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Is 12.7:1 CR way to high for a pinto!
garage19 - 15/12/04 at 01:00 PM

Is 12.7:1 CR to high for a road going pinto engine? I fear so!

The problem is i am building theis engine for a friends locost and he has sourced all the bits and just gave them to me to get on with it.

The Holbay head he bought from ebay already has a lot skimmed from it (43.5 cc chambers) and to make it worst the 93 mm pistons and 1.5mm stroked crank have increased the swept volume by quite a bit!

In the past i have built road going pintos to 11:1 at the most.

If he uses optimax and CVL turbo mix he can run an 102ron fuel but i still don't know if he will be ok with this engine without dialling out all the advance and loosing shed loads of power!

Any thoughts?

stephen_gusterson - 15/12/04 at 01:04 PM

go the whole hog and run it on diesel

Im not an engine expert, (or anything for that matter) but the highest I think ive seen an engine at is 11:1.


atb

steve

garage19 - 15/12/04 at 01:14 PM

WSB zxrs used to run 16:1

Deckman001 - 15/12/04 at 01:31 PM

Yeah, maybe, but how often does your friend want to rebuild his engine, every 100 miles or so ??

Jason

MikeRJ - 15/12/04 at 03:11 PM

12.7:1 might be ok if he's going for a ridiculously wild cam, but I'd say that's really going to be too high otherwise.

Is there enough meat in the pistons crowns to have them machined down in the middle?

timf - 15/12/04 at 04:14 PM

open the cc in the head to lower the cr

else look for a spacer shim for a janspeed turbo pinto conversion

dblissett - 15/12/04 at 08:05 PM

what about using a different thickness head gasket in the burton catolouge they list different types and iirc the felpro one is alot thicker than standard for a road engine you should be at about 10.5 if posable
cheers dave

Stu16v - 15/12/04 at 10:07 PM

11 - 11.5/1 is the absolute limit on pump fuel.

Check out Ferriday Engineering, they will make metal head gaskets to the thcikness IIRC.


HTH Stu.

MikeRJ - 15/12/04 at 11:11 PM

Big problem with compression plates and thick head gaskets is you lose squish, which itself helps prevent detonation.

Stu16v - 16/12/04 at 06:04 PM

quote:
Originally posted by MikeRJ
Big problem with compression plates and thick head gaskets is you lose squish, which itself helps prevent detonation.


Indeed, but with 12.7/1 CR, the holes in the pistons will be preventing detonation if it goes anywhere near pump fuel...

MikeRJ - 16/12/04 at 08:40 PM

quote:
Originally posted by Stu16v
Indeed, but with 12.7/1 CR, the holes in the pistons will be preventing detonation if it goes anywhere near pump fuel...


Hehe, very true!