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frenchyd
frenchyd MegaDork
2/23/22 7:25 p.m.

In the past I'd watch video's of cars tach and try to calculate how much time a car spends at various RPM  at certain spots on the race track.          
     Then using the computer's Engine analyzer program  try to figure out which camshaft will give me the strongest power at at that RPM. 
    Since I had to accept what was available.  I figure that's the best I can do. 
     Last night Lor and I were discussing the possibility of him creating me  a couple of cam billets. 
     The problem is I know too much and not enough. For example a longer rod leaves the piston dwelling at various points. But does a short stroke benefit or lose at those points?  
    I've got the flow bench readings someplace.  But how does a Hurron Head affect  those numbers?  
     If I trade lift for duration or visa Versa  do I win or lose. 
       What if I swap heads and pistons  trading flow for compression?   Does boost just help or can it hurt too?  
  There is a guy over in England who's making impressive numbers with 2 turbo chargers.  But he's more interested in Selling than sharing. 
  Tell me what you know, rules to live by, 

Opti
Opti Dork
2/23/22 8:33 p.m.

If you want to learn cam basics, look at stuff like SBCs and LSs. 

They have a ton of options available and a bunch of people installing all options with results. Then you can take the information and actually compare it to results.

Or you can find something with a similar design and copy what everyone else is doing and grind it onto you cores.

Patientzero
Patientzero Dork
2/23/22 9:13 p.m.

Most of it comes down to airflow and cylinder pressure.  If you don't have much airflow then you need to crank up the compression and rev it to the moon to get the most out of the air you do have.    

Duration is what is going to affect where it makes power.  Duration is always the important part.  More duration will incidentally give you more lift.  Lift is just icing on the cake but more lift also requires more valve spring pressure to keep everything in check.  Usually on a high rpm motor you're looking at big bore/short stroke for a couple reasons.  It keeps piston speed lower, it unshrouds the valve to get more air in the cylinder, and it keeps the air from separating to stuff the cylinder.  With that being said I've seen a 434cu.in LS motor turning over 10,000 rpm.

The biggest task with turning more rpm is keeping the valvetrain stable which usually turns into $$$.

Your head can also only move a certain amount of air. Short stroke/big bore will move your power range higher than small bore/long stroke but may not make any more power.  Although you can use the extra rpm to your advantage with gearing.

frenchyd
frenchyd MegaDork
2/23/22 10:03 p.m.

Thanks but the difference is massive. It's like telling me to check Packard straight 8's   The LS isn't allowed in group 10 so It's against the Small Block. 

   Jaguar has 2.75 inch stroke. a Chevy has a longer stroke. 3.5 The Jaguar rod lengths  are longer 7.2- 5.7   Jaguars 3&1/2 bore to Chevy 4" 
Cylinder heads you have to give it to Chevy.   
    Well except the Jag has 1&1/2 for every Chevy. Except I'm sure Chevy has aftermarket heads  while Jag doesn't  have that.   
   Chevy has millions of engines to Jaguars 121,000 over 21 years. 
        Plus At any one time there are 1000's  of Chevy's  racing any given weekend  and it rare Jaguar has 1 

   To follow Chevy  isn't going to give me anything other than a weak Chevy. It's like putting your shoes on your children. Just won't fit. 
     

Patientzero
Patientzero Dork
2/23/22 10:09 p.m.

It doesn't matter what motor you have.  Changing the camshaft is going to effect every motor the same.  I think he's trying to say there are thousands of pages of info on the internet pertaining to LS and small block chevy engines.  Read some of that to educate yourself.  The principles apply to your Jaguar motor just the same.

The LS in an evolution of the small block chevy, they have much in common.

mke
mke Dork
2/23/22 10:11 p.m.

These days software really is the best, it lets you "try" 100s of combinations so you know what parts you want to spend money on.  I use dynomation6 and am pretty happy with it.  You can change compression, add your turbos, switch to E85.....it even gives you decent ignition curves and VE numbers to baseline the tune in your ECU.  I haven't looked at the other software options recently so might be worth your time to see what the options are, but for sure DM6 works well.

 

The other option is of course talk to a cam grinder or engine builder you trust or who has experience your application.

frenchyd
frenchyd MegaDork
2/23/22 10:18 p.m.
Patientzero said:

Most of it comes down to airflow and cylinder pressure.  If you don't have much airflow then you need to crank up the compression and rev it to the moon to get the most out of the air you do have.    

