What engines have dual overhead camshafts and a hemi or pent roof combustion chamber?
Seems like the Quad Four was built like that.
Sort of a toned down production Offenhauser 50 years later.
What other engines have that type of head?
V8 would be nice.All aluminum too.
Northstar?
Nearly every DOHC engine has a pent roof or hemi chamber, simply because of where the valves end up.
Duesenberg was one of the first domestic production cars to have them, Stutz as well.
Harry Miller designed the Offenhauser as well as the cylinder head on the Stutz DV32 engine.
Offenhauser (Miller) engines didn't actually have "cylinder heads" as such, the head and cylinder block were one piece. Part of why they can handle goofy amounts of boost.
Hemi is not pent roof.
All DOHC engines except for VW* are pentroof. Hemispherical, however, is really rare in the 4-valve world. As far as I am aware, only some 50s motorcycles had hemispherical 4v heads, because having four valves with their own planes of motion is really, really hard to make a valvetrain for.
* - VW are historically weird. The VW DOHC head has its design dictated by the original DOHC VWAG head, the 20-valve Sport Quattro, which for space reasons required that the valvetrain be rotated a lot towards the intake side so that there'd be room to cram a large turbo next to the engine that was already leaned way over to the exhaust side of the engine, and placed right-justified in the chassis in order to clear the radiator that was actually behind the front of the engine. Because of that functionally-fixed, toolings-paid-for-already engineering decision, every multivalve VW has a reallly compromised valvetrain.
In reply to The Californian :
older Jaguars. the iron block 3.4 3.8 4.2 and 2.4 but they are all inline 6's
The earliest ( non production ) V 12's were all Hemi head but 2 valve. Those heads are now in limited reproduction to bolt onto later Jaguar V12's
Also Alfa Romeo 4 cylinders.
ShawnG said:Nearly every DOHC engine has a pent roof or hemi chamber, simply because of where the valves end up.
Duesenberg was one of the first domestic production cars to have them, Stutz as well.
Harry Miller designed the Offenhauser as well as the cylinder head on the Stutz DV32 engine.
Offenhauser (Miller) engines didn't actually have "cylinder heads" as such, the head and cylinder block were one piece. Part of why they can handle goofy amounts of boost.
They to a degree are patterned after the early Peugeot
I thought this was going to be a discussion of engines with the cylinders cast with the cylinder head.
I am disappoint.
Can we still cover why the Offy is different or special?
RossD said:Can we still cover why the Offy is different or special?
The main thing I recall of them besides the intergated head/jug assembly, was that the cylinder block was end-loading. It didn't have main bearing caps, it had a one piece block and you assembled the main bearings and such to the crank and slid it in endwise. It's like the engine was designed to be machined with a lathe.
it IS a design dating back to the 30s, so this is probably the case.
This same design also allowed it to take ridiculous amounts of boost. No head gaskets to blow, no main caps to rattle.
RossD said:Can we still cover why the Offy is different or special?
So in addition to what Kurnled mentioned about the tech part (forgetting the OP's question about a hemi head, which allows for bigger valves, and thus more airflow and the general determent of combustion volume- which wasn't a big deal in the 30's....), the Offy/Miller engines were American and thus available to the US based racer. These were considerably better than the production engines available when factoring all things racing, and they were far easier to get than anything from Europe.
I didn't realize that the design was easily laid out in a lathe, but that also makes it desireable, since that was a VERY common and easy to use machine tool- forever, not just the 20s- 50s.
The odd part about the engine that at it's end, it was not a good gasoline engine. When Scarab put one into their Grand Prix car, and tried to make it run on gas- which was the F1 regulations at the time- it just didn't work. Based on it's layout, it *should* have been more than a match to the other F1 engines at the time, too bad that didn't happen. On methanol and with boost, that was an amazing engine- it won races into the 70s.
In reply to alfadriver :
The front engine era had been over for years when finally the Scarab came out.
if that engine had been in the back things might have been different.
Another thing about the Offy was that the bore was much smaller than the stroke as was common in engines of that era.
Due to the small bore the 4 valves were needed to get it to breath and why it ran so much better as a turbo/supercharged engine than NA.
