What is the best camshafts choice for automatics?

[turbotom]

Ok, I'm not new this DSM game but new at picking the right parts for what I need and not slap things to together to see if it works. I have been doing a lot of research and really haven't found my answer.

I have a 92 Eagle Talon FWD which I converting to automatic and most of it's time it is going to be frag racing form. I have a light mods as engine is concerned:

refresh 6 bolt

BS removed

MLS head gasket

ARP head studs

port and polish head

stock valve train

running a PTE 50 trim

stock FA433 with stock converter or stall (I don't know yet)

Now seeing that I'm going auto, the low end suffers a little vs a 5 speed. I have a set of WEB cams 547/546.......272 intake / 256 exhaust (which I don't understand that combo.

Pretty much, what cams will benefit me more?

Should I use the WEB cams? and why?

 

[BogusSVO]

For one the stock valve springs will not take the .547/.546 lift of the cams.

Also if you you go with much more than a stock cam profile, you will need to have a higher stall torque converter.

 

[LandSpeed-DSM]

Are they really ~13.9mm lift? That doesn't sound right.

 

[DSMTyson]

Like BogusSVO said, you are going to need aftermarket valve springs. The stock valve springs can't handle much more than 264 duration cams before getting valve float or spring bounce at high RPMs.

I used stock valve springs on my DKS 272s for a while, and eventually I started to get valve float above 5300rpm. Swapped them out for some SuperTech Dual springs, never had an issue again. Now it pulls harder/smoother up top too.

With a 50 trim, some BC 272's, GSC S2s(274s), FP2(Forced Performance), HKS 272's, or Delta HKS 272 regrinds would all be good choices.

The HKS 272/264 combo would be nice too, it would retain better off boost power. But you wouldn't really have much room to grow. If you change to a bigger turbo you would want to swap that 264 out for a 272 cam.

 

[BogusSVO]

.547 x 25.4 =13.89mm

Those are some big lift cams to say the least.

A cam of that lift in a SBC, would want about 3800-4000 stall converter.

Turbotom, take some pics of any ID marks on the cam, and take a couple measurements please.

Post what you find.

http://www.dsmtuners.com/forums/art...-how-figure-camshafts-lift.html#post153121578

 

[LandSpeed-DSM]

.547 x 25.4 =13.89mm

Those are some big lift cams to say the least.

A cam of that lift in a SBC, would want about 3800-4000 stall converter.

Turbotom, take some pics of any ID marks on the cam, and take a couple measurements please.

Post what you find.

http://www.dsmtuners.com/forums/art...-how-figure-camshafts-lift.html#post153121578

Right that's where I got my numbers I just find it a stretch to think that the Web 547/546 name is referring to net lift after the 1.7 rocker.

My S3s are only ~.46x" haha

I wasn't sure our head geometry would take too kindly to that sort of lobe.

 

[BogusSVO]

Some of the aftermarket springs will take the lift of the cams, but I have a few things would nave to be reworked so they would actully work. one of the main ones would be retainer to seal/guide clearance.

Also I bet side loading of the valve would cause the guides to wear quickly.

 

[DAO 1950]

I used to run those web 546/547 cams in my 91 talon. I'm not real sure where they got those numbers from ( I think it's just their grind number ) but it doesn't designate valve lift. From their web site the valve lift is ( in inches ) .400/.385 and the duration is 272/256. They are not nearly as wild as you think. They make a nice lope at idle but nothing like a set of Kelfords as far a power production. I ran the stock springs with mine but never really did any track time with them.

 

[BogusSVO]

I used to run those web 546/547 cams in my 91 talon. I'm not real sure where they got those numbers from ( I think it's just their grind number ) but it doesn't designate valve lift. From their web site the valve lift is ( in inches ) .400/.385 and the duration is 272/256. They are not nearly as wild as you think. They make a nice lope at idle but nothing like a set of Kelfords as far a power production. I ran the stock springs with mine but never really did any track time with them.

Ok well that clears it up.

With the 547/546 being the lobe grind number.

With a net lift of .400/.385 the stock springs would be able to handle that.

 

[Mark L]

S2 or Kelford 272's will be a nice fit with the 50 trim, however the increase of cam sizing will effect spoolup for launching. Plan on a higher stall converter when upgrading too if your goal is the 1/4!

 

[turbotom]

Ok well that clears it up.

With the 547/546 being the lobe grind number.

With a net lift of .400/.385 the stock springs would be able to handle that.

Yeah sorry about that because that is the grind number, should have gave more info



Ok, now I had the assumption that on a auto to get on the boost quicker, it should go with a lower duration on intake and higher on exhaust.

Because the way I'm thinking is, having a auto you suffer a bit on the low end so anything to do to get up the boost quicker I should take advantage of it.

Manual cars have crazy low end but top end some times suffers that's why with a bigger intake cam and bigger turbo you will gain on top end.

Is this correct? and Would this benefit in a auto?