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I'm " Blocked" off.

There seems to be a shortage of good reboreable block in this neck of the woods. More and more are being bored out to .060. It is possible to bore now to .080 using Tony's Australiian pistons. I hear from him that he is just about to have a massive price hike imposed on him for them. Ideally what "WE" want are blocks that can be bored to .040. to 060. that have seviceable valve seats. Sleeved blocks are being rejected ,I understand, by the Racing boys.So these are available.But there may have well cut,poor valve seats. I spoke to Tim Myall of Pig sty Racing and he is doing an interesting mod.They are using Honda generator pistons.. A Max size that can be bored out is 071 thou. in 020 thou increments. In order to fit them it is necessary to first to machine 030.thou off the top of the block to accomodate them. This means that one is able to recut a perfect set of valve seats. THe little end of the con rod has to be reamed out to accomodate the gudgeon pin which has to have a slot filed in it for the clamp bolt. It is of course necessary to do a dry assembly of the block to crank case, so that the 2 centre pistons can be machined 020. below the block surface.. Phew! So lay one up like wine.

Re: I'm " Blocked" off.

Phew, that's something to take in. I believe someone bored out a Block to 120 thou (they thought the setting was 60 thou!) without going through to the water jacket, very lucky. I can't remember if they had any pistons to fit or they sleeved, just in case.

It's a good point you raise though Mac. One of my blocks is still 'Standard', the others are + 20, + 40 and + 60 thou, eventually they'll all be the same + 60, which will make it easier stocking pistons and rings.

"Blocked Off"? Hope your not firing blanks now!

Naomi

Re: Re: I'm " Blocked" off.

Mac

You mention that sleeved blocks are rejected by the racing boys so these are available but may have poor seats or larger seats.
So the question is has anyone fitted valve seat inserts to a block with any success?

I have an interest in this as my block was sleeved on one cylinder and one exhaust valve has an insert fitted.
A friend in an engine reconditioning shop recut the seats for me and pronounced that the valve seat insert was in his opinion perfectly OK (he fits lots of these).

Steve

Re: I'm " Blocked" off.

Mac, why are the sleeved blocks being rejected. Apart from the fact that it implies they have had a lot of use and thus the valve seats will be deeper than standard after many grindings, I cannot see why the blocks would be no good.

The Racing fraternity seem to be stripping down their engines often, so although I accept the steel liners may wear much quicker than the cast blocks, especially the earlier ones (I understand there seems to be a change in the metal structure circa early 1930's), they should be able to spot any wear between races.

Steve - In our village we have a number of classic cars, 1950's XK's, early Morris Minors, Rileys etc, fitted with Valve inserts and I'm not aware of anybody having a problem.

Sandy

Re: I'm " Blocked" off.

Ooops, just posted last message and then picked up Bill Williams book "Austin Seven Specials", I think this extract fully explains why the racing people don't want sleeved blocks. (Page 49 in 1964 reprint), OK it starts with the High Lift Camshaft, but you'll get there.

"The fitting of a high-lift camshaft (as used in the sports engine) to a modified standard engine is not recommended. These camshafts give very little power at engine speeds below 2,000 r.p.m. The valve opening period is not good and the high-lift cams cause excessive wear of the valve gear. Cylinder block holding-down studs are apt to be pulled out or sheared with consequent lifting of the block. The extra power at the top end provided by this camshaft does not compensate for the amount of trouble it causes. The standard modified camshaft will give more power at the bottom end, a more valuable asset than power at the top.

One word of warning here. Never fit a sleeved cylinder block to an engine which has a high-lift camshaft—unless it has double cylinder block holding-down studs. If you do—there is a strong possibility that the cylinder block will crack round the base. There have been several instances of this happening on specially tuned engines, but never with one using a standard or modified camshaft.

For this reason, it will be understood that a rebored block is preferable to a sleeved one, when building up a tuned engine. Perhaps the ideal would be to obtain a block in which the cylinder bores are worn to the extent of being about .030" oversize. Then have it bored out to .060", the maximum permitted by the thickness of the casting This little bit of extra cubic capacity will undoubtedly produce extra power. It has one disadvantage in that the engine is perhaps inclined to vibrate more.

Make quite certain before reboring a cylinder, that the existing bore measurement is no more that .040" oversize, otherwise there will be a possibility of penetrating the water jacket.

The cylinder block may be tested for water leaks by plugging the water inlet casting on the side of the block, and leave it to stand overnight with a full water jacket."

Sandy

PS Mike Whittome, yes another late night.....

Re: Re: I'm " Blocked" off.

