Why not have a Hemi?

[heyjohnxx]

With the notable exception of the Monteverdi Hai 450SS, no one else used the Chrysler Hemi in sports cars or in Can Am racing. Considering the Hemi's advantage was better breathing at high rpms, makes me wonder why it wasn't used more. I know it's 50 to 75 lbs heavier (in iron block form) than a big block Chevy and maybe a little wider also, but things like that shouldn't be a big problem for a racer. Sorry about this, sometimes I get random thoughts in the middle of the night.

 

[waynehulsey]

What about the McKee. It ran at least one race in 1967 IIRC. I would say that it was much heavier then a BBC, especially since the Chevy was aluminum and its a lot wider.

There was a KB hemi powered super mod from Montana or somewhere in that area that I saw at the old Copper Classic a couple of times. The last time there it got away from him in turn 2 and almost killed him. Never heard of the car again.

[Miatatom]

  On 10/3/2017 at 10:35 PM, heyjohnxx said:

I know it's 50 to 75 lbs heavier (in iron block form) than a big block Chevy and maybe a little wider also, but things like that shouldn't be a big problem for a racer.

 

I think you have the answer. Weight is the biggest issue.

[1930fordpickup]

As I was told by a tractor puller one time, it is all about the r&d that makes people choose the engines they use. So much money was put into the Hemi but it was for drag racing two different animals when talking about engine life on a track that has to last more than 2 minutes running from start to finish with most of that time not a full throttle. Reading an interview from Connie Colletta he said the same thing about the S.O.H.C. 427 with drag racing. It was designed for N.A.S.C.A.R. not N.R.A. 

Wayne not all big block Chevy's are aluminum in fact very few from the factory were. Aluminum heads was an option though. 

I am by no means an expert on this just from what I have read and talked to the people that have and run this stuff. 

[waynehulsey]

  On 10/4/2017 at 6:16 PM, 1930fordpickup said:

As I was told by a tractor puller one time, it is all about the r&d that makes people choose the engines they use. So much money was put into the Hemi but it was for drag racing two different animals when talking about engine life on a track that has to last more than 2 minutes running from start to finish with most of that time not a full throttle. Reading an interview from Connie Colletta he said the same thing about the S.O.H.C. 427 with drag racing. It was designed for N.A.S.C.A.R. not N.R.A. 

Wayne not all big block Chevy's are aluminum in fact very few from the factory were. Aluminum heads was an option though. 

I am by no means an expert on this just from what I have read and talked to the people that have and run this stuff. 

I was talking about the Can Am engines being aluminum. At that time there wasn't an aluminum block available for the hemi that I'm aware of. I used to hang out with Skip Hess and the Revell Kit AA/GS Mustang some in the early 70's. Other then plug changes that engine was a bear for between round maintenance and for running on nitro the bottom end didn't hold up that well. That probably could have been solved, but not enough of them around and end of factory money kept that from happening. In case you don't know that car it was a SOHC similar to Ohio George's. Actually was build before his, but Revell dinked around and MPC beat them to do a kit of Ohio George's car.

Edited October 4, 2017 by waynehulsey
added info

[afx]

The McGee Wayne mentioned above:

https://www.hemmings.com/blog/2013/11/20/the-king-in-can-am-hemi-powered-mckee-mk-v-sports-racer-heads-to-auction/

Edited October 4, 2017 by afx

[1930fordpickup]

  On 10/4/2017 at 7:02 PM, waynehulsey said:

I was talking about the Can Am engines being aluminum. At that time there wasn't an aluminum block available for the hemi that I'm aware of. I used to hang out with Skip Hess and the Revell Kit AA/GS Mustang some in the early 70's. Other then plug changes that engine was a bear for between round maintenance and for running on nitro the bottom end didn't hold up that well. That probably could have been solved, but not enough of them around and end of factory money kept that from happening. In case you don't know that car it was a SOHC similar to Ohio George's. Actually was build before his, but Revell dinked around and MPC beat them to do a kit of Ohio George's car.

That makes more sense Wayne, and thanks for the new info.  

[afx]

Been racking my brain for days and finally I remember: the Hussein which also competed with a Hemi.

http://www.conceptcarz.com/vehicle/z11315/Mecom-Hussein-MK-I.aspx

Edited October 5, 2017 by afx

[Ace-Garageguy]

Both shortcomings of the cast-iron Chrysler hemi for road-racing have already been mentioned.

