Are your YT rockers the latest beefed up version? They are certainly heavier than the previous version that had the breakage issues.
I believe my Vette lost a bit of rpm when I switched. But it's not a scientific study.......
I'd put stock rockers in, but have concerns about the guides in the AFR heads.

 

Looks like valve float on the exhaust side? I posted up on yellowbullet and someone said if you can see a star or * pattern on the valve tip its floating. If you look closely at the picture you can see a star pattern. Interesting too because the intake lobe is LXL and exhaust HUC lobe. They are PAC 1905 springs from BTR. I specced out huc intake and exhaust lobe on my buddies orange car and he has no problem spinning to 7500 rpm with 26.5 psi so far but hes using stock rockers.

They are the 1.7 ultralights but how do I know what version they are? Here are some pictures. If I really am floating the valves I'm pretty damn excited right now. I went 9.6@142 mph with the stupid air filter on (100hp loss) and floating valves maybe? This bitch is going to fly when I add another fuel pump and some 3.40 gears on 25 psi.

 

I grabbed my old busted YT's and yours are the latest version. The early ones were thinner in the trunion area.

The star pattern is a good indicator.

What heads?

Got a nice set of stockers? Some sort of trunion upgrade, and prob diff length pushrods and give it a whirl.

I've got stockers on my 5.3 and it has no rpm issues

Ron

 

Yeah, you have the good set of rockers (Version 2 if you will). I have the same set on my car, and I pull the car to 7200rpm as well. They shouldn't be giving you any problems at all. The springs SHOULD be good too. Best thing to do obviously would be to check the seat pressures and stuff like that on the springs. It would not be impossible to get a bad spring, or have one that prematurely might have gone bad.

Also, I don't think a roller tipped rocker is going to give you as much of that star pattern as a non-roller (Like stock) tipped rocker would.

 

They are just stock 317 heads. A buddy has a set of stock rockers I'm going to try. You think I will need a shorter pushrod ?

 

When I clicked the car in 3rd going down the track it sounded like it was fluttering and I instantly suspected valve float. I only back halfed 27 mph and then the dyno results from the next day kind of prove something odd is going on. I would expect atleast 30 mph back half in an aerodynamic fbody even with 4600' da.

 

Stock rockers don't give any sort of pattern at all.

I always saw a star pattern on my rat motor. Intakes only because the valves are huge and heavy.
When I finally pulled the heads off and apart, it was clear the springs were dead and everything had been dancing out of control.
Measured the springs and they had lost 50lbs of seat pressure.
Star pattern is a clue.
Replaced the springs and picked up ET and mph.

With 317 heads, you are good to go with stock rockers.

Just best to measure for correct PR length. If you used the washers under the YT stands, I'd guess you may need shorter push rods. If not, you may be fine.

Finally, I would expect valve float to affect all gears. Not just high gear. I agree you should back half 30 plus. My nova does and it's a brick aero wise.

FWIW, I had terrible luck with YT. Busted a few of the ultra lights. My first set of the new and improved, failed the roller tip axles. I was accused of not soaking them in oil for two days..... But they stood up and replaced them.

BTW, just got my L33 short block back. Yahoo!

Ron

 

It probably does happen in every gear but with 3.90s 1st and 2nd go by really quick. It seemed like I just kinda sat there for a long time in 3rd with the shift light on the entire time lol. Awesome man get the car back on the road and tear it up! We have a event friday and saturday which should have some of the best track prep all year. Hope I can get the stock rockers in and make some really nice hits. I think with the air filter off and hopefully stable valvetrain I can cut atleast half a second off. With a 1.3x 60' I'm really hoping I can be in the 8's on 15 psi. This car already wants to wheelie hard so I might have to actually put the chains on the travel limiters and strap the front end down. Maybe I'm dreaming though!

 

How much weight is on the nose? it looks like its squatting then going into a small wheelie by the one picture above. Get some anti-squat in it, dead hook the radial and use power management to go sub 1.20s

Also what shocks are on the front and rear? what are they set at

 

To put it in perspective, back in the day, I ran a pass that was very similar to yours It was as follows:

1.36
6.05
115
9.50
142.XX

So I picked up the same 27 mph as you did. Now I don't know if there was an issue with my car, or if this is a normal pickup. haha

 

For reference, I picked up 31 mph last fall, but my converter locked in 3rd. It felt like a 100 shot. However, the car picked up 29-30 mph without locking the converter.

The best pass was:

1.43
6.16
116
9.54
147

 

Now that you mention it, yeah I do remember now that I was blowing through my converter by 26% at that time.

 

Looks like valve float to me and with those rockers on a turbo setup I'm not surprised either.

