Changing Up My SBE LS3 Combo
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Joined: Feb 2004
Posts: 818
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From: VA
[QUOTE=old motorhead;20213195]I'm far from an expert. But, I believe that excessive preload (which you would get from pushrods being too long) will cause the valves to be held open once the lifters are "pumped up". At that point, you lose the hydraulic portion of the lifters and they essentially become solid lifters. As rpm rises, this becomes more pronounced.
I probably just butchered that all to hell. Maybe some of our more learned and experienced members can clear the fog I created.[/QUOTE
this was an issue back in the SBC day. These lifters don’t pump up like that. Some guys run ls7 lifters with just .010 left of travel for race applications because they have to use hydraulics.
I probably just butchered that all to hell. Maybe some of our more learned and experienced members can clear the fog I created.[/QUOTE
this was an issue back in the SBC day. These lifters don’t pump up like that. Some guys run ls7 lifters with just .010 left of travel for race applications because they have to use hydraulics.
[QUOTE=lazerlemonta;20213198] So, 7.4" pushrods took 1.67 turns past 0 lash to get to 22ft/lbs on the rocker bolts. The LS3 absolutely died at a little less than 6300 rpm with those push rods. Looking at the dyno sheet, I wondered why the tuner stopped the pull at 6250 rpm. Apparently, car owners can't talk directly to tuners in Houston, Tx. You have to go through the shop manager....Shoot. Never could get a straight answer.
Did my own testing and sho nuff, she quit pulling at that same rpm. Almost like a shut off and I know the red line in the tune was set at 6800rpm. I figured those stock length push rods were too long with the slight head milling and the thinner head gasket. The 7.35" pushrods I ended up with took about .67 turns past 0 lash to get to 22ft/lbs on the rocker bolts. It revs free and easy well past 6500 rpm now. You can draw your own conclusions, but I'm convinced that the push rods were too long initially and are just right now.
I'm far from an expert. But, I believe that excessive preload (which you would get from pushrods being too long) will cause the valves to be held open once the lifters are "pumped up". At that point, you lose the hydraulic portion of the lifters and they essentially become solid lifters. As rpm rises, this becomes more pronounced.
I probably just butchered that all to hell. Maybe some of our more learned and experienced members can clear the fog I created.[/QUOTE
this was an issue back in the SBC day. These lifters don’t pump up like that. Some guys run ls7 lifters with just .010 left of travel for race applications because they have to use hydraulics.
I probably just butchered that all to hell. Maybe some of our more learned and experienced members can clear the fog I created.[/QUOTE
this was an issue back in the SBC day. These lifters don’t pump up like that. Some guys run ls7 lifters with just .010 left of travel for race applications because they have to use hydraulics.
Did my own testing and sho nuff, she quit pulling at that same rpm. Almost like a shut off and I know the red line in the tune was set at 6800rpm. I figured those stock length push rods were too long with the slight head milling and the thinner head gasket. The 7.35" pushrods I ended up with took about .67 turns past 0 lash to get to 22ft/lbs on the rocker bolts. It revs free and easy well past 6500 rpm now. You can draw your own conclusions, but I'm convinced that the push rods were too long initially and are just right now.
So I follow Billy Godbold when I find time. He’s an absolute brilliant valvetrain engineer, and spends his time chasing what hasn’t been found yet, meaning he never stops researching. Billy has determined that valvetrain harmonics...just like ANY harmonic in a vehicle anywhere, engine, drivetrain, suspension, wheel, etc...will severely slow or stop an engine (or vehicle) from accelerating any farther at certain rpms. He’s stated that certain engines respond better to a lighter lifter preload, because it allows a faster recovery rate from harmful valvetrain harmonics. While other engines prefer a heavier or deeper preload because oil volume beneath the plunger is decreased, thus increasing lifter stiffness, affecting and absorbing harmonics differently.
Having said this, I’d suggest here in this situation, your engine prefers the shorter pushrods from a harmonics standpoint. Harmful harmonics will shock the springs into “shortchanging” themselves, basically shocking them into failing, before they actually are failing from load. Which either way the springs are causing valvefloat which is why most engines stop producing power, most of the time. Valve control is paramount in making power. So, in my opinion here, the change to shorter pushrods simply moved the harmonics in the valvetrain in such a way that the valvesprings are able to hold on for a few hundred more rpm.
Having said this, I’d suggest here in this situation, your engine prefers the shorter pushrods from a harmonics standpoint. Harmful harmonics will shock the springs into “shortchanging” themselves, basically shocking them into failing, before they actually are failing from load. Which either way the springs are causing valvefloat which is why most engines stop producing power, most of the time. Valve control is paramount in making power. So, in my opinion here, the change to shorter pushrods simply moved the harmonics in the valvetrain in such a way that the valvesprings are able to hold on for a few hundred more rpm.
Thread Starter
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Joined: Feb 2004
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From: VA
Little update. Finally got it back up and running. After many many hiccups along the way this thing is just flat out raunchy. I had 180 cranking compression with the old set up and now its at 210.... I was rolling the engine over putting my belt on and it hit a compression stroke and it was all i had with a 22mm wrench to pull it up lol Big thanks to John Mclaughlin, Jacob Selzer and Doug Clark for helping me get it going and the greatest group of guys in our chat group for the new Darth_V8r spec cam motion cam. I wanted it to have the most cylinder pressure we could get to utilize the ethanol to its maximum potential but not have to much DCR that I couldnt beat on it with 93 in the tank. All I can say is Jacob nailed it! You put this thing in 6th gear at 40 mph and set the cruise control with no issue and will accelerate under light throttle to 80mph in no time. Only bad thing is 1st gear is useless with the NT05Rs now on the street lol at 2500 they just give up and say screw you I dont get paid for this kind of work lol Little idle clip for you guys
Last edited by lazerlemonta; Apr 20, 2020 at 08:54 AM.
