I decided to go with Brodix's IK180 cylinder heads over the IK200's because they flow slightly better where i need it.

The only thing is that the 200's have a max lift of .575, and the 180s have a max lift of .525 with the springs that are in there. The cam I am putting in has a max lift of .503. That is more than in the safe zone for the 180s with a 525 limit right? Should I go with a stronger spring or will I be fine?

 

which cam?

know what exact springs come on those heads? part # perhaps?
Max lift of .525" head limited probably isn't right, spring limited ok, but that means those are lower end springs, i'd think.

When they say .525" lift max, they probably mean, "will work with .585", but subtract .060" safety to get the max lift you should use."

at least I hope so.

 

Max lift and spring bind are 2 different things. Max lift is the most the valve should be opened. A solid cam also has valve lash which is also removed from the number. Coil bind is the point when the spring coils are completely compressed. If you lift past that point, you will break the valve springs or cause other damage.

There should always be about .060" between max lift and coil bind.

Example:
If a spring has an installed height of 1.800 and has coil bind of 1.150 then there's a total of .650 of spring travel. You can't use all of that because you need that .060 clearance so .650 - .060 gives a total of .590 lift. A hydraulic cam with a max of .590 lift can be used. Since a solid cam has valve lash, it will depend on how much vash. If it only has .022" lash then the cam can have lobe lift up to .612" because .612 - .022 = .590". If the cam has .028 lash then it can have a max lobe lift of .618".

Increasing the installed height of the springs can increase the amount of lift available but also lowers the seat pressures which isn't good.

 

Thanks for your replies thus far.

Sonix, to answer your question, the cam is a Comp Cam XE270HR - hydraulic roller.

I don't know the exact springs on the heads, they just come assembled. The heads are Brodix IK180's though. Here are the specs listed on Jegs:

 

the lift is based on the springs, or the clearance down to the guide boss. Based on the way it's worded, i'd guess it's the springs.

I think you're ok. What spring pressure is recommended for the cam? 100/300lbs? That's a pretty common spring.

 

The 1.250" is the spring diameter. That's a typical SBC factory size spring. The .525" will be the total lift at the valve. Installed height is probably 1.800"

The XR270HR-10 cam , which I assume is the grind you ment to say you have, has a max lift of .495/.502 which is well under what your heads are set up for. Comp recommends a 986 valve spring for that cam which has a diameter of 1.437" and 120 pounds seat pressure but only 290 pounds at .550 lift.

Personnally, although those springs that came in those heads could work fine, I'd recommend getting a larger diameter spring installed that has the higher seat pressure.

That's the trouble with buying fully assembled heads. They're usually never assembled to best suit your application.

 

Swap the springs for comps new beehive springs for Hyd rollers. Much better.
sell your springs to some one using a moderate hyd flat tappet cam.

Phone or email comps tech line to get the right beehive spring for your application.
Should go on without mods other than new retainers. They have the right seat pressure, spring rate and spring dynamics for your hyd roller plans.

 

See, my thing is, I am running out of cash, and time. I'll have enough money for this in about 2 weeks, and after that, I go to Ireland until mid august, and two weeks later, it's back to college for me. So I was kind of hoping that the assembled heads would be okay for what I was doing.

Oh and how about this hoard of crap: Jegs just upped the price of the 180cc heads to $1039.99 from $999.99. LAST NIGHT both the 200s and the 180s had the SAME 999 price tag, and today the 180's are 40$ more.

Should I just sacrifice the intake velocity flow, and save 40$ whilst also getting stronger springs? The difference in HP could range from 5-15hp depending on how I do my intake down the line.

 

imho, i'd go with the bigger heads. from what i've seen, the loss of low rpm velovity is minimal, but the overall power curve is improved. several of my friends have noticed this.
plus the bonus of the better springs. do the 200 cc heads have bigger diameter springs? if so, i'd say it's a no-brainer!

Eric B

 

Yes they have larger diameter springs. But Im just worried about the loss in velocity. The flow numbers for the 180s are better, and when plugging it into DD, I get gains of about 10hp. More If I do the intake as well.

Maybe I will take the safe route and do the 200s. I have time, I'll see.

 

for a 350 motor i'd go with the 200cc and leave yourself room for more motor or cam in the future.

 

i'll bet the 200's flow better with 1.6 rockers, which you would be able to use with the larger springs. the 2.02 intakes would appreciate the higher lift anyways. that's an upgrade you could do down the road when you have the $. they would also respond better to porting. something else you could keep on the back burner for when the power bug bites, and it will!!!
desktop dyno may or may not give an accurate representation of the way a head flows. i have heard good things about the iron killers and will try to find actual dyno tests comparing the two.
personally,i'm not sure about the beehive springs just yet. i have lot of experience with spring design and a spring of this shape will definately keep valve float down with a bit lower pressure, they are pretty pricey though. the one issue i have with them though is that there is only one spring. if in the unlikely event the spring fails there is nothing else to keep the valve from dropping into the cylinder! i know comp swears there has never been a failure of this sort, but i'll stick with the standard design springs until i see more field data in a few years. besides, the roller cams can easily handle the extra pressure, it's the lifters you need to worry about (but not really with the cam you have chosen).
by the way, what's your compression ratio?
Eric B

 

Compression Ratio is 9.3:1. I believe that is the CR stock, and nothing has changed to alter that.

That's a good point about the 1.6 rockers, I forgot about that aspect. If I do the 180s, I will be pretty much maxing out my cam's lift. And I know I can get 1.6's for cheap down the line.

Thanks for your input man.