Ian,

At sub-6000 RPM there may be a better option than the 9988 RAD spring for what you are trying to accomplish, particularly in light of the fact you’re utilizing a tall deck application with a significantly longer pushrod

Your cam yields .694” at the valve, after lash, requiring a shorter spring to keep your stack value at .060” @ max lift. The key is to control the dynamic mass of the system while minimizing compliance in the pushrod. The additional PR length required in a tall deck application is a definite negative. Column width trumps wall thickness, however when you run out of real estate on diameter you can only move in toward wall thickness.

If exchanging the springs with your vendor is an option that would be helpful. When you calculate the spring force necessary to control the mass of a SS 2.300” intake and a 1.880” inconel exhaust, and the extended length pushrod, this may require a tapered pushrod if you’re maxed out at 3/8”.

What is your max WOT RPM?

Bob

Isky RAD 9988

I have not got pushrods yet as im going to check the geometry when the rockers arrive, and i was going to get heavy wall with tapered ends

I will check open pressure today

Max WOT 6500

I was going to get heavy wall tapered end pushrods

I will check pressure at full lift today

Open pressure @ 1.330 is 490 pound
I checked spring coil bind and it is @ 1.100

hope this helps

Thanks
Ian.

Your installed height is 1.950 and at full lift only at 1.330 with a 714 lift cam?

I re checked and spring compresses to 1.280 at full lift this gives me 520psi

table
 

Ian,
There appears to be a calibration issue with your spring measurement apparatus, or you have the incorrect spring for the part number RAD 9988.

Your measurements provided a height / force of:

1.330” @ 490# measured
This is;
1.330” @ 616# actual

1.280”@520# measured
This is;
1.280”@644# actual

Attached is a height/force table for the RAD 9988 to validate your springs in conjunction with.

Bob

Well i have got it all back together again

Both motors ended up getting:

Jesel Pro steel rockers with roller tips
New Crane lifters
New Manton push rods 3/8 - .145 wall
New 9988 RADS 250 psi closed
New steel Retainers and locks

I stuck with the 9988 RADS

Re heli coiled most threads in heads where rails bolt on

set tappet clearance to 8# cold

timing is at 32*

also found crack in my tailpipe right at the collector ? not sure if water was getting in with reverberation

going out on sunday so fingers crossed

Well i have taken the "Cannon" out for 4 runs now, 3 tanks of gas, Man does it like a drink, phew.

Been running pretty hard in the flat water up to 160-165 and 6500 rpm for a good 5-6 Mins at a time, also cruising at 125-130 for 15-20 mins

engines have been perfect, bit of an oil leak from 2 piece covers, even with new O rings.

Going to put some Billet "Noonan Race engineering" ones on ( very nice )

I know i had some mixed reaction to my spring choice but all seems to be ok.

I went with the manton push rods as recomended and they are a heavier wall than i had.

Jessel Pro steel are just a nice piece.

Now just learning to drive this Beast has been a blast, she is pretty happy at 150,at 160 im feeling a little uneasy making sure im running flat

I Had it out in some Big water and that was an eye opener, Launching 10-12 ft in the air, it was choppy crap water and was not that much fun

https://www.youtube.com/watch?v=BIXvKhiuDRQ

Please enjoy my little fly buy @ 150

I think i had the trim tabs set a little low pushing the nose down

I have had times where she just sits beutifull and smooth with no porpise

cheers

Ian.

thanks for the update.hope your problem free for a long time.