Yes the weight of the pistons and the constant revs mean it stretches the rods then they snap lol
Yes the weight of the pistons and the constant revs mean it stretches the rods then they snap lol
As mentioned, oval engines have to use standard crank, rods and pistons and regularly see 8000+ rpm on 11-1 compression. Although this is only for a brief spell at the end of each straight, its twice every lap for up to 50 laps and often in nose to tail traffic. People do have failures but not that often and its never crank, very occasionally rods and the most common thing is to crack the ring land on number 4 piston.
I think they're strength is often underrated and id happily pull 8000rpm on a track day.
Hi . Im using forged H beam Maxspeedingrods and Mahle cast pistons with thinner top compression ring , also running around10.9 to 1 comp.At the moment i rev it to 7krpm and have rev limiter set at 7500rpm. I want to upgrade my camshaft to something equivalent of RL31 and maybe set rev limiter to 8krpm . Do you think this would be ok?
So maybe a few hundred rpm after peak power? I understand pinto heads dont flow beyond 7500rpm . Even now mine peaks at 6300rpm but i usually shift at 7000rpm . Have hit the rev limiter at 7500 a couple of times in first gear. Unlike twin cams my engine still make reasonable power after the peak. 153hp at 6300rpm and still 140+ at 7000rpm .
air flow through the head doesn't really relate to rpm as such, it will limit how far the engine wants to rev, and the smaller the engine the higher ( cam and everything else allowing) it will want to rev, hillman imp heads dont flow much air, but on a 998cc bottom end the engines can and will rev to 10,000 rpm.
if your engine peaks at 6300 rpm, unless it falls off cam because your gear ratios are to wide, your probably going slower by revving it to 7000 than changing up @ 6500
With type 9 gearbox a shift at 7000 in first drops back to 3778 in second or back to around 85hp . Shift at 6500 drop back to 3508 or 70hp . All other gears are much more closely spaced . Taking it to 7000 in second is 99km/hr which is convenient .
your going to be better off fitting a gear kit to your gearbox than changing the cam and revving the engine harder
Or lower the axle ratio and forget about using 1st (its a damn caravan gear in my opinion!)
Lol yeah 3.65 is pretty low with a 3.9 diff hence hitting the rev limiter a couple of times. Guess ill play with my shift light and a stopwatch and see.
V6 gearbox makes a little bit useful difference, I’m looking to put a 2.7 first in mine.
Yes I know the input shaft is longer so I used a 30mm spacer between box and bellhousing, bit of fiddling with gearbox and engine position but works well
Crow 26661 290 0.448
Ok cool i didn't know you can change just first gear in the type9 . Ill definitely look into that .
you have to by a modifed gear kit to do it though, but its obviously cheaper then a proper gearkit
Use a V6 box as your base, it’s got better ratios all round, add a long first and it pretty good. Most oval racers will have very close 2nd & 3rd changing diffs for the circuit.
Nay be 3rd 4th are close (200rpm), I’ll try and find the ratios they use, no good for the road though
snapping off the throttle at full revs puts an engine under the worst stress, its where most rods fail. Heavy compressive forces suddenly stop as engine pulls a vacuum.
Last edited by wozzah1975; 23-07-2020 at 06:58.
WARREN HEATH PERFORMANCE
https://www.facebook.com/Warren-Heath-Performance-135194779879292/
Hi Warren what's a good off the shelf cam to buy here in Australia cheers mario
Clive & Tighe both offer decent grinds to suit multiple applications, and Camtech offer a some grinds which work pretty well.
I've never seen anything made by Crow for a Pinto (or a lot of other 4 cylinder engines for that matter) work as it should. When you start checking the lobes on the cam dr on that 26661 grind you start to realise why its so doughy, it's seriously one of the worst cams for a Pinto I've seen on offer.
WARREN HEATH PERFORMANCE
https://www.facebook.com/Warren-Heath-Performance-135194779879292/
Good to know . im making 155hp and 192nm with the 26661 so hopefully with a cam swap and remap ill get a bit more.
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