flak monkey
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| posted on 2/3/19 at 07:42 PM |
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Pinto cam choices
Looking at cam choices for the pinto I'm building. Total can of worms.
Big valve and ported head, at 10.5:1 compression ratio. It's going to either be running twin 45 DCOE or DHLA or R1 bike carbs.
So
FR33?
RL21?
GTS1
Burton BF63?
Choices, choices...
Sera
http://www.motosera.com
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overdriver
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| posted on 2/3/19 at 10:28 PM |
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Not in a position to have undertaken any comparisons but the Piper 285 seems to perform admirably in my Pinto - twin 45 DCOEs but not aggressively
tuned - c. 130 - 140 bhp.
Sorry if that throws another worm into the can!
Michael.
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snapper
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| posted on 3/3/19 at 06:26 AM |
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The choice depends on rods and pistons.
I fitted Cosworth rods and V6 Kolbeinschmit pistons but wish I had fitted forged pistons that way I could use a higher compression without
worrying.
FR33 is a good choice same as the piper 285
The FR21 is an older version of the FR31 which I fitted to one engine good cam but sluggish below 3500 but WOW when you go above that.
The other cams are considered old now and different from the high duration low lift profiles of yesteryear.
Burtons have a diagram showing that valve lift over ¼ of valve diameter is waisted as you get no more flow but I disagree as the longer the valve is
open at max flow the more volume you will get in to the cylinders.
Area under the curve.
[Edited on 3/3/19 by snapper]
I eat to survive
I drink to forget
I breath to pi55 my ex wife off (and now my ex partner)
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Dingz
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| posted on 3/3/19 at 05:54 PM |
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There is a good article on Pinto cams in Dave Andrews old site DVA
I've a flowed injection head, standard valve sizes, bike carbs and a Piper 285. I haven't noticed any tractability problems at low revs
which I think may be due to the bike carbs being constant velocity, perhaps it would be more noticeable with conventional sidedrafts. If you are
looking for big output figures with Bike carbs I may be tempted to go to the next cam up.
Phoned the local ramblers club today, but the bloke who answered just
went on and on.
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flak monkey
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| posted on 3/3/19 at 11:20 PM |
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Thanks guys.
Also considering the Piper A8 cam, which seems to get a good rap.
I will be going strong with the bottom end on this....
Sera
http://www.motosera.com
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snapper
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| posted on 4/3/19 at 08:42 AM |
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I’ve fitted a crank scraper to the high power Pinto which is supposed to give a couple of bhp at high revs.
I also grafted a Cosworth spraybar to an RS2000 oil pickup and found out afterwards that simply notching the rods would have given me the same spray
effect
I eat to survive
I drink to forget
I breath to pi55 my ex wife off (and now my ex partner)
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mcerd1
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| posted on 4/3/19 at 09:13 AM |
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I've also gone with a piper 285 for now (fingers crossed it'll be running soon) - but that might not be aggressive enough for you 
how wild are you planning to make this one ?
quote:
Originally posted by snapper
I’ve fitted a crank scraper to the high power Pinto which is supposed to give a couple of bhp at high revs.
I also grafted a Cosworth spraybar to an RS2000 oil pickup and found out afterwards that simply notching the rods would have given me the same spray
effect
I don't much fancy notching or drilling the rods so I fitted the whole cossie pickup pipe on mine instead (shortened to suit my sump) - only
it's needing a little tweak to work: linky
I reckon its down to it being a brand new one thats never been fitted to an engine before
[Edited on 4/3/2019 by mcerd1]
[Edited on 4/3/2019 by mcerd1]
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IanSouthLincs
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| posted on 8/3/19 at 10:40 AM |
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This is something I’ve not long done. I still have the original engine, ported carb head with 44.5mm inlets and 38mm exhausts, 10.5:1 comp ratio and
piper 285 cam. Running twin 40 Weber’s, it was (and still is) a very strong pulling engine.
However in the quest for more, I’ve built a forged bottom end with Wossner and PEC equipment 92mm bores, injection head, extensively ported with
45.5mm inlets and 38mm exhausts. Kent RL22 with double valve springs. Running twin 48 Webers and with 11.8:1 comp ratio.
Let’s not beat about the bush, I’ve spent quite a bit on this engine and by the hell its quick, not been on a dyno yet and still haven’t really pushed
it as it’s still very new but it’s not even thinking about letting up power at 7500rpm. There’s the obvious big BUT..... I always knew it would be the
case and I really don’t mind as it’s nowhere near a daily drive, IT IS A PIG below 2000rpm there’s nothing there, you have to be very gentle with the
throttle otherwise it will bog down. Now I personally love it, as the revs climb the horizon starts to really come at you.
You really must be honest with yourself how wild an engine you can live with, or suits what you use the engine for. I’ll be honest with you if you’re
keeping comp ratio to 10.5:1 you’re wasting your time using any more than FR33 or Piper 285, I just don’t think anything wilder will work properly and
it will actually cost you power.
Hope this helps 👍
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