Terry,
How do you identify a L18w block and what are they out of ? What steel cranks
are available for these? Thanks.
Andrew Smith
Terry Rudd wrote:
> Brad,
> Craig is correct stating the factory bore was 87.8 mm with the L18 crank of
> 78 mm (this is the engine I have in my road car) Back in the days when these
> engines were around the rally scene you were able to get 4 oversize pistons
> sizes up to +0.040" which is 1 mm and so Arthur Jackson & co would build you
> an engine using the L18W block that gave you 1932 cc. This is likely to be
> the configuration of John Spensor's engine but the only problem is if the
> bore wears then that all folks for that block.
>
> regards
> Terry
>
> -----Original Message-----
> From: [EMAIL PROTECTED]
> [mailto:[EMAIL PROTECTED]]On Behalf Of Brad HALLETT
> Sent: Monday, 30 October 2000 4:28 PM
> To: [EMAIL PROTECTED]
> Subject: RE: Factory 87.8mm pistons
>
> Craig,
> Thanks for your advice. I still haven't had a chance to calculate anything
> because of work commitments so I am glad you did it for me (5hrs sleep since
> Friday - things have gone nuts here.) I came up with the same conclusion
> that the Factory teams would have built strokers if they were permitted or
> if they were more efficient, my only thought was why did they use 87.8mm,
> and not 88mm?
>
> When I planned my engine I was unaware of the L14 rods, and they are now
> what I will use. Compression ht is no probs as I am ordering custom forged
> slugs from Precision (when I save some $$$)
>
> I figure if I build the stroker and it's a slug I'll bolt in a std L18W
> crank with 32mm comp ht pistons/L14 rods and see if it works better.
>
> Regards
> Brad HALLETT
> http://www.powerup.com.au/~bhallett
>
> Proudly Endorsing:
> ...DATRATS...
> http://203.33.35.34
> Datsun Dedicated
> For Nissan Motorsport Components
> Professional Budget Priced competition equipment
> Contact Errol SMITH
> email: [EMAIL PROTECTED]
>
> -----Original Message-----
> From: [EMAIL PROTECTED]
> [mailto:[EMAIL PROTECTED]]On Behalf Of Craig Overend
> Sent: Monday, October 30, 2000 10:43 AM
> To: [EMAIL PROTECTED]
> Subject: Re: Factory 87.8mm pistons
>
> Brad,
> I have looked into the factory engine and they are not 88.7mm but
> 87.8mm X 78mm for 1889cc. Here are some of my thoughts. I too was
> planning on an 88mm bore and 82mm stroke until I did some calculations
> and measured my L18W block. One problem is rod length. 133mm rods are a
> bit too short for ideal and this moves the whole torque curve down and
> also reduces volumetric efficiency(torque). Ideally ~135mm rods are the
> go for the 82mm stroke when combined with 44mm inlets, 40mm port at seat
> and a cam with about .510" of lift. For this reason I have been trying
> to track down whether there was an L20 6 Cylinder model that used 135mm
> rods. All my calculation says there is such a rod but so far I cant find
> reliable info or rods to support that. Near ideal stroke/bore ratio for
> the widest possible powerband comes from a ratio of about .88-.90
> varying depending on friction, rpm operating range and other factors.
> For this and reliability reasons to do with bore diameter, I assume
> these are the reasons they designed the factory L18W rally engines the
> way they did. Also instead of stroking the engines for more capacity
> they just ran more rpm to use the available flow through the heads.
> While the engines might not have been as torquey as they could have they
> would be good HP producers. Other factors may have included rulebook
> limits though. I'm sure that if they could reliably bore the block out
> further they would have and stroked them too and run bigger valves
> etc... Guess what I'm looking at doing. :)
>
> L14 rods being ~136.7 would be a better choice for an 88x82mm engine
> just depends on valve/ports/cam. You'd need ~30mm pin height.
> 136.7/82=1.67 ratio same as L18 for similar reliability. L14 rods use
> the same journal size as L16/L18. I'm sure Errol could tell you if he
> has bent any.
>
> The current factory VW Golf kit car that Simon Evan runs uses something
> near 90mm bore x 78.5, can't remember exactly. This is excellent for a
> 2L and one reason why it screams and goes so well.
>
> cheers,
> Craig.
>
> Brad HALLETT wrote:
> >
> > Gday everyone
> > There has a been a lot of talk about the factory rally cars using 88.7mm
> > pistons. Whilst I was planning to build a stroked L18W with 88mm bore, I
> > have become more and more interested in the factory engine.
> >
> > I therefore have two questions:
> >
> > 1) The engine I am building is L18W block, 88mm bore, with the crank
> > stroked to 82mm, L18 conrods with forged flat tops at custom compression
> > heght to suit. This gives a swept volume of 1995cc to keep in the
> 1600-1800
> > class. Would it be more beneficial to not build this stroker but to copy
> > the factory engine spec?
> >
> > 2) Are 88.7mm flattops still available?
> >
> > Whilst I personally can see no problems with the stroker in terms of
> > reliability I am interested to hear your opinions.
> >
> > Another question I must ask, whilst I have done no calcs or schematics so
> > may be way off the mark, would L14 rods be worth looking at for the
> stroker?
> > I have had nothing to do with them so I don't know there strength, weight,
> > or even journal size.
> >
> > Regards
> > Brad HALLETT
> > http://www.powerup.com.au/~bhallett
> >
> > Proudly Endorsing:
> > ...DATRATS...
> > http://203.33.35.34
> > Datsun Dedicated
> > For Nissan Motorsport Components
> > Professional Budget Priced competition equipment
> > Contact Errol SMITH
> > email: [EMAIL PROTECTED]
> >
>
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