What is the best lobe center for a street cam on 91 octane at 9 to 1 Compression

[rick m]

This is a topic that really gets bantered around on the V8 forums. If you were to build a 2275 street engine, run 9.0 to 1 compression, want all your driveability and torque between 500rpms and 5500rpms, what lift, duration, lobe center and type of cam would you run? Also, what size valves and flow per port would you look for not taking your lift over .500?

RM

[DKK Ted]

I built a 2275cc for a guy with JD 44X37 heads, W/IDA's using a K-8 on a 106* LC, made some good #'s on JC's dyno, and alot of torque.

Ted

[hotrodsurplus]

Here's my experience with an engine that had traits similar to what you're looking for. Consider this a baseline.

In the very early '90s I ran an Engle W-110 in a 2110 with 40x35.5s, 8.5:1 static, and 44 IDFs with I think 34mm venturis. It came to life explosively and by 3,000rpm it got really fun. It ran like gangbusters right to about 5,500 at which point it pretty much hit a wall. Some additional porting and chamber work by Shaun McCarthy and 8.9:1 static made it more powerful across the board and let the engine run closer to 6K. It didn't accelerate as hard at that speed as it did at say 5,500 but it still ran well.

On the FAT dyno that engine made 122hp right at 5,500. I remember that it made peak torque right at 3,500--that engine made peak torque and HP at basically the same speeds that everyone told me that it would make. I wish I could remember the torque figure but the engine made so much over such a broad range for an 'ordinary' cam built for 1:1.1 rockers that it made Fleming sort of chuckle--I tell you that was a good feeling. I bought a lot of parts from FAT but this was an engine that I built with the help of a mentor.

For reference the W-110 cam has 247 degrees @.050. It also has a 108 LSA. That engine made good power but I really feel that it could've handled a few more degrees duration. The torque was so solid that I would've noticed the high-speed gain more than the low-speed loss.

I've thought about building a similar engine. If I did, I'd seriously consider about similar duration but with faster ramps--think FK-43 or FK-44 or Pauter K7 or even Web Cam 110 or 109. You gotta run a really good spring and in probably all cases sleeve the lifter bores but there's nothing saying the valvetrain wouldn't live long if set up right. And boy the torque would flat-out scare you--it would be meaty across most of the power band. I mean a 2276 is a big engine compared to a 2110 and a 2110 is a pretty damn stout engine in its own right--mine was a hoot to drive.

Oh, and all of those cams have 108 LSAs right out of the box. I don't know if I'd deviate much from that. I think you could do more harm than good.

I think the best thing you could do is call a friendly cam grinder. I say call Laurie Dunlap at Web Cam. She knows her stuff.

[rick m]

Hot Rod....

I have been talking with a lot of V8 guys and a well known VW cam grinder and we ground my cam on a 106 lobe center. Many a V8 guy has run this LC and built killer torque motors for up to 5500 to 6000 rpm.  The key I am working toward is the fact that I do not DRAG RACE my car.  I do 100% of my driving on the freeway or stop and go. 

I like your 2110 motor. Sounds a lot like the one I built and had in my 67 street car. I had a PAUTER F8E7 cam in that engine. It was measurably smaller than the K8. I could park it on 7000 rpms in the burnout box.  However, with the duration 0f 274 and 108 lobe center, most of the power came in after 2500 rpm. It felt a little soft in the mid-range so I am planning a motor that will come off idle and pull like a banshee up to 5500 with the redo of my 2276.

My heads and motor size, including the IDAs, will give it all the volume and flow it needs.  My dynamic compression ratio target is between 7.5 to 7.8.  The exhaust on the new grind will close at 35 degrees ABDC to give me the static compression I am looking for.  The duration at .050 would make some think we were nuts.  The overlap on the cam (we collaborated with a cam grinder on) will not have much overlap but will have close to .473 lift with the 1.25 SCAT pro rockers. 

I am going for torque that plants you in the seat early (off idle to 5500) and not concerned about horsepower made after 5500. Motors that make more power at the bottom end don't have to be twisted to 6,000 to 7,000 rpms to be a fun ride.

