OHC vs Pushrod
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TECH Enthusiast
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OHC vs Pushrod I found this link on another board and thought some might find interest in it. Good read for some that may be just starting out with learning about engines and the differences.
http://www.cheersandgears.com/forums...opic=15551&hl=
It basically reaffirms what most of us all say here, get the air in and get the air out. Even uses the LSx engines in its comparison to other OHC engines.
It does a good job of pointing out the Pros and Cons of each engine out there.
http://www.cheersandgears.com/forums...opic=15551&hl=
It basically reaffirms what most of us all say here, get the air in and get the air out. Even uses the LSx engines in its comparison to other OHC engines.
It does a good job of pointing out the Pros and Cons of each engine out there.
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They left out so many things, they discussed how it was impossible to have a pushrod 4 valve per cylinder head, what about the Dominion 32 valve heads ?! They say no major advances have been made in spring technology in the past 40 years, what about beehive springs? These are two MAJOR factors they completely ommitted, If someone has an account please, notify those people of these two factors. Both of these close the gap between pushrod and OHV engines. BTW no the dominion 32 valve car is not mine, I merely hosted the pics for someone. There are at least 3 32 valve headed LT1s in existence. This is just lt1s! There is a lot of work to convert the dominion heads to the LT1 I have no idea how many dominion headed cars there are outside the LT1 arena.
Launching!
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From: Exton, Pennsylvania
Aren't the Dominion and Arao heads one and the same? If they are, I don't think there are many engines out there sporting them, which is ashame. I have never actually seen them in person, but read on boards like this that they are a great head when they are finally hooked up to block, although installation can be a nightmare.
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Originally Posted by RussStang
Aren't the Dominion and Arao heads one and the same? If they are, I don't think there are many engines out there sporting them, which is ashame. I have never actually seen them in person, but read on boards like this that they are a great head when they are finally hooked up to block, although installation can be a nightmare.
LiENUS and Russ,
I don't think that the write-up in the link is attempting to be comprehensive regarding the latest state of technology of pushrod engines. I think that this guy is just saying that it is a commonly held misconception that overhead cam (SOHC and DOHC) are superior in every way to pushrod engines. He's also debunking the myth that pushrod engines are outdated. The write-up also mentions that OHC engines have been around for a long time and they are not the latest nor the greatest in every respect (power versus weight, engine exterior volume versus power, etc.).
Yes there are probably a lot of other things that could be said both for OHC and pushrod designs. However, I think that this guy was just trying to set the record straight to the extent that he could.
Steve
I don't think that the write-up in the link is attempting to be comprehensive regarding the latest state of technology of pushrod engines. I think that this guy is just saying that it is a commonly held misconception that overhead cam (SOHC and DOHC) are superior in every way to pushrod engines. He's also debunking the myth that pushrod engines are outdated. The write-up also mentions that OHC engines have been around for a long time and they are not the latest nor the greatest in every respect (power versus weight, engine exterior volume versus power, etc.).
Yes there are probably a lot of other things that could be said both for OHC and pushrod designs. However, I think that this guy was just trying to set the record straight to the extent that he could.
Steve
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Great article.
One EXTREMELY important point they missed (also something that ricers cannot get through their heads) is that the smaller an engine is, the more HP/L it is capable of. Or more precisely, the shorter an engine's stroke is, the more HP/L it is capable of.
Obvious reason being: shorter stroke enables greater RPM's. This is why tiny crotch rocket engines can achieve nearly 200 HP/L at like 14,000 RPM's.
One EXTREMELY important point they missed (also something that ricers cannot get through their heads) is that the smaller an engine is, the more HP/L it is capable of. Or more precisely, the shorter an engine's stroke is, the more HP/L it is capable of.
Obvious reason being: shorter stroke enables greater RPM's. This is why tiny crotch rocket engines can achieve nearly 200 HP/L at like 14,000 RPM's.
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Teching In
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Originally Posted by Louie83
Great article.
One EXTREMELY important point they missed (also something that ricers cannot get through their heads) is that the smaller an engine is, the more HP/L it is capable of. Or more precisely, the shorter an engine's stroke is, the more HP/L it is capable of.
Obvious reason being: shorter stroke enables greater RPM's. This is why tiny crotch rocket engines can achieve nearly 200 HP/L at like 14,000 RPM's.
One EXTREMELY important point they missed (also something that ricers cannot get through their heads) is that the smaller an engine is, the more HP/L it is capable of. Or more precisely, the shorter an engine's stroke is, the more HP/L it is capable of.
