I have a question about camshaft overlap and driveability. My current 407 LS2 based motor runs very strong but suffers a tad bit with low rpm driveability. I am assuming it is due to the large overlap of my cam. My current cam has an overlap of 14 degrees. I am considering changing shafts in an effort to gain more low rpm driveability, but I am not smart enough to know how far I should go. I realize that I will most likely give up peak power, and I am OK with that. I am considering a cam with only 4 degrees of overlap. Will that change significantly increase my low rpm driveability? Thanks in advance.

 

That amount of change should help a lot. The better the tune the better it will drive also. What size, ICL and LSA is the current cam? What cam are thinking about going to?

 

I have a brand new 4 deg overlap cam 228/232 LSA 113, 600 lift. Lemme know if you interested.

 

Current cam is a 242/242 114+2 installed at 111. (Again in a LS2 based 407). I am considering a 232/232 114 installed straight up. It has been tuned and tuned (my tuner probably hates me because he has gone out of his way numerous times to try and get it to drive better below 2500rpms. I cant thank him enough). The car is just a little too "herky-jerky" below 2500rpm and during cruise. My wife doesnt much care for it LOL!

 

I'll keep it mind. Thanks.

 

I tried to figure out what your engine build from your signature, seems you are running a Tony package?

If so did he select the cam?

Ahhhhh! I knew there was something familiar bout this Just did a little searching.

What are Tony comments regarding this cam choice & your drivability concerns?

Are you HPT capable?

 

Not enough info to know for sure, but that sounds like a excellent size for a street cam.

 

232/242 .590/.590 112+2

More exhaust then intake should provide more torque

may want to go smaller to get low rpm livability.

228 / 232 .588/.595 112+2

 

A speed density tune would help and probably rid all of your driving issues. Is it currently a MAF tune or SD?

 

That cam would really wound the OP build, that motor is a very well optimized build.

I'm extremely interested in this as I have just finished my 416 with a slightly larger cam......& I don't want no cranky ***** Phk'r.

I'm curious if all the little tuning tricks are exhausted, there are many.

 

Everybody is different when it comes to what they will and will not put up with. My 383 has a 238 242 on 114 stright up and it has some drivability issues also. I've thought about changing it to tame the car some, but probably will try running it in SD first and see how it goes. When you get a engine that is a little cranky down low mixed with a harsh clutch it's a parking lot nightmare. I'd probably do the same thing the OP is doing if it doesn't get any better after SD and add a nice smooth organic type clutch (either single or twin). It usually costs a lot for a clutch that will hold a lot of power and abuse, but drive nice.

 

How often do you drive at what rpm?

some times it is very cool to have lots of High RPM HP, but if you never or seldom drive in that RPM range, why go there? For the bar / bench racing bragging rights?

 

 

Not sure about the OP, but I have 3.90's, etc so I can use the high rpm stuff. I'd consider my cam to be in the mid/high range when sizing a cam for a 383. Hell it's not much bigger than the g5x3, ms3, m4, etc that people use on stock cube builds, but then again they might not care about drivability as much or have a different view of what is ok, etc. I also built my engine a few years back so what I wanted then might be a little different now as i get old

I'm helping a friend build his engine after a rod bearing problem and I know he wants it to drive very nice. I think we will be staying around 218-220 on the intake on stock cube or just a touch bigger if he decides to go 383. Nice smooth power under the curve.

 

slow ride you are making very good points, my question for you is tuning, you or some else?

 

Thanks everyone for the responses. I apologize for not being more readily available to answer questions as they come, unfortunately this thing called WORK got in the way LOL! I will try to answer all of the questions asked......

