picking up a 95 reg cab 2wd auto. i have a ht60 for the big charger and have a line on a 40 for the top, but i will probably use a hx35 i have now. i am trying to come up with a 30 mpg truck that can run 11's. but it is killing me to pay as much for a tranny as the truck. thanks for the info guys. mike

 

DonM,

I will be rebuilding mine in the near future, probably starting in Jan. '08 (as soon after graduation as possible). I would like to have some of your engine parts (cam, valve springs, injectors, etc.), and would like some suggestions on others (pistons and coatings, rods possibly, and whatever else can be thought of).

If possible, could you "guide" me in the proper direction on some of the things that will be needed?

Scott

 

I am not 100% sure on this one, but I think I read somewhere that Jeff Garmon dropped a twin turbo 12 valve in a 1500 Dodge single cab short bed, and got 26 mpg and ran in the 12's

personally, I dont think your goals are un-reachable, but it will be a stretch

hope this helps

 

My wife and I were talking about project 11:30 last night. It would be tough, and take a lot of tuning, but I think it is doable.

 

DonM I would also like to know what these valve train tweaks are if you could please ...
Merrick so your saying unless I was to have a true billet cam 4200rpm or higher would snap the shaft? That sucks...

 

man this is a old thread

 

Once you get past 4,200 you'll be fine, but hover at 4,200 and it'll snap.

Drop me a PM if you are interested in a 12v motor.

Merrick