In reply to jimbbski :
When boosted the stroke of the Offy was reduced from 4.6125 ( bore 4. 312 ) to as short as 2.750 ( bore 4.281)
horsepower went from
375 hp. @ 270 cu in.
to 1200 hp. @ 158.25 cu. in.
now to be fair the former was in 1937 while the later was 40 years later. In 1977
The reason the bore was smaller than the stroke varied. In England for a long time engines were taxed based on bore of the engine but the stroke was free.
Hench only a 3&1/2 inch bore and a 4.17inch stroke on Jaguars.
While in America a long stroke developed more torque than a short stroke.
In reply to The Californian :
There were several aftermarket heads made, the most common was the Duntov heads for the Ford Flathead.
they also made several heads for the MGTD ( Hemi with twin cams )
alfadriver said:RossD said:Can we still cover why the Offy is different or special?
So in addition to what Kurnled mentioned about the tech part (forgetting the OP's question about a hemi head, which allows for bigger valves, and thus more airflow and the general determent of combustion volume- which wasn't a big deal in the 30's....), the Offy/Miller engines were American and thus available to the US based racer. These were considerably better than the production engines available when factoring all things racing, and they were far easier to get than anything from Europe.
I didn't realize that the design was easily laid out in a lathe, but that also makes it desireable, since that was a VERY common and easy to use machine tool- forever, not just the 20s- 50s.
The odd part about the engine that at it's end, it was not a good gasoline engine. When Scarab put one into their Grand Prix car, and tried to make it run on gas- which was the F1 regulations at the time- it just didn't work. Based on it's layout, it *should* have been more than a match to the other F1 engines at the time, too bad that didn't happen. On methanol and with boost, that was an amazing engine- it won races into the 70s.
I think part of the problem also was it was an engine designed for top speed at constant higher rpm on speedways and not for road courses which would require some actual ow e d torque for coming out of slower corners etc.
In reply to MotorsportsGordon :
The lack of acceleration does it. Like trying to use an aircraft engine in a drag racer... "can't accelerate but it will taxi all day at 150"
BUT.. aren't/weren't these popular Midget motors? Granted that is a bit more specialized than a road racing engine, but you still need to be able to accelerate.
MotorsportsGordon said:alfadriver said:RossD said:Can we still cover why the Offy is different or special?
So in addition to what Kurnled mentioned about the tech part (forgetting the OP's question about a hemi head, which allows for bigger valves, and thus more airflow and the general determent of combustion volume- which wasn't a big deal in the 30's....), the Offy/Miller engines were American and thus available to the US based racer. These were considerably better than the production engines available when factoring all things racing, and they were far easier to get than anything from Europe.
I didn't realize that the design was easily laid out in a lathe, but that also makes it desireable, since that was a VERY common and easy to use machine tool- forever, not just the 20s- 50s.
The odd part about the engine that at it's end, it was not a good gasoline engine. When Scarab put one into their Grand Prix car, and tried to make it run on gas- which was the F1 regulations at the time- it just didn't work. Based on it's layout, it *should* have been more than a match to the other F1 engines at the time, too bad that didn't happen. On methanol and with boost, that was an amazing engine- it won races into the 70s.
I think part of the problem also was it was an engine designed for top speed at constant higher rpm on speedways and not for road courses which would require some actual ow e d torque for coming out of slower corners etc.
Should I remind everybody about the time the Offy with a one speed gear box won the race at Lime Rock?
Have you ever seen a sprint car race? On a 1/4 mile dirt track they haul er, is saying butt in this context OK? Anyway they slide around and then haul the Er••• to the other end.
It's anything but a steady RPM.
Knurled. said:In reply to MotorsportsGordon :
The lack of acceleration does it. Like trying to use an aircraft engine in a drag racer... "can't accelerate but it will taxi all day at 150"
BUT.. aren't/weren't these popular Midget motors? Granted that is a bit more specialized than a road racing engine, but you still need to be able to accelerate.
The midget engines were 97 cubic inches not sure the other differences in desk between the engines though roger ward did win a formula libre race against sports cars at lime rock in a offy midget.
Knurled. said:In reply to MotorsportsGordon :
The lack of acceleration does it. Like trying to use an aircraft engine in a drag racer... "can't accelerate but it will taxi all day at 150"
BUT.. aren't/weren't these popular Midget motors? Granted that is a bit more specialized than a road racing engine, but you still need to be able to accelerate.
