[Chris-in-Cali]

Need help here.
A few months back I had my engine dyno'd for the first time. I currently only have 2,900 miles on the engine. While on the dyno the technician said that my valves started "floating" after 5,000 rpm, and the engine started to fall flat on it's face. He tells me that valve float is cause by the use of the wrong springs being used in the heads. Not matched for the cam used. If this is truely the case. Is this just a matter of getting the properly matched springs for the cam and putting them on? Like I said I've only got 2,900 miles on the engine and I NEVER take it past 5,000 rpm. Or .... is more surgery required on the heads?

[JimM]

It depends on the exact spring requirements of the cam, and what heads you are using, but generally speaking, yes, you can put on better / stiffer springs (same diameter and installed ht as what's on there now)

You can do it with the heads on, too.,

[Chris-in-Cali]

Jim ..
I'm looking at the Cam Card that has the recommended spring info. How will I know if what is already on the engine is wrong? I've got a Crower Cam # 00241. Duration 270 Lift .458 1.5 roller tip rockers. The card says to use a Crower spring# that has been discontinued. They suggest with this cam a single spring, valve close 090/110 lbs, valve open 260/290 lbs. I've tried search for matches to this on summit and jegs, but none of what I am seeing are "exactly" matching what the cam card is calling out ?

[eville]

what are your heads?
call crower and ask them for a new recommendation.

[Chris-in-Cali]

That's one of the problems. I know nothing about the heads other than they are cast iron, 76 cc, and 202/160, with compression "about" 9:1. Have also been tossing the idea around about seeing what a head shop can do with these heads. Port, polish, anything ... A buddy of mine tells me that for a shop to put 3 to 6 hours worth of work into the heads would be about $300 to $500. Anyone know anything about that ?

[zdld17]

Idea on spring pressure settings it to prevent just what is happening. The cam card says X spring = xx #'s at x .000 installed height. The only way to measure this is find someone that has a spring pressure checker, (Most head shops), and chuck them in the press, bring down to measured recommended installed height and see what they record. The main idea is to get the recommended closed valve at an assembled height with the correct closed seat pressure. Not all springs are created equal. Some taller unassebled will stack out sooner that others. You have to becareful when going off the mainstream path is chosing springs not recommended. You can used other spring companies springs , providing you do the checking. Most of the smaller 1.250 etc are soft springs and will give you 90-110# closed installed
height. You also need to keep in mind what full open pressure is also. So keep this in mind when setting up springs on your own head when you have no documentation. I will guess here and someone tell me how far off i am.
If I had no access to the correct spring for your cam, I would recommend Comp spring # 981 for starter. I say this b/c its a generic spring. You want more pressure? Then you have to go down the spring list and see whats there to fit your needs. Use caution as too much spring pressure will wipe out your cam lobes,, especially if you are breaking the cam in.

Now as for fitting into the head, you have to use mill tools that are set for this, some combo tools that not only cut spring pocket but mill down valve guide boss to allow room for some inner springs and cut step down for after market valve seals. Caution: when cutting spring pockets, pay attention to water jacket areas. Sometime better to put a thin shim under the cutter to give you an added amount of depth protection .
I can go on with stuff but if you need more information, every one is here.

For me, I know that springs are replacement items and they do loose pressure over time due to heat and cycles open and close, not to mention the months in collasped position when car has not been driven.
I like to use a very large spring that has the seat pressures I need and then a little above. My installed height is more than cam card indicates but pressures are spot on. And due to the size of the spring and wire, they take more time to collaspe or loose pressure and " float" . My card calls for 1.4" spring dia. I use the 1.55. Its just a matter of preferance.


don

[JimM]

That is a pretty mild cam, and the spring requirements are pretty standard. For now, you can use a caliper to measure the existing spring diameter and get a good idea of the installed ht, tho installed ht is much easier to measure with the spring removed.

Most likely, the standard TRW replacement "Z/28" spring will be a match for a stock diameter and ht, and will provide the pressures you need.

[mkpatrick]

I have a question concerning this. I'm not trying to hijack the thread but I figured, while we're on the subject......

I too have no info on my cam other than its a solid roller cam. I see the springs are double springs with an included dampener. So it looks like 3 springs in there.

How often during the winter, should I rotate the engine a few times to keep from having springs sitting there compressed for a long time? I probly get a chance once or twice a month, on the occasional no rain day in the Seattle area to actually drive it for longer than 10 minutes. Last Sunday I went for a hour drive.

I'm trying to minimize that wear from just sitting with high pressure springs holding a valve open.

[zdld17]

That sounds better than having 5 ft snow out side, plumb some tubing out the door when you do run this as well as open some vents to allow fresh air in. I would allow to warm up until theromstat opens up, want to try to burn all condensation you created.