Duration is what is going to affect where it makes power.  Duration is always the important part.  More duration will incidentally give you more lift.  Lift is just icing on the cake but more lift also requires more valve spring pressure to keep everything in check.  Usually on a high rpm motor you're looking at big bore/short stroke for a couple reasons.  It keeps piston speed lower, it unshrouds the valve to get more air in the cylinder, and it keeps the air from separating to stuff the cylinder.  With that being said I've seen a 434cu.in LS motor turning over 10,000 rpm.

The biggest task with turning more rpm is keeping the valvetrain stable which usually turns into $$$.

Your head can also only move a certain amount of air. Short stroke/big bore will move your power range higher than small bore/long stroke but may not make any more power.  Although you can use the extra rpm to your advantage with gearing.

That's really good.  The factory tested the stock springs and they didn't float until 8300 RPM and Isky has even better springs. Plus the Cosworth springs. Used in formula 1 and Indy also fit right in. 
   The Jag V12 was primarily used in endurance racing so rpm was limited nothing was really developed for sprint racing like vintage is all about. 
Chevy has plenty of that. 

DarkMonohue
DarkMonohue Reader
2/23/22 10:26 p.m.

What exactly are you building? Is it an 1800-pound hot rod or a 6500-pound 4WD pickup or a race car of some kind? Stick or automatic? Three speed manual box or six? Two speed automatic or eight? 

Naturally aspirated? If so, factory EFI plenum manifold with long runners, sheet metal tunnel ram, ITBs, Quadrajet, eight Strombergs? Turbo? Street turbo or race turbo?  Nitrous?  Supercharged?  Rootes or centrifugal?

What are the practical mechanical limits of the engine?  Does the crank walk off the job at X horsepower?  Do the valves go through the pistons at .400" lift or at 7000 RPM or never at all? Are the head gaskets made of Kleenex or the rods made of stained glass?

What is your tolerance for modification?

What is your budget?

Here's my rule to live by: if you need to know it, learn it. Read books. If you don't need to know it, pay someone who knows it.  That applies especially well to camshafts.

 

 

frenchyd
frenchyd MegaDork
2/23/22 11:18 p.m.
DarkMonohue said:

What exactly are you building? Is it an 1800-pound hot rod or a 6500-pound 4WD pickup or a race car of some kind? Stick or automatic? Three speed manual box or six? Two speed automatic or eight? 

Naturally aspirated? If so, factory EFI plenum manifold with long runners, sheet metal tunnel ram, ITBs, Quadrajet, eight Strombergs? Turbo? Street turbo or race turbo?  Nitrous?  Supercharged?  Rootes or centrifugal?

What are the practical mechanical limits of the engine?  Does the crank walk off the job at X horsepower?  Do the valves go through the pistons at .400" lift or at 7000 RPM or never at all? Are the head gaskets made of Kleenex or the rods made of stained glass?

What is your tolerance for modification?

What is your budget?

Here's my rule to live by: if you need to know it, learn it. Read books. If you don't need to know it, pay someone who knows it.  That applies especially well to camshafts.

 

 

2750 pound vintage sports car. Err sedan. ( Jaguar XJS V12 5.3 liter) race car only. 
 Mechanical limits?  None!!!!! It is the most robust engine I've ever seen in my life ( I've been racing since 1962). Really tough aluminum block. 6 ( studs) rear mains 4 studs the other 6 mains. 3" main journals  2.300 rod journals. forged EN 40 steel crankshaft  ( that's what Indy cranks and some Formula 1 were made from. Then it's hardened. The rods use  rod bolts that look like ARP ( quality ) 

 54 studs holding the heads on. Most of those go right down near the mains.  The die cast block, heads, everything is aluminum, the oil pump was copied by Chevy in their LS engines. 
     Transmission?  Yes  GM turbo 400, 5 speed science dog ring quick change, T5 and Trimec 5 speed, triple disk clutch if manual    Dana 44 IRS 

 SOHC ( 2 valve)  stock the valves float at 8300

   Finally. Bruce Crower developed Group 44's heads and camshafts.  Isky basically just Re- ground camshafts to what they could get out of the stock cores.  
Kent Cams in England actually reground the factory cores considering it was a V12 not a V8 ( it's better than Isky's ) 

   

DarkMonohue
DarkMonohue Reader
2/23/22 11:30 p.m.

