Motor falls flat after 6800
Thread Starter
Joined: Jan 2002
Posts: 4,072
Likes: 75
From: Casselberry FL
I spoke with Texas Speed (TSP) and Raymac Racing. The former built the assembled heads and the latter sold me my LS1 rev-kit and also has contracts for Nascar engines and the Craftsmen truck series engines.
TSP said the cam is out of it's RPM range by 6800. They said they setup the spring height to 1.81-1.82 when assembled. They suggested I could try reducing the installed height to 1.79 and that should take care of any valve float. They didn't feel it was necessary to shim to within .050 of coil bind for this cam. If adjusting the installed height didn't fix the issue, they said to look in the tune.
Raymac said I'm experiencing valve float. They also said the cam is out of RPM and when it gets that far out of it's range it will cause float. They thought I might be able to get another 100RPM by switching from 3/8" pushrods back to 5/16" pushrods (as well as some HP), but the best bet is to get a better valvespring than my current Platinum Duals sold by TSP. The have a drop-in kit which would get me another ~30-40lbs open pressure. They also said that Ferrea recently released a valve spring kit good to .670 lift, but Ferrea wants about $1000 for the kit. Um, no...
Raymac also mentioned that they always shim to within .050 of coil bind on street motors, and within .030 of bind on race motors.
So I guess I'll try swapping back to 5/16" pushrods just to see if there's any more power. If not, I'll keep the 3/8". I'm not sure if getting that extra 400RPM is worth the hassle of buying new valvesprings and installing them. But I guess for peace of mind I'll need to confirm the current installed heights.
TSP said the cam is out of it's RPM range by 6800. They said they setup the spring height to 1.81-1.82 when assembled. They suggested I could try reducing the installed height to 1.79 and that should take care of any valve float. They didn't feel it was necessary to shim to within .050 of coil bind for this cam. If adjusting the installed height didn't fix the issue, they said to look in the tune.
Raymac said I'm experiencing valve float. They also said the cam is out of RPM and when it gets that far out of it's range it will cause float. They thought I might be able to get another 100RPM by switching from 3/8" pushrods back to 5/16" pushrods (as well as some HP), but the best bet is to get a better valvespring than my current Platinum Duals sold by TSP. The have a drop-in kit which would get me another ~30-40lbs open pressure. They also said that Ferrea recently released a valve spring kit good to .670 lift, but Ferrea wants about $1000 for the kit. Um, no...
Raymac also mentioned that they always shim to within .050 of coil bind on street motors, and within .030 of bind on race motors.
So I guess I'll try swapping back to 5/16" pushrods just to see if there's any more power. If not, I'll keep the 3/8". I'm not sure if getting that extra 400RPM is worth the hassle of buying new valvesprings and installing them. But I guess for peace of mind I'll need to confirm the current installed heights.
Your spring heights are at 1.81-1.82? There's your problem. You are very far away from coil bind and your pressure is too low to pull that kind of rpm with those lobes. Depending on spring type and cam lobe, I usually set my springs up between 1.74-1.78". The springs on my TA (same as you have) are set up at 1.775". At this installed height, I get 170 lbs open and 450 lbs over the nose. I'd keep the thicker pushrods until you can futher isolate the problem. They're worth power.
__________________
2013 Corvette Grand Sport A6 LME forged 416, Greg Good ported TFS 255 LS3 heads, 222/242 .629"/.604" 121LSA Pat G blower cam, ARH 1 7/8" headers, ESC Novi 1500 Supercharger w/8 rib direct drive conversion, 747rwhp/709rwtq on 93 octane, 801rwhp/735rwtq on race fuel, 10.1 @ 147.25mph 1/4 mile, 174.7mph Half Mile.
2016 Corvette Z51 M7 Magnuson Heartbeat 2300 supercharger, TSP LT headers, Pat G tuned, 667rwhp, 662rwtq, 191mph TX Mile.
2009.5 Pontiac G8 GT 6.0L, A6, AFR 230v2 heads. 506rwhp/442rwtq. 11.413 @ 121.29mph 1/4 mile, 168.7mph TX Mile
2000 Pewter Ram Air Trans Am M6 heads/cam 508 rwhp/445 rwtq SAE, 183.092 TX Mile
2022 Cadillac Escalade 6.2L A10 S&B CAI, Corsa catback.
2023 Corvette 3LT Z51 soon to be modified.
Custom LSX tuning in person or via email press here.
2013 Corvette Grand Sport A6 LME forged 416, Greg Good ported TFS 255 LS3 heads, 222/242 .629"/.604" 121LSA Pat G blower cam, ARH 1 7/8" headers, ESC Novi 1500 Supercharger w/8 rib direct drive conversion, 747rwhp/709rwtq on 93 octane, 801rwhp/735rwtq on race fuel, 10.1 @ 147.25mph 1/4 mile, 174.7mph Half Mile.
