What is the largest camshaft I can run

[AleroB888]

It's funny you say that because you can't get a Porsche Turbo S with a "stick" Only an automatic with a torque converter Yes it has manual mode but it doesn't have a clutch pedal.

I use this car as an example because I know someone who just purchased one and he wanted a true manual but when he tried driving one of the autos in manual mode he couldn't even react quick enough due to the power, so never mind having a clutch and shifter to operate.

I don't know why it was, but my first 4T45E tranny really banged the shifts in here, I have a switch to force full line pressure. Then the next two I got did not nearly do as well in that area. But then again, that first one leaked a little tranny oil every time I used the switch, and needed more brake pressure to hold it at a stop.

[3400-95-Modified]

Life sure looks complicated with an automatic, seems best to just run a stick and have the stall speed any thing you want it to be. Never could understand a performance car with an automatic. Gues it is good for the Wife or your Mother to drive. Larry

It's funny you say that because you can't get a Porsche Turbo S with a "stick" Only an automatic with a torque converter Yes it has manual mode but it doesn't have a clutch pedal.

I use this car as an example because I know someone who just purchased one and he wanted a true manual but when he tried driving one of the autos in manual mode he couldn't even react quick enough due to the power, so never mind having a clutch and shifter to operate.

[Superdave]

more consistent times at the drag strip is usually why, other tracks like road course are more suited to manual though.

[trotterlg]

Life sure looks complicated with an automatic, seems best to just run a stick and have the stall speed any thing you want it to be. Never could understand a performance car with an automatic. Gues it is good for the Wife or your Mother to drive. Larry

[Blacktree]

Looks like I dropped in too late, but...

Wow, you guys are auto Noobs.. lol

Converter stall speed needs to match the peak torque of the engine, with a stock converter probably being 1800-2000 then not much cam.

With a cam that's large enough that it needs to idle higher, you also need to run a higher stall so the car doesn't constantly try to lurch at stoplights. The emailer is correct, it's a bitch to have a lopey cam and a low stall converter.

^ THIS

I'm guessing the stall speed on the stock torque converter (for what car? what engine?) is probably not going to be above 2500 RPM. So a mild performance camshaft (i.e. for midrange torque) should work well with it.

Anyway, I guess it's too late now.

[caffeine]

I had to cut my pistons to clear the exhaust valves with my cam so that's probably farther than the inquirer wants to go based on the fact he refuses to upgrade the converter.

[19Cutlass94]

Oh shoot. I though I had a decent cam lol


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[ForcedFirebird]

Yeah that cam I bought from Mars is probably as big as anyone would go without ported heads but it still idles at 900ish with a nice lope.

BOOM!

[caffeine]

Yeah that cam I bought from Mars is probably as big as anyone would go without ported heads but it still idles at 900ish with a nice lope.

[SappySE107]

Shelf cams?! Im gonna hop in my pregen and drive down to Florida to have a talk with John:P

I guess there is the "smooth idle" that this guy probably wanted to know, and then there is the "not gonna idle below 1200 RPM no matter what" that I was thinking of as being too far. Lot of cam between those 2 points. I don't know think anyone with a hydraulic roller cam has gone too big for the engine to not idle at 1000 or less.

[Superdave]

I wasn't talking about our shelf cams

Ben doesn't sell shelf cams. (kidding)

[ForcedFirebird]

I wasn't talking about our shelf cams

[Superdave]

Very true, Ben's cams seem to have a better idle quality than the one I designed. Mine sounded better though. :P

[ForcedFirebird]

FF, it has NOTHING to do with lock up.

It has to do with flash speed, or "stall speed" of a converter and the new necessary idle RPM, along with how the torque curve comes in. A more shallow torque curve needs a higher stall to be effective (which is usually those larger cams), where as a cam that promotes the torque curve to come in more steeply can use a lower stall speed, but there are a bunch of other factors that can influence the torque curve as well.

This is a valid question, though a bit sparse on the information needed.

I said "lock" but meant stall speed. We have sent people some pretty radical cams that were still able to idle 7-800, albeit very lopy.

The closer your idle is to the "rated" stall speed the more your converter is going to pass power on to the trans. With my 4K stall in the Camaro I could take my foot off the brake and the car would barely start to roll at 1K RPM, with the 3200 stall it was just a little worse than that, I could idle and do like 5-10 MPH.


Jump in an auto car and go drive it like normal, then at each stop light or in a drive thru give it just a little gas so the idle comes up to 1K or so. You're always on the brakes hard to keep it from rolling. Now imagine that with a fat lumpy cam and the car shaking all over the place.

A higher stall converter will engage less at idle RPM's than a lower stall converter.

Yes, I understand perfectly, but again it's not often that a street driven daily car is going to have a cam that requires a 1k idle.

[Superdave]

Yah, need more info for sure. I assumed it was for a stockish Gen 3 in something like a GAGT but you never know...



I would just dig through cam cards for LS engines, that will give you an idea of what works ok with stock converters and what needs more.