Thick Flange or Thin Flange ?

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exminiman
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Thick Flange or Thin Flange ?

Post by exminiman »

Appreciate some opinions chaps (dont hold back :whistle: )

Building new 1275 engine and piecing parts together for machining.

Got choice of thick or thin flange block matched with EN40B crank AND trying to decide which block to use

Initially was going for thick flanged block, however has casting window below centre main bearing ( as most seem to). Three also seems to be some debate that thin flange works better with EN40B crank.

Will be using steel centre main strap and will be used for road and hill climbing.

Am tempted to go for thick flanged block just for rigidity....and stress relive ( round off any sharp edges) around casting window -

Wot do you think ?

decisions decisions :cheers:
exminiman
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Re: Thick Flange or Thin Flange ?

Post by exminiman »

In case it helps anyone else - or sparks a conversation, theres some info here

http://www.mgexp.com/phorum/read.php?3, ... sg-1622123

Need to thumb through first few posts

:cheers:
Dave Clark
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Re: Thick Flange or Thin Flange ?

Post by Dave Clark »

For what it is worth I would avoid the thick flange block with the casting hole when building a competition engine if you have the choice.

With the EN40B crank and AEG521 rods 8000rpm+ could cause a problem with the block that has an acknowledged weakness and we all know about the red mist of competition.Probably important to have crank,rods flywheel and clutch dynamically balanced if you are thinking of that sort of revs.

Is this engine destined for a mini or the A30 ?

Just for comparison I used standard Midget crank, rods and bearings (all used parts except for the bearings) and saw 7200 rpm+ on a regular basis in my A35, so that old A series is a tough old lump.
Big Daddy
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Re: Thick Flange or Thin Flange ?

Post by Big Daddy »

Preferred block for racing Fully Modified Midgets taken out to 1460cc was A-Plus because it was stiffer which compensated for all that material removed from the cylinder bores. As shown by photo below, it has external ribs and thick flanges.

I've run all sorts of powerful A-series engines and never experienced block failure or seen it suffered by others. However 995 racing A-series modified to take 12G940 heads tended to blow head gaskets which I suspect was due to poor stiffness of the thin flange 948 block. Thick flange 1275 blocks running same compression ratio did not suffer head gasket failure.

Thick or thin flange is probably a moot point unless seeking the ultimate. My preference would be a block with solid tappet chest covers and thick flanges, ideally A-Plus with externally stiffening ribs (radiated noise attenuators). However availability of any 1275 block in decent condition is likely to be a bigger challenge... :whistle:
A+ Block.jpg
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exminiman
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Re: Thick Flange or Thin Flange ?

Post by exminiman »

Thanks guys, all good advice, this is going into A35, with S Rods

In the end, its sort of what i expected, will get both blocks inspected, crack tested etc...unless i am really lucky one will come out on top or be scrap!

:clapping:
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Re: Thick Flange or Thin Flange ?

Post by gazza82 »

Take it this A+ block is from a Marina?
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Re: Thick Flange or Thin Flange ?

Post by Big Daddy »

Or is that Ital :?:

Seems Ital was the only in-line application for A+ which is probably why I couldn't find a photograph of it on the web... :whistle:
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Re: Thick Flange or Thin Flange ?

Post by gazza82 »

Big Daddy wrote:Or is that Ital :?:

Seems Ital was the only in-line application for A+ which is probably why I couldn't find a photograph of it on the web... :whistle:
Sorry Ital ... renamed Marina to hide it is still a Marina :rol:

Like todays Chevy's .. they are really Daewoo's :whistle:


Just wondered due to the different rear main cap you find on Mini/Metro blocks.
"If you're driving on the edge ... you're leaving too much room!"

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Re: Thick Flange or Thin Flange ?

Post by Big Daddy »

gazza82 wrote:Just wondered due to the different rear main cap you find on Mini/Metro blocks.
Found it :!: Searching Ital engine made all the difference... :mrgreen:

In-line A+ block is a different casting to transverse engine with integrated oil filter, which tends to foul RH bulkhead brace in an A35... :whistle:
ital-engine.jpg
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gazza82
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Re: Thick Flange or Thin Flange ?

Post by gazza82 »

I think there is a remote adaptor that makes the filter position more acceptable.
"If you're driving on the edge ... you're leaving too much room!"

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Dave Clark
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Re: Thick Flange or Thin Flange ?

Post by Dave Clark »

And there are smaller filters which will fit
exminiman
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Re: Thick Flange or Thin Flange ?

Post by exminiman »

Big Daddy wrote:
gazza82 wrote:Just wondered due to the different rear main cap you find on Mini/Metro blocks.
Found it :!: Searching Ital engine made all the difference... :mrgreen:

In-line A+ block is a different casting to transverse engine with integrated oil filter, which tends to foul RH bulkhead brace in an A35... :whistle:
ital-engine.jpg
Do i spy a pink sack trolley ! Very metro sexual :rol:
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Duncan
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Re: Thick Flange or Thin Flange ?

Post by Duncan »

exminiman wrote:
Big Daddy wrote:
gazza82 wrote:Just wondered due to the different rear main cap you find on Mini/Metro blocks.
Found it :!: Searching Ital engine made all the difference... :mrgreen:

In-line A+ block is a different casting to transverse engine with integrated oil filter, which tends to foul RH bulkhead brace in an A35... :whistle:
ital-engine.jpg
Do i spy a pink sack trolley ! Very metro sexual :rol:
that dipstick looks bent.
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Re: Thick Flange or Thin Flange ?

Post by A40FARINAGURU »

Duncan wrote: that dipstick looks bent.
can't really follow up to that :whistle:
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Countryboy
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Re: Thick Flange or Thin Flange ?

Post by Countryboy »

For what it's worth Motobuild have told me that they wish they had opted for Spridget engines over A+

They felt that the heavier A+ cranks give reliability problems

I also got chatting to a chap in his seventies at a show this summer. He was an apprentice building A35 vans and finished off as head of power train until the BMW buyout. He felt that a centre strap was unnecessary and his Mini with nitrous oxide runs fine without one. From memory TMT has withstood years of spirited driving without one
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