Do I have PMR's
Post Fiend
Joined: Jul 2005
Posts: 14,582
Likes: 12
From: 21791
The main killer of PMR's is excessive engine speed, and way advanced injection timing. I know a guy on here who raced a kid in a ricer and got the engine up to 3825 and then the next week or so just going down the road POP the engine let go. As long as you keep the engine under 3400 you will be OK if you aren't close to 400hp, and the tuner knows you have PMR's. I dynoed at 309 on 37's with my old chip and with 32's and the new chip im hoping im in the neighborhood of 320/650.
New User
Joined: Mar 2006
Posts: 21
Likes: 0
From: Oregon
I didnt forget about this guys! It has been fairly crummy weather up here in Portland for the last month. I am planning on taking a look at mine this weekend. The build date on my motor is 01 Sep 00.
That and my 2 yr old son helped bring me a galss of wine and spilled it on the laptop. POOF!! Magic smoke gone.
That and my 2 yr old son helped bring me a galss of wine and spilled it on the laptop. POOF!! Magic smoke gone.
Senior User
Joined: Dec 2006
Posts: 230
Likes: 0
From: Cheyenne, WY
I disagree that excessive engine speed is the killer of PMR's.
The sole enemy of PMR's is cylinder pressure and since cylinder pressure is greatest at lower rpms, how can it be engine speed that kills them?
My engine made peak hp at 2700 rpms, compressive loads on the rod are greatest at that point, regardless of how fast I spin the engine.
What does go up as a function of rpms is tensile load, which could contribute to the failure of PMRs, but not nearly as much as cylinder pressure resulting in compressive load on the rod.
I do agree with you that advanced ignition timing is hard on them too, because that directly affects (read increases) cylinder pressure.
Just my thoughts.
The sole enemy of PMR's is cylinder pressure and since cylinder pressure is greatest at lower rpms, how can it be engine speed that kills them?
My engine made peak hp at 2700 rpms, compressive loads on the rod are greatest at that point, regardless of how fast I spin the engine.
What does go up as a function of rpms is tensile load, which could contribute to the failure of PMRs, but not nearly as much as cylinder pressure resulting in compressive load on the rod.
I do agree with you that advanced ignition timing is hard on them too, because that directly affects (read increases) cylinder pressure.
Just my thoughts.
Last edited by GREGROB; Feb 8, 2007 at 12:14 PM.
Senior User
Joined: Jan 2004
Posts: 205
Likes: 1
From: Houston, TX
I'll try to check on mine this weekend. It's an '01 that I ordered new in the fall of '00. I took delivery on 9/29/00. I checked the valve cover sticker, but the whole bottom half is torn off. Truck was built in Ky, but no idea about the engine.
-Craig-
-Craig-
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