Interesting your comment that early blocks were not as good. At the risk of sounding controversial, I found the opposite - more metal available when re-boring, thicker bases for more strength, longer lasting etc. I haven't found any difference in possible stud-pulling between early and 30s blocks either. (I must say my idea of "early" is '24 to '26, which may be different to your thoughts). Re the racing peoples' rejection of re-sleeved blocks - I always thought this only applied when you supercharged the engine with it's greater loads everywhere & on everything and only then because of problems with the liners lifting. Glad to learn something new every day. Also, for those who don't know, our Austin 7 Club located here in Melbourne is still working on the new design blocks, these include elimination of all the faults in the original design. Casting completed but sadly in need of accurate drawings for the boring and drilling. It's difficult to get everything exact when relying on measuring old, old originals. However a draughtsman with substantial engineering background is working on it now so that we can eventually just hit a computer key and the machine does the rest - accurately. Now for a question on blocks : a couple of years back on the Austin Seven Motoring Pages there was debate on whether Blocks (and Heads?) were originally painted or left virginal. My memory was that the consensus plumped for unpainted, though in real life I prefer painted to the rusty look or weekly maintenance. David Howe seems to have done a lot of research on what's original and what's not and I notice his block and head (well, that of his '26 Top Hat) are both painted. What say you lot? Cheers, Bill

Re: I'm " Blocked" off.

My apologies Bill, I meant it the other way round, earlier blocks have a higher grade metal, sorry about that, I must get to bed earlir and clear my mind.

Sandy

Re: Re: I'm " Blocked" off.

Dear A7ists here and in Oz.

My two penn'orth-

Our welsh sec Hayden (still smarting from the hammering we gave then yesterday with the oval ball)
says...did I know this discussion was ongoing.
Well I recall someone asking me if the A7CA Archivist had any block drawings-yes and no. Yes in a GA drawing of the whole engine but no the foundry drawing of block alone with all machining tolerances. I seem to recall posting one GA to Oz, I suggested useing this and accurately measuring one or two older blocks but as we all know the AMCo were continually adding or taking away flanges, webs etc. Not just on blocks but eg rods-as I found out weighing various sets of 1&5/16" to create a hot engine for the Super 750 I ran early 90s.

From my 60s days buying from Northwoods or Jack Dalby I recall pistons were available +20 40 60. Then I soon found a boxed set of original AMCo pistons +1/64". My engineer friends said this was about +15 and older sets were 1/64 1/32 3/64 and 1/16 which were about 15 30 45 60 weren't they?

Clearly changing to the 20 40 60 range meant only 3 sizes needed to be kept on the stockshelves not 4...but then along came +80 and more power. Most blocks will take this, I think it was just bad luck if you hit the water jacket on any rebores.

Metal for blocks? yes the prewar stuff WAS better because I understand AMCo specified from 1922 even for regular castings added nickel or chrome. The best blocks came in the 30s and heads were specifically CHROMIDIUM with the diamond raised marking. Years ago I never realised their value and have let them go on one of my regular clearouts.

Valve seat inserts? Yes they can be done. I saw a 7 block last year at Beaulieu jumble on either Tony or Wayne's stall. I cannot recall which as I alternate helping them each year! Last year I did Wayne, this year Tony.

Shaving the block? well I guess if it achieves the result do it. Provided pistons don't meet heads it will work. I understand some racing blocks are now shaved on a slight incline no doubt to accomodate some better available part.

The weak point has to be the block/crankcase trying to separate, well recognised by 10-stud blocks, weren't the front and rears simply doubled?
Trouble is the thrust is at the sides and I saw this when spannering for both of Chris Gould's 10,000 mile record attempts at Goodwood in the late 70s it was this that lifted and we had to cobble up a halfshaft and brake cable lashing the head down round the sump.
You have to see the video "In search of a record"
I guess I could copy one on to DVD now if you have never seen this. Unless someone has already done it?

The late Stanley Edge said that when designing the engine he put a bit more on the head so that by a simple skim the compression and performance could instantly be raised. The familiar figure of 8 recess could become a pear shaped Ricardo type head... that AMCo introduced in the 30s as high compression.
Super forethought from a young man!

Enough of that, I wish the disbelievers would stop putting Stan down. No he did not design the car, the genius concept was by Sir HA. But he needed the draughtsman to put his ideas onto paper-and he picked a better than average young man whose work was not
influenced by years of designing heavyweight cars and lorries. Stans own words... if anything I was responsible for persuading Sir Herbert to use the small watercooled 4 cylinder....
Stan said when he returned from private payment at Lickey Grange to full time back in the AMCo DO he was shunned by the established older draughtsmen who considered they should have been given the job he got.
Hence he left.

End of two penn'orth.

Phil.