Cam Regrinding Anyone?

[MV8]

So I'm collecting bits for my planned build. They don't offer a camshaft with the specifications I want so I'm having an oem cam reground.

I contact a well known cam regrinder with a good reputation that has been in business for decades. He sends me the patterns he has in spreadsheets. I ask for hydraulic roller, hydraulic flat tappet, and solid lifter flat tappet (these all have basic ramp differences). I settle for a cam that checks all the blocks for building dynamic compression to the max for the octane I want to run and still have a static 9:1 compression and around 10 degrees initial timing. A full length header and three cv carbs on short runners should take care of the curve above the torque peak and overlap was kept low for that reason. This cam is the only solid lifter grind which has a "D" on the end of the grind number.

 

He says he can't do it. I ask if it is because of the difference in LSA, which can be changed during setup to something closer to the oem cam. He says the "lobes are oddly shaped" because it is a diesel cam. I said that makes perfect since and exactly what I want. He mentioned another cam he recommends for the engine, that makes the lumpy sounds with much overlap but little lift, and with my combo, I would be blowing gas right out the header at lower rpm. I spec my second best and he thinks that will work so we will see. I have respect for his work and appreciate he is still working and not retired. He probably gets less technical folks calling him on a regular basis, but it kinda reminds me of the concrete guy last year or when I ordered a 3.1 crank (internal balance) from the machine shop working on my 2.8, so they try to give me a 2.8 crank (external balance) and say nothing. Funny story to share imho. Funny these situations have one thing in common. ME.

 

Before you ask, these are chill cast through hardened oem iron cams so I am not concerned about grinding through the hardening. 

[Dave W]

Try contacting Jones Cam Design in Denver NC.  Mike Jones @ 704-489-2449

[MV8]

Found it. http://jonescams.com/custom-camshafts/

I was fortunate that the shop doing my work had a core available to grind for my engine, since it has been out of production for about 35 years.

 

I could have a cam made without limitation on a new blank for around $300 by any that offer new cams for this engine, but this is just an experiment at this point so I'm into it for about half that now, including their supplied core.

[ashyers]

I’ve used Delta Camshafts in Washington. They’ve been good to work with.

 

Andy

[mrmustang]

I'm wondering what the stage "1" and stage "2" cams from Caterham are (or were for my US based Zetec) and whether they might be a place for you to start before you start to redesign a cam profile from scratch.

 

Bill

[MV8]

20 hours ago, ashyers said:

I’ve used Delta Camshafts in Washington. They’ve been good to work with.

 

Andy

I've been intending to contact him for profile charts but he says he has around 10,000? I've not because I waiting on the cam I ordered for this engine, but I am looking at a cam for another. Did he provide you any charts? Jones has his charts listed on the site. I expect it is up to 10,000 combos because his masters are just lobe profiles where the others list an entire cam. You can only grind one lobe at a time so I don't know that there is any difference except someone can point to the cam they want instead of figuring everything out. 

Edited Monday at 10:30 AM by MV8

[MV8]

4 hours ago, mrmustang said:

I'm wondering what the stage "1" and stage "2" cams from Caterham are (or were for my US based Zetec) and whether they might be a place for you to start before you start to redesign a cam profile from scratch.

 

Bill

Too late! They've had my order for about a week so it should ship soon. What are the specs on those?

 

Not really from scratch. I start by deciding on the fuel quality which brings me to a reasonable 9:1 (that I can tweak later depending on the other specs). I use 25-30% of the intake valve diameter for a target lift unless the flow rate is known. A target lobe separation angle (LSA) can be determined by taking the cubic inches per cylinder divided by the intake valve diameter, multiplied by 0.91, then subtracted from 128. The intake lobe centerline (ICL) and intake duration can be adjusted for an intake valve closed (IVC) degree that provides a dynamic compression of about 8:1 or 160psi, to aid cylinder filling from cranking to the torque peak rpm. Finally, the exhaust duration split of maybe 10 degrees. This would be a cam for average torque over the range rather than peak hp a the cost of mid-range torque. I could have gone more aggressive with duration and give up some efficiency but that was not my goal. This cam should allow 89 octane and 10 degrees initial advance with a normal curve and no detonation on top.

 

Here is a clip of the cam testing competition performed on an LS by Eric Weingartner a few months ago https://www.youtube.com/@WeingartnerRacing

 

Notice the specs are all over the place with different methods but I think drastically different efficiencies. I built a spread sheet to fill in the blanks.

Edited Sunday at 08:51 PM by MV8