Camshaft specs?

A longtime friend still retains his cam grinding equipment including the ability to weld and parkerize them.  He’s offered to do my Jaguar V12 cams really inexpensively since this is his off season.  

  Now what should I go for?  To review it’s a 5.3 liter V12 that will have a 250 cu. in. Roots type supercharger, and I’ll be using 85% ethanol alcohol with my gasoline.   Roughly 3&1/2” bore by 2.75 inch stroke.  Stock the factory took the engine up to 8300 rpm before any signs of valve bounce occurred. But with the extremely mild camshaft used power is all in at 5500 rpm  

i think more lift would be called for but what about duration  or is lobe separation angle the important number?  

What are you using the engine for (street car, road racing, drag racing, marine, swamp buggy....?  What's the max RPM you want to turn?  How heavy is the vehicle?  What are you running for transmission, gears and tires? 

In reply to APEowner : weight goal is 1500 pounds (dry) prime use will be road racing  but I’ll tune it on a local drag strip.  I suspect without any port work the airflow will limit peak power to around 7000 Rpm but the engine is capable of turning  over 8300 rpm without issues should I decide to do port work. 

transmission likely will be my Saenz 5 speed dog ring, quick(gears) change non overdrive ( 5th is 1-1)  Hooked to a triple disk 7&1/4 inch Tipton clutch.  I’ll likely run mainly a 3.54 rear ratio with about 25.5 diameter tires. 

I'm no expert but I would look at low overlap so you don't blow all your boost out the exhaust. 

Rpm may well be more dependent on your supercharger than your head/valves/bottom end.

In reply to Robbie :

This^^

Reducing overlap can be done by minimizing duration, increasing LSA, or increasing ramp acceleration rates

Usually it's some optimized combination of the three.

The key word is 'optimization'.

That's traditionally done by trying a bunch of different grinds on a dyno.

Nowdays, a talented cam designer can get pretty close with software and simulation.

Refresh my memory, does the Jag have roller followers, or friction?

frenchyd said:

In reply to APEowner : weight goal is 1500 pounds (dry) prime use will be road racing  but I’ll tune it on a local drag strip.  I suspect without any port work the airflow will limit peak power to around 7000 Rpm but the engine is capable of turning  over 8300 rpm without issues should I decide to do port work. 

transmission likely will be my Saenz 5 speed dog ring, quick(gears) change non overdrive ( 5th is 1-1)  Hooked to a triple disk 7&1/4 inch Tipton clutch.  I’ll likely run mainly a 3.54 rear ratio with about 25.5 diameter tires. 

 

This is looking like a really fun project.  If you're not in a hurry I can run a simulation for you in a couple of weeks.  If you'd like me to do that I'll have a bunch more questions for you when I'm at a computer and not typing on a tablet.

I would try to get in touch with a big cam grinder and have them help you spec something out. Places like COMP Cams have people that do literally nothing but spec cams for people. I've heard that Crane has ground Jag V12 cams, so someone there might have more specialised knowledge (if that is applicable in this situation). Alternatively, 2/3 of 327 is 218, so copying a pattern from a 215 Buick could get you at least somewhat close.

Here's an article that may help as well

In reply to clshore : it’s an overhead camshaft so the lobe sits directly on top of the valve activating a lifter.  Brilliantly simple and light arrangement without the losses of rocker arm or weight of A pushrod. 

The other thing is the combustion chamber is hemi. Unlike a combustion chamber in the head which will limit flow on one portion of the valve  as the valve opens the piston is moving away giving unshrouded access to the whole cylinder. 

In reply to Homework : three shortcomings of a Buick/ Rover engine compared with Jaguar. 

pushrods and rocket arms 

combustion chamber shrouded by recessed valves in head 

In reply to APEowner : I have a program myself  that will get me there but this is one of those chicken and egg questions  I’ve come to realize. Once I know what is possible then I can play around with finding better.  

I already know the engine will be 520 (+ or - 2% ) horsepower with a stock camshaft. If I still had my flow bench numbers I could do porting estimates that would reduce some variables  Stock lift is only .375  and timing of 17 before. 59 . after intake and exhaust means even if I just max out lift to .500 there is going to be more power

its possible to go further than .500 but requires oversized lifters( readily available ) and remarkably they are lighter than stock. 

In reply to Homework :

I’ll probably talk to Bruce Crower , he worked with Group 44 and I believe his camshafts were in every one of their engines.  

But I have a bit of a problem, moral one. Is it fair to use the knowledge of someone and have the camshaft ground locally simply because it will be a lot cheaper and local?  

Reading that the answer has to be NO it’s not fair.  

So I’m back to this group.  

Everything I read says stock is just fine.  But with only .375 lift at the valve and 17-59  59-17 valve timing I know there is plenty of room for improvement. 

Heck Isky’s XM3 grind would be better. And that barely made any difference over stock. Sitting on one of my old computers is all of Offenhauser  cam grinds for really serious peak power (including their whole turbocharged engines) that at least would tell me which way to go.  

But I don’t remember which computer up in the attic and none of them work because of various viruses they’d get. 

Also I’d like to discuss my various options regarding regrinds.  Should I go reduced base circle to keep it a simple regrind and hope I can find enough thick Saab shims to cut adjustment shim out of.  Or go the weld up and regrind with stock base circle  so I can use my collection of Jaguar shims. 

See if you can contact Demetri Elgin.  He is now (or was) consulting after he sold the business.  

Here are some random thoughts without doing any math or simulation.

As I recall this car is being built more for fun than to contend for a championship in any particular class.  If that's not correct then some of the below would be off base.

