Can Someone Please Explain A Pushrod Engine.
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crew_dawg16
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In a pushrod engine, you have a single camshaft that is in the engine block. It has lifters that ride on the cam lobes which in turn have pushrods on top of them. The pushrods run up through the heads and push up on the rocker arms, the rocker arms then push down on the valve stem.
In our motors, the cams are in each head and are directly over the valves. This way the cams are pushing directly on the valve stems. The downfall is a heavier engine due to extra valve train components like chains and sprockets and a big ol' cover on the front.
In our motors, the cams are in each head and are directly over the valves. This way the cams are pushing directly on the valve stems. The downfall is a heavier engine due to extra valve train components like chains and sprockets and a big ol' cover on the front.
Comparison pushrod to ohv
http://forums.autoweek.com/thread.jspa?forumID=31&threadID=14700&start=300&tstart=0
http://forums.autoweek.com/thread.jspa?forumID=31&threadID=14700&start=300&tstart=0
Back2Mustangs
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- Sep 2, 2004
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300bhp/ton
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Yeah damn I can't think of ANY push rod engines in production today, or any older one's still used in hot rods and modified cars................Back2Mustangs said:Pushrod motors already a forgotten thing of the past
Despite the fact that OHC has been around just about as long.
QU!CK
New Member
300bhp/ton said:Yeah damn I can't think of ANY push rod engines in production today, or any older one's still used in hot rods and modified cars................
me either...
get used to the view
-J
StangIt #1
Founding Member
300bhp/ton said:Yeah damn I can't think of ANY push rod engines in production today, or any older one's still used in hot rods and modified cars................
Isn't the new 5.7L HEMI a pushrod design?
mity2
I like Pro3 and all I got was this crappy CT.
main deifference between pushrod(OHV) and overhead(OHC) is way valve is actuated.
In OHV engine, Camshaft is located just above crankshaft which is connected to crankshaft via timing chain. The cam actuates long rods that go up through the block and into the head to move the rockers. These long rods add mass to the system, which increases the load on the valve springs. This can limit the speed of pushrod engines. But not all of them are. New LS7 for instance are said to be having 7500RPM limit. Some NASCAR engine can rev to astonishing 9000RPM!
good pic of how OHV works is in here
the overhead camshaft, which eliminates the pushrod from the system, is one of the engine technologies that made higher engine speeds possible.
Most can easily rev to 5500RPM~6500RPM with ease. some can go as high as 9000RPM. one of the biggest advantage of overhead cam is that u can place more then 2 Valve. in OHV, u'll have 1 intake and 1 exhaust Valve. where as in OHC engine, even some cheap kia engine have 2 intake and 2 exhaust valve, and some have 3 intake and 2 exhaust totalling 5 valves
we all know that more Valve means more air in&out of engine. that means power. Back in late 80's, Honda introduced NSR 500 race bike, witch had oval cylinder and 4intake and 4 exhaust valve(total of 8 valve PER cylinder!) here is basic how OHC owrks. Below is SOHC(much like our engine in 96+ GT. Notice one camshaft? DOHC Cobra engine has 2 camshafts on each cylinder bank(total of 4 camshafts, and 32 valves)
In OHV engine, Camshaft is located just above crankshaft which is connected to crankshaft via timing chain. The cam actuates long rods that go up through the block and into the head to move the rockers. These long rods add mass to the system, which increases the load on the valve springs. This can limit the speed of pushrod engines. But not all of them are. New LS7 for instance are said to be having 7500RPM limit. Some NASCAR engine can rev to astonishing 9000RPM!
good pic of how OHV works is in here
the overhead camshaft, which eliminates the pushrod from the system, is one of the engine technologies that made higher engine speeds possible.
