What is the largest camshaft I can run

[1988GTU]

Why do I get the feeling I know the respondee

Just reply with.

"You would need to provide more vehicle engine specs otherwise, a 255/75R15 tire is needed. Only a single 255/75R15 tire, and none more!"

[SappySE107]

What kind of build/application are we talking about? Solid lifter, 8000+ RPM? Is this a 2.8 race motor? There is nothing listed on the store that comes close to what you describe. We can design something, but it really needs to be serious to make full use of a cam designed for high RPM only.

Ben Phelps
WOT-Tech

That was my reply, hoping for more info. alas...this came back.

Never mind. I'll find out for myself. I can't believe a site that sells performance parts doesn't know anything about what size camshaft is the biggest for street use with a stock torque converter....smh. Someone building a race engine wouldn't be using a stock converter.

So...he isn't building a race engine! Thats all I know. I don't know what overlap/cam specs would be "too much" that the car can't idle below the speed in which the converter is trying to pull the vehicle. I know what has worked but never anything that wouldn't have.

[Superdave]

Idle in gear, engine running at ~800rpm with 1800 verter and 3k verter, what's the difference? The lock won't start until well over 1k. You have me confused as well now. Sure, vacuum will suck (pun), but no matter what the verter won't lock until XXX-ish RPM.

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.

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.

[ForcedFirebird]

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. .

Idle in gear, engine running at ~800rpm with 1800 verter and 3k verter, what's the difference? The lock won't start until well over 1k. You have me confused as well now. Sure, vacuum will suck (pun), but no matter what the verter won't lock until XXX-ish RPM.

[Superdave]

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.

My Nova has this issue, needs a 3k+ stall and has something around a 2K. The RPM drop between Neutral and Drive also makes tuning suck, I have about a 200 RPM drop in the Nova.


design the cam to idle around 900 RPM and make peak torque at 2K-2.5K and he'll get what he wants. Or he could just man up and order a new converter.

[caffeine]

Obviously a big cam would benefit from a higher stall torque converter. I don't really know much about automatics though. Obviously the engine would idle the same regardless of stall speed haha

[robertisaar]

wait, legit opinions are desired?

would need to know which converter it has at the very least, the 4T60E in 95 alone lists converters that range from ~1400 to ~2400 depending on application.

[ericjon262]

I will say that for the overall performance of the car, stall speed needs to be taken into consideration, but overall, it's one factor in a sea of many that should be considered.

[SappySE107]

Let me help you guys out. I asked what the torque converter has to do with the camshaft.

"Having to idle the engine up to compensate for the overlap of the camshaft. If the torque converter doesn't have a high enough stall, it won't idle properly. "

[robertisaar]

that's a pretty awesome email.

so, i have 255/75R15 tires on a geo metro, how much lifter preload do i need?

[ericjon262]

based on the information given, stock.

[SappySE107]

What is the largest camshaft I can run with a stock torque converter?

That is the email I got. Makes no sense to me because I have never speced a cam based on the torque converter. What do you think?