Down on Power After Head Intake Swap
Down on Power After Head Intake Swap This spring I installed PRC as-cast heads, LS6 intake and converted the fuel system to E85. I retuned the car for E85 and based on the wideband etc. everything looked ok. Car drives good and seems strong.
Today I went to the track and the car is slower than before these mods. Previously with just a Torquer V2 and supporting mods it ran 12.4@119mph street tire 2.1 60ft. Now, with the heads, intake, E85 I could only a 12.8@115mph same 60ft.
Car was hot so I couldn't do much tonight with it. I'm brainstorming what could be wrong to lose maybe 80hp and the car still drive good.
Wrong pushrod length (I think this would cause other problems)
Not firing on one cylinder (possible, I'll pull the plugs)
One injector clogged or otherwise not working (I could hear each of them ticking)
Cracked ringland (no smoke, no oil contamination)
Bad tune (seems unlikely at WOT to cost that much hp and the wideband is ok)
Vacuum leak (this is a real possibility, I have noticed something like an exhaust leak and this was a used intake)
I'll pull the plugs tomorrow. I will also try to identify any possible vacuum leak.
Anyone with a similar experience, or other ideas to try?? I expected to be pushing 11's not running the same as I did with only headers.
Thanks - Brian
Today I went to the track and the car is slower than before these mods. Previously with just a Torquer V2 and supporting mods it ran 12.4@119mph street tire 2.1 60ft. Now, with the heads, intake, E85 I could only a 12.8@115mph same 60ft.
Car was hot so I couldn't do much tonight with it. I'm brainstorming what could be wrong to lose maybe 80hp and the car still drive good.
Wrong pushrod length (I think this would cause other problems)
Not firing on one cylinder (possible, I'll pull the plugs)
One injector clogged or otherwise not working (I could hear each of them ticking)
Cracked ringland (no smoke, no oil contamination)
Bad tune (seems unlikely at WOT to cost that much hp and the wideband is ok)
Vacuum leak (this is a real possibility, I have noticed something like an exhaust leak and this was a used intake)
I'll pull the plugs tomorrow. I will also try to identify any possible vacuum leak.
Anyone with a similar experience, or other ideas to try?? I expected to be pushing 11's not running the same as I did with only headers.
Thanks - Brian
Are the combustion chambers the same size on the old and new heads? Tune would probably need adjusted for better flowing heads. Specs on old and new heads? Compression ratio? You might want to pick up a good temperature gun. They are great for comparing cylinder temps, By comparing temps you can help narrow down the problem cylinder/injector is there is one.
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Joined: Jan 2007
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Just a couple of ideas, like you said, it could be a vacuum leak. Do you have a scan tool/ hp tuners? See what the map sensor is reading. Also, before you dig in too deep, take an infared thermometer and check the temp of each header tube, that will give you a good idea if you have a dead or weak cylinder. And more importantly, which cylinder it is.
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Stock heads were on the car, switched to PRC as-cast heads milled so now it is 11:1 compression.
After the cam the car was tuned at CARS Waterford originally, I forget his name but I'm not impressed with what they did. I used HPT to modify the tune for E85. The tune is using the MAF running in open loop and CARS did not adjust the VE table at all. They adjusted the PE table / spark etc. So the VE table is still wrong as I have not went back to fix this. The AFR at WOT is fine, I'll log it again tonight, but it is around 0.8 lambda which is ok for E85. I never had a wideband on the car before, so I do not know what it was previously.
I do have HPT and will pull the plugs tonight. I would expect if it is down a cylinder I should be able to see this in the plugs.
At this time I'm still inclined to think it is a vacuum leak at the back of the intake, I just don't know what impact this would have.
Brian
After the cam the car was tuned at CARS Waterford originally, I forget his name but I'm not impressed with what they did. I used HPT to modify the tune for E85. The tune is using the MAF running in open loop and CARS did not adjust the VE table at all. They adjusted the PE table / spark etc. So the VE table is still wrong as I have not went back to fix this. The AFR at WOT is fine, I'll log it again tonight, but it is around 0.8 lambda which is ok for E85. I never had a wideband on the car before, so I do not know what it was previously.
I do have HPT and will pull the plugs tonight. I would expect if it is down a cylinder I should be able to see this in the plugs.
At this time I'm still inclined to think it is a vacuum leak at the back of the intake, I just don't know what impact this would have.
Brian
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Verdad Gallardo When I purchased my ride it had a tune from CARS, and it was horrible lol. My new tuner is in Milford and has been phenomenal.