I see.

With all due respect, it seems as if your parameters have not been fully established. 

If you are building a race car, you'll have rules to comply with.

Not sure whether you are running a TH400 or a stick shift? That's a huge factor.

You don't have to sell us on the choice of engine.  Just help us understand how yours will be built and how you will use it.

Have you talked to Crower yet?

 

frenchyd
frenchyd MegaDork
2/23/22 11:33 p.m.
Patientzero said:

It doesn't matter what motor you have.  Changing the camshaft is going to effect every motor the same.  I think he's trying to say there are thousands of pages of info on the internet pertaining to LS and small block chevy engines.  Read some of that to educate yourself.  The principles apply to your Jaguar motor just the same.

The LS in an evolution of the small block chevy, they have much in common.

So in NASCAR  Chevy Ford and Toyota all use the same camshaft?  
  
    I've been building engines ( including Chevy's)  since 1962.  I understand duration,  lift, lobe Center.    Dealing with domestic engines it's simple.  Check the catalogs. Order the cam 

  What I don't understand is nuances like long rod, short stroke. 60 degree V instead of 90 degree. Hurron head, vs Buick's Fireball head.   
      Not too many people have dealt with those.  E85 & turbo charging?   Nobody has to my knowledge.  So I have to ask for input. 
     
     

frenchyd
frenchyd MegaDork
2/24/22 12:13 a.m.
DarkMonohue said:

I see.

With all due respect, it seems as if your parameters have not been fully established. 

If you are building a race car, you'll have rules to comply with.

Not sure whether you are running a TH400 or a stick shift? That's a huge factor.

You don't have to sell us on the choice of engine.  Just help us understand how yours will be built and how you will use it.

Have you talked to Crower yet?

 

Thanks. Too much information but you are right it's all relevant.  I have at least one of each transmission I mentioned.  
     GRM ( this magazine) has a $2000 challenge the car will go to.  I'm sitting at less than $1000 by their rules. Probably  won't have enough to do the camshafts but it's possible.  (  I'll lend it to the 2 guys who have been helping me)    
    Probably go there using the automatic. It's a drag race and autocross event.  
     When I drive it I will use the Sienz dog ring.  That allows me to select completely different different gear sets and slide them in and out without tearing apart the gearbox.   Wonderful for very narrow power bands on race tracks where peak power is called for.  Tracks like Elkhart Lake. 
  The T5 is a cheap used gearbox maybe will be used to sort out the car.  And the Trimec is strong enough to hold up to whatever power I can make.  ( no budget in Vintage racing ) 
  Rules?   Well,  I can pretty much do whatever the rules are between 1973 & 2017.   At least according to SVRA  But I see way too much stuff that doesn't even comply with those rules. In 40 years of vintage racing I have never seen an engine torn down or even checked for size.  Basically if it's safe it races. 
     
   I'm telling you about how strong the engine is  so you understand I really have no worries.  Besides they are silly cheap. I've got 3 spares and more if I want them. So if it goes bang. So what!!! 
   Budget        When it goes to Florida for the $2000 challenge that's all I can spend on the whole car.  At this point I'm at less than $1000   I've got a local cam grinder who for $150 per cam will grind whatever I want. ( if he has a workable master )     
   Isky wants $240 per cam  Kent $612 plus air freight both ways and import duties.  
I haven't spoken to Bruce Crower  he doesn't waste time unless he respects you and I'm too ignorant at this point to even know what to ask for.  
     At this point I have a chance to get a pair of blanks for the cost of the metal  my friend will do the machine work to turn the steel into cam blanks to be ground. 
  After the GRM challenge  I'll do some local vintage racing here but I doubt I'll use the turbo's  

 

Patientzero
Patientzero Dork
2/24/22 1:07 a.m.
frenchyd said:

So in NASCAR  Chevy Ford and Toyota all use the same camshaft?  
 

No, but adding duration or changing overlap has the same effect no matter if it says Chevy, Toyota, or Briggs & Stratton on the side of the motor. 

frenchyd
frenchyd MegaDork
2/24/22 7:56 a.m.

In reply to Patientzero :

So just add as much lift and duration as possible?    I know there is more to it then that.  That's all  I did back in the 60's-70's-80's.  Since then I've found out about lobe centers,  acceleration ramps etc. 

