KRC Pump

Badride · May 19, 2016

patooyee said:
I've heard of tons of people over-revving the cast iron pumps as well.

No one can afford those aluminum ones. It wouldn't seem like the difference in material would justify such a drastic price difference but I guess that's why I'm not in the casting business.

Make sure to read the link that drivermod posted. It's more accurate than my description. My understanding was roughly similar though.

I am think about buying one of the cast pumps. I am just worried about turning it to fast. How much over you think will be fine?

patooyee · May 19, 2016

Badride said:
I am think about buying one of the cast pumps. I am just worried about turning it to fast. How much over you think will be fine?

I have no clue. That's why I am interested in your question about speed as well.

Over-revving is an issue on LS engines because the crank pulley is bigger than the SBC's and the engines spin a bit faster. Combine those two factors and the ps pump spins about 2-3k faster on an LS than a SBC at redline. No one makes a ps pulley big enough to slow the pump back down to where it would have been on an SBC. It's frustrating to me that the industry hasn't dealt with this by now since LS engines have been so popular for so long.

Badride · May 19, 2016

patooyee said:
I have no clue. That's why I am interested in your question about speed as well.

Over-revving is an issue on LS engines because the crank pulley is bigger than the SBC's and the engines spin a bit faster. Combine those two factors and the ps pump spins about 2-3k faster on an LS than a SBC at redline. No one makes a ps pulley big enough to slow the pump back down to where it would have been on an SBC. It's frustrating to me that the industry hasn't dealt with this by now since LS engines have been so popular for so long.

I have it at 6,000 rpm the pump will be at 6,925 so that is 1,500 rpm to fast. May buy one and make my own pulley if I have to.

That is with a 7-1/2 crank pulley and a 6-1/2 pump pulley.

patooyee · May 19, 2016

Badride said:
I have it at 6,000 rpm the pump will be at 6,925 so that is 1,500 rpm to fast. May buy one and make my own pulley if I have to.

That is with a 7-1/2 crank pulley and a 6-1/2 pump pulley.

You would need about an 8.25" pulley to slow it down to the rated 5500 rpm max. A lot of guys don't have space for that big a pulley inside their frame rails.

Another option is underdrive crank pulleys but then you're screwing with water pump and alternator speeds as well.

jmf · May 20, 2016

Reinstalled and still nothing. Sending pump back today.

drivermod · May 20, 2016

Badride said:
I have it at 6,000 rpm the pump will be at 6,925 so that is 1,500 rpm to fast. May buy one and make my own pulley if I have to.

That is with a 7-1/2 crank pulley and a 6-1/2 pump pulley.

I know I had the 6" serpentine pulley on my pump but I cannot remember the size of my crank pulley. I think it was 7.5". This was on a SBC with the rev limit set at 6500. No issues. I didn't have the keeper welded in that pump. On Todds supercharged 3.8 (Silencer buggy) he was running the 4.2" serpentine pulley with a stock 7" crank pulley (6200 rpm rev limit). Almost double the recommended max rpm. He did pop the keeper early on (now I know why) but tig welded it on and never had another issue. Ran that way for 3 years without a problem out of the pump. His buggy gets beat down a lot too. I think their rpm limit is designed for long periods of continuous use like in a round track racing situation. I would have no concerns running a 7.5" crank pulley with a 6.5" pump pulley based on past experience.