Let's talk about cams!

[Futures Passed]

I'm not too familiar with cam shaping and its effects on performance, but I understand the basics of why the lobe shape and position are important.

This is probably a dumb question for the experienced, but why isn't there a cam that is geared at half the speed of a normal cam, but with a lobe on two sides, so you use half as much energy to turn the cam (through the half-speed gearing) while the lobe on the other side makes up for the number of rotations the camshaft makes in relation to the crankshaft(so it's still a four-stroke engine)? I suspect is has to do with limitations in lobe geometry.

On a different note, I've had my eye on this WOT-TECH Low RPM/Fuel Economy Cam for a while. I can't get it right now due to the amount of downtime my only vehicle will have, though, but in the future sometime... Has anyone here installed one?

[Kenova]

This is probably a dumb question for the experienced, but why isn't there a cam that is geared at half the speed of a normal cam, but with a lobe on two sides, so you use half as much energy to turn the cam (through the half-speed gearing) while the lobe on the other side makes up for the number of rotations the camshaft makes in relation to the crankshaft(so it's still a four-stroke engine)? I suspect is has to do with limitations in lobe geometry.

This was tried during the late'50s early '60s. They were known as half speed cams. I've even seen adds for 1/4 speed cams.
I believe they didn't gain in popularity because of the cost of production, difficulty with the cam drive (current cams have a gear twice the size of the crank- slower cams would require even bigger gears) and they really were not any better than the regular cam design.

Ken

[trotterlg]

Takes just as much energy to open the valve no matter what the gearing on the cam is. And, because the ramp angle on the cam is limited, you will just end up with a slower valve opening and closing speed. Larry

[NateD4]

Yes. The only gain to be had is lower friction and more balanced reaction forces, but a cam is naturally unbalanced in terms of reaction loads). Other than that it's probably more costly to produce, but would work.

[NateD4]

I still have a cam for sale that will fit the 3400 (and I think the 3500 LX engines). Let me know if anyone is interested.

[SappySE107]

I guess you didn't think I was interested in the other thread.

[ericjon262]

I guess you didn't think I was interested in the other thread.

funny, I sent him a pm asking for specs and a price and didn't get any response...

[NateD4]

Specs are as posted from a previous post:

260 Adv. Duration
112 degree centerline
210 duration at 0.050" cam lift

Lift is 0.310" at the cam (multiply by rocker ratio to get net lift at the valve).

Don't have a whole lot more information than that.

So far you've been the first person to actually contact me with a PM about the cam. I guess I forgot about it or missed it with the holiday. If you are still interested PM me and we'll talk details.

[ericjon262]

how many different cam sensors were there? would the cam sensor/cam from a 3500 work with a 3400 PCM?

[NateD4]

Not sure. The 3.9 cam has a special end for the vvt mount. I'll have to see if the sensor teeth are different.

Maybe someone else can give you a better answer.

[ericjon262]

I'm asking specifically if the LA1 and LX9 PCMs use the same cam signal to the PCM, if not, a cam swap is in my future.

[NateD4]

Can you post pictures of the cam you have? I can compare to the LA1 and LZG cam. Check advanceautoparts web site to see if the cam position sensor is the same part number on both engines. If it is then the cam will be the determining factor. If not.. It'll take a bit of extra work.

[ericjon262]

Can you post pictures of the cam you have? I can compare to the LA1 and LZG cam. Check advanceautoparts web site to see if the cam position sensor is the same part number on both engines. If it is then the cam will be the determining factor. If not.. It'll take a bit of extra work.

no, it's in a 3500 still. but if the cam signal won't jive with the 3400 PCM, I'll have to swap cams to one that will.

[NateD4]

The only way to know is to hook an Oscilliscope to it (which means both engines have to be running) or find someone who has already done this and knows.

Maybe one of the tuning forums would be better??

[ericjon262]

well, a quick look at the two cam triggers would tell me everything I would need to know.