 

Looking at my track video it looks like the rear separated after I installed the stock rear springs. I don't know about the weight but it's not light on the nose with the turbo and iron block I need to scale it when I get a chance. Fronts shocks are QA1 singles and the rears are strange singles also. I only have the AEM truboost for now so that doesn't really manage ramp rates or anything but I plan to get a true boost controller down the road.

Looking at your signature I would like to see one of your dyno graphs to 7000 rpm or so. If you are running the yella terras with the 96mm hotside on that borg I would say you do have some sort of valvetrain issue up top.

My converter is damn near a lock up converter with only 2% slip so I would expect atleast a 30mph back half.

 

Yes I am pretty sure too and hopefully I will find out tomorrow. It's pretty nice being friends with someone who owns a dyno!

 

I'm friends with a guy who runs a dyno. Me!
Do I ever get to dyno my own cars? Nope! Ha!

Good luck. Looking forward to your results!

Ron

 

If I can cut down the video for reference, (we're using a set of borrowed shock sensors) we're seeing 3-5" of separation... on the footbrake. Only time it comes down is when he applies the Transbrake and lets off the foot brake. keeping the weight on the nose definitely helps with the wheelies, along with managing power though the ECU/PCM.

A good set of at least double adjustable rear's will help out a ton. Getting the control of the extension and compression will make a big difference in what the car wants to do and how it acts. Granted, applying power, and doing chassis adjustments can make things complicated and seem overwhelming, I think you could get a handle on it.

I'm assuming since you're using a tru-boost.. that you're on the stock PCM. We do all of our boost control through the BS3, and using that to apply/dump CO2 for boost control.

 

Trust me I would love mensner double adjustable afco's and a holley dominator with co2 boost controller just like my buddies chevelle but I'm going to work with what I got for right now. Which is hptuners 2bar O.S. single adjustable shocks a msd 2 step and the electronic boost controller which just is a glorified manual boost controller.

Another day of thrashing I almost didn't go out tonight and I didn't want to load truck and trailer so I said screw it and drove it to the track about 30 minutes away. Normally not a problem for most similar cars but I've been plagued with overheating issues and cruising 3.90's isn't fun but I've got ear plugs.

Anyways I swapped the stock rockers in and found a set of 7.400" pushrods from my buddy that put my preload around .070" vs the 7.425s I had in there. I'm running the comp 850 lifters and they recommend .030-.040" preload but oh well for now. I hate these lifters too they always tick like crazy.

I'm going to have to check the springs out and maybe shim them up but I swear I can still hear it floating the valves on the top end. This is what it ran driving the car to the track and just removing the air filter with the stock rockers on 14-16 psi who knows I'm only on a 2 bar map. After this hit the track took a dump but what do you expect when you roll in at 9 o clock at night Going to give her hell tomorrow I left the car out at the track and the prep should pull your shoes off tomorrow.



One for the suspension experts. Launch; 8 psi, 3300 rpm, 4 from full loose front and rear at 5 out of 10, 15.4 psi in the tires. Old style MT 275 drag radials.

https://www.youtube.com/watch?v=wqIo...ature=youtu.be

 

Nice. Improvements come a little slower once you get going this fast.
Until you turn the **** a bit.
Are you going to upgrade to a 3bar tune?

Got to be happy driving that far, laying down a low nine and driving home.

I looked into those fancy shocks.....until I saw the price. Yikes. So I put Viking DA on the front. Haven't got to test them yet.

Sent you a PM

Ron

 

I plan to do a 3 bar soon probably when I upgrade the fuel pumps. Debating between triple 255's or just running dual 450s. I already have 2 used 255 walbros laying around so I might just add another. I really need a good alternator this thing is killing me, it barely puts out 12.5 volts when it gets hot and is causing all sorts of headache. Fuel pumps, gears, 3 bar, alternator, cage upgrades, 275 pros, send the converter off to be loosened up man this **** never ends I might need a break from the car.

Got to make a bunch of hits today and play around with suspension, 2 step, tire pressure and etc. Cut a 1.403 60' on one pass. I was pulling 3 degrees of timing over 170 degree IAT and I was seeing about 180 by the end of the pass. I checked my plugs and it looked safe to add a bit more up top so I removed the 3 degrees to run about 16-17 degrees for a full pass. Car picked up a little bit and I decided to bump my total timing up to 18 degrees up top. Track was biting pretty hard and a few hits I tried to get really aggressive and spun the tires while wheeling. When the track cooled down I never got much over 160-170 IAT but I do have a real small air to air intercooler that doesn't seem to do ****. The car really liked the extra timing and this is still on 15-16 psi.