Discussion in 'Modified Shizzle' started by Owen Snell, Aug 22, 2015.
So 2056 cc sounds like the option.
Carbs or FI?
Crank fired ECU or programmable 123?
Not much bigger is it?
No, but it's all stroke so the torque gain will be greater than just the cc increase. I think bigger starts to get rather expensive, if @Paul Weeding can advise.
How big are you planning?
2400cc - 104 B&P's (maybe 103's if that's what's about).
2L 71mm crank
Standard cam or as near as possible.
Heads like yours.
I hope it sounds and goes like a tractor.
Interestingly.... You can have 2 different length strokes, on two very similar CC engines, and the peak torque will be almost identical... Mathematically it makes no sense, as we both know that the longer the leaver, the greater the torque, but I should imagine that the bigger stroke engine has less dynamic stress going on...
I prefer the longer stroke crank for cc increase... So @zed is doing a 71 crank with 103/104 B&Ps, whereas I prefer staying within the stock barrel fin OD, so I try to do things around the 96mm ID barrel option... so my 2.3 (2270cc) is a 78.4mm stroke crank, and 96 B&Ps... The crank then has counter weights, and is also knife edged for better airflow dynamics..
I also up the rod specs too... something I'd be doing on zed's engine too if I was building it... Stronger rod, that is also approx half the mass... so less strain on the crank, plus free BHP... ARP cap bolts too... What are you doing with yours Steve?
Giving a pile of parts to Rob Parry.
Slower piston speed with stock crank.
Essentially all I'm doing is making it a big bigger capacity and upping the valves sizes to compensate. I hope it will have the same character as a 2L but a bit more oomph.
Do you think I'm a daft bugger going too large on the pistons regarding cooling? I've done zero research...
Short stroke with a big bore gives problems with cylinder filling as the intake air flow doesn't have time to get moving. That's the problem I've got. Also at that bore, you must be into twin spark territory to get all the fuel to burn properly. Mine's done about 5,000 miles on the 1911 cc engine and more stroke is what I'm after, not more bore!
What's a sensible stroke increase that doesn't cost and arm and a leg?
The stroker pistons available say 71 to 78mm.
I had the same prob with 76 x 94, I don't think that's your problem, it's valve overlap hence why I'm going for a stock cam and Paul advised similar up there^.
Stock cam on a type 4 is like 230° and .335in lift... So you can understand why they are so weedy on the power output stakes... But the heads do need looking at when you start dropping a cam in...
The AMC heads are based on the late T25 aircooled design, so out of the box they flow better than the old 2l heads, and they aren't that far behind the 1800 heads, but with a better exhaust flow...
You can go bigger stroke on the stroker pistons... 86mm stroke I think is the max, but you getting into the realms of longer rods and large barrel spacers to get the deck height...
I think you might really need to up your valve sizes... I wouldn't even dream of building an engine that big on stock valves... You could well potentially cause head generation in the heads by restricting the gas flow... I'd be running 44x38
You don't have to go crazy on the cam... Just something more than stock and you'll be a happy man
My 2020 didn't seem to have a problem breathing and revved to 7,000 without a pause with 40 x 35.5. I won't be revving this one so high, I do not want top end power, I just want low end grunt. I think I'll risk it. Less is more and all that.
What are standard 2L valve sizes? 39.3 or something?
Out of interest what are the valve sizes on a 2 ltr scooby engine or are they 16 v ? Still think you need to turbo the ass of it ....
For comparison my stock 2,litre with 40 dells, 30 vents and standard everything is very happy at 65. 2 litre box and 205 tyres. It will rev through 60 in third and runs out of puff early 80s, or did today. Compresion is ok. 130 ish all round. Its only got around 80 ponys and not sure on torque but no problem through 3rd. 4th a bit long with the tyres. Im going smaller on the vents (to try) shortly.
Why build an engine for a bus that you have to rev the nuts off or destroy clutches to get it to pull.
big stroke adds friction losses
Please correct me if im wrong but you sound like a bloke with money to spend for the best that suits you?
I've got some money now, but not unlimited and I want to get it right this time to suit what I actually need rather than what I think I want. Putting miles on the van on a wide range of roads with a fully loaded van has been a bit of an education!
I don't think a longer stroke is a bad thing, it does help with low speed torque because the cylinders fill better and even with a stroke increase it will still be well over square.
The situation is not that bad! I'm sure Owen's engine (and my old one) were perfectly good at lower revs, but just not as good as at higher revs. Mine would still accelerate up hills in 4th at low revs, it was just a bit "fluffy" about it.
I think you missed where I said that I built the engine to go on the original 1700 box... It was later changed for a 2l geared box... So the engine spec no longer matches the box spec...
And it's not so bad that you'd be destroying clutches
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