  By the 90's I was using bigger cam followers  and radiusing clearance ramps  to allow cam lobes to clear.  Bigger base circles, etc. 
      Yet that was 30 years ago.   I know cam's have improved since then. What I don't know is what's changed, where attention has focused.  What yields what.  

Paul_VR6 (Forum Supporter)
Paul_VR6 (Forum Supporter) SuperDork
2/24/22 8:10 a.m.

Yes the right cam has the most lift and duration as you can mechanically fit, while keeping the valve in control while keeping in mind valve weight and spring, and being able to deal with any downsides of that lift and duration, or changing them so you can live with it. The thing I have learned about cams is there is no free lunch. There are reduced cost ones if you can change intercam timing, have vvt, etc.

frenchyd
frenchyd MegaDork
2/24/22 8:59 a.m.

When I raced my Black Jack special I used the master lobes  for Offenauser which were also used for Ford Flatheads. ( no rocker arms to affect lift) plus Offy, Ford, Jaguar all had a 4 inch stroke 

    Maybe I'm over thinking this. Just use the profile of a SOHC with a 2&3/4" stroke.? 

mke
mke Dork
2/24/22 8:59 a.m.
Paul_VR6 (Forum Supporter) said:

Yes the right cam has the most lift and duration as you can mechanically fit, .....

Careful with that path.  As duration goes up the peak torque RPM goes up but redline does not so at some point the average torque and hp begin to drop and you've built an engine that it both harder to drive and slower.

This is the 3rd or 4th conversation about cams for this engine I've seen with no talk of changing anything else.   As I understand it its a stock engine, with stock flowing heads, intake and exhaust That is getting a cam upgrade and turbos added.  The stock cams are pretty mild at 211 degree@.050, and peak at 5500 the "race" cams for that engine are 240@050 and peak at 7k and assumes its been given headers and a decent intake and still will yield a narrower power band, but he's not adding any of that so that's probably too much cam.  I'm honestly not sure any cam change makes a lot of sense $$ wise vs investing in a better intercooler.

....a simulator program will answer all these questions though. 

frenchyd, if you think you can find reliable head flow numbers I get my software key back (lent it to a buddy) and run this for you.....but you won't like the answers as I've done it enough to be pretty confident in what its going to say which is drop the compression or increase the octane enough turn up the boost and call it a day.  You have a 300hp engine and you want 500?,  so 300/500*15 = 9psi ballpark and your done...but I'll let set the software up to tell you the same thing if you like.

Saron81
Saron81 Dork
2/24/22 9:34 a.m.

Most boosted engines won't like a lot of overlap either from what I've seen. Don't see much of a gain here... and certainly not any that couldn't be made (for free)  with a little more boost, or even timing changes.  Custom billet cams for a challenge car is crazy talk. 

Paul_VR6 (Forum Supporter)
Paul_VR6 (Forum Supporter) SuperDork
2/24/22 9:49 a.m.
mke said:
Paul_VR6 (Forum Supporter) said:

Yes the right cam has the most lift and duration as you can mechanically fit, .....

Careful with that path.  As duration goes up the peak torque RPM goes up but redline does not so at some point the average torque and hp begin to drop and you've built an engine that it both harder to drive and slower.

Without changing LCA I'd agree, but that's a variable in cam design OR you can keystroke change that on an engine that wasn't designed by people with slide rules.

frenchyd
frenchyd MegaDork
2/24/22 9:58 a.m.

When I ported V-12 heads in the past I started with hand porting  and by the time I had 12 cylinders flowing the same  I had over 100 hours  in them.  
    Then I switched to using my vertical mill and the hours dropped to 12. ( and I had nearly identical flow numbers).  
     Turns out there is a better way. If I undercut the seat and radius the entry instead of a straight shot flow numbers go up significantly. While added time should be musicale 

DarkMonohue
DarkMonohue Reader
2/24/22 10:12 a.m.
Saron81 said:

Most boosted engines won't like a lot of overlap either from what I've seen. Don't see much of a gain here... and certainly not any that couldn't be made (for free)  with a little more boost, or even timing changes.  Custom billet cams for a challenge car is crazy talk. 

Yes and yes again.  If you only have $2000 to spend on the entire car, don't even think about camshafts.

If and when it makes sense later on to invest in cams, talk to Web-Cam or Engle or a recognized Jaguar V12 expert about custom cams, and let them worry about the length of the stroke and the Heron head design and all those things.