Obvious reason being: shorter stroke enables greater RPM's. This is why tiny crotch rocket engines can achieve nearly 200 HP/L at like 14,000 RPM's.
All the way through I was thinking to myself, "What about the bottom end?" In the end the ultimate potential to develop power in all engines is limited by piston acceleration forces.
I understand that GM built 2 black vettes in the early 90's. One with a lt4 and the other with a lt5. Then a bunch of the GM brass went out to test each car, not knowing what engine they were driving behind. One car got complaments as pulling hard from low rpms. The other seemed to "wind up" then press you in the seat. At the end of the day the hoods were opened and the lt4 was the winner. From that point on "If I understand the story correctly" GM gave the "ls1" project the green flag to go into production.
Originally Posted by nitsudls1
I understand that GM built 2 black vettes in the early 90's. One with a lt4 and the other with a lt5. Then a bunch of the GM brass went out to test each car, not knowing what engine they were driving behind. One car got complaments as pulling hard from low rpms. The other seemed to "wind up" then press you in the seat. At the end of the day the hoods were opened and the lt4 was the winner. From that point on "If I understand the story correctly" GM gave the "ls1" project the green flag to go into production.
GM will never let the pushrod design die(at least i hope)
Originally Posted by mcamarols1
that storie is in the the book "How to build hi-preformance Gen3 v-8" i forgot the author but it was two equally dis. engines, one being pusrod the other being OHC.
GM will never let the pushrod design die(at least i hope)
GM will never let the pushrod design die(at least i hope)
Unless GM dies.
EVER!!!!lol 
Originally Posted by nitsudls1
I understand that GM built 2 black vettes in the early 90's. One with a lt4 and the other with a lt5. Then a bunch of the GM brass went out to test each car, not knowing what engine they were driving behind. One car got complaments as pulling hard from low rpms. The other seemed to "wind up" then press you in the seat. At the end of the day the hoods were opened and the lt4 was the winner. From that point on "If I understand the story correctly" GM gave the "ls1" project the green flag to go into production.
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Originally Posted by nitsudls1
I understand that GM built 2 black vettes in the early 90's. One with a lt4 and the other with a lt5. Then a bunch of the GM brass went out to test each car, not knowing what engine they were driving behind. One car got complaments as pulling hard from low rpms. The other seemed to "wind up" then press you in the seat. At the end of the day the hoods were opened and the lt4 was the winner. From that point on "If I understand the story correctly" GM gave the "ls1" project the green flag to go into production.
For the LSx engines it isn't just down low where all the power comes in, but it can still be felt up top. Everytime I go from my GTP to my TA and go WOT, it amazes me how it is a nonstop and consistant pull on the top side, the GTP falls off after a bit and starts to struggle. 
Good article with some interesting historical points. Not sure how push rod engines got labeled as being old fashion or out of date considering the ancient history of both designs. The bottom end design of both engines is the same, the last I checked they were both reciprocating engines? You can trade your 12 foot worth of chain on the dohc for 16 pushrods on the other, worst case call it a wash for valvetrain loss. The DOHC has some advantages for low lift flow, but 400 cfm potential on newer LSX heads with good torque and horsepower were race car only #'s just a year ago. With how fast the cars on this site are getting as of late I will be building an LSX motor for my next project. The design is light, compact, inexpensive, great power output over a real world rpm range, and an aftermarket controller is not needed to program the computer. Amazing how GM hit on another winner in spite of the execs.
another factor is that people say with ohc engines that there is less parts and drag. in fact there is the smae amount or more moving parts then a pushrod.
and yes you can have a pushrod 4valve cyl head. the ford 6.0L TDI, yes a diesel but still a pushrod, the rockers on that engine control two valves, why no one else tried this theroy in a performance engine i dont know,
but i think it would be a good idea for more airflow IMO
and yes you can have a pushrod 4valve cyl head. the ford 6.0L TDI, yes a diesel but still a pushrod, the rockers on that engine control two valves, why no one else tried this theroy in a performance engine i dont know,
but i think it would be a good idea for more airflow IMO
Teching In
Joined: May 2007
Posts: 23
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HI all,
I'm new to both this forum, and the world of large displacement V8s.
Q:
Does anyone know anything about the heads on this engine:
http://tinyurl.com/3bu277
(I was hoping for something other than the evils of the OHc layout...)
Thanks
I'm new to both this forum, and the world of large displacement V8s.
Q:
Does anyone know anything about the heads on this engine:
http://tinyurl.com/3bu277
(I was hoping for something other than the evils of the OHc layout...)
Thanks
Last edited by ThinkingGTM; May 12, 2007 at 11:52 AM.