Most can easily rev to 5500RPM~6500RPM with ease. some can go as high as 9000RPM. one of the biggest advantage of overhead cam is that u can place more then 2 Valve. in OHV, u'll have 1 intake and 1 exhaust Valve. where as in OHC engine, even some cheap kia engine have 2 intake and 2 exhaust valve, and some have 3 intake and 2 exhaust totalling 5 valves
we all know that more Valve means more air in&out of engine. that means power. Back in late 80's, Honda introduced NSR 500 race bike, witch had oval cylinder and 4intake and 4 exhaust valve(total of 8 valve PER cylinder!) here is basic how OHC owrks. Below is SOHC(much like our engine in 96+ GT. Notice one camshaft? DOHC Cobra engine has 2 camshafts on each cylinder bank(total of 4 camshafts, and 32 valves)
300bhp/ton said:Yeah damn I can't think of ANY push rod engines in production today, or any older one's still used in hot rods and modified cars................
Despite the fact that OHC has been around just about as long.
ahh......Corvette's?? LS1, LS6 both pushrod motors I belive the ZR1 was a DOHC
ts1lmayb said:
OHV = Over Head Valve. Almost every engine since WWII has been OHV. You meant OHC (Over Head Cam).
SOHC = Single Over Head Cam like the Mustang GT
DOHC = Double Over Head Cam like the Cobra/Mach 1
Pushrod motors are plentiful over at GM. Most diesels are pushrod engines. It is rumored that Ford is developing a new pushrod engine for the F series. Push rod engines can easily live in environments under 6500 rpm. The main limitation to a push rod engine is valve train mass. Ford going to the SOHC and DOHC engines was foolish IMO. They are great engines. Smooth and quiet.
Take a look at the new Corvette. 6.0 Litre, 6 speed, 400 hp/400 ft/lbs, and it's fuel economy is rated at 18 mpg city/28 mpg highway. Or look at the new 7.0 Litre LS7 with 500 hp and 475 ft/lbs and 7000 rpm redline. Granted it has titanium connecting rods.
Ford could easily build a much more compact, larger, more powerful engine and still get as good or better mpg out of it.
mity2
I like Pro3 and all I got was this crappy CT.
300bhp/ton
New Member
Sarcasmmustangmatt said:
Yes the ZR1 Corvette had an LT5 (?) OHC design, partyl developed by Lotus.
It does show quite nicely the benefit that can be achieved, the regular 5.7 push rod engine of the day only managed a measly 285bhp, where as with the same capacity of 5.7 litres and still meeting the same emmissions and fuel standards (was probably slightly better in fact) the ZR1 engine developed 385bhp then in the later years was upped to 405bhp stock.
Ford can and has done the same thing too, the Cobra DOHC 4.6's could produce 320bhp n/a whereas even the mighty LS1 push rodder was only 345bhp with an EXTRA 1.1 litres.
In pure bhp terms a SOHC design offers nothing over a push rod, what it does offer is how and where the power is made in rpm terms. DOHC units offer much more potential but at the downside of extra weight and increasing the height of a cars centre of gravity.
300bhp/ton
New Member
mity2
I like Pro3 and all I got was this crappy CT.
Only non OHV engine I can think of is a two stroke...which is also an interesting type of combustion engine to learn about.
car engines are called 4 strokes becuase each cycle takes 4 different steps
1. intake
2. compression
3. combustion
4. exhaust
this basically means that it completes the cycle every time the piston goes up TWICE.
two strokes are in lawn mowers and dirt bikes and stuff...
Compression and combustion happen in the same step and intake and exhaust happen in the same step.
EDIT: remember, although two strokes seem more efficient because they get the same job done in less steps, they are actually much worse on gas and pollute much much more; due to the oil consumption. The engine has no lubricating system, so oil is mixed in with the fuel which is burnt.
car engines are called 4 strokes becuase each cycle takes 4 different steps
1. intake
2. compression
3. combustion
4. exhaust
this basically means that it completes the cycle every time the piston goes up TWICE.
two strokes are in lawn mowers and dirt bikes and stuff...
Compression and combustion happen in the same step and intake and exhaust happen in the same step.
EDIT: remember, although two strokes seem more efficient because they get the same job done in less steps, they are actually much worse on gas and pollute much much more; due to the oil consumption. The engine has no lubricating system, so oil is mixed in with the fuel which is burnt.
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