I guess I'll try that when I dip into the car this weekend.

I wish somebody who knew what they were doing could come by and look at the car... it really is a shame for it to be sitting in the garage and not roadworthy. I've put so much time into making everything just right, the tuning, etc. and I haven't even got to enjoy it yet.

What kind of variances do you guys usually get when you mic the spring install heights? I'm sure they are all pretty close, but how close exactly? I am correct in assuming that even with a good margin, say 0.05" tolerance, I still would not hit coil bind with this setup. Honestly, I don't think coil bind is the issue anyway. The valves are not closing properly or tightly or whatever you want to call it. Does the install height affect seat pressure???

I'm tempted to lash the lifters just a hair past zero. I know it will run good that way but I know it's a bad idea. Could it be that I don't have enough seat pressure, so when the lifters are bled down (ie after sitting for a few days) it works but when they are pumped the springs are not strong enough? What factors affect spring pressure? Install height I presume...

I'm talking myself in circles. Comments please.

 

Here's the way I checked for coil bind on my '918s. As far as I could see, using a feeler gage wasn't going to be accurate, because of the way the '918 stack up when compressed. So, I put in a two roller lifters that I converted to solid, with washers inside. Then I adusted the valves to zero lash and set up a dial indicator on the spring retainer. Next I started cranking down on the polylock until the spring coils were bound up, and noted the reading on the indicator. I did this on a few cylinders and as I remember, they were all between .065" and .085". This was with my 1.6 pro mags and .606" lift. So at max lift, I still had .065" - .085", seemed OK to me, so I let it go at that.

 

I didn't mention that when I started tightening down on the polylock, to further compress the spring, I had the cam positioned at max lift. So, of course, any further movement would be way beyond what was caused by mechanical action of the valvetrain.

 

1.085" is what Comp states coil bind to be for the 918s, but interestingly enough their spring chart doesn't list any pressure #s past 1.150". There have been reports from other members of problems getting this close to the coil bind #s on the 918 springs.

What is also interesting, is they recommend a 1.800" install height and then say the spring is good for maximum .600" lift. This puts the spring at 1.200" fully compressed. Maybe they tested the spring down to 1.150" because of the common 1.750" install height? (1.750" - .600" = 1.150")

If this is true, then an install height of 1.75" - .577" max lift = 1.173" height for the spring when fully compressed. If 1.150" is the true limit, it's pretty close



Thomas.

 

Thomas, the springs do coil bind around 1.085" you can run them pretty close to that without any problems.

Bret

 

Ahh ok ... thanks for the clarification Bret. You probably tested the spring beyond what comp tests them at

I still wonder why they don't list pressure #s past the 1.150" mark?

Thomas.

 

no need to, for every .010" of lift you just add 3.13 lbs of pressure.

1.15" would be 333.45lbs
1.085" would be 353.8lbs

 

Are the springs big enough for the cam?

Are the push rods the correct length?

What are those locks? Why aren't you using 7deg or 10 degree locks? Would it make any difference in the installed height---sorry, unfamiliar with .05+ locks.

If the springs are sufficient and the geometry is correct and the adjustments are in the ball park, I can't think of any other problems if the timing is correct. JMHO

 

The +.05 locks seat the retainer a little higher on the valve so you get a slight bit of extra clearance. With non-sa rockers it's all good because there are no locators on the rockers, just bare roller. That said, I am pretty sure that they are 10* locks but I could be mistaken... it doesn't really matter though as long as they work.

I had a thought... could the guideplates somehow be affecting the valvetrain? They are the EX component ones that combo motorsports sells. The rockers look pretty centered and when I glanced at it last weekend I didn't see much wear in them. What other things can affect geometry? Should I be running GM guideplates or something?

I also noticed that my valvetrain clicks a lot... even with a stock lifters lashed 1/4 turn past 0 lash. With the car running when I unscrew the rocker nut it just clicks louder but even at zero lash I still hear them tap a bit, they never get completely quiet like when I had the stock valvetrain in the car. Any reason for that or is it normal?

 

Any thoughts on that last post?

Is there anybody from the bay area who knows what they are talking about that could help me fix the car?