I've run 918's and crane duals with my YT's and .598/,585 lift Cam with no float to 7000rpm.
Just a little info.

 

I wonder why the 987's are having this problem.

I may just splurge for the Comp 921's next.

 

It seems the 987's do float with the higher lift cams. The 977 springs along with comp R lifters set a zero lash + 1/4 turn seem to remedy the problem. Comp supposedly found out this problem with the 987's with a high speed video of the valve train.Word has it that the retainers were coming completely off the spring during the floating.

 

So 977 springs and Comp R lifters should do the trick as well? Who sells the 977 springs? I've only seen 978 springs for sale.

Would just the Comp R lifters be enough with my setup or do I really need to change the springs.?

 

Setting comp r lifters to zero lash plus a quarter of a turn might be a little tricky with the YT's especially since they have a shaft between the intake and exhaust. I would think you have to use the same shim on both so getting the lash right might be hard to do. Could be wrong, but I think an adjustable valve train is the way to go for the Comp-r's.

 

What is the cost of the adjustable rockers? That would solve a lot of issues for folks. When I upgrade springs I am going with 977's as well. (Might get adj rockers too)

 

Anyone have any issues with using YT's, crane doubles and the comp R lifters (using 231/237 TSP cam)? I'm a bit nervous about using the YT's now with all this talk about valve float. I may just stick to using the stock rockers til I hear some good news..

 

That's exactly what I'm thinking...there's been a lot of talk about springs, etc., but the issue remains that changing from YTs to stock rockers solved the problem with Mikey's other customer...I'm still confused!

 

I wonder if anyone actually checked the yellow terras to see if they really are 1.7 rockers ?
We know the Gm are ?
John

 

Anybody want to buy a set of 1.7 Yella Terra's????

-Sly

 

The YT's are 1.71:1, GM's are 1.68:1

 

I have installed several sets with comp R lifters you can get it right it just takes time. I have yet to see a set cause these issues. They are great rockers.

Nate

 

If YT's are setup right and the right spring is used there should be no problems.YT's are just like Jessel's and comp rocker's? I can see people having problems with ussing a Cam that is near the spring max lift while hitting high rpms though.

 

Well I just removed the YTs and replaced them with the stock rockers. Before that we went out for a little drive. The car has a TR 220 cam and GTP heads with 987s. The rockers were setup correctly with the correct shims on stock lifters for the correct preload. After I put the stock rockers back on there was a noticable improvement up top over 6200 RPM to 6600 RPM. The car did not "give up" up top like before with the YTs, it pulled strong all the way to redline now. I don't doubt for a second it was the YT's that caused this. I pulled up the dyno graphs of before and after and it gained a few HP over the middle of the curve up till ~6200 where it promptly took a nosedive compared to the previous dyno with the stock rockers. The YTs gained a few ponies peak, but after that went downhill in a hurry compared to the stock rockers. The 987s with less than 10k miles on it paired with this mild cam by today's standards should not be having valve float issues with the YTs, or does it? What else could it be?

 

Back to the weight thing. While I was up in New Jersey we weighed the YT's and stock at the tip by holding it and just letting the head rest on the scale. The YT's were alot heavier at the tip than the stockers I can't remember how many grams exactly but they were nearly twice as heavy. I almost used my stock rockers because of this.

FWIW using the 918's I dont have any float with the YT's.

 

How much hp do you think the extra weight over the valve is going to cost and how much more abuse is the extra weight going to add to the valvetrain ??

 

I've been running the YT's 918 springs and the TSP231/237 without any valvetrain problems.. it is a very quiet combination, not as ticky sounding as the dual springs, TR220 and stock rocker combo I used to run.

 

Thats good info. I figured the YTs were heavier at the valve (where its important) than a stock rocker.

Just wait untill you get some miles on those springs and see what happens. You still have new springs on there

I guess the YTs arent all they were cracked up to be, glad I didnt buy them

Chris ARE 360: Check out the Comp Pro Mags. They are the only affordable adjustable rocker out there and they fit under the stock covers. Thunder sells them for like $460, I think. The only bad thing is they are only 1.75 and 1.85s

 

What about the comp shaft mount "red" rockers ?? Those require valve cover spacers , but other than that are they a direct bolt on part ?

 

Im probably gonna switch to some duals here shortly, after reading this post I may go back to the stock rockers as well.

YT plus's Quiet, No needle bearings to worry about.
YT con's possible valve float and hp loss

Seems like the stockers are the way to go if you havent already paid the cash for they YT's.