1) It is a heavy beast. Though it makes good power, the heads are huge and sit up high on the engine, obviously; this raises the center of gravity of the vehicle, and that's NOT where you want weight on something that has to go around turns fast.

2) The bottom end of the factory engines is somewhat weak compared to other choices. Though Mickey Thompson had a lot of experience going fast with Chrysler hemis, he chose the Pontiac V8 for his LSR-attempt Challenger I specifically because the bottom-end in the Poncho was a lot tougher than the Chrysler.

 

Edited October 5, 2017 by Ace-Garageguy

[Mark]

  On 10/4/2017 at 7:02 PM, waynehulsey said:

I was talking about the Can Am engines being aluminum. At that time there wasn't an aluminum block available for the hemi that I'm aware of. I used to hang out with Skip Hess and the Revell Kit AA/GS Mustang some in the early 70's. Other then plug changes that engine was a bear for between round maintenance and for running on nitro the bottom end didn't hold up that well. That probably could have been solved, but not enough of them around and end of factory money kept that from happening. In case you don't know that car it was a SOHC similar to Ohio George's. Actually was build before his, but Revell dinked around and MPC beat them to do a kit of Ohio George's car.

Didn't the Revell Kit Mustang have a 392 Chrysler?

[Mark]

Nope, just checked...Ford power all the way.

[slusher]

  On 10/5/2017 at 5:07 PM, Ace-Garageguy said:

Both shortcomings of the cast-iron Chrysler hemi for road-racing have already been mentioned.

1) It is a heavy beast. Though it makes good power, the heads are huge and sit up high on the engine, obviously; this raises the center of gravity of the vehicle, and that's NOT where you want weight on something that has to go around turns fast.

2) The bottom end of the factory engines is somewhat weak compared to other choices. Though Mickey Thompson had a lot of experience going fast with Chrysler hemis, he chose the Pontiac V8 for his LSR-attempt Challenger I specifically because the bottom-end in the Poncho was a lot tougher than the Chrysler.

 

 Ace is the Hemi a more durable engine today then years ago?

 

[dieseldawg142]

..........

Edited May 9, 2018 by dieseldawg142

[Ace-Garageguy]

  On 10/6/2017 at 12:08 PM, slusher said:

 Ace is the Hemi a more durable engine today then years ago?

In a word, yes. 

But generally, most of today's engines are more "durable" (although this is really subject to how you define "durable"), and 200,000 miles with no major mechanical problems (and very little maintenance) is common. The old engines would be considered to be doing well if they made it to 100,000 miles, though they were good for a lot more with careful maintenance and competent repair when required.

The original Chrysler Firepower hemi, intro'd in 1951, came in 331, 354 and finally 392 (built through 1958) cubic inch displacements. Advertised horsepower ranged from 180 to 375, and the engine's design was perfectly adequate at those power ratings, and considerably more. The problem arose when the engines were spun at a lot higher RPM (for racing) than they had been intended for. The cast-iron main bearing caps were a little on the weak side, and could "walk" or go oval-shaped if they weren't reinforced with steel bars, or replaced entirely with forged steel caps, or a full girdle. The bottom end wasn't configured to make a 4-bolt cap configuration easy, as the main bearing webs next to the bearing saddles were quite narrow. They didn't allow cross-bolted mains like the deep-skirted Ford FE block did, either. A full main-bearing "girdle" was the best way to get it all to stay together for a little while in a racing application, and lotsa blown Chrysler Firepower hemi engines ran very successfully in fuel dragsters.

The later 426 hemi ('64) was an entirely different design, with a deeply skirted block, and provision for 4-bolt main caps, cross-bolted through the sides. It's a much stronger design right out of the box.

I have no direct experience with the current Gen III Chrysler Hemi engines, but I would have to assume they're pretty stout, as nobody is going to warranty a factory engine capable of the power a Hellcat or Demon puts out if there's any possibility of bottom-end failure. The high-output engines have 4-bolt main caps from the factory, and some even have 6-bolt caps.

 

Edited October 6, 2017 by Ace-Garageguy

[waynehulsey]

Are the new hemi's a true hemispherical combustion chamber motor or they somewhere between a BBC and a Boss 429 setup?

[Ace-Garageguy]

  On 10/7/2017 at 6:04 AM, waynehulsey said:

Are the new hemi's a true hemispherical combustion chamber motor or they somewhere between a BBC and a Boss 429 setup?

There's been a lot of debate over the past few years, and a lot of people screaming the Gen III isn't a "real" hemi. When cornered, few know what they're talking about.