I am for sure not interested in an SD tune. The car is located in Indianapolis, weather conditions can vary from 40 degrees F to 90 degrees F and the humidity can swing wildly as well; I do not tune, and want the car to simply be a “turn the key and go” and not have to worry about weather conditions and tuning. Everyone has told me I should stay with the MAF tune. The car is not a "daily driver", but it spends 99.9% of its time cruising around town, stop light to stop light during the spring/summer/fall months when the weather is nice. I drive to work every now and then, I take the wife out to dinner often in it, and we go shopping in it. So it is every bit an in town, parking lot, stop sign warrior, with the occasional "spirited" romp on an on ramp, passing a guy on the interstate, or doing a 1-2-3 gear burnout to put a smile on the little kids face in the next lane kind of thing. So as you can imagine, the car spends most of its life below 2500rpm (I have 3.90's in the car - Z06 tranny - so I cruise down the road between 1700 and 2200rpm). I have spent as much as I am willing to spend (money and time wise) having the car tuned (two well known tuners have touched the car and they got it as good as they could get, and both of them told me, "you are not going to get the kind of low RPM driveability you are looking for with that size of cam in the car". I am gladly willing to drop 20HP peak to gain low rpm driveability, as I have no need to impress anyone “with a number”. I like torque, low rpm torque and instant throttle response at any rpm (ex road racer mentality).

The car has an RPS twin carbon clutch in it. GREAT clutch, very easy to maneuver in tight parking spaces, but it is VERY light weight (clutch/flywheel combo), and I think that light mass coupled with the large cam overlap just exacerbates my low rpm issues.

I have pretty much decided that I am going to change the cam, but like I stated, I simply don’t know enough about camshafts to make a decision on my own, and I don’t want to take one guys advice, I like getting several different options, different perspectives, points of view, etc. Is going from 14 degrees of overlap to 4 degrees of overlap a big enough change to significantly increase my low rpm driveability and not completely choke the motor off? Is it too much? I don’t know, hence my question. FWIW – my car makes 540RWHP and 500RWTQ right now. I would be tickled pink if I can gain a bunch of low rpm driveability and still make 525RWHP and 490-500RWTQ.

Thanks again everyone for taking the time in trying to provide me with suggestions.

 

You are making fantastic power in my opinion. What heads are you running? CTD made reference it might be a "Tony" build. I am running a set of his massaged AFR 205s on a 418. He spec a 236/236 114+2 cam for me because I told him I was worried about low RPM driving. It wasn't horrible but I got tired of trying to clean it up. CTD actually offered me help. I swapped the cam out to a 234/234 116+2. I went from 8 degrees to 2 degrees of overlap. It drives really smooth now except for a little hiccup at 1600 rpm transitioning from little to no throttle. I never had it dyno'd but a ZR1 could not pull me down the main straight at Summit Point. The power seems to carry higher. It will easily bang the rev limiter (6800) in 4th if you are not paying attention. I did it a couple of times chasing the ZR1. However based off of the numbers in my VE table I am probably down 5% on power between 4400 and 6000 rpms. Bottom line is that I don't regret going to a smaller cam. Exhaust smells better too! Good luck!

 

It's been on the dyno by another tuner. I'm not not a rookie to engine tuning in general and have a good grasp on stuff, but just never got around to getting HPT or EFI live yet. My plan is to buy one this year and work on the low throttle stuff in the current tune and maybe try SD later on. Not saying it would stay that way, but I wanted to eek everything out of it I could before changing something down the road. I'm open to all suggestions though. My current cam has 12 deg overlap.

i'm actually looking forward to my friends small cam setup just to see how things turn out and how nice it drives.

 

This is exactly the kind of real world experience I am looking for. THANKS!! Based on your experience, it sure seems that going from my 14 degrees of overlap to 4 degrees of overlap would indeed be a good change to get a significant increase in low rpm driveability without taking away too much power.

 

Not new to tuning I'm assuming Carbs? In some ways Carbs are easier because the motor will tell you how it runs & of course very few items to work with. If you are able to make a carb run properly then you know it can be done with EFI & better.

I'm HPT, I don't think you can go wrong with either software. The learning curve is steep so I would make your purchasing decision based on the education material available as well as support. Maybe a mentor.

I started self tuning to try & correct some of the very issue's being discussed in this thread. Many things are a test & tune, some work some don't, you have to try. Difficult to pay a tuner for the hours that it takes for that perfect tune. Resilience