Holy moly that first post is 10752 characters long....!

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http://www.youtube.com/user/Hanras

Most of them commas!!!

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Simon

The adventures of an owner builder in the Tallarook Ranges

Hey this is all good stuff...

Now on shrouding and valve sizes, I'm planning the worst of those combos - a 940 style head on a small bore block!

Obviously the exhaust valve will be shrouded by the block so the relief's cut in the block do more than just allow the exhaust valve to not hit the block, they let the exhaust by as well?

Low lift flow is something I'm always chasing - tell us what mods enhance them Matty! 30 degree valve backcut? 3 angle seats? super-thin seats?

cheers

Jacob

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'72 Clubman Van - 1022cc, 295 head, 731 cam - Daily Driver
'69 Morris 1100 S - Dinged by a bus, in shed under repair
'64 Morris 1100 - Early 1100, long term project

After that I feel a little exhausted, so I'm going to get a little intake and idle down.

heee hee... that was witty,,, very nice,,, well done

i`ll throw some more on this subject up next week, i`m just letting my typing fingers heal a bit first

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No offence intended here but--> anyone writing a book about minis 30 years ago may not have experienced such worn or stuffed-with components as we are finding these days.

You should put your heart & soul into everything you do.

I had a 12G940 head (1100S valves, some porting) on a 1220 smallblock back in `68. With a 544 cam and twin HS4s it was good for low 16s down the Castlereagh dragstrip. Pretty quick time with road tyres ((Olympic GT radials?) on back then.

For the cutout shape I put an 850 gasket on the block, and traced the outline on the exhaust side. Depth was .100".

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Hey Jacob,

Another option on the large bore head on a small bore, measure the amount of valve protruding below the head face a max lift and sink the valve seat by this amount, no pockets needed in the block, ask Keith....

a very jet lagged Kevin

Oh and Matty, haven't read most of the rest but methinks 'maximise low lift flow and port speed...'

Yeah that works, but not if you have a hi lift cam and/or rockers...

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Kev you're back!!

Beginning to wonder if you got lost over there

Ok Kev & Kev (just realised, I know rathcoole is Kev... but u too Drmini..yeah?) Yeah I thought I might be okay with the "sink the seats" trick, but I'm using 1.3:1 rollers & a cam with 0.268" lift - when you measure it all up, the exhaust valve *just* makes it past the face of the head.

So some shallow cut-outs should be fine, I need to remeasure everything for an exact figure.

cheers

Jacob

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'72 Clubman Van - 1022cc, 295 head, 731 cam - Daily Driver
'69 Morris 1100 S - Dinged by a bus, in shed under repair
'64 Morris 1100 - Early 1100, long term project

ha ha,,, Kev & Kev,,,, Kev you`re back,,, how was the "Home-land" ????

eye to be sure to be sure are you sick of Guiness yet????

what happened to you tonight??? was waiting up for you,,, still am

& yes Jacob,,, leave about 40 or 50 thou clearance for those "missed gear" over revs,,, you know,,, when things tend to grow a tad longer

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No offence intended here but--> anyone writing a book about minis 30 years ago may not have experienced such worn or stuffed-with components as we are finding these days.

You should put your heart & soul into everything you do.

Great thread Miniman,
Makes sense what you are saying, as much of it as I can take in atm anyway
1 Question, would it be better to compare the porting dia to the valve shroud diametre using cross sectional area calculations?


Valve shroud cross sectional area calculation

7mm valve stem cross sectional area =
3.14 x (rxr)
3.14 x (3.3x3.5)
3.14 x 12.25
38.47mm sqr

31mm valve outside - 1.5 seat radius = 28dia
3.14 x (rxr)
3.14 x (14x14)
3.14 x 196
615.44mm sqr

615.44mm sqr - 38.47mm sqr = 576.97mm sqr (cross sectional area through valve shroud area)


Inlet port cross sectional area calculation

Ported area of 26mm dia =
3.14 x (rxr)
3.14 x (13x13)
3.14 x 169
530mm sqr (cross sectional area of port)

Slightly different results but still your methodology stands up.

I actually have a 12G202 head that has some mild porting similar to what you have described. Might just give it a bit of a clean up around the chambers and use it for a nice road performance head.

Cheers

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