Badass Heads, Lost Power
10-23-2012, 08:56 AM
#22
Le Mans Master
Thread Starter
Looks like my initial dyno on 12.5lbs of boost. My issue turned out to be a bad lifter. I was told it was valve springs and then seat pressure. Change to better valve springs and then bumped up the seat pressure to close to 175lbs and still had the problem. Eventually I found out what the problem was.. Lifter completely failed and lucky for me I only had bent valves and a broken timing chain.
Lifters are brand new, not that one or more couldn't be defective.
I'm going to run the engine before I take the valve covers off to make sure the lifters are pumped up. Something I realized today is it starts up fine cold but is hard to start hot so it could be that the rockers are not adjusted right as they were adjusted before the lifters were pumped up.
10-23-2012, 09:19 AM
#23
Drifting
Do you have the spring data? What lifters? I can't remember what cam you were using, but which lobe is it on? It seems like every time I see people using the big 3/8" pushrods, big rockers, etc it's on a solid roller setup. There might be limits as to what spring pressures you want to run on a hydraulic setup are, but I've never ventured out to this area so it's a really interesting problem. I'm anxious to see what you find out thats for sure.
10-23-2012, 09:34 AM
#24
Safety Car
Boost PID is:
[PID.11]-[PID.51]
Log Manifold Absolute Pressure and Barometric Pressure.
Cal data for the sensor comes with the sensor shipment.
[PID.11]-[PID.51]
Log Manifold Absolute Pressure and Barometric Pressure.
Cal data for the sensor comes with the sensor shipment.
10-23-2012, 09:45 AM
#25
Le Mans Master
Thread Starter
Do you have the spring data? What lifters? I can't remember what cam you were using, but which lobe is it on? It seems like every time I see people using the big 3/8" pushrods, big rockers, etc it's on a solid roller setup. There might be limits as to what spring pressures you want to run on a hydraulic setup are, but I've never ventured out to this area so it's a really interesting problem. I'm anxious to see what you find out thats for sure.
10-23-2012, 11:01 AM
#27
Drifting
Ha Ha Ha! I like all the imput, good thoughts from most of you guys. I kinda agree it is a valve float issue, but whats causing it is still not conclusive. And like we talked about earlier Bill the size of the spring doesn't mean more pressure. I remember seeing the setup height of the springs being 18.14 etc... all in that range so just need to check spring presures Bill to see where there at. And go from there. The adjustment could always be off a little like we talked about.
10-23-2012, 12:54 PM
#29
How much bigger is the cross sectional area of the ports?
You also realize that different chamber = different timing curve, right?
I think you're on to something with the valve adjustment/float issue.
You also realize that different chamber = different timing curve, right?
I think you're on to something with the valve adjustment/float issue.
10-23-2012, 01:18 PM
#30
Le Mans Master
Thread Starter
Now sure if these will help but:
All Pros
Old 317's
They sure look pretty...
Last edited by 5 Liter Eater; 10-23-2012 at 01:42 PM.
10-23-2012, 06:50 PM
#33
10-23-2012, 06:57 PM
#34
Drifting
10-23-2012, 07:13 PM
#35
Drifting
1.847-valve lift which I don't remember I'm guessing .625" -coil bind 1.085 = .137 of clearance before reaching coil bind. You need usually a minium of .060 minimum clearance so. you end up with .077 that you could shim the springs if my guess is right. I'd probably put a .065 worth of shims in there and see what that gets you presure wise.
10-23-2012, 08:56 PM
#36
Drifting
What he said 
. I would pull a spring though and do all the measurments so you know what it was and will be set up to with the shimming. What cam lobes are they? Make sure the wipe on the roller rockers is good also.
. I would pull a spring though and do all the measurments so you know what it was and will be set up to with the shimming. What cam lobes are they? Make sure the wipe on the roller rockers is good also.
10-23-2012, 09:35 PM
#38
Drifting
Is that a Comp cam? looks like a LSL lobe, but the lift is not quite whats in the catalog for a 231 and 239 lobe, but it's close. The LSL lobes are up there on the agressive list, but worked fine for you on the old heads so....
10-23-2012, 09:50 PM
#39
Le Mans Master
Thread Starter
It's a a custom Comp grind by Brian Tooley. I need to look at the cam card but I believe LSL is the lobe. It did work fine with the old heads and stock rockers. BTW, I think the springs on the old heads were set at 140# closed pressure.
Last edited by 5 Liter Eater; 10-24-2012 at 09:56 AM.
11-12-2012, 02:20 PM
#40
Le Mans Master
Thread Starter
So I had a few of the springs tested. The 1.845" numbers on the heads are the installed heights and the 1.080" numbers are coil bind. At 1.800" the springs are at 160# and at .621" lift they are at 390#. At 1.780 they are at 165# and 410# at lift. I didn't have them tested at 1.845" but at that installed height I just don't think there is enough spring pressure for the heavy valvetrain (2.10" stainless intake, 1.60" inconel exhaust, both solid I believe, 3/8" thick wall pushrods, Jesel J2K's) in addition to what I'm sure is greter than a 2:1 backpressure ratio. You can see in the dyno graph that the issue is much less noticable on the wastegate pull.
I measured a few of the valve heights and found that the intake and exhaust spring pockets are different heights, off by ~.030". There is an extra .030" shim in the deeper pocket in addition to the .060" shim and .060" locator which are on all the springs. I can't really add more shims because the seal is almost up against the locator as is so I'm goint to get keepers that locate the retainer .050" lower and go from there shim-wise shooting for 180# closed if I can get that high but I don't thik I will be able to go lower than 1.760" installed height due to coil bind which will probably put me at ~170#. Going to try this first before getting new springs and/or downpipes.
Jesel makes a stand that is held down with bolts the same diameter as the stock rocker bolts but for some reason these heads were machined to accept larger bolts to hold the stand down. So if the Jesels are contributing to the valve float I couldn't go back to stock if I wanted.
I measured a few of the valve heights and found that the intake and exhaust spring pockets are different heights, off by ~.030". There is an extra .030" shim in the deeper pocket in addition to the .060" shim and .060" locator which are on all the springs. I can't really add more shims because the seal is almost up against the locator as is so I'm goint to get keepers that locate the retainer .050" lower and go from there shim-wise shooting for 180# closed if I can get that high but I don't thik I will be able to go lower than 1.760" installed height due to coil bind which will probably put me at ~170#. Going to try this first before getting new springs and/or downpipes.
Jesel makes a stand that is held down with bolts the same diameter as the stock rocker bolts but for some reason these heads were machined to accept larger bolts to hold the stand down. So if the Jesels are contributing to the valve float I couldn't go back to stock if I wanted.
Last edited by 5 Liter Eater; 11-12-2012 at 02:27 PM.