Beehive spring

quote:

PAC 1220

Maybe he means PAC-1220X which has a higher specification. Best check with Bullet.

quote:

Originally posted by ilyes:
Hey guys,

So I need to get new springs for my heads. I went ahead with a Bullet cam ff280/371 and their guy told me to run the PAC 1220. I read something similar over here as well. What I don't get is this spring calls for 600' of maximum ift on PAC website. The cam has about 633 of lift after ash adjustment. Am I wrong or this spring is not enough?

You can answer your own question by measuring the clearances between the coils at your maximum lift.

I forget what the recommended clearances are but probably are going to be something like .100"?

That information IS on all the manufacturers web sites. You do have to find it and sometimes that alone is a chore.

What you are trying to do here is avoid coil bind and provide a margin of safety.

Coil bind is defined but in my layman terms if means avoiding the spring to completely close and act as one solid mass.

http://www.racingsprings.com/1...es/PAC-1220/Item/208 Max Lift .600"

http://www.racingsprings.com/B...s/PAC-1220X/Item/785 Max Lift .650"

You can also buy yourself some insurance. Comp Cams introduced DUAL beehive springs at SEMA last month. The coils in this spring set do not touch like those in cylindrical springs- the small inner is in case the main spring breaks. Which has happened a few times recently. The results are always really bad. Comp has apparently had the springs out for test in street and pro-race engines for most of 2014.

If you don't like Comp, just wait a bit- there will be dual beehive spring sets from all the major players in a couple of months. And Mike at Bullet may be able to tell you if the Comp inner will fit inside a PAC outer, with a Comp dual-spring retaining washer.

Do NOT use the PAC-1220 spring - you will experience coil bind with your cam. I used that spring and my cam spec was only .588" lift, but due to some of the springs being out of spec (I trusted the mfgr spec and didn't measure each spring's compressed height myself) I suffered a coil bind situation and broke a valve spring after only 987 miles! The valve dropped down into the cylinder - piston damage, head damage, destroyed valve guide and metal bits through the engine, etc. Had to pull the engine and spend another $4,000 rebuilding the engine AGAIN! Went with time-tested conventional dual valve springs the 2nd time around.

If you use the PAC-1220X spring, you MUST measure each spring under full compression and use that measurement with your calculations of actual cam lift and head seat height measurements to verify you will not have a coil bind situation.

There are American businesses selling beehive springs manufactured in economically depressed Asian countries. Apparently they are telling people they are sourced from PAC. I've heard nightmarish tales of troubles with these springs. You can't trust them, and you can't trust the parts houses (i.e. Summit) or the cam manufacturers (i.e. Comp Cams, Lunati, etc) to tell you the truth about the source of their springs. Everyone knows PAC is the good spring, but the American businesses are competing in a situation where everyone wants the lowest price. To stay in business they must have a livable profit margin, so they acquire the springs in Malaysia, China, etc. (just like everyone else) at far less than what acquiring the springs from PAC would cost. This allows them to attract your business by pricing their springs competitively.

I recommend PAC #1520. The only way to be sure it is a PAC spring is to purchase it directly from PAC. #1520 is their top of the line spring, good for up to 0.650" maximum lift ... IF it is installed at the proper seated height, i.e. 1.88". Expensive yes. When it comes to valve springs you get what you pay for.

Garth's suggestion to check each spring is not out of the ordinary, its good engine assembly technique.