5 Liter Eater

I picked up a set of AllPro cathedral heads with Jesel J2k rockers a little while back. There was a miscommunication on the chamber size and they ended up bumping my SCR back up to ~10.9:1 which I initially didn't like but then I changed my mind because I was having to push the turbos to almost 20# to make good power when I had stock 317 heads at 10:1 so running less boost on hight SCR seemed like it would keep the turbos closer to their sweet spot. Anyhoo, they've been on the car for 2-3 weeks now and the car seemed like it was running well. A few days ago I threw my car on the rollers expecting to easily crack 900 RWHP and tark but it was not the case. The graph has what looks like valve float on 17# of boost while the wastegate run (~11-12#) didn't show that, although it was ugly too:


The traditional definition of valve float (the springs being too weak) seems unlikely as the springs are much larger diameter than stock, they almost look like solid roller springs. So one thought is that they have too much pressure and are collapsing the lifters or something similar which is causing a form of valve float. Another theory is that the heavier valvetrain (Jesel J2K's and Smith Bros 3.8" pushrods) is causing the valves to hang. Another theory is that since the heads are no longer a bottleneck, the exhaust backpressure is through the roof and causing the exhaust valves to hang open.

I plan to take some of the springs off and have their open and closed pressure determined but wanted to solicit anyone's input.

Here is the old dyno for reference on 18# and 19# with a 10:1 SCR and stock 317 heads. I liked the look of this curve much better...

silvzo6

hmmm curious what the issue is

White_Lightning

Clearly the problem... is that you are from houston

Is it possible your pushrods are to long? just throwing stuff out there.. i know a while ago some one had pushrods just a little to long and power up top tanked..

5 Liter Eater

Rocker adjustment is a good point too. It's possible the pushrods are too long but its more likely the Jesel rockers are out of adjustment. I got them to zero lash and went another 1/2 turn on the rocker adjuster which is .040". So theoretically the lifters have .040" preload. The lifters were new and not pumped up so it was a little difficult to determine zero lash but I'm fairly confident I was within ~.010" and definitely on the loose side, so .040" - .050".

White_Lightning

i know nothing about the heads. but is it possible to put less baller rockers on it "for testing"? or do you have to run these rockers for these heads?

ZO6er

Doesn't Viagra have something for that?

5 Liter Eater

I'm not sure but thats something else I will look at when I take the springs off. I know Flash has stock rockers on his AllPros but I don't know if my heads have been machined to accept the Jesels and are now incompatible with stock rockers.

White_Lightning

you could always start doing Cross fit and you Houston boys would be the experts on viagra

White_Lightning

were your heads run in the exact config they are in now? might want to check. seems odd that with such baller heads its falling off up top.

ajrothm

Damn Bill, that sux man.. Assuming the 17 psi the same level you were running on the 879 pulls, it looks like you are down on power all the way across the board.. Seems the power comes in a little later or it's just down. You would think the 2 point bump in compression would have gained you more power across the board, plus the gain from better flowing heads.

You definitely have some serious valve float going on at higher boost. Are the heads/springs new? It straight up looks like soft springs to me, especially with the heavier valve train. (I fight this on my BBC). I don't think your preload has anything to do with this personally..


It's pretty depressing to spend some good loot to gain power and go the other way....it has happened to me countless times..


No doubt you'll figure it out though....

I'm subscribed that's for sure. Good luck!

Icevettez06

If you have valve float I would think it would not be boost related. Usually valve float is high RPM related. I would think you had lost some boost psi 5600-6300 RPM.

5 Liter Eater

Alan, yea I had weak spring valve float in my A&A C5 and it looked exactly the same, ~100 HP dip in the graph at almost the exact same place. I agree it looks down on power even before the valve float starts. IT was a 1 point bump in compression and that coupled with the extra airflow from the heads has me SWAG'ing that 16-17# should equate to the old 19# numbers. Not sure though.

Ice, I do my own tuning so I was logging each run. Boost was steady between 16# and 17# from 4000 on. AFR was high 10's, low 11's and timing was 14-15 degrees.

ajrothm

Boost and nitrous both will definitely aggravate a valve float issue. I see this all the time on the turbo bikes I build. We spin em to 12k+ and on NA they are perfect.. Put 10 psi of boost thru em on stock springs and they will show power loss at high rpms just like Bills, sometimes even go into full float and sputter/back fire. We have even had a couple that pushed the keepers out and dropped valves.. Good springs are a must for boost. Spring rates must be sufficient for the RPMs, weight of the valve train and amount of cylinder pressure (exhaust valves).


Bill hopefully it's just a spring issue. You shouldn't need more then 160/450# assuming your intake valve is not TOO big or too heavy.

On mine we did a 2.16" hollow stem intake valve and my final setup was 155/410#. This is with heavy 7/16" and 3/8" 1 piece hardened push rods from Trend. Using stock rockers. I am hoping I have no issues at 7k.

It may be as simple as your installed height is off.

I hope you figure it out soon!

Icevettez06

Ice, I do my own tuning so I was logging each run. Boost was steady between 16# and 17# from 4000 on. AFR was high 10's, low 11's and timing was 14-15 degrees.[/QUOTE]

Bill.

What do you use to log the Boost? Can you log it in to HP Tuner? I´m like you I need to do me tuning as well but without the dino.

Ingó

5 Liter Eater

I have run 2.5 bar speed density but even with a MAF tune you just need to have a 2-2.5 bar MAP installed and the MAP linear and offset adjusted for it. Then HPT see's up to 256 kpa and you can create a custom PID to turn that into boost. DSteck makes custom MAP sensors like the one I made for mine.

5 Liter Eater

Yea I agree that should be plenty. Donno when I'll take them off but when I do I'll have them checked for installed pressure, open pressure and coil bind.They are just so damn big I can't imagine them not having enough pressure. Got to be the other way around but I've never dealt with that.

madmax4499

I say look at your post#4 I think you are holding the valves open with your adjustment.

also check your plugs, im guessing you are on pump+meth,

anytime i play over my limit on pump fuel 700rwhp, i dump the pump, and spend a 100.00 on 5 gal of c-16, it's cheap insurance!

why mess with so little timing and over rich AFR's

ajrothm

Bill, you need to measure the installed height of the springs so you will know where to set the spring tester up at. You can get a cheapy spring height tool from jegs.

You may have plenty of spring but if the installed height is wrong, both the seat/open pressures will be off. I kind of doubt this as well but...it's the only thing that makes sense. It doesn't really take a lot of spring pressure to keep these under control.. Especially with stock lifters.

The whole deal still sux for you though. I feel for you man. If you need a hand, lemme know. Out of curiosity, I wonder how heavy those Jessel rockers are on the nose? Usually shaft mounts help with valve train control since their weight is not supported by the spring but.... Just thinking out loud..

Vince99FRC

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.

Icevettez06

Ok. I have sensor from DSteck. I just need to install it and find out the custom PID.
Thanks.