You're not taking this to Talladega. Wringing your hands over minute and likely meaningless details so that you can tell a cam grinder how to do his job - a job he probably spent decades learning - is a gross waste of time. 

You can get wrapped around the axle over things like the short stroke or the Heron head combustion chamber or the 54 head studs or whatever, but their effect on camshaft design will be absolutely trivial. What's important is playing nice with the valve train geometry, working with your compression ratio and intake tunner length and exhaust system, and making enough thrust at low RPM to push that TH400 around. 

Find a good cam guy, tell him how the engine is built, what it is in, how you are driving it, and what you want the engine to do. Then pay him. His job is to figure out what works. Let him do it.

Or leave the cams stock and focus on literally any other part of the car.

mke
mke Dork
2/24/22 10:31 a.m.
Paul_VR6 (Forum Supporter) said:

Without changing LCA I'd agree, but that's a variable in cam design OR you can keystroke change that on an engine that wasn't designed by people with slide rules.

Even then....yes can shift things a bit by changing the lobe centers, but not a ton.  The both the cam and the engine are what they are.  Peak torque will happen when the port velocity is happy so you need the cam to be happy at the same place. Too much duration and and the air is blowing out the exhaust and back out the intake.  Yes you can roll them around a bit, but the best result is almost always achieved by picking the right part to begin with.

Variable cams does  help preserve the bottom for sure, but only when the cams are low enough duration.   I played with it in the simulator for hours on my engine thinking I would retrofit some cam actuators I had on hand, but just gave up as there wasn't enough gain to make it worth the bother....a set of tri-y headers gave me about 90% of the effect.   But if I had lower duration cams it was a different story, I could get a much smoother, all be it lower, power curve

I'll also say that I know for sure the first thing they do when they take a ferrari racing is disable the cam and intake actuators....just t 1 more thing to break

...again, this is where simulators really shine

Here is my engine cams at 98-98 (dark red/green) vs 104-114(ligh red/green) lobe centers


Here is about the best I thought I could do....its a 20 degree actuator on just the exhaust cam with base timing at 104-114

Here is just general optimization 100-110 vs 110-110

and here is changing just the lash setting, the intake master lobe I picked has quite long accel/decel ramps so a bit more lash reduces the seat to seat timing and really improves the bottom end.

and all this has to be matched to the headers and intake runner length...change one and you kind of have to start over dialing it back in.  For this build I did the heads first and got basically as much flow as I could which also set the intake other than finished lengths, then I picked a cam lobes, then played with header options and cam timing (it 4 cam, so I can install them at whatever lobe center and separation I please) to make the most of it.  I probably spent a over a hundred hours on the simulator optimizing so I could buy/build stuff once smiley

frenchyd
frenchyd MegaDork
2/24/22 10:32 a.m.

I apologize for the disjointed conversation we're having. I write while I'm waiting and often fail to complete my thought. 
   I'm also talking about multiple events. Probably even multiple engines. 
  When They go to the challenge  I will remain inside that $2000 budget. I've got new gaskets from 30+ years ago that I bought in bulk. But if I can't afford to grind the billets and stay inside the budget the engine will go down as is. ( with the pair of turbo's).    
  But once they return I'll be focusing on Vintage racing.   No turbo's. But also a bigger budget.   

    The V12 engine will easily survive way past the factory Red line. (6500 rpm) the factory ran it up to  (8000+ rpm ) for 12 hours,  stock except for camshaft. 
      There are Tricks I can use because the equipment the V12 was built on.   For example all the valves have the same stem, length,  and keeper  design. 6 cylinder or 12. The cam followers come in 2 sizes.  With the 12 cylinder the smaller.    I can use the bigger valves without replacing the seat. Just opening the throat to take advantage of the bigger size.  The stock cam follower is something like 1&1/2" while the bigger one is 1 &3/4". Allowing a bigger base circle  to provide more lift and duration. 
     It's real straight forward to open the cam holders up to the new size.  Minimum set up time.  
  

frenchyd
frenchyd MegaDork
2/24/22 10:52 a.m.
mke said:
Paul_VR6 (Forum Supporter) said:

Yes the right cam has the most lift and duration as you can mechanically fit, .....

