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May 30, 2025 | 04:22 PM

#21

BCNUL8R

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From: Oskaloosa, Iowa

Quote:

Originally Posted by gametech

As with anything, be very careful with that. Steve Morris showed us what happens when you REALLY overspin a centrifugal. It damn near destroyed the entire dyno room, along with the motor and dyno, as well as sending shrapnel outside of the dyno enclosure.

I get it there are risks. I'm basing this on what I'm seeing tons of coyote guys do with p1x, d1x, and f1a-94 head units. I was curious how they are making so much more power with those same head units than LS combos can, so I dug into it. They are spinning them 20,000 rpm over the max recommended impeller speed and continuing to make more power. It's not like they are spinning them higher and not continuing to pick up major power either.

I don't know what head unit Morris was using and I'm not sure what guys with the really big blowers are doing. I've only researched what guys are doing with the newer street head units I mentioned have done.

I've honestly got a lot of parts that are probably near the breaking point and I'm aware of the risks. I'm only spinning 10,000 rpm over max recommended impeller speed now which only occurs about the last 900 rpm or so before the shift. They are 20,000 rpm over the max recommended impeller speed shifting at 8500+ rpm.

May 30, 2025 | 04:32 PM

#22

Keith

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From: Mefis

Quote:

Originally Posted by BCNUL8R

I’m the odd ball… I don’t have a back up built because I can’t make up my mind what I direction I want to go.

I’ve got funds set aside but can’t decide between using a sleeved lc9 or lsx block or a 388 or 427.

I just went 6.1 at 115 and added 2 more psi since then.

I found out the coyote guys are spinning Prochargers 15-20,000 rpm over max recommended impeller speed so I figure spinning it 10g over can’t hurt lol. It’s not that they become inefficient it’s the reliability of the gear set at those Rpm’s but it’s only for a second that it’s over the recommended range lol.

If I had the funds, I'd be willing to try this block with an L8T crank, 6.2 rods and some 4.125 1.115 compression height shelf pistons. 412 cubes, right in the middle of a 427 and 388.

https://www.summitracing.com/parts/s...make/chevrolet

May 30, 2025 | 05:40 PM

#23

gametech

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From: Stockbridge GA

They said max rated impeller speed of 65,000rpm, and it spun to 105,000rpm. Oops.

May 31, 2025 | 06:57 AM

#24

BCNUL8R

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From: Oskaloosa, Iowa

Quote:

Originally Posted by Keith

I'm not familiar with that block first I've heard of it honestly. The L8T crank is very interesting to me, but in one of the videos I watched there was something slightly different with the snout that caused issues with the balancer. I can't remember if he needed to machine the snout or the balancer to make it work. My issue is I'm a procharger guy and have no plans to switch to turbo. I may switch head units when the f1r-103 is released, but definitely staying procharger so I don't want to deal with any crank snout concerns.

That block is cheaper than the dart or lsx so I'm interested maybe there will be more data out on this before something breaks with me current combo. I plan on running the current combo another year or so or until it breaks which ever comes first.

May 31, 2025 | 07:00 AM

#25

BCNUL8R

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From: Oskaloosa, Iowa

Quote:

Originally Posted by gametech

They said max rated impeller speed of 65,000rpm, and it spun to 105,000rpm. Oops.

https://youtu.be/wE2kWLyzQZY

I'm only 11,000 or so rpm over max if my math is correct. F1a-94 max recommended is 72,000 rpm. I'm running an 8.25 crank pulley and 3.9 blower pulley. Step up is 5.4 and I'm shifting at 7300 rpm.

I'm seeing coyotes running the f1a-94 with 7.65 crank, 3.9 blower, and shifting at 8700 rpm which puts them 20,000 rpm over max recommended.

Definitely not pushing mine any further and wouldn't think of going 40,000 rpm over.

May 31, 2025 | 08:32 PM

#26

Pro Stock John

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From: Chicago, IL

Quote:

Originally Posted by Forcefed86

Depends on the year of the LM7 and the load you put on them. You want 2005+ some late year 2004's had the GEN4 rods, but its a crap shoot as to which ones. If its earlier than that, they have baby GEN3 rods and most don't get away with much more than 600hp. They can bend at much less if ya load them hard at low RPM or detonate.

Come to think of it, I don't remember what year my SBE Gen 3 LM7 is.

I've run this in 12 passes, and only half of the passes were decent I screwed on some and had tire shake on another.

Wallace says this is 920HP @ 3200 raceweight. This was on 18 psi (S485), 1.2 ramp, 15 total timing on E85. I'm hoping to run 5.30 with this ol' SBE then retire it.

Jun 1, 2025 | 04:08 AM

#27

Alaseh

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From: Denver, Colorado

I'd be happy with 750whp on pump gas honestly..

Jun 1, 2025 | 05:55 AM

#28

BCNUL8R

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From: Oskaloosa, Iowa

Quote:

Originally Posted by Alaseh

I'd be happy with 750whp on pump gas honestly..

We all said that once

It's much harder on pump gas since the tuning window is smaller. Probably wouldn't even need to gap the rings or anything at 750 if you were on E85.

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Jun 1, 2025 | 02:19 PM

#29

gametech

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From: Stockbridge GA

Quote:

Originally Posted by BCNUL8R

We all said that once

It's much harder on pump gas since the tuning window is smaller. Probably wouldn't even need to gap the rings or anything at 750 if you were on E85.

Unfortunately, I'm probably going to be testing that theory soon enough. I'm on the stock (other than heads/cam) low mileage ls1 in my gto, and I feel safe on the wastegate 8# springs, but I always wonder what is going to happen when I flip the boost controller switch and get greedy with the regulator ****. So far I have not turned it past 13#, but I haven't gotten to a dyno yet to see where that is in terms of rwhp. I just can't bring myself to pull a perfectly good engine just to gap the rings.

Last edited by gametech; Jun 1, 2025 at 05:59 PM.

Jun 1, 2025 | 05:46 PM

#30

Pro Stock John

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From: Chicago, IL

I think 750rwhp on pump gas is doable if the vehicle isn't too heavy and you read plugs. I've never messed with alchohol injection systems but some folks have good luck with them.