Most of us VW guys have been used to building a big motor and throwing a cam grind off the shelf in it. Some play with the cam advance or retard to help change a few characteristics.  I like the idea of having a custom cam grind made that is purpose built for what I want to do.  The current cam I will be experimenting with to achieve my desired results is patterned after what V8 guys have been doing. This is where most VW grinds originated anyway....from V8 cam profiles. 

It will be interesting to see what it produces with the chamber design, compression ratios (Static and Dynamic) as well as the motor size and flow of the heads at a lower RPM. I am always game for trying new things...to get my motor to do what I like for every day driving.

Rick M

[hotrodsurplus]

I have been talking with a lot of V8 guys and a well known VW cam grinder and we ground my cam on a 106 lobe center. Many a V8 guy has run this LC and built killer torque motors for up to 5500 to 6000 rpm.

If you're working with a cam grinder that fully understands the game (not all do) then you're in good hands futzing with LSA. When I worked at Kymco Ron Silva built a 2276 (I believe) for a play car. He had Web grind the cam to a narrower LSA (initially against the recommendations of the grinder) and that car ran very low 11s on pump gas.

The key I am working toward is the fact that I do not DRAG RACE my car.  I do 100% of my driving on the freeway or stop and go.

 

Well that's sort of a given--I wouldn't have talked about such a mildly cammed engine otherwise.

However, with the duration 0f 274 and 108 lobe center, most of the power came in after 2500 rpm.

Mine wasn't exactly a slouch when slower than 2,500rpm but I wouldn't exactly expect an engine with any sort of cam and the ports to use it to make brag-worthy power in that range. I mean I could pussyfoot my engine around just off throttle and have fun just the same. You can get a nice flat torque curve but as a rule you're going to concentrate most of the power at a higher speed.

The exhaust on the new grind will close at 35 degrees ABDC to give me the static compression I am looking for.

 

Static CR is simply swept volume to chamber volume. Effective is determined by the static and the point where the

intake

valve closes. Dynamic gets used interchangeably with effective but dynamic is technically determined by the effective CR and charge velocity.

I am going for torque that plants you in the seat early (off idle to 5500) and not concerned about horsepower made after 5500. Motors that make more power at the bottom end don't have to be twisted to 6,000 to 7,000 rpms to be a fun ride.

Torque is what made the Olds W30 package so fun to drive. Torque makes cars launch hard. It fries tires. It does all the things kids (like us) like to do.

Most of us VW guys have been used to building a big motor and throwing a cam grind off the shelf in it.

You're preaching to the choir. Volkswagen guys at one point were pretty damn savvy but then somewhere along the line they lost their way. It just blows me away that so many people consider a generic ignition curve from an off-the-shelf distributor will work properly for a performance engine. The whole industry is lacking things like affordable dished pistons, things that the corn-rocket industry takes for granted.

This is where most VW grinds originated anyway....from V8 cam profiles.

 

I got one better for you: most older V8 cam profiles were taken directly from Flathead grinds.

It will be interesting to see what it produces with the chamber design, compression ratios (Static and Dynamic) as well as the motor size and flow of the heads at a lower RPM. I am always game for trying new things...to get my motor to do what I like for every day driving.

Experimentation is the name of the game. You have me on everything except the big chambers--that's a lot of area to light off completely in such a short amount of time. Don't take that as me saying it won't work; it will. But I think there are better ways. I respect your motivation, though.

[rick m]

Thanks HOT ROD for the feedback.  In the last 42 years, I have tried all the conventional combos.  I am trying to work from a new PARADIGM.  I have some friends doing some pretty non-conventional things right now and they are proving that continuous improvement pays off through R&D.  Proof is in the doing. My future hot rod (VW that is) will have some new ideas as well.  Can't wait to fire this one off.  Will be a couple weeks before it is back in and running. Will break this one in on my test stand to have a chance to break in the new cam, re-torque the heads, set jetting, etc. before putting back in the car.

Rick M