2016 Corvette Z51 M7 Magnuson Heartbeat 2300 supercharger, TSP LT headers, Pat G tuned, 667rwhp, 662rwtq, 191mph TX Mile.
2009.5 Pontiac G8 GT 6.0L, A6, AFR 230v2 heads. 506rwhp/442rwtq. 11.413 @ 121.29mph 1/4 mile, 168.7mph TX Mile
2000 Pewter Ram Air Trans Am M6 heads/cam 508 rwhp/445 rwtq SAE, 183.092 TX Mile
2022 Cadillac Escalade 6.2L A10 S&B CAI, Corsa catback.
2023 Corvette 3LT Z51 soon to be modified.
Custom LSX tuning in person or via email press here.
Thread Starter
Joined: Jan 2002
Posts: 4,072
Likes: 75
From: Casselberry FL
We didn't check the installed height during motor assembly. The heads came assembled, and the local machine shop dis- and re-assembled them to mill the heads more. TSP says they're typically at 1.81-1.82 when they leave TSP. Having the local shop work on them throws in another variable.
So are there any how-to's around here for resetting the installed height? I've got a comp cams 4928 spring micrometer that I bought but never ended up using from years ago, but I don't have any experience installing valvesprings or altering the setup. To reduce the installed height, I take it I'll need some sort of shim... Summit lists a variety of ID and OD shims, what size do I need? Heck, I don't know how to determine coil bind either. Can I measure that or do I rely on published specs?
So are there any how-to's around here for resetting the installed height? I've got a comp cams 4928 spring micrometer that I bought but never ended up using from years ago, but I don't have any experience installing valvesprings or altering the setup. To reduce the installed height, I take it I'll need some sort of shim... Summit lists a variety of ID and OD shims, what size do I need? Heck, I don't know how to determine coil bind either. Can I measure that or do I rely on published specs?
Last edited by JimMueller; Feb 12, 2008 at 08:38 PM.
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YOU KNOW!!! I just had a deja vu..... I had an issue with my 234 cam and certain heads not carrying the way I thought it should. We checked pr length but never checked spring pressure DOH!!!!! Hmmmm. There is a common factor here is the only reason I mention it and thats the prc setup.
I had a custom ground cam. TSP set thier stuff up for their cams is my guess and no one takes that into account.. at least we didnt
I had a custom ground cam. TSP set thier stuff up for their cams is my guess and no one takes that into account.. at least we didnt
Thread Starter
Joined: Jan 2002
Posts: 4,072
Likes: 75
From: Casselberry FL
My previous cam which I spun to 7200 easily was a 228/228 113+1 (I think, bought used). I was using Comp 918's with them.
After a brief search, it looks like my friend has done this before from another post. How much of a pain is this with the heads installed? Can I just leave my RPM limiter say at 6600 for now pending setting the correct installed height or having better springs installed altogether?
After a brief search, it looks like my friend has done this before from another post. How much of a pain is this with the heads installed? Can I just leave my RPM limiter say at 6600 for now pending setting the correct installed height or having better springs installed altogether?
Int Dur / 2 + ICL - 180 = IVC
228/2 + 112 -180 = 46*
For its size, you have excellent power down low and up high. However, with an intake valve closing point of 41.5 degrees ABDC at .050", your ICL is probably a little too far forward and your duration is a little too small to give you big power at 7200 rpm. You would need more like a 46 degree IVC, more duration and more overlap to enjoy extended power in that area.
Thread Starter
Joined: Jan 2002
Posts: 4,072
Likes: 75
From: Casselberry FL
Some more questions ...
- Will my Caddy lifters have any problems handling the additional spring pressure?
- Does additional spring rate have an effect on spring life, guide life, or any other valvetrain component?
- Will my Caddy lifters have any problems handling the additional spring pressure?
- Does additional spring rate have an effect on spring life, guide life, or any other valvetrain component?
Yeah, you don't need to mess with the pushrods or springs to get more rpm. More spring pressure can be had if you are floating the vlaves, but you are not going to see any rpm gain with your current cam.
Jim, shim your springs to within .050" of coil bind, then retest. I'm pretty confident you can rev to 7200 with ease. I have a 224/230 cam in my TA and even with heavy 2.08 intake valves and 3/8" pushrods, it revs to the 7200 rpm rev limiter with ease. That's using the same springs you are, but with a 1.775" installed height. You'd be amazed as to what .040" of shimming will do for valve control.