Careful with that path.  As duration goes up the peak torque RPM goes up but redline does not so at some point the average torque and hp begin to drop and you've built an engine that it both harder to drive and slower.

This is the 3rd or 4th conversation about cams for this engine I've seen with no talk of changing anything else.   As I understand it its a stock engine, with stock flowing heads, intake and exhaust That is getting a cam upgrade and turbos added.  The stock cams are pretty mild at 211 degree@.050, and peak at 5500 the "race" cams for that engine are 240@050 and peak at 7k and assumes its been given headers and a decent intake and still will yield a narrower power band, but he's not adding any of that so that's probably too much cam.  I'm honestly not sure any cam change makes a lot of sense $$ wise vs investing in a better intercooler.

....a simulator program will answer all these questions though. 

frenchyd, if you think you can find reliable head flow numbers I get my software key back (lent it to a buddy) and run this for you.....but you won't like the answers as I've done it enough to be pretty confident in what its going to say which is drop the compression or increase the octane enough turn up the boost and call it a day.  You have a 300hp engine and you want 500?,  so 300/500*15 = 9psi ballpark and your done...but I'll let set the software up to tell you the same thing if you like.

I have my own ( older but still accurate simulator ).  But the one thing I understand about those is, it's like filing your taxes.  The preparer doesn't know what you don't tell him and because you don't know tax law you aren't properly prepared to tell him. 
      That's why I'm asking here.  
  Oh and with regard to redline.  Have you ever been inside a Jaguar V12?  If you have you know how robust that engine is built.     6500 rpm redline is a real joke.  Because of the long rods and short stroke piston speed at redline is trivial. The valves are light and simple. No rocker arm or VVT 

  In the European racing series during the 1980's stock intake and stock (ish) cast iron manifolds  made over 500 horsepower. 
A properly designed set of racing headers only picks up 20 horsepower. 
       

frenchyd
frenchyd MegaDork
2/24/22 11:05 a.m.
mke said:
Paul_VR6 (Forum Supporter) said:

Without changing LCA I'd agree, but that's a variable in cam design OR you can keystroke change that on an engine that wasn't designed by people with slide rules.

Even then....yes can shift things a bit by changing the lobe centers, but not a ton.  The both the cam and the engine are what they are.  Peak torque will happen when the port velocity is happy so you need the cam to be happy at the same place. Too much duration and and the air is blowing out the exhaust and back out the intake.  Yes you can roll them around a bit, but the best result is almost always achieved by picking the right part to begin with.

Variable cams does  help preserve the bottom for sure, but only when the cams are low enough duration.   I played with it in the simulator for hours on my engine thinking I would retrofit some cam actuators I had on hand, but just gave up as there wasn't enough gain to make it worth the bother....a set of tri-y headers gave me about 90% of the effect.   But if I had lower duration cams it was a different story, I could get a much smoother, all be it lower, power curve

I'll also say that I know for sure the first thing they do when they take a ferrari racing is disable the cam and intake actuators....just t 1 more thing to break

...again, this is where simulators really shine

Here is my engine cams at 98-98 (dark red/green) vs 104-114(ligh red/green) lobe centers


Here is about the best I thought I could do....its a 20 degree actuator on just the exhaust cam with base timing at 104-114

Here is just general optimization 100-110 vs 110-110

and here is changing just the lash setting, the intake master lobe I picked has quite long accel/decel ramps so a bit more lash reduces the seat to seat timing and really improves the bottom end.

and all this has to be matched to the headers and intake runner length...change one and you kind of have to start over dialing it back in.  For this build I did the heads first and got basically as much flow as I could which also set the intake other than finished lengths, then I picked a cam lobes, then played with header options and cam timing (it 4 cam, so I can install them at whatever lobe center and separation I please) to make the most of it.  I probably spent a over a hundred hours on the simulator optimizing so I could buy/build stuff once smiley

I did that too, worked with my simulator. 
    But I only had the ability to use  100% Methanol 

    Am I overthinking E85?   If I stayed at 12 pounds of boost  with Methanol my air temps only went up to around 150 degrees.  Changing timing gave a really serious power increase. Close to 50 hp if I remember it correctly. 
but I'm sure that's wrong. Because there was no power difference between the heron head and the fireball head. 
   I'm sure you know this but for others. The heron head is flat with a Hemi combustion chamber in the piston. 
The Fireball head is designed to concentrate the fuel charge around the spark plug. 

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