If you wanted to accelerate Miller, Offenhauser, Meyer Drake offered many different camshafts.
frenchyd said:MotorsportsGordon said:alfadriver said:RossD said:Can we still cover why the Offy is different or special?
So in addition to what Kurnled mentioned about the tech part (forgetting the OP's question about a hemi head, which allows for bigger valves, and thus more airflow and the general determent of combustion volume- which wasn't a big deal in the 30's....), the Offy/Miller engines were American and thus available to the US based racer. These were considerably better than the production engines available when factoring all things racing, and they were far easier to get than anything from Europe.
I didn't realize that the design was easily laid out in a lathe, but that also makes it desireable, since that was a VERY common and easy to use machine tool- forever, not just the 20s- 50s.
The odd part about the engine that at it's end, it was not a good gasoline engine. When Scarab put one into their Grand Prix car, and tried to make it run on gas- which was the F1 regulations at the time- it just didn't work. Based on it's layout, it *should* have been more than a match to the other F1 engines at the time, too bad that didn't happen. On methanol and with boost, that was an amazing engine- it won races into the 70s.
I think part of the problem also was it was an engine designed for top speed at constant higher rpm on speedways and not for road courses which would require some actual ow e d torque for coming out of slower corners etc.
Should I remind everybody about the time the Offy with a one speed gear box won the race at Lime Rock?
Have you ever seen a sprint car race? On a 1/4 mile dirt track they haul er, is saying butt in this context OK? Anyway they slide around and then haul the Er••• to the other end.
It's anything but a steady RPM.
Offy made different sizes of blocks. The f1 engines was 2.5 litres air about 150 cubic inches. With the exception of the midget engines all the normally aspirated Offenhauser engines were much bigger,their sprint car engines were 220 cubic inches.
Can someone post pics of the block / crank etc. Still trying to get my head around what people are saying for the assembly of the lower end.
thx
In reply to Adrian_Thompson :
Hot Rod did a article on buliding an Offy: https://www.hotrod.com/articles/assembling-270ci-offenhauser-indycar-engine-step/
MotorsportsGordon said:frenchyd said:MotorsportsGordon said:alfadriver said:RossD said:Can we still cover why the Offy is different or special?
So in addition to what Kurnled mentioned about the tech part (forgetting the OP's question about a hemi head, which allows for bigger valves, and thus more airflow and the general determent of combustion volume- which wasn't a big deal in the 30's....), the Offy/Miller engines were American and thus available to the US based racer. These were considerably better than the production engines available when factoring all things racing, and they were far easier to get than anything from Europe.
I didn't realize that the design was easily laid out in a lathe, but that also makes it desireable, since that was a VERY common and easy to use machine tool- forever, not just the 20s- 50s.
The odd part about the engine that at it's end, it was not a good gasoline engine. When Scarab put one into their Grand Prix car, and tried to make it run on gas- which was the F1 regulations at the time- it just didn't work. Based on it's layout, it *should* have been more than a match to the other F1 engines at the time, too bad that didn't happen. On methanol and with boost, that was an amazing engine- it won races into the 70s.
I think part of the problem also was it was an engine designed for top speed at constant higher rpm on speedways and not for road courses which would require some actual ow e d torque for coming out of slower corners etc.
Should I remind everybody about the time the Offy with a one speed gear box won the race at Lime Rock?
Have you ever seen a sprint car race? On a 1/4 mile dirt track they haul er, is saying butt in this context OK? Anyway they slide around and then haul the Er••• to the other end.
It's anything but a steady RPM.
Offy made different sizes of blocks. The f1 engines was 2.5 litres air about 150 cubic inches. With the exception of the midget engines all the normally aspirated Offenhauser engines were much bigger,their sprint car engines were 220 cubic inches.
Once the Offy was turbocharged ( about 1970's ) the blocks shrank to a little less than 160 inches which made 1200 horsepower in quailifying trim 1000 horsepower for the race.
06HHR said:In reply to Adrian_Thompson :
Hot Rod did a article on buliding an Offy: https://www.hotrod.com/articles/assembling-270ci-offenhauser-indycar-engine-step/
Wow, I had no idea they were like that. I kinda want to swap one into a Miata now...
In reply to Pete Gossett : that's the old 270 cu in engine also called the long block. The last Offy's were only about 160 cu inches but made 1200 horsepower in qualifying trim and between 900-1000 horsepower for the race
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