engine modification

[f1zzm]

Hi
I wonder if any one could tell me, If i fit a 1500 dolomite head (YC) to a 1300 dolomite engine (DH) would this lower the compression ratio? if so what would be the resulting compression ratio?
Just getting the germ of an idea. ;)

[JohnD]

If they both had the same compression ratio, then the 15 head would have to have bigger chambers.  Put those onto a 1300, whoch will compress 70mls less per bore  into the chamber  and the CR will be even lower than you started with.

But no need to speculate.  MEASURE the chambers, and KNOW what the CR is, instead of guessing/

John

[f1zzm]

Thanks John.
I have a 13 block and a 15 complete engine so i cant measure the 13 chamber and compare it to the 15. Im not sure what the
compression ratio is for the 13 although i have read that its 8.5/1 but that may just be for the US market, ideally i would want
8.0/1.

[f1zzm]

Thanks John.
I have a 13 block and a 15 complete engine so i cant measure the 13 chamber and compare it to the 15. Im not sure what the
compression ratio is for the 13 although i have read that its 8.5/1 but that may just be for the US market, ideally i would want
8.0/1.

[Clive]

Assuming th e1500 is a 9.1  head on that engine, you should get:
13/15 x 9= 7.5
think that is about right. Can't quite get my head round how gasket thickness etc will affect all that.

Alternatively there were some USA low compression pistons kicking about.....Canleys?

[JohnD]

Thanks, Clive for that confirmation!
You're not thinking about turbos, are you?

Thread on this for a GT6 at Sideways, plus a cautionary tale from long ago:
http://sideways-technologies.co.uk/forums/index.php/topic/6500-supercharging-a-triumph-gt6/page__p__86110__hl__jalopy__fromsearch__1#entry86110

John

[f1zzm]

Thanks Clive and John
Yes i am toying with the idea of a 1300 turbocharged engine for the herald, I want something different  and an engineering challenge.
I am not new to turbocharging and have some experience with them, i want to make this a relatively simple lowish pressure set up
including the mega spark programmable ignition system with a knock sensor.
I would much rather have a turbocharged 1300 than a tuned 1500.  
  

[Mark Hammond]

In which case you might want a tuffrided crank as in my experience it'll break within the first 5 minutes of use in anger.

M.

[f1zzm]

Hi Mark
tuffrided crank with main cap straps, corello type rods, ARP bolts and possibly ceramic coated piston crowns.
This will be a road car and wont be using huge amounts of boost but needs to be reliable.  

D  

[Nick Jones]

Josh Bowler used a reasonable amount of boost on his supercharged 1300.  That engine was carefully prepared, originally for high rpm rather than forced induction, but I don't think it had many special parts.  Std pistons (hard anodised), standard rods (shot peened).  Std crank (balanced and tuftrided).  Initially had high compression too but IIRC he reduced that a bit so he could use more boost.  Certainly went well.

Is true that the small cranks can break but this is usually the result of incorrect regrinding without correcting the fillet radii rather that real weakness.

Nick

[esxefi]

I agree,apart from thermal barrier treatment to pistons etc,boosted engine bottom ends don't usually suffer the same rigours as their counterpart n/a tuned cousins because in day to day use they don't need to rev as high to produce the goods(unless you are going for extreme power)
I didn't think tuftriding actually increased the cranks torsional strength but was for wear resistance on the journals as the surface was harder.there is much discussion as to whether the journals should be ground before or after the process.