Questions about Crow 14770 cam?

[Anonymous]

I was going back through many of the post on cams and HP for Crossflows in previous posts from Dynoe250s, XT Falcons, Falcon XF and Tags281. Was a worth while excercise.
In one post found one post from Jan last year that discussed with Addo the use of the 14770 cam. Someone had got a price for a full Crow cam install kit from Repco and it was $780. The kit had special valve stem seals amoung other things that reqiured special machining to fit. Does anyone know why this is needed. Dynoe 250 did you have to use special valve stem seals that required machining with any of your hotter cams.
Im curious because I found out through hard experience how important valve stem seals are when a machinist who ported by 2v head left them off the exhaust thinking it would be ok. It would fill a 4 berth garage full of smoke very quickly until I had them put back on at a cost of about $130. That was with my old cam, my new cam is close to that 14770 duration
The Crow 14770 is a .510 lift 214-224 at 50 and is a terrific cam.

 

[Anonymous]

I e-mail Crow cams this is a responce from them.
Hi
There are 2 kits that would work Ok with the 14770 the recommended kit has a
spring with a damper this uses the std ford type umbrella seal K1402
the next valve train kit up K1403 for severe duty has a double spring and
comes with a Teflon type severe duty seal the top off the guide mast be
machined to fit it
the reason we use this type off seal is the STD ford seal fouls on the inner
spring some engine builders use 1600 escort umbrella seal as these are
smaller in OD and will fit inside some inner springs
Yours Ray

 

[alloydave]

Some of the late xf heads came out with the poistive type stem seals and
wont need to be machined . Im using the sealed power double springs and use the stock positive type stem seals (not umbrella).
Im using the 14892 cam ,but cant tell you how it goes yet as its still sitting there unstarted .been a few months now time to pull finger me thinks.

cheers Dave

 

[addo]

Ha! Sounds like a perfect occasion to bang my "Don't overspring it" drum.

Dick Johnson's engine building caper up in Brizzy used to test springs with a machine that used a simulated lobe profile on a "camette" (I just invented this word), which acted on a lifter, pushrod and rocker, and a valve set in a chunk of head. The machine spun the mini-cam up through the revs, to check for float or bounce. They weren't game to trust maker's recommendations, and not prepared to err on the side of overly cautious, losing precious HP. If it worked, it worked.

I would reckon the roller setups should be pretty neat, if anyone here's game to try the Argentinian "windowing" of the block.

Regards, Adam

 

[Anonymous]

Thought I might mention my small experience with springs. When I bought 250 2V I just assumed I should replace my springs in the rebuild and didnt realise the springs on it were in fact very good and 90 pounds pressure. I had great trouble getting some others and had some thicker heavy duty springs sent to me for about $120 from the mainland . Had them installed and Machine shop said it was 140 psi installed and that I needed to get it down to about 110 max. To lower the pressure I then had to spend another $100 dollars to get crome moly ressesed retainers to go on top of new springs.
Pressure was still about 120 psi and then rocker arm would not reach top of valve because of recess (by then my machinist was getting tired of the delays). Sent springs and retainers all back, they wouldnt take a refund so I ended up getting a taco in exchange that arrived with a cracked face, sent that back also.
I then got some springs sent from Crow $80 that were undampend and were also 120 psi at installed height. I then discovered my original springs were what I had been looking for all along.
Crow wouldnt take the springs back because I had cut up the pretty box they came in. I had cut it up so that I could have their yellow and red Crow logo on the wall in my garage.
If anyone would like some cheap springs I still have them.

Anyone know what is the advantage with double valve springs Id Imagine they would exert a lot of pressure (maybe needed in some cases perhaps?)

 

[xctasy]

The type of seals depends on use. It is the most common engine oiling problem. I've seen it most on OHC Pinto engines, but also XF's.

In New Zealand, lo-lead gas in 1996 caused massive problems, as engine builders were still using there leaded fuel thinking caps. There are quite a few types of seal, and they are changed by if you K-liner the cast guides, or use big ticket phospher bronze exhast valves, or if you are going adjustable valve gear, propane, street and strip, or whatever. The space restrictions, or how the engine builder likes to install the valves if there is valve seat recession can change the types. On Red Holden L6's, some people machine the guide boss and spring mounts so you can fit good 308. Others machine the groves, and use V8 valves. Base circle diameters of the cam, the kind of keepers/retainers you use.

This is why you must rely on the experienced machinist.

Propane engines tend to expire in the exhast guide area, and any information from these building sources is best.

The single springs are best in most cases. Flat wound dampers are good for dampening spring surge, but do tend to break.

As Adam has said, DJR used a stroboscope to pin point the minimum spring tension to still eliminate valve float. This was for Clevlelands which had huge problems with even stainless valves spot welding themselves to the heads seat. The aim was to use the lightest spring you can get away with.

As for the cam specs, I tend to think that finish set-up is more important than cam to cam racing. If a cam needs degreeing, or the timing chain has more than 0.5" of slack between unloaded and loaded states while measring with a steel rule, then you will loose timing. It's more likely that the valve gear will add too much nose tension on the cam lobe, and timing gear wear will result. The Argentine Roller Cam kits are the answer...at a cost!There is also a harmonic period which can vibrate the timing chain on any engine, but it needs to be checked in a vibration lab to find where it comes in. It varies with capacity and possibly cam type.

There is such a lot in this game.

David Vizard found the Mini A-series loved adjustable cogged belts to replace the chain drive. This ensured the harmonics were isloated from the cam. They also used solid Windsor Engineering carbon fiber push rods. Until we get a decent cogged tooth variable vernier crank and cam belt drive for the OHV engines, the maximum cam profile must follow the low load stress formula, eg "HX" cam Torana XUI GTRs used, or the #392 grind Dick Johnston used on his 351 XD. Dynoed250 has it sorted, guess what he uses?.

Load stress is the intensity off the base circle. Holden engineers have found it is the primary cause of valve and timming gear failure on pushrod engines, so they just ran long duration cams with very mild 50 thou figures. Chev has been doing this for years.

Even through the Holden V8 Walkinshaw days, Wade 169 cams were redone with milder intensity. Most of the cam makers in Australia want more control over the whole package, and are prepared to go for very agressive ramps if they are screwing the engine together. If not, people like Crow go for conservative ramps.

Summary?

Use a lower load stress cam, stick with single springs, and concentrate on the basics, rather than the radical. It's more likely changing a cam chain once every while and setting it up correctly will give you more satisfaction than an extra 10 to 20 hp that goes away after 9 months on the road due to the chain wearing from excessive tension.