Well guys, tell me what you think. I put a boost gauge in today. Holding it at wide open throttle pulling a pretty steep grade I hit 30 psi. The gauge is a genuine Peterbuilt Manifold Pressure gauge out of a 1979 Peterbuilt. The gauge was bought new a couple years ago so I am pretty sure it is right on. Is that typical of the 1st. Gen Cummins? Read my sig. I am bone stock except for the fuel being turned up about 20% and I have drilled out my stock air box with 9/16" holes all through it.

 

Looks good compared to my ~25lbs. max!

 

Thats impressive!!! I have a nonintercooled with injectors, pump cranked, and fuel pin and only hit 32-34, which I consider pretty good.

 

Seems a little high to me, but then again I know that the non intercooled trucks have pretty large injectors stock. 30PSI is totally safe, but get a pyro!!

 

mine was hitting 25 pis then when turned my fuel up a little it went to 28pis or little highter i think it good 4 a kid

 

Mine is turned up a bit more, but I believe my timing to be stock. I have seen 38 psi with it. The way I have it tuned now, I get about 34 psi backing out of it at about 1300 degrees with the hot needle still climbing. So, I wouldn't say it is high for what you have.

-Steve

 

Now on to my next question. Would replacing the stock H1-C with a HX-35 give me more boost, quicker boost, or what would be the advantage to doing this? Thanks in advance.

 

Depends on the size of the exhaust housing, but since the H1C and HX35 have smaller wheels than the 40, they should spool faster.

 

I was thinking a HX-35 with a 12cm wastegated housing.

 

The 35 with the 12CM will spool VERY fast. When I had one on my truck it seemed to spool almost instantly.

 

Will it help/hurt fuel mileage? My truck has the 3spd tranny. At 80 I am governed completely out. Zip--no more. If the 35-12 spools that fast will it hurt me on top end? Thanks!

 

You'll probably lose 1-2 mpg with the 12cm housing, especially since you'd be running higher RPM's with the 3spd auto. Also, on an auto the smaller housing doesn't make as much of a difference as on a manual truck.

 

Thanks. I am pretty happy with what I have. I think I will just leave well enough alone! Thanks for the info.

 

If I were you, I'd at least get a pyrometer. It's useful for keeping the pistons from melting, and it can be used to diagnose problems as well. It's money well spent.

Plus, it's fun to watch.

 

Or scary, if you're overfueled