Cupcar

Anyone used a set of custom heads made by CMW Motorsport?

They can make a complete CNC machined set of heads from virgin aluminum.

Customer can specify port specs, valve sizes, valve material and combustion chamber volume to order.

Seems a nice way to go, any experience out there?

Kevin

Heads alone won't give you the HP holy grail.. Chip tuning, or Motec, displacement change, custom dyno tuned headers, 102mm P & C's, where does it end at what cost.. Then find a proven shop that has real world flow and velocity numbers for a set of heads..

Cupcar

I understand all that, jeez I wasn't born yesterday.

Have you ever gone through a set of heads? It costs around $2500 to $3000 to do a set right if you port and use quality springs, retainers and valves. CMW will build a set from scratch to your specs for around $3500 with Ti retainers, nice springs, stainless intakes and Inconel exhaust. You can give them a piston dome volume and they will give you the combustion chamber volume to get the compression you want. They have done flow bench work ad nauseum and can give you tilted intake ports and "D" shaped exhaust ports yada yada.

Here is link to heads http://www.cmwmotorsports.com/CMW%20BILLET%20HEAD.htm

I just want to know if any body has used the heads and had any issues with the product.

Kevin

I've probably have done more porting of heads, turbo's and intakes than most.. Like I said, it's the whole package.. You pay for what you get.. I'd take the factory castings everytime... CMW's product has been out for quite sometime.. Others and myself have been able to get the gains that we want with factory components, for alot less $$$

Steve Weiner-Rennsport Systems

Hi:

I've tested CMW's billet heads against several of our own that we have done here and IMHO, they are nothing to write home about,....

While they are pretty, I saw no flow improvements on the intake or exhaust side over a well-done set by someone who REALLY knows what they are doing. As you know, this is a complex subject and there is a lot to getting optimal airflows through the entire range of valve lift.



You are correct about the real-world price for doing a set of race heads and IMHO, the CMW ones are not worth the money.

Cupcar

Thanks everyone, I understand also that the head porting that is correct for a given 3.8 liter is not what the 2.5 I am building would require in port dimensions, nor am I looking of the absolute ultimate here in ports- a nice set of 70-71 911 S heads would be nice but are hard to find.

I have no heads in hand at the moment.

I figure that a set of heads is going to cost me ~$350 for the 70-71 911 head cores I need. Then I figure $156 for a set of 46 mm ATE intake valves and $172 for the exhaust valves, $667 for Aasco springs, spring seats, Ti retainers, and keepers, and ~$1200-$1700 to give them a port and valve job, plus whatever $$$$ for the radius on the combustion chamber for the 89 mm bore, a head resurface, exhaust stud replacements and new guides cost.

It starts to add up and the one stop shopping is attractive.

Steve Weiner-Rennsport Systems

Hi:

You didn't say whether your 2.5 build is going to be a nice street engine or a race motor, but I'd offer that your estimate of "$1200-1700" for a proper valve job and worthwhile flow enhancement is low. It depends on what your power objectives will be.

FWIW,........A valve job should include head resurfacing (it does here) and any parts such as guides, seals, valves, springs and retainers are always extra, as required.

Port enlargement, flow work, is always extra,....

Cupcar

Engine for vintage sports racer that weighs in at 1100 pounds. Target is 250 to 260 HP.

If you figure that a port and valve job costs $2000 then you are over the cost of CMW heads when you add in the cost to procure head cores and the parts to rebuild and modify stock castings. After this you still have massaged old castings.

I am not sure I see the argument for not going with the CMW heads.

I am going to call a CMW user I have heard about next week to check on their experience.

Steve Weiner-Rennsport Systems

1) With all due respect, making a real honest-to-God 250-260 HP from 2.5 litres takes a REAL good set of heads, and all the correct camshafts, intake and exhaust components.

2) LOL,.....It matters not whether the castings are 30 years old or not, its all about preparation. The only time I'm concerned about how many heat cycles a head casting has undergone is with high-boost, high output turbocharged engines. "Massaged old castings" have worked VERY well over the past 35 years and still do to this day.

Cupcar

Last engine I built for the car with regular old "S" 36 X 35 mm port heads (nice valve job, no other mods to heads) and 66 mm stroke X 87.5 mm bore (2338 cc displacement) made 237 HP at 7600 rpm on Jerry Wood's dyno.

That's around 101 HP/liter so I figured approx same for an 89 X 66 engine and 2466 cc, maybe I'm wrong to think that...

Rick DeMan

Cupcar,

I've used 2 sets of CMW heads on a 3.8 turbo engine. I would have to say my experience is a mixed one...First the quality of machine work on the first set was very poor in the non critical areas and average in the important spots...flow #'s were very good and the service life was not anything to write home about.

I agree with you about the cost verses time and effort issue, that's why I went that direction in the first place. I had a melt down and needed a new set in a hurry.

All in all I would have to say they were worth it...I got to choose valve sizes, port sizes, bolt configuration for intake and lots of other things specific to my application that would have taken time and $$ to set up myself. Scott provided flowbench results that were accurate when checked on my own and they did perform very well...

It was not an easy transaction and would be hesitant to do bussiness again...

Good luck

Boosted9nine3

I actually have a set of these I didn’t use and listed for sale