__________________
2013 Corvette Grand Sport A6 LME forged 416, Greg Good ported TFS 255 LS3 heads, 222/242 .629"/.604" 121LSA Pat G blower cam, ARH 1 7/8" headers, ESC Novi 1500 Supercharger w/8 rib direct drive conversion, 747rwhp/709rwtq on 93 octane, 801rwhp/735rwtq on race fuel, 10.1 @ 147.25mph 1/4 mile, 174.7mph Half Mile.
2016 Corvette Z51 M7 Magnuson Heartbeat 2300 supercharger, TSP LT headers, Pat G tuned, 667rwhp, 662rwtq, 191mph TX Mile.
2009.5 Pontiac G8 GT 6.0L, A6, AFR 230v2 heads. 506rwhp/442rwtq. 11.413 @ 121.29mph 1/4 mile, 168.7mph TX Mile
2000 Pewter Ram Air Trans Am M6 heads/cam 508 rwhp/445 rwtq SAE, 183.092 TX Mile
2022 Cadillac Escalade 6.2L A10 S&B CAI, Corsa catback.
2023 Corvette 3LT Z51 soon to be modified.
Custom LSX tuning in person or via email press here.
2013 Corvette Grand Sport A6 LME forged 416, Greg Good ported TFS 255 LS3 heads, 222/242 .629"/.604" 121LSA Pat G blower cam, ARH 1 7/8" headers, ESC Novi 1500 Supercharger w/8 rib direct drive conversion, 747rwhp/709rwtq on 93 octane, 801rwhp/735rwtq on race fuel, 10.1 @ 147.25mph 1/4 mile, 174.7mph Half Mile.
2016 Corvette Z51 M7 Magnuson Heartbeat 2300 supercharger, TSP LT headers, Pat G tuned, 667rwhp, 662rwtq, 191mph TX Mile.
2009.5 Pontiac G8 GT 6.0L, A6, AFR 230v2 heads. 506rwhp/442rwtq. 11.413 @ 121.29mph 1/4 mile, 168.7mph TX Mile
2000 Pewter Ram Air Trans Am M6 heads/cam 508 rwhp/445 rwtq SAE, 183.092 TX Mile
2022 Cadillac Escalade 6.2L A10 S&B CAI, Corsa catback.
2023 Corvette 3LT Z51 soon to be modified.
Custom LSX tuning in person or via email press here.
Hmmmmm. I see. I will of course defer to PatrickG since he is far smarter on these things. I don't see why your new lifters would have any problem with the slightly higher spring pressure. Since your power peaks around 6,300 and carries to your current problem point of 6,800 why exactly do you need the extra 400 rpm? Is it gonna be a drag car or are you going to be doing rolling starts? Road racer where you might stay in one gear longer? 
Silver State Classic ??
Silver State Classic ?? You set your shift point beyond the max power so when you shift it doesnt drop out of the power zone...
You know this might explain a lot of the differences people see with the almost same combination... Spring pressure is not looked at enough. I didnt even think about it with the Term heads issue. Maybe that was the whole problem.
Is it the lobe and pressures that need to be matched?
You know this might explain a lot of the differences people see with the almost same combination... Spring pressure is not looked at enough. I didnt even think about it with the Term heads issue. Maybe that was the whole problem.
Is it the lobe and pressures that need to be matched?
Last edited by 99blancoSS; Feb 13, 2008 at 10:24 AM.
Thread Starter
Joined: Jan 2002
Posts: 4,072
Likes: 75
From: Casselberry FL
1CAMWNDR: Because at some RPM one gear has more mechanical leverage than the next gear due to the combined gearing of the transmission, the rear-end and the engine's torque output. So I may be making more force to the wheels in 2nd gear at 6900 than I would be by shifting to 3rd gear. I want to stay in the lower numerical gear until the force in the next numerically higher gear is greater. No, I don't drag race, from a stop or a roll. But the straights at Sebring are 3-5000' long and if I'm out of gear in 4th and still 100m from my braking point, then I have shifting decisions to make. Less shifting is preferred.
Thread Starter
Joined: Jan 2002
Posts: 4,072
Likes: 75
From: Casselberry FL
I found an old post of mine which indicates the current springs are already shimmed. It was the final post with no responses.
https://ls1tech.com/forums/showpost....8&postcount=17
Also, it looks as if my .050 IVC is actually 38.6 per the cam doctor report, so it's worse than 41.5
https://ls1tech.com/forums/showpost....59&postcount=6
https://ls1tech.com/forums/showpost....8&postcount=17
Also, it looks as if my .050 IVC is actually 38.6 per the cam doctor report, so it's worse than 41.5
https://ls1tech.com/forums/showpost....59&postcount=6
Last edited by JimMueller; Feb 13, 2008 at 08:59 PM.
