Sled Pulling Rev Limiter - Help Needed
Thread Starter
Staging Lane
Joined: May 2013
Posts: 67
Likes: 2
Sled Pulling Rev Limiter - Help Needed Hi Guys,
Very curious what everyone will say and looking for assistance as I didn't get very much help on Performance Trucks. Over the winter I have assembled an LQ9 and have installed it in my pull truck for sled pulling this season. The name of the game for me will be RPM to beat the Big Blocks, and I need everyone's help in figuring out how high this motor will spin and stay together. Engine Specs:
- LQ9 Stock Short Block w/ LS2 Style Floating Rods
- 799 Heads Milled to 60cc, Hand Ported
- LS9 Head Gaskets
- Manley Race Valves
- BTR Dual Springs with Titanium Retainers
- Manton Series 5 11/32" Pushrods, .040" Oil Restrictors in Machining
- Stock Rocker Arms with BTR Trunion Upgrade
- ARP Rod Bolts
- ARP Head Bolts
- Tick SNS Stage 2 Camshaft (231/235, .625"/.605", 111+2)
- 42lbs Injectors, NNBS Intake Manifold, 92mm Throttle Body
Imagining that the engine would run to whatever RPM I desired, what would everyone say would be a maximum RPM before eventual detonation is inevitable? I have read a lot and seen that everyone shifts around 7,500 on the 1/4 Mile, but when sled pulling I'll be maintaining that RPM for around 20 seconds, and I know that may begin to exhaust the valvetrain after sustained high RPM. RPM is ground speed for me, and the more speed I can get the better I'll be.
I'm wondering what everyone thinks about spinning this motor 7,200 and sustaining it for 20 seconds?
Any help or guidance anyone can approve is greatly appreciated!
Very curious what everyone will say and looking for assistance as I didn't get very much help on Performance Trucks. Over the winter I have assembled an LQ9 and have installed it in my pull truck for sled pulling this season. The name of the game for me will be RPM to beat the Big Blocks, and I need everyone's help in figuring out how high this motor will spin and stay together. Engine Specs:
- LQ9 Stock Short Block w/ LS2 Style Floating Rods
- 799 Heads Milled to 60cc, Hand Ported
- LS9 Head Gaskets
- Manley Race Valves
- BTR Dual Springs with Titanium Retainers
- Manton Series 5 11/32" Pushrods, .040" Oil Restrictors in Machining
- Stock Rocker Arms with BTR Trunion Upgrade
- ARP Rod Bolts
- ARP Head Bolts
- Tick SNS Stage 2 Camshaft (231/235, .625"/.605", 111+2)
- 42lbs Injectors, NNBS Intake Manifold, 92mm Throttle Body
Imagining that the engine would run to whatever RPM I desired, what would everyone say would be a maximum RPM before eventual detonation is inevitable? I have read a lot and seen that everyone shifts around 7,500 on the 1/4 Mile, but when sled pulling I'll be maintaining that RPM for around 20 seconds, and I know that may begin to exhaust the valvetrain after sustained high RPM. RPM is ground speed for me, and the more speed I can get the better I'll be.
I'm wondering what everyone thinks about spinning this motor 7,200 and sustaining it for 20 seconds?
Any help or guidance anyone can approve is greatly appreciated!
To do this right you should be going with a solid roller and forged rotating assembly. If it's a budget deal I get that and would want to turn no more than 7200. Realistically you should only be there a few seconds at most on start and a few more seconds later in the run.
Also, why did you get oil restricted pushrods? The lifters do the restricting not the push rods.
Also, why did you get oil restricted pushrods? The lifters do the restricting not the push rods.
Thread Starter
Staging Lane
Joined: May 2013
Posts: 67
Likes: 2
Last season, when I ran, I spent a lot of time around 6,500-6,800 with a nearly stock LQ4 Junkyard truck. I added the Oil Restrictors to the Pushrods at the advice of Al @ Manton Pushrods. He recommended Oil Restrictors to keep more oil in the bottom end and stop from flooding the top end with oil during sustained High RPM. I'm wondering if I would be safer setting the limiter at 7,200 as well. Likely the difference between 7,200 and 7,500 won't be much in ground speed and will save the engine considerably.
TECH Fanatic
Joined: Jan 2018
Posts: 1,060
Likes: 198
I was hoping to see more ideas on this thread too, as I'm interested in sustained high RPM for road racing.
Which, incidentally, is another scenario where some people say oil-restricted pushrods are a good idea.
Which, incidentally, is another scenario where some people say oil-restricted pushrods are a good idea.
9 Second Club
Joined: Nov 2003
Posts: 13,616
Likes: 185
From: Norn Iron
In the grand scheme of things, 20 seconds isnt huge.. 1/2 mile run ? 1km run ? Standing mile would be longer than that...and often with more power
Likewise powerboats ?
I'm sure GM do much worse testing on their standard motors too.
Again no doubt there are hydraulic cams/lifters that could do that with ease..
Perhaps more important, oil, oil cooling, oil pump/flow, oil pan and engine cooling given you probably arent having a lot of airflow with that type of work ?
Surely whoever specced your cam should be able to tell you if your valvetrain etc is up to the job ?
And perhaps again on top of that.
There have been quite a few threads where people have bent rods on stock/SBE type motors when they've hit the factory ecu rev limiter. I've no idea what the ecu could ever be doing that might cause that to happen, but it is something to consider.
Likewise powerboats ?
I'm sure GM do much worse testing on their standard motors too.
Again no doubt there are hydraulic cams/lifters that could do that with ease..
Perhaps more important, oil, oil cooling, oil pump/flow, oil pan and engine cooling given you probably arent having a lot of airflow with that type of work ?
Surely whoever specced your cam should be able to tell you if your valvetrain etc is up to the job ?
And perhaps again on top of that.
There have been quite a few threads where people have bent rods on stock/SBE type motors when they've hit the factory ecu rev limiter. I've no idea what the ecu could ever be doing that might cause that to happen, but it is something to consider.
I'd consider a full solid roller or even a LLSR for your valvetrain. Contact Kip at Cam Motion and let him know what you're doing with the engine.
I'm sure you're working on that engine all of the time anyways. That will give you a little more power and a very stable valvetrain. It won't be cheap converting everything over, but I believe it'd be worth it in the long run.
Some good aftermarket heads to go with it, too
I'm sure you're working on that engine all of the time anyways. That will give you a little more power and a very stable valvetrain. It won't be cheap converting everything over, but I believe it'd be worth it in the long run.
Some good aftermarket heads to go with it, too
