Hey Ya'll,
I know it's been forever since I last posted. I have a question about my cam swap. So I have a 305 motor with ported and polished heads, a 51002 SLP cam and GMPP 1.6 roller rockers. Apparently (conflicting numbers) the SLP cam has close to .510/.522 lift with the 1.6's.
To my dismay, I'm uncertain that the springs I put in my engine (while still with the stock cam) are any better than the stock springs. So I'm wondering if I can stick with a stock spring with lifts around .510 or if I have to go to a higher spring rate. To check for coil bind, do I just turn the motor over until the valve is completely open and see if the spring binds? Is there anything else I need to check? ANy help would be appreciated.. Thanks,

Bruce

 

What's up Bruce, don't know if you remember me or not, but I used to live in Dallas, moved to Nashvegas a few years ago.

Anyway, you need the spring installed height for your springs, probably around 1.70-1.80 inches. Then you need the coil bind height of the spring you are using, example, say coil bind is 1.100. Subtract the coil bind height from the installed height 1.700-1.100 = .600 lift. Subtract .060 from the .600 as the minimum clearance between coils(coil bind) and you have .540 as the max you can go with the cam lift.

You can check for coil bind by rotating the motor over by hand and sticking a .060 feeler guage in between the coils at max lift. If the .060 gets in there with no problems, then you are OK.

You can buy a height mic from Summit or comp cams to check the height of the valve spring, and you adjust the height with shims that go under the spring, or by changing valve length, or springs.

BJ

 

Hey BJ! How's your 383 doing? I checked the website.. It looks like it's doing well.

Thanks for the post.. I figured that was what I was supposed to do but I had to make sure.. Okay so my springs have a helper coil inside (I dont' think it counts as a dual spring, does it?) Now that spring doesn't have .600 in there.. I need to check exactly how close that one is... the other thing is that my lifters are not pumped up.. So I'm thinking it's possible that when I start the engine the lift might be more than it is while I turn the engine over by hand.. Is that a concern or not? Please let me know...

Take care and it's good hearing from you,

-Bruce

 

Is the cam in the motor? I'm guessing you can't remember where you got the springs or what the specs are on them? In that case, you would have to use the feeler guages and find out how much clearance you have at full lift. The lifter will pump up a little more with oil, but not a whole lot more. As long as you have the minimum .060 you should be okay. The spring inside is a dual spring, mine are the same. You can always turn the oil pump with a drill and primer to pump the lifters up before you check the clearance.