Below is the Gen III Hemi Hellcat chamber. Hemi-like, but more a pent-roof (to my way of thinking...though Hemi sounds cooler and it's arguably still a hemispherical chamber). It does have parallel rocker shafts, like Chrysler's "true" hemi engines that went before it.

Below is the Gen I 392 hemi chamber. The included angle between valves is greater, and the dome is more pronounced. 

Below is the general layout of the big block Chebby chamber. Valves are roughly side-by-side, roughly parallel to the head's longitudinal centerline, rather than across from each other as in the chambers shown above.

And last, below, is the general layout of the "semi-hemi" Boss 429 chamber.

Here's a pretty good illustration of various combustion chamber designs, showing what the terms actually mean.

Edited October 7, 2017 by Ace-Garageguy

[waynehulsey]

Thanks for all the additional info. Neat little chart, never seen that before. Would agree with you that its starting to approach a pentroof chamber. Just don't keep up with this stuff like I used to.

[slusher]

  On 10/6/2017 at 2:22 PM, Ace-Garageguy said:

In a word, yes. 

But generally, most of today's engines are more "durable" (although this is really subject to how you define "durable"), and 200,000 miles with no major mechanical problems (and very little maintenance) is common. The old engines would be considered to be doing well if they made it to 100,000 miles, though they were good for a lot more with careful maintenance and competent repair when required.

The original Chrysler Firepower hemi, intro'd in 1951, came in 331, 354 and finally 392 (built through 1958) cubic inch displacements. Advertised horsepower ranged from 180 to 375, and the engine's design was perfectly adequate at those power ratings, and considerably more. The problem arose when the engines were spun at a lot higher RPM (for racing) than they had been intended for. The cast-iron main bearing caps were a little on the weak side, and could "walk" or go oval-shaped if they weren't reinforced with steel bars, or replaced entirely with forged steel caps, or a full girdle. The bottom end wasn't configured to make a 4-bolt cap configuration easy, as the main bearing webs next to the bearing saddles were quite narrow. They didn't allow cross-bolted mains like the deep-skirted Ford FE block did, either. A full main-bearing "girdle" was the best way to get it all to stay together for a little while in a racing application, and lotsa blown Chrysler Firepower hemi engines ran very successfully in fuel dragsters.

The later 426 hemi ('64) was an entirely different design, with a deeply skirted block, and provision for 4-bolt main caps, cross-bolted through the sides. It's a much stronger design right out of the box.

I have no direct experience with the current Gen III Chrysler Hemi engines, but I would have to assume they're pretty stout, as nobody is going to warranty a factory engine capable of the power a Hellcat or Demon puts out if there's any possibility of bottom-end failure. The high-output engines have 4-bolt main caps from the factory, and some even have 6-bolt caps.

 

Thank you Bill for the info!

[Dodge Driver]

  On 10/5/2017 at 5:07 PM, Ace-Garageguy said:

Both shortcomings of the cast-iron Chrysler hemi for road-racing have already been mentioned.

1) It is a heavy beast. Though it makes good power, the heads are huge and sit up high on the engine, obviously; this raises the center of gravity of the vehicle, and that's NOT where you want weight on something that has to go around turns fast.

2) The bottom end of the factory engines is somewhat weak compared to other choices. Though Mickey Thompson had a lot of experience going fast with Chrysler hemis, he chose the Pontiac V8 for his LSR-attempt Challenger I specifically because the bottom-end in the Poncho was a lot tougher than the Chrysler.

 

Is there also an issue with high-rpm valve train binding/breakage concerning second-gen Hemis?

Would valve train issues have hampered Can-Am racers of the day? I don't know the rules or technology in use at that time.

Thanks for that combustion chamber design chart, also. For the first time, I can truly grasp the various designs. Burn rates and the timing advance required by each make perfect sense now.

Edited October 8, 2017 by Dodge Driver

[Ace-Garageguy]

  On 10/8/2017 at 11:29 AM, Dodge Driver said:

Is there also an issue with high-rpm valve train binding/breakage concerning second-gen Hemis?

Would valve train issues have hampered Can-Am racers of the day? I don't know the rules or technology in use at that time.

I'm definitely NOT a Mopar engine expert, but to the best of my knowledge, there are no inherent weaknesses or problems with the Gen II Chrysler hemi valvetrain. The long exhaust rocker arms may be a limiting factor as to high RPM, possibly requiring very high valve spring seat pressures to avoid float, but I just don't know.