On a different note you ever head to Bakers car show on Sundays? There's also a big one in Hartland this Saturday as well
On a different note you ever head to Bakers car show on Sundays? There's also a big one in Hartland this Saturday as well
The infrared gun looks like a fun tool, I think I'll pick up one of those today! Pulling the plugs sounds easy but some are a PITA, I'll check temps first, thanks for the idea.
Yeah Sean at CARS is who tuned it and now I can see with HPT the minimal work was performed.
I talked to someone at Camaro Superfest that also had their car tuned by Jesse. Mike or Mark, I'm bad with names. My neighbor was a calibrator for crate engines so he has helped me, but doesn't have experience with cobbled parts like my car.
I haven't been to the Bakers show this year. I'll be at the car show this weekend at St Johns church. I planned to bring this car, depending on what I find wrong, but we will bring our LS4 Fiero.
Yeah Sean at CARS is who tuned it and now I can see with HPT the minimal work was performed.
I talked to someone at Camaro Superfest that also had their car tuned by Jesse. Mike or Mark, I'm bad with names. My neighbor was a calibrator for crate engines so he has helped me, but doesn't have experience with cobbled parts like my car.
I haven't been to the Bakers show this year. I'll be at the car show this weekend at St Johns church. I planned to bring this car, depending on what I find wrong, but we will bring our LS4 Fiero.
If you did not change pushrods when swapping the heads, that's part of your problem. On average the aftermarket casting PRC AsCast heads need a .050 longer pushrod than a stock casting due to the thicker deck surface. We still always recommend everyone to measure for proper preload with a pushrod length checker to be 100% sure on the length that you need.
Lonnie
Lonnie
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-Lonnie,
Heads were milled for 59cc... I bought 7.45 pushrods from TSP since that was the recommendation. Though I didn't check that they were correct. I think I'm good, but I'm not ruling anything out. I don't hear a lot of tapping, pretty quiet actually. Any other sign before pulling it apart that the pushrods are too short? Thanks for the feedback and great service when I purchased my stuff.
Heads were milled for 59cc... I bought 7.45 pushrods from TSP since that was the recommendation. Though I didn't check that they were correct. I think I'm good, but I'm not ruling anything out. I don't hear a lot of tapping, pretty quiet actually. Any other sign before pulling it apart that the pushrods are too short? Thanks for the feedback and great service when I purchased my stuff.
Teching In
Joined: Jun 2007
Posts: 39
Likes: 0
From: Barrington, IL
-Lonnie,
Heads were milled for 59cc... I bought 7.45 pushrods from TSP since that was the recommendation. Though I didn't check that they were correct. I think I'm good, but I'm not ruling anything out. I don't hear a lot of tapping, pretty quiet actually. Any other sign before pulling it apart that the pushrods are too short? Thanks for the feedback and great service when I purchased my stuff.
Heads were milled for 59cc... I bought 7.45 pushrods from TSP since that was the recommendation. Though I didn't check that they were correct. I think I'm good, but I'm not ruling anything out. I don't hear a lot of tapping, pretty quiet actually. Any other sign before pulling it apart that the pushrods are too short? Thanks for the feedback and great service when I purchased my stuff.
-Lonnie,
Heads were milled for 59cc... I bought 7.45 pushrods from TSP since that was the recommendation. Though I didn't check that they were correct. I think I'm good, but I'm not ruling anything out. I don't hear a lot of tapping, pretty quiet actually. Any other sign before pulling it apart that the pushrods are too short? Thanks for the feedback and great service when I purchased my stuff.
Heads were milled for 59cc... I bought 7.45 pushrods from TSP since that was the recommendation. Though I didn't check that they were correct. I think I'm good, but I'm not ruling anything out. I don't hear a lot of tapping, pretty quiet actually. Any other sign before pulling it apart that the pushrods are too short? Thanks for the feedback and great service when I purchased my stuff.
Lonnie
__________________
NOW OFFERING TSP BY YANK CONVERTERS
COMP - FAST - PACESETTER - WISECO PISTONS - LUNATI - CALLIES - NEW TSP BRAND CRANK & RODS - COMETIC GASKETS
RAM CLUTCHES - MOSER ENGINEERING - ARH HEADERS - ARP - GM BOLTS AND GASKETS - MSD - NGK
POWERBOND - ASP - PRECISION INDUSTRIES - YANK - CIRCLE D - AND MORE!
COMP - FAST - PACESETTER - WISECO PISTONS - LUNATI - CALLIES - NEW TSP BRAND CRANK & RODS - COMETIC GASKETS
RAM CLUTCHES - MOSER ENGINEERING - ARH HEADERS - ARP - GM BOLTS AND GASKETS - MSD - NGK
POWERBOND - ASP - PRECISION INDUSTRIES - YANK - CIRCLE D - AND MORE!
NEW NUMBER (512)863-0900
