....soooo I'm in the process of choosing the proper heads and cam. Without getting too brand specific, a lot of reading/research shows that there are a LOT of really good heads that come assembled with only fair to average valvetrain components. ...and of course most all heads are available as bare castings. ...add to that the fact that there are several decent heads on CL or swap meets, with unknown valvetrain components. I've decided that looking into buying the valvetrain separately may be a very good option.

....one of the cams on my shortlist is the venerable LT4 Hotcam. ....and of course, GM sells it as cam only or in a complete kit. (minus the valves themselves of course). If you have an opinion on the valvetrain in the kit, please share.

My question is this. If I have the perfect bare head, and the perfect cam, but no springs, rockers, retainers, pushrods, etc. etc., how do I know what to get so that everything works together? What do I start with? I understand how coil bind is bad, and that the spring needs to control the valve so as not to float, but not be TOO heavy either, but I don't understand all the numbers and how they relate? I also don't wanna buy top of the line parts that aren't necessary, or be sold junk that'll underperform.

Thoughts?

 

Use the springs that are recommended by the cam manufacturer and get them in at the proper installed height. Stock heads with stock retainers it's 1.70". But on an aftermarket head (with who knows what length valves or how deep the spring pockets are machined), you have to measure.

 

You can't go wrong choosing a conical spring, better known as a "Bee-Hive" spring.
What you get is better valve train stability with less spring pressure both on the seat and over the nose as well as the reduced mass that comes from the tiny retainer and the general overall size of the spring itself. There's also the added benefit of more clearence both in the retainer to valve guide and coil bind areas.
They're highly recommended for a hydraulic roller application.
If you intend to go beyond the LT4 cam (and there are better/more modern choices for the application) the Comp 26918 will still be an excellent selection. Once you get into very high RPM and larger cams, then you may have to step up in spring but that's another story.
For what it's worth, I purchased my RHS heads in bare form. Fitted them with Ferrea valves and the previously mentioned 26918 springs and appropriate retainers. Valves are .100" longer than stock and spring installed heights are 1.8". It took a selection of spring locators (as my heads came cut with pockets for a large diameter spring) and shims as well as offset keepers to get the spring height within spec.
I have valve lifts approaching .580" and very little duration (224/230) with my hydraulic roller. A very fast acting lobe profile. Engine speeds to 7000 rpm haven't resulted in anything untoward happening (although I'm certainly well past my peak HP by then).
Of course there are other options for a conical spring (GM, PAC, etc) however my experience lies with Comp.

 

Oh yes you can, I have had two of those things break, one destroyed the motor.
The other one I caught in time, just bent the intake valve.
I will never use those again.

 

I can't comment on your failure. I don't know your application, the spring part number or your installation methods.
The Comp 26918 I've installed in several engines have all performed as expected. I've one set approaching 60 000 miles in an engine that saw plenty of drag strip duty. Other sets installed in various small blocks all with engine specs very close to my own (and beyond). Lifts approaching .600". 292 ADV duration. 7500 rpm is some cases. Of course the rest of the valve train is up to par. Perfect valve train geometry. Quality (not original OEM hydraulic) lifters. Etc.
The conical spring is a general term and I'm sure there a inferior imitations out there. Could be too that Comp (if that's what you had) has had QC issues. Seems that pops up every now and then too.

 

For my money, too risky to take a chance on them.

 

There's so much more than just having the proper springs.

Use springs recommended for the cam or very similar springs from a different manufacturer. Springs with a little more spring rate at the same install height than recommended isn't going to hurt anything but you shouldn't go with a spring rate less than recommended.

Getting them installed to the recommended install height so that they won't bind at max lift. Depending what's required, longer valves may be required which will also mean different length pushrods to maintain proper valve train geometry.

Making sure the heads are designed for an increased lift. That means the bottom of the spring retainers won't hit the top of the valve guide/seal at max lift.

Using rockers designed to work with increased lift. The slot in stock rockers will normally make contact with the rocker stud before max lift in a higher lift cam. Long slot rockers or a good roller rocker will work better.

 

That's pretty vague Don. Some specifics would be nice as the OP is looking for advice. Maybe your application doesn't match his.

 

Absolutely. We've had a discussion on valve train geometry in the past. I had to go to the expense of offset trunion rockers to get my contact patch precisely how I wanted it. You, I understand have a shaft mount system on your BBC which takes some of the guess work out of the calculation.
The checks for retainer clearance and coil bind are a standard procedure for any build other than perhaps an OEM replacement, part for part.

My point is, with respect to the OPs original question, is that for the LT4 cam, or a cam similar, is that the Comp 26918 is well suited and would most certainly meet the specs of the cam manufacturer.
It's not the only choice but still one worth considering if any of the better engine builders have a say anyway. Lots of research and support out there. GM seems to like them too.

 

I'd use pac springs over comp. pac used to make the beehives for comp. they switched from pac to someone else and had failures. Comp now uses someone else but not sure who. Havent heard of the failures since but things can happen.

 

There you go.
I had some problems with Comps standard retro-fit hydraulic lifters and it panned out that Comp had changed suppliers and the result was a QC problem. Or so I was told.
That's always a tough one to work out because you just never know.

 

START WITH THE SPRINGS. As I said above. Get the right ones, install them at the proper installed height. Aftermarket heads will have PLENTY of clearance between the retainer and the guide/seal for that cam.

That's job one ALWAYS.

Rockers are your choice, but the HotCam is designed for 1.6 ratio rockers to get the full .525" lift it is spec'ed for.

Pushrods are LAST. Getting pushrod length right is a whole separate subject since it affects rocker geometry and damned near everything can affect the proper pushrod length. Like Alky said, there is a whole other post on it. MANY posts, actually.

BUT GET THE SPRINGS RIGHT FIRST. If you don't the rest won't matter.

 

Thanks for the info guys. I'll go with the cam manufacturers recommendations regarding springs and go from there...

I've been reading a bunch of posts...piecing together info. ...hopefully I'll get to put this into practice sooner rather than later!

 

You'll do fine with that approach. Just remember, if the cam manufacturer is someone like Comp that doesn't know your particular setup (even though the greenhorn tech guy on the line will say he does ), use their recommendation as a MINIMUM spring requirement. Ie. they miss the boat totally when spec'ing valvetrain components for short runner high rpm intakes like the Gen 2 LT1.
You cannot correlate spring failures to either conical or conventional spring types. It all depends on the material and manufacturing quality. I've had name brand conventional springs break twice (same batch) on a 5500 rpm motor lifting to .510". I've run a set of Manley beehives on a 7100 rpm motor lifting to .617" for five years without a failure.
Beehive isn't better than conventional for durability, and vice versa.
If you're operating a spring anywhere near it's rated lift, don't skimp!

 

As said above, be careful with comp cams recommendations lol.