CanAm cars were pretty much unlimited run-what-ya-brung, if I remember right, so I doubt any mods to make a hemi work would have been verboten. There was a minimum weight, and requirements as to door openings and "passenger" seat (to kinda pretend they were cars rather than purpose-built racing machines), but that's about it...far as I remember.

The weight and physical size issues worked against the Gen II hemi for road-racing more than anything, I imagine. Factory alloy heads were available from the beginning (again, if I remember correctly) but the blocks were still cast iron. Reynolds Aluminum built the special big-block Chebbys in the McLaren cars, and the iron-block hemi would have still been at a weight disadvantage there anyway.

And road-racing is terribly hard on any engine. Constantly running up and down the rev range with varying loads and throttle openings for a half hour at a stretch (CanAm) is an entirely different game than going mostly wide-open-throttle for a 12-second run. Not that drag-racing is easy on engines, but it takes a whole different mind-set to build a road-racer that stays together.

Sorry I can't give a more definitive answer here.

[Dodge Driver]

  On 10/8/2017 at 1:19 PM, Ace-Garageguy said:

I'm definitely NOT a Mopar engine expert, but to the best of my knowledge, there are no inherent weaknesses or problems with the Gen II Chrysler hemi valvetrain. The long exhaust rocker arms may be a limiting factor as to high RPM, possibly requiring very high valve spring seat pressures to avoid float, but I just don't know.

CanAm cars were pretty much unlimited run-what-ya-brung, if I remember right, so I doubt any mods to make a hemi work would have been verboten. There was a minimum weight, and requirements as to door openings and "passenger" seat (to kinda pretend they were cars rather than purpose-built racing machines), but that's about it...far as I remember.

The weight and physical size issues worked against the Gen II hemi for road-racing more than anything, I imagine. Factory alloy heads were available from the beginning (again, if I remember correctly) but the blocks were still cast iron. Reynolds Aluminum built the special big-block Chebbys in the McLaren cars, and the iron-block hemi would have still been at a weight disadvantage there anyway.

And road-racing is terribly hard on any engine. Constantly running up and down the rev range with varying loads and throttle openings for a half hour at a stretch (CanAm) is an entirely different game than going mostly wide-open-throttle for a 12-second run. Not that drag-racing is easy on engines, but it takes a whole different mind-set to build a road-racer that stays together.

Sorry I can't give a more definitive answer here.

Thanks for the response. I know more now than I did prior to your answer. Even with the info posted here, road racing Hemis are an esoteric subject.

[Richard Bartrop]

That's a good question.  The first gen Chrysler hemi found its way into a number of sports cars.  Cunningham, Allard and Facel-Vega spring to mind off the top of my head.

The 426 Hemi was originally designed for NASCAR racing, where it did so well  it was banned, so obviously they could go the distance.    Maybe it was just a matter of availability?

[Ace-Garageguy]

  On 10/8/2017 at 6:04 PM, Richard Bartrop said:

That's a good question.  The first gen Chrysler hemi found its way into a number of sports cars.  Cunningham, Allard and Facel-Vega spring to mind off the top of my head.

The 426 Hemi was originally designed for NASCAR racing, where it did so well  it was banned, so obviously they could go the distance.    Maybe it was just a matter of availability?

The first generation Chrysler Firepower hemi is good for maybe something a little over 500HP on the essentially stock bottom end. The problems start with very high compression ratios, high RPMs, or supercharging. The resulting increased forces naturally try to push the crank out the bottom of the main caps. Cunninghams, Allards and the like probably never saw 500 horsepower hemi engines, and they were relatively unsophisticated compared to later CanAm cars.

The gen II Chrysler hemi engines built for NASCAR in '64 would necessarily have been cast iron blocks (and heads I believe), but in a big heavy US production chassis, weight could be offset somewhat by brute force (more power). And once set up to do the oval turn-in-one-direction thing, engine weight's effect on handling has been pretty much dealt with.

A CanAm car, on the other hand, has to turn in both directions, through many different types of turns of varying radii, accelerating and braking constantly. A CanAm car also weighed in the vicinity of only 1500 pounds, so the hemi's seemingly small increased weight turns out to be a pretty significant percentage of overall vehicle weight...which directly influences acceleration, braking, and handling in turns.

Without the availability of alloy blocks as well as heads for the second generation hemi, the potential power gain could very easily be offset by weight-related handling and response issues.

Edited October 8, 2017 by Ace-Garageguy

[heyjohnxx]

Thanks for the great info guys! I've learned some things here. Now, I just have to wait for my next night of insomnia for the next great ponderable thought.