Pushrod engines are more compact .
That was the point I was making about the engine in my truck, a simple, little inline 4. Its valve cover can't be much higher than a similar pushrod one. Same with the Tech 4 that was in my daughter's 90 Beretta. Both engines had good enough low end torque for easy launches with a manual.quote:
Originally posted by Spitty:
I think we nned to decide if we are talking about In line engins or V engines, a V engine can be smaller and lighter due to it useing a single cam in the middle of the V.
In an in line engine there is not much advantage in having the cam in the block.
snip...
The Honda GC OHC lawn and garden motors are terrific, though they do seem to be an exercise in engineering. Nonetheless, and contrary to what many people thought would happen with Honda’s use of an internal timing belt to drive the plastic camshaft, these engines have proven to be durable, run flawlessly, use little gas, always seem to start on one pull, and sound very refined (I know that’s only aesthetics). So, based on my experience of currently owning both types (a flat head and a SOHC) I’ll take the pleasing, if not gimmicky, OHC over the crude, raspy, pollution belching, hard starting flathead any day. Besides, I can buy a sticker to put on my mower that says “Powered by Honda.” Now, if I could only get a NOS kit, K&N, and coffee can muffler for it…quote:
crypto,
just what do you need a belt driven OHC in a garden mower for anyway ?
I'll choose rugged simplicity any day over gimmicky technology.
quote:
Originally posted by HEV:
Nonetheless, and contrary to what many people thought would happen with Honda’s use of an internal timing belt to drive the plastic camshaft, these engines have proven to be durable, run flawlessly, use little gas, always seem to start on one pull, and sound very refined (I know that’s only aesthetics).I don't doubt that any honda product is reliable; however, Briggs flatheads are pretty **** reliable too. I've got one from 1960 that has at least 1000 hours on it, still starts on the second pull. (like it's designed to) I really don't see any good reason for OHC in a small engine - performance isn't an issue and it will never be MORE reliable than a flathead or OHV. Flatheads do drink the gas, but OHVs are quire efficient. I doubt there's enough difference to worry about in fuel use between briggs OHV, honda OHV, and honda OHC. I'm sure the OHC is reliable, but how much does it cost to fix/rebuild? Probably alot more than any OHV from the same manufacturer.
Aircooled engines have the pushrods external to the block. All small aircraft engines are still made that way. Aircooled VW's with external pushrods were still common in the 1970's. There are tremendous packaging and simplicity advantages to OHV in horizontally opposed designs. A single cam lobe can actuate valves on two oppsed cylinders, something a "V" engine cannot do.quote:
Originally posted by labman:
... I once saw an engine from the 20's where the pushrods were external to the block.
SOHC still has the advantage of being able to move the valves quicker with much less spring force since the spring doesn't have to handle the pushrod too. Quicker valve actuation, lower wear on high speed engines.quote:
Originally posted by T-Keith:
OHC engines tend to have better valve control, but only if their are DOHC engines. A 2-valve OHC engine has little benefit over a 2-valve OHV engine. However they can more easily adapt a 4-valve head.
-T
Pushrod engines usually get better fuel economy than a DOHC engine of the same displacement.quote:
Originally posted by Spitty:
I see the difference in OHC v OHV this way, traditonally in the US, Gas has been cheap, and the roads have not favoured High Speed travel, people have bought Large cars with big lazy 'V' engines, and Bags of Torque. In Europe gas is expensive, yet for 50 or more years there has been a network of High Speed roads, cars purchased tend to be small (ease of parking) and of small displacement, 4 cyl is typical (good gas consumption)
From three-speed automatics, to distributor caps (as opposed to distributorless ignition), to vacuum-servo (as opposed to electronic-servo) cruise controls, Japanese manufacturers stick to existing designs as much as (if not more than) American manufacturers do.quote:
Originally posted by John K:
A little off topic, but I think Detroit sticks to existing designs due to cost savings and resistance to change, Japanese mfrs are quicker to adopt variable valve timing and other advances.
That's an interesting idea, can you give an example, you must also consider power out-put.quote:
Originally posted by sbc350gearhead
Pushrod engines usually get better fuel economy than a DOHC engine of the same displacement. [/QB]
The new Malibu's 3.5 has more power and better gas mileage then Toyota's 3.0.quote:
Originally posted by Spitty:
quote:
Originally posted by sbc350gearhead
Pushrod engines usually get better fuel economy than a DOHC engine of the same displacement.That's an interesting idea, can you give an example, you must also consider power out-put. [/QB]
problem is, the Toyota 3.0L v6 is 10+ years old. The comparable GM v6 in 1993 was the (bark, bark) 3.1..... ?quote:
Originally posted by T-Keith:
quote:
Originally posted by Spitty:
quote:
Originally posted by sbc350gearhead
Pushrod engines usually get better fuel economy than a DOHC engine of the same displacement.That's an interesting idea, can you give an example, you must also consider power out-put.The new Malibu's 3.5 has more power and better gas mileage then Toyota's 3.0.
-T [/QB]
no.....the 2.5L v6 (156 hp, btw) was last used in the Camry and Lexus 250 in 1991. I had one. A different 2.5L was used in TMC trucks for a awhile longer, I'm not sure what was different about it but it wouldn't swap when my 1st 2.5L spun a rod bearing...quote:
Originally posted by T-Keith:
Toyota had a 3.0 back in 93? I'm pretty sure it was a 2.5 back then. The 3.5 isn't exactly cutting edge either. Simply a freshened and enlargened 3.1. Sounds a lot like the Toyota V6 to me.
-T