[critter]

So here's the deal. I got home today and my christmas present was under the tree. I asked the wife if she'd checked
the package to be sure there wasn't any damage. She hadn't. We opened it up to confirm that none of those roller
rockers were damaged. Only problem is, the 1.6 ratio rockers I thought I was getting are now 1.65's. Brand is Crane if
it matters. We goofed ordering from Jegs website.

I'd rather run 1.65 for some added lift but I have several questions.

1 - Will my stock SD (#16) heads take these without pushrod interference?

2 - Will stock pushrods take the additional lift?

3 - Will I be able to use a stock valve cover, provided I use the thick gaskets?

4 - How do I determine if my springs can take it (spring pressure, coil bind)?

5 - Are there any other factors I'm missing?

Specifics on the cam are:

Ultradyne 280/288 advertised

223/231 @ .050
.3088..3233 lobe lift
112 degree lobe seperation
.463/.485 - this goes to 509/533 with the 1.65 rockers.

[critter]

So here's the deal. I got home today and my christmas present was under the tree. I asked the wife if she'd checked
the package to be sure there wasn't any damage. She hadn't. We opened it up to confirm that none of those roller
rockers were damaged. Only problem is, the 1.6 ratio rockers I thought I was getting are now 1.65's. Brand is Crane if
it matters. We goofed ordering from Jegs website.

I'd rather run 1.65 for some added lift but I have several questions.

1 - Will my stock SD (#16) heads take these without pushrod interference?

2 - Will stock pushrods take the additional lift?

3 - Will I be able to use a stock valve cover, provided I use the thick gaskets?

4 - How do I determine if my springs can take it (spring pressure, coil bind)?

5 - Are there any other factors I'm missing?

Specifics on the cam are:

Ultradyne 280/288 advertised

223/231 @ .050
.3088..3233 lobe lift
112 degree lobe seperation
.463/.485 - this goes to 509/533 with the 1.65 rockers.

[GTO Karl]

Hi Critter:

I had to be careful ordering rockers for my SD heads as well. I did not have enough spring to run more than .600" lift and 1.65 would have put me over. I ended up buying Crower Enduro stainless 1.6's for .590" lift.

The SD heads can take the pushrods without modifying, at least the stock diameter. When I purchased better pushrods, I made sure they were the smaller dia stock style. To really know for sure whether your springs can take the lift, you need to measure your installed height, then remove one spring, clamp it in a vice until it is completely smashed shut, and measure this distance. Now, add .015" for each coil of the spring to the lift, then add the smashed spring length to this, and the sum should be less than or equal to the installed height of you spring. Also, measure from the bottom of the retainer to the top of the valve seal (or guide if no umbrella seal) to be sure there is clearance(only the lift figure is important here).

In other words:

installed height - lift - coil bind clearance(.015" per outer coil) - smashed spring length >=zero

The stock pushrods will work with the lift you are describing.

I had to use double gaskets to make the stock valve covers work on mine with 1.5 rockers, when I moved to 1.6 and high quality poly locks, I had to get new covers. You will just have to check and see with your setup.

Hope that helps

Karl



[This message has been edited by GTO Karl (edited 12-08-2000).]

[critter]

Thanks for the help. From the information I've gathered I think I'm OK on all fronts. I'll check for coil bind after the install. Time to order those thicker gaskets.

[Skip Fix]

The advertised ratio is ususally just a ballpark. Playing with different length pushrods also can tweak the actual ratio some.

Easy way to check ratio Dial indicator on pushrod tip(unless you have a real extension to go down to lifter) and rotate motor-gives lobe lift

put dial indicator on valve retainer after collapsing hydraulic lifter(as good as you can) gives you actual lift

Divide the two and get ratio
My H.S 1.65s are closer to 1.70-1.72s depending on pushrod length.

Then using one of the on motor hand valve spring compressors pull dowm(while indicator still on) and get the clearance between your actual lift and retainer and set motor about 10 degrees before and after TDC and can valve to piston(deep chamber SDs have plenty)

[critter]

Thanks Skip. I think I'm set now. I installed about half of them yesterday. Checked for coil bind or pushrod itnterference. Looks OK on all fronts. I haven't checked the geometery yet.