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I love ls3's. Is it possible to say that they're underrated? Or maybe just under utilized..
That light clutch is ridiculous.
Is that the RPS BC3 or back to the Canton small diameter?
Throttle response sucks.
Why cut off the video when it was just getting good?
That light clutch is ridiculous.
Is that the RPS BC3 or back to the Canton small diameter?
Throttle response sucks.
Why cut off the video when it was just getting good?
Thread Starter
9 Second Club
Joined: Feb 2004
Posts: 818
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From: VA
This is a quartermaster 7.25" triple disc now. Well The rest of it is just a slow shift to third and a short shift to 4th for a good pull in the log lol Was making sure the clutch was going to work properly as I had an issue with some air stuck in the line. Hopefully get a decent vid soon......
Thread Starter
9 Second Club
Joined: Feb 2004
Posts: 818
Likes: 215
From: VA
Hio has a draggy we can use but not sure when I can get back up there with everything going on in the world.....
This is a quartermaster 7.25" triple disc now. Well The rest of it is just a slow shift to third and a short shift to 4th for a good pull in the log lol Was making sure the clutch was going to work properly as I had an issue with some air stuck in the line. Hopefully get a decent vid soon......
How's the pedal feel with the 7.25" disk diameter? Is it heavier because of the small diameter? Will the 7.25" triple withstand repeated launches/street driving in traffic? I think your old 5" Tilton died being over heated and slipping if I remember? What's the deciding factor on clutch disk diameter?
The RPS is appealing because it should have very good heat capacity and life, but is still very light compared to stock. I have an RPS on the shelf with the steel flywheel to go in my car which will replace a monster LT1-S with lightened flywheel.
How do the two clutch types compare?
Your quartermaster looks like its popular with the road race guys too. Danny Popp used the same/similar one in his Optima challenge cars.
I'm salivating over the snappiness of the revs in your car. It sounds righteous and looks like so much fun.
Thread Starter
9 Second Club
Joined: Feb 2004
Posts: 818
Likes: 215
From: VA
You've had a few different very unique clutch setups in the car now. If you don't mind, can you share some more info about your experiences?
How's the pedal feel with the 7.25" disk diameter? Is it heavier because of the small diameter? Will the 7.25" triple withstand repeated launches/street driving in traffic? I think your old 5" Tilton died being over heated and slipping if I remember? What's the deciding factor on clutch disk diameter?
The RPS is appealing because it should have very good heat capacity and life, but is still very light compared to stock. I have an RPS on the shelf with the steel flywheel to go in my car which will replace a monster LT1-S with lightened flywheel.
How do the two clutch types compare?
Your quartermaster looks like its popular with the road race guys too. Danny Popp used the same/similar one in his Optima challenge cars.
I'm salivating over the snappiness of the revs in your car. It sounds righteous and looks like so much fun.
How's the pedal feel with the 7.25" disk diameter? Is it heavier because of the small diameter? Will the 7.25" triple withstand repeated launches/street driving in traffic? I think your old 5" Tilton died being over heated and slipping if I remember? What's the deciding factor on clutch disk diameter?
The RPS is appealing because it should have very good heat capacity and life, but is still very light compared to stock. I have an RPS on the shelf with the steel flywheel to go in my car which will replace a monster LT1-S with lightened flywheel.
How do the two clutch types compare?
Your quartermaster looks like its popular with the road race guys too. Danny Popp used the same/similar one in his Optima challenge cars.
I'm salivating over the snappiness of the revs in your car. It sounds righteous and looks like so much fun.
Last edited by lazerlemonta; Apr 20, 2020 at 03:01 PM.
Thread Starter
9 Second Club
Joined: Feb 2004
Posts: 818
Likes: 215
From: VA
The 5.5" weighed 16 pounds complete. Drove fine just couldn't handle me hot lapping the car and launches. Went to the rps which was 26 pounds complete but the moi is much greater due to diameter. That clutch drove great and I had no issue with performance I just missed the snappy throttle and instant acceleration. So after a few chats with hio I decided on a 7.25 and was going to use Ralley disc which are thicker but I could only get them in a twin. They rate these clutches with flywheel torque plus 30% so i was at the limit of the twin. I decided to go the triple which is rated to 950 torque. I had some issues bleeding the master and finally extended my speed bleeder (thanks to darth_V8r for the tip) to reach the reservoir and it is by far my favorite clutch I have had in it. It modulates nice and still only weighs 18 pounds complete. I am not sure how it will hold up to the track, but my friend had a 7.25" in his car with many passes and street miles and it still going strong. I made the 5.5" live through 30 passes in my 5th gen but on a drag radial and 10-15k miles of street driving. I know this clutch has a lot more surface area. The pedal is amazing as well as drive ability.
Our 8" converter needed to be adjusted for the 415" build vs SBE and we put an old 9.5" in to get the car running and despite dragging the bumper off the line, just perception wise the engine felt like dogshit when driving around anywhere other than WOT so I know how you feel. Put the 8" back in and the thing hits 6000 from a small blip. It is too much fun lol.
I have had a speed bleeder in my clutch slave since forever and honestly have never really used it. I've had so much luck bleeding from the master reservoir with the Mityvac. You make a seal to the port in the master cylinder reservoir and can pull the air out directly from the clutch line. It works wonderfully even on a new master cylinder installation which can sometimes be tricky. Found this video which shows it pretty well.
Congrats bud, its a great feeling when a combo gets sorted out. I ve been showing your vids to a few vette friends, including my engine builder. He s a huge fan of less is more. He says theres no reason for every vette to be a full send race car.