[upstand2]

Anybody have experience with this?
I suppose you have to have a bare block to install it.
https://www.competitionproducts.com/...sp?number=8271

[ap72]

I talked with the guy that designed it- I wouldn't run it. It kind of does do what it says it does, but it only does under engine acceleration AND it messes with your ignition timing. If I was running a crank trigger ignition and a good FI system it may be worth looking into but WAY too hard to tune with a dizzy and a carb.

[sam-missle]

Originally Posted by ap72

I talked with the guy that designed it- I wouldn't run it. It kind of does do what it says it does, but it only does under engine acceleration AND it messes with your ignition timing. If I was running a crank trigger ignition and a good FI system it may be worth looking into but WAY too hard to tune with a dizzy and a carb.

Please explian how this item (messes with ignition timing).

sam-missle

[ericnova72]

Originally Posted by sam-missle

Please explian how this item (messes with ignition timing).

sam-missle

If you mess with the cam timing, you mess with the ignition timing too, in relation to the position of the piston in the bore relative to TDC. They are connected by gear mesh at the rear of the cam. Move the first (cam), you moved the second (distributor shaft) too.

[upstand2]

Thats something I did'nt consider. Too bad, looked good otherwise.

[ap72]

Originally Posted by ericnova72

If you mess with the cam timing, you mess with the ignition timing too, in relation to the position of the piston in the bore relative to TDC. They are connected by gear mesh at the rear of the cam. Move the first (cam), you moved the second (distributor shaft) too.

gracias! ..

[sam-missle]

Originally Posted by ericnova72

If you mess with the cam timing, you mess with the ignition timing too, in relation to the position of the piston in the bore relative to TDC. They are connected by gear mesh at the rear of the cam. Move the first (cam), you moved the second (distributor shaft) too.

Valve timing is valve timing, ignition timing is ignition. the dist. is driven off the cam gear only. you rotate the dist. around the driven shaft to set the ign. timing relative to TDC. Has nothing to do with valve timing. if that were the case millions of vehicles would have messed up ignitions, as most engines have timing chain or belt tensioners on them.

sam-missle

[ap72]

Originally Posted by sam-missle

Valve timing is valve timing, ignition timing is ignition. the dist. is driven off the cam gear only. you rotate the dist. around the driven shaft to set the ign. timing relative to TDC. Has nothing to do with valve timing. if that were the case millions of vehicles would have messed up ignitions, as most engines have timing chain or belt tensioners on them.

sam-missle

millions of cars (old ones) do have misadjusted ignition timing.

When you phase the cam in and out with relation to TDC of the crank the ignition timing changes along with it as it is driven off of the back of the cam. If your cam timing changes under acceleration then if the distributor is driven off the back of the cam, it will change too.

This is also a reason for a lot of spark scatter on older worn SBC engines.

[ericnova72]

Originally Posted by sam-missle

Valve timing is valve timing, ignition timing is ignition. the dist. is driven off the cam gear only. you rotate the dist. around the driven shaft to set the ign. timing relative to TDC. Has nothing to do with valve timing. if that were the case millions of vehicles would have messed up ignitions, as most engines have timing chain or belt tensioners on them.

sam-missle

We are discussing moving (variable) cam timing in a RUNNING SBC engine by way of a chain tensioning device. If the tensioner advances the cam, this will advance the ignition timing too because they are geared together. Unless you have an idea for a variable distributor housing positioner that will counteract the variable timing chain tensioner, the timing IS going to change.

[ap72]

Originally Posted by ericnova72

We are discussing moving (variable) cam timing in a RUNNING SBC engine by way of a chain tensioning device. If the tensioner advances the cam, this will advance the ignition timing too because they are geared together. Unless you have an idea for a variable distributor housing positioner that will counteract the variable timing chain tensioner, the timing IS going to change.

Because having two moving parts where there used to be none is always a good idea.

The best thing I can think to use to get around it is just going with crank fired ignition.

[cobalt327]

That gizmo has been around for ages- and it never caught on.

If done "right", like the OM's do it, it can work very well.

Ford uses it on their cammer engines, Honda as well, IIRC. Prob. others. But done by an entirely different system hydraulics and ECM, etc.), although the basic principal is similar between them all.

Recently, Comp came out w/a variable timing deal for the Ford OHC that replaces the OEM unit that would (in stock configuration) advance the cam up to like 40 degrees, IIRC.

Problem was, with a healthy aftermarket grind, the valves would get too cozy w/ the pistons. The Comp mods brought this figure down considerably, but still allowed for a lot of degrees of movement. This has to be better than the previous option of eliminating the advance feature all together.

[Guy Hiltz]

I would think that any difference in cam or ignition timing with this device is going to be very minimal,its a copy of this Comp Cams peice;
http://www.compcams.com/technical/Ca...106-07/320.pdf
The timing chain would have to have an awful lot of stretch in it before there would be an advantage to using this.And to call it a variable valve timing control device seems to be a bit of false advertising,its is a tensioning device,period.And 7-30 hp gain,this isnt even realistic !!! And the parts are affected by wear and need to be checked on a regular basis.Just another case of someone trying to lighten our wallets with an unecessary peice. JMO !!!
Guy

[timothale]

Rhodes Hyd lifters did a similar thing. The lifters had a controlled bleed down so at lower rpm the lifters would bleed down giving less duration and lift and at higher rpm less bleed down time and closer to what the cam grind would do with solid lifters. I had a set years ago and they were noisy like solids at lower rpms.













r

[ap72]

Originally Posted by Guy Hiltz

I would think that any difference in cam or ignition timing with this device is going to be very minimal,its a copy of this Comp Cams peice;
http://www.compcams.com/technical/Ca...106-07/320.pdf
The timing chain would have to have an awful lot of stretch in it before there would be an advantage to using this.And to call it a variable valve timing control device seems to be a bit of false advertising,its is a tensioning device,period.And 7-30 hp gain,this isnt even realistic !!! And the parts are affected by wear and need to be checked on a regular basis.Just another case of someone trying to lighten our wallets with an unecessary peice. JMO !!!
Guy

Its not a guy tryiong to pawn off snake oil- it actaully does work, its just that like most first steps it has a lot of flaws and needs refining. Not a bad idea, just hard to implement effectively. I could see 30hp on a big block given the right parameters.

[Guy Hiltz]

There is no way on earth that taking any play out of a timing chain is going to result in a gain of 30 hp on a big block,a little common sense should tell you this.Again,this device does not control variable valve/cam timing,it puts tension on the timing chain,plain & simple.
Guy