That's how you build an engine....

Homer raved thus:

::

The bastard son of a Chevy big block and a giant squid...

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Jesus, is that Semi detached house at the front the Intercooler? It's nearly as big as my engine?

If you are impressed by big numbers it's quite impressive. But when you look at specific output it's not so good.

2139bhp 442ci = 7243cc = 295bhp/l

You can buy 300bhp/l for £16K from the web page of Norris Designs in the UK. Not a GRP alloy con rod in sight.

Real turbo race engines run over 600bhp/l some made over 900bhp/l.

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I had an old moped once that I got working and rode around places offroad. It was 50cc and made 5hp, thats 100bhp/litre and it cost me £6 ;)

Cubes count - and 7243 would do nicely.

Theres no replacement for displacement ;-) Rich

Is it just me who thinks it rather bizarre that the americans are still using pushrod engines when setting out from scratch to build a race engine (says the man with a pushrod engine in his car)?

Whats wrong with pushrods?

They're shit. Makes a twin cam engine a pain in the arse, which means you've got 2 valves per cylinder rather than 4 or 5 (though there's little to no advantage with having 5). You've also got frictional losses from the pushrods, rockers etc., and of course they have weight, so take power from the engine when they're moved up and down. If you have DOHC instead you can have different inlet and exhaust cam profiles on a 16V motor, and there are the various variable valve timing systems about...

Not correct!

The replacement for displacement is even more displacement.

;)

TDM

Push rods are fit only for vintage and classic racing. Build that motor with a pair of twin cam 16v heads and it could run 3000+bhp.

There have been some 4 valve pushrod motors. Weslake and Jawa speedway/grasstrack engines come to mind. Methanol fueled, 2 speed and low weight is more important than the power that high revs gives. The Triumph Bonneville TSS used a head derived from a Weslake 8 valve conversion. All too little to late.

Honda were making 320bhp/l back in 1966 without a turbo. 50 cc RC116

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The heathens ought to be using straight 6s ;).

Wouldn't it be simplest to run a pair of belts, or are the yanks terrified of timing belts?

But at higher revs you've got the pushrods bouncing up and down faster and faster, rather than a chain / belt speeding up. Surely the inertia of the pushrods will get to be more and more of a problem as revs increase?

Yep, very interesting.

Yes, that would rock !

I must admit I prefer the v8 myself, but that's all down to taste.

My favourite layout is a boxer, e.g. a flat 12. Dunno if there are any of these left nowadays.

Belts? I doubt they can carry the forces involved in a quad overhead cam layout, as well as the observation that the existence of two pulleys on the crank will lengthen it an inch or so. Plus you have two points of failure.

Of all the V engines I know about, all use chains, which includes all the modern engines. The smaller straight four engines, most of these seem to use a belt these days, the obvious advantages of weight saving is no doubt compromised elsewhere, though.

The inertia of pushrods is part of the overall work done by the cam, for sure. But to understand a bit more, a pushrod won't get shorter and won't bounce about, nor should the rocker arm although that will flex a little, I daresay.

It's certainly true that the added weight on the valve gear will increase the work being done by the cam lobe and require slightly stronger springs, but there is also a saving of large lengths of chain (which is fairly heavy stuff) to offset against it.

I reckon it boils down to the application you have in mind, understanding what options you have and where their strengths and weaknesses lie is important. On most european cars, we have overhead cams, this I would guess makes it easy to rev the engine on a budget so there's a lot to be said for it.

If designing an engine, I would certainly look at cogs rather than pushrods or chains, it adds expense but makes the valve timing precise enough to look for the limits on valve timing and I would expect an engine with cogs to last much longer, not that this is a criteria for hot rods.

BMW have already done that with their Valvetronic engines.

No they haven't. The valvetronic system still uses a conventional camshaft, but it also has electrically controlled adjusters which alter the position of the pivot point of the rocker arm, and so controls valve lift.

Solenoids and hydraulic rams fail... camshafts push the valves aslong as the engine is going round and the cam shaft is still connected to it.

How often? How do the you think they move the control surfaces on a BFO plane?

Well, yess, but the solenoids driving the valves would have to perform

300,000+ operations every hour. Mind you, fuel injectors use solenoids to open the valves, and are very reliable, so it's not a fundamental problem, and you would think it would be possible to arrange for a fail-safe design.

I came up with an idea for this some time ago, which used butterfly valves rather than conventional ones, since you need much less powerful solenoids, it's realtively easy to achieve a non-interference design and have large effective valve sizes. The numbers seemed sensible, but I had no way of trying it out.

Oh! The way I heard it, it sounded like they'd done away with cams fully. I suppose this way it's more failsafe. Mind you, between that and the VANOS, it must come very close to being as controllable as is possible.