Ok I did get one thing wrong and overlooked about loosing power when having to compress the valve spring more...

I got this info from here:
http://www.cranecams.com/?show=faq&id=5

Common Misconception:
Many people mistakenly think that using higher seat pressures causes a reduction in the horsepower delivered to the flywheel because higher seat pressures (and also higher spring rates required for high performance) require horsepower to compress the springs. This thinking is simply incomplete! For every valve that is opening and its valve spring being compressed, another valve is closing and its valve spring is expanding. This expansion returns the energy to the valve train and the engine. This results in a net power loss of "0" hp. Many engineering texts refer to this as the "regenerative characteristic" of the valve train. Recent tests at Crane have shown no horsepower loss on a hydraulic roller equipped engine when changing the seat pressure from 135# to 165#. Power actually improved significantly at top end, probably due to better control of the relatively heavy valves in the engine.

 

So you called them Jim???

Actually you can get someone like that at Comp (if it's in the "book", which modified Ls aren't) but you may also end up speaking with someone who has 20 years of experience with valvetrain related components for thousands of different vehicles/combinations, including modulars. A few people have run boosted modulars in the past.

I'm sorry but getting valvetrain advice from a small blower case manufacturer or a tuner is not the way to do it.

 

If a tuner/blower mfr. takes the initiative and has the "experts" design and build a spring for a "specific" application....how could that possibly be wrong ??

I got a funny feeling that if we were talking about a glue-on carbon fiber widget...you peaple would be all over it but since this mod takes some thought and skill....all of a sudden its voo-doo.
Dale

 

It takes lots of thought and skill, that's the point! You think there's anyone at MP or JDM that can calculate or test for the critical frequency of a spring?

 

Yes! When it comes to a motor, Shawn Lacko (JDM)is one of the most knowledgable people I have ever met and if im not mistaken I think Jim Sr. has an engineering degree also but I could be wrong.
Any way you look at this all the info is very good and we are all that much smarter for it so lets leave it at that

 

If the critical frequency of these springs were within the rpm range they operate in then I'm sure Ford would have used a second spring also. Oh and they would all be breaking.

 

WOW!

This is true for the masses.

Rich

 

Maybe Jim Sr. or Shaun can chime in with what springs (and seat pressures) they used on project ice box. Considering the boost it must have run, the fact that it had oversized valves, a 6700 rpm shift speed, and that it used stage 2 cams, I don't see why the L motors in question would need anymore seat pressure than that application.

 

How about applying this info to the do it your selfers here?

I would like to mod my basicly stock truck. I'm not as interested in huge hp gains as I am in having more usable power in a broader range of the rpm band. I also would like to limit the expendetures somewhat. I would proceede with the possability of more boost in the future. Can people achieve this with cams and stronger valve springs? Can we do this without being an engineer?

 

I'm certainly not accusing anybody of not knowing what they are doing, in fact the opposite. I'm just wanting to know what the rest of the specs are on the springs that they are offering. They don't have to give out all their secrets, but knowing the spring rate (or the compressed force at the given coil bind height) is an important piece of information in the fundamental operation of the engine, it can aid in tuning and knowing the limits of the engine.

 

I've probably missed something really simple in this discussion of valve
springs. But I have a few questions.

Does this only apply at boost levels approaching and/or over 18psi?
I'll probably never exceed 16#. Stock Eaton for now, ported is next. I
do plan to spray though (not sure if that matters or not)

W/aftermarket cams (550ish lift) and aftermarket springs advertised as .600" capable is coil bind ever a concern when shimming the springs?

Can the hydraulic lash adjusters withstand the extra spring pressure,
i.e will they collapse? Or does the OHC design negate that problem? Or are
solid adjusters required?

 

This is a great question. At what spring pressure will we experience problems with the adjusters? And are there worthwhile gains going solid?
Jim

 

Okay so you speak to someone with 20 years experience and then they go ahead and sell you a valve spring that gives you 85lbs of seat pressure and as soon as you start the enigne, your 85 lbs are now down to 75lbs. Thats where it will remain for most of its life. Eventually the will go down to about 65lbs with 25-30K miles on them.

I am almost 45 years old that gives me 28 years of experience in engines. I have exclusivley worked on the modular motors for going on 14 years.

Your little comment was very uncalled for. Charles, I, and every other vendor out there want the best for our customers. Every single work day of the week, my hands are on a 4.6, 5.4, 2v, and 4v engines.

Jim@JDM

 

When we installed the heads on the ice box it used .550 lift cams. The seat pressure ranged between 102 and 105 lbs. When the heads came from patriot they were between 72 and 77 lbs of seat pressure. That means as soon as we started ice box we lost 5-10lbs of seat pressure. So if we left their original springs in there it would have never made the power it did.

Jim@JDM

 

There is alot more that goes into our heads than just seat pressure of the springs. We use a specially made case hardend guide, the clearance between the valve guide and the stem of the valve is unique for our heads as well. When the heads are CNC machined we also machine in the spring pockets because when they come from ford they are as much as .015" off from one end of the head to the other end. The same goes for the Lifter bores. They are also machined all to match within .001". We just recently started mikronite coating the valve springs to de-stress them so they wont lose spring pressure after the engine has been fired. You also, when setting your cams up, have to check your lifter pre-load. Too much pre-load will cause the engine to rev slower, have less top end, and basically cost you HP. I have seen too many head companies use the specs for pre-load actually tighter than Ford will use factory, Ford runs theirs very tight. Then comes the camshafts. Both comp and crower stage 2 cams are a decent cam, but there again with the both of them are too much my liking because they blow boost that we are making out the exhaust. The engine never gets to use it to make HP. The different compression ratios that you can run in our engines will also change the cam profiles. Bottom line is in our trucks a built short block no matter who it comes from, its not really going to make you huge power number differences. But the cylinder heads will. Anywhere from the spring pressure to the lifter pre load, valve guides themselves, port work, and last but not least the camshafts. I dont think that anyone can dispute that our engine program makes the most reliable horsepower period!

CT Topgun,

As far as a the hydrolic lash adjusters go otherwise know as lifters, even if you machine the spring pocket to accept a double valve spring at say 160 closed pressure and 300 open pressure your lash adjusters will be just fine.

Jim@JDM