I'd look at a max RPM of around 7k so the engine has plenty of extra durability.  As light as the car is there's no need to wring every last bit of power out of it and overhaul it every few races.  With the blower and the displacement you should be able to get a pretty flat torque curve from about 4K to 7K and some pretty impressive HP.  That combined with your light car and five speed gearbox should make for a fast, reliable car that doesn't need a gearing change for every track.

With un-ported heads I don't think you're going to see any significant benefits with lift over 0.5 so I wouldn't bother with the lifter change.  Are you going to be able to get that much without coil bind?

I suspect that some additional duration on the exhaust side and a wider LSA will be beneficial and that's going to require welding and if that's the case then I'd keep the base circle stock.

In reply to APEowner :

You reflect nearly perfectly my thoughts exactly, having built some V12 s for racing  I am pretty aware of the potential and  have a good feeling for what works in a normally aspirated engine  A V12 has a significant increase in torque over the same size V8. In fact that little 326 cu. in. Engine made more torque than the same year Chevy 454 

For example the exhaust side flows 95% as-well the intake.   Normally 80% meets exhaust needs  Unlike V8 configuration there isn’t the exhaust pulse interference so headers only offer trivial ( less than 5% )  power gains over the stock cast iron manifold. So that won’t need attention.  

The intake is plenty large enough for good power production in the stock configuration right up to 6500 rpm. My experience with port work showed  only modest power gains up through 7500 rpm. With actually a loss of torque and power below 3500 rpm.

I’m hoping the supercharger will make port work not so critical. Hand porting took over 60 hours with another 40 spent to equalize The ports.

For the second engine I purchased a ball mill for my vertical mill and spent less than 20 hours with better flow bench numbers.However I no longer own the vertical mill. 

The new camshafts out of England like Kent Cams and Piper Cams do show real gains over American regrinds.  But none of them exceed .450 lift. That plus the piston profile developed by Cosworth  combined. offer more than 100 horsepower my best’m  efforts produced.  

True, I was able to bore and stroke the engine easily and cheaply enough and that showed real worthwhile power gains at a modest cost as it was  to bore and stroke it’s still a thousand  plus dollars I won’t spend  this time. 

All of my numbers are off the top of my head since the actual Dyno sheets went with the car when I sold it.  I can reverse engineer things  but that’s based on my best estimates of over 20 + years ago.  None of which were supercharged. 

I did once  build a twin turbo V12 using a pair of junkyard Saab turbos but everything was stock.  

I was hoping some here had experience and could guide me in camshaft selection with a super/ turbo charger. 

You have pics of your engine? 

In reply to yupididit :yes  which engine would you like to see?  ( I have 5  plus many pieces and parts of others) but I’ve never been able to figure out posting.  I can sometimes get my daughter to do it for me when she stops over.  

Pictures of the twin turbo v12 and of your supercharger setup. 

You can email them to me mahalregina@gmail.com

If you ever need any pics posted just let me know visa email and I'll gladly post them until you figure it out. 

frenchyd said:

 

 

I was hoping some here had experience and could guide me in camshaft selection with a super/ turbo charger. 

I do and I grind cams as well. If your buddy is going to grind for you he'll need a master which you'll likely have to get from an existing cam, and if I recall, the Jag is a small base circle (?) which makes it a little more difficult.

I think your stock cam is .375"L and (from memory) 211" duration at .050"?. The XM3 is (I think)  .424"L 242 at .050"?. For a bucket style mechanical lifter setup, that sounds pretty close to what I would recommend for an application like that. Don't worry about "blowing boost out the exhaust" and stuff like that, it's mostly a myth.  Cam for your intended RPM range and that will work best. I can look at my masters and see if i have anything, but most of my good bucket grinds are lower lift hydraulic because of the applications I mostly work with.

In reply to Suprf1y

pretty good memory. That sounds spot on .  In the past he’s used Ford Flathead masters and they work pretty well. I think Isky uses Ford Flathead masters as well but they reduce the base circle and force me to find  thick shim material.  

I used to cut up Saab shims because there were so many around from Ice racers.  Now days I think it would be just as hard finding the right size Saab as buying over-thick Jaguar shims.  

Buying thick Jaguar shims is probably more expensive than getting the lobes welded up. 

You could also use lash caps if you can find them in your stem size, and custom grind them. Done that before.

It's a tough application. With a 2V head you want lift but all the good higher lift cams (VW, Q4) are all large base circle so you can't rip a master from one of those. That XM3 looks pretty good if that's the best you can do. A lot better than stock.

Just checked my book. The jag master I had was .390L/.211D.

Alfa grinds should work if you find any. I have nothing worthwhile

Conventional hot cams don't work well on blown engines. You want reduced overlap or too much charge goes out the flue.  Comp Cams were helpful with my last turbo build.

In reply to wspohn : if you know Jaguar specs  you’ll realize how modest they are.  Only a .375 lift and modest duration.  

Even using Isky’s  XM3 grind doesn’t leave the valves open enough to make any difference.  

wspohn said:

Conventional hot cams don't work well on blown engines. You want reduced overlap or too much charge goes out the flue.  Comp Cams were helpful with my last turbo build.

Internet myth. And hot is not a cam spec.

You cam for your intended RPM range. That's where you want your efficiency to be, boosted or not.

In reply to Suprf1y :

You also need to focus on  budgets ( at least most GRM people) 

the best Cams for a Jaguar V12 are made in England by companies like Piper and Kent. But would escalate the build cost too far over a local regrind.   

Pistons too are best made by Cosworth in England and combined with the good Cams could easily add another 100 horsepower or more but a complete set would add another $4500 to the budget  over reusing the stock ones.  

My goal here is not to make another high end max power engine. But stay within the spirit of the 2018 challenge.  Even if I can’t stay technically inside of the rules.