4AG Cam comparison

[Ben Wilson]

I'm planning a NA 4AG in the future and I was looking at the cams which are out there, It all got a bit confusing, so I compiled a table of everything I could find and did some conversions so I could compare them directly.

I thought this might be of use to others.

I just used a conversion of 1.24:1 for advertised duration vs duration at 0.050", so it probably won't be anywhere near 100% correct, but is does give a comparison.

[Starfire]

While lift and duration are important figures you should probably look in to the profiles used on the lobes and the base radius as well. I know that TODA use different profiles on the leading and trailing edge of the lobes to open the valve quickly and reduce the wear on the valve seat.

[Ben Wilson]

Find me the information (and a way to format it), and I'll add it to the table...

Seriously, this isn't supposed to be a bible for cams or anything, just a simple list showing what you can get off the shelf.

[monkeymajik]

Very cool!

Those Kelford cams have some crazy lift.

[Ben Wilson]

Those Kelford cams have some crazy lift.

The simulations I've been doing recently and flow bench testing I've seen seem to indicate that lift is gold for 4AGs, far more important than duration.

[GUN METAL]

great spread sheet Ben, REP for you.

Its got me really interested to find out whats in mine.

All i know is they are HKS and have bigger valve springs and pushing bigger valves i dont know if they are using shims or what it was not on the invoice

Is it possible to measure the specs without taking them out ? never even looked in there

Sorry if this is a stupid Q

Also you were saying lift is the go rather than duration right ? is that for NA or forced induction as well.

This has probly been discussed a million times before but what is the max lift while still being a non interference design ie no smashing of pistons and valves should the timing belt break ? suppose valve size plays a part as well

[Ben Wilson]

My old HKS cams had the size stamped on the end of the cam. Pull of the rocker covers and have a peek

[Ben Wilson]

Here's a quick and dirty comparison for the lift vs duration thing.

Using Engine Analyser Pro, I first mapped an engine with something like factory cams - light blue.

I increased to lift to .35" (green)

Took the lift back to standard and increased the duration to around 288 degrees (dark blue).

I wouldn't take any of the actual numbers as gospel, but you get the idea of the differences.

[GUN METAL]

Sounds good its been on my list of things to do for a while but my inrigue has not currently outweighed my time available/lazyness/ priority scale.

I know that nick is interested maybe he can come over and do it for me

[Starfire]

Older HKS cams don't have the specs stamped on them - just a part number.

Lift is more important than duration in a boosted engine. If you want big power from a NA then you want plenty of both!

There would be shims in your engine as they adjust clearance between your cam and your valves. Whether they are under or over bucket you would have to have a look to see.

To determine the specs of your cams you need a degree wheel and a dial indicator. Fix the degree wheel to your crank pulley and remove the cam covers from your engine. Set up the dial indicator so that it is in contact with the lowest part of your cam lobe (the base circle). Rotate the engine a couple degrees, measure the dial indicator. Rotate the engine a couple degrees, measure the dial indicator. Rotate...

Once you have completed a full rotation you would be able to work out both the duration and the lift of the cam. You could also plot the results on a graph, which will show you how rapidly it opens and closes the valve - something that can vary quite a bit between cams of the same lift and duration.

It is worth noting that most cam manufacturers quote their lift and duration as being from a certain amount of lift (usually 20 thousandths of an inch). This is to compensate for the reccomended clearance of the shims. If you don't account for this you will end up with bigger numbers than the cam actually is.

Cheers,
Terry

[Ben Wilson]

Older HKS cams don't have the specs stamped on them - just a part number.

My table has the HKS part numbers on it

It is worth noting that most cam manufacturers quote their lift and duration as being from a certain amount of lift (usually 20 thousandths of an inch). This is to compensate for the reccomended clearance of the shims. If you don't account for this you will end up with bigger numbers than the cam actually is.

I've found 0.05" is the usual number for 'serious' manufacturers, the 'big number' brigade usually give full advertised duration.....

Rather than to compensate for shim clearance, it's just easier to measure exactly. Otherwise you're looking for the moment the dial indicator starts to move, watching the indicator ramp up to 0.05 is much simpler and more repeatable.

[GUN METAL]

This is all good stuff excellent, the intigue is building

So i will rip of the cam cover and have a look see if i cant find the info i am going to need a dial indicator and degree wheel. Where can i get em from and what would i pay for em.

The thing i think of with cams is COMPROMISE.

I suppose the intended use is going to be the determining factor on selection oh and maybe emisions (go and hug a tree somewhere else i say) i am riding my pushy to work most times so the rest of you get stuffed i will put as much crap out of my exhaust as i like HAHAHAHAAHAHAHA SORRY.

Anyway for my money i want the most power under the curve NOT peak power. So for my application on the track with the current gearing i want it making good power from 4 to 7 grand which it pretty much does So basically max torque available at 4 grand where you need it to pull you out of the corners, it will rev to 8 but i just dont need it.

So if it doesnt do much below 4 grand i dont think i would care, it would probly be crap on the road, but thats where we come back to compromise

So with this vast array of cam profiles how do we best determine what will be best for the application.......without actually trying every combination etc etc or can you engine analyser give you a good idea of the torque / power delivery / spread

[Joshstix]

You can get a free printable degree wheel from http://www.toymods.net/forums/showth...e+degree+wheel

[Ben Wilson]

So i will rip of the cam cover and have a look see if i cant find the info i am going to need a dial indicator and degree wheel. Where can i get em from and what would i pay for em.

I got mine at Bunnings, I think it worked out to $80 or so with an adjustable magnetic base. Borrow one if you can.

So with this vast array of cam profiles how do we best determine what will be best for the application.......without actually trying every combination etc etc or can you engine analyser give you a good idea of the torque / power delivery / spread

That's the big question with anything car related. The only real answer is experience, either yours from trying it and learning, or getting advise from an expert..

[GUN METAL]

Josh, thanks for the link

Ben, was looking at the curves you posted from the analyser thats pretty cool what is the extent of the data do you enter to get that output, like how specific is it ?