Bore VS Capacity

[Gene Gillam]

Does anyone have a table which shows what changing the bore does to the capacity of the XPAG? Bore: 66.5mm Stroke: 90mm Capacity: 1250cc In other words, what is the capacity when bored .010, .020, .030., etc., oversize? Also, (1) what is the maximum the XPAG can safely be bored; (2) is it safer to insert a liner and bore that out or just bore the normal cylinder? Thanks all for the responses on the 1 1/4" vs 1 1/2" carburetors. I know now not to bid too much on the MGA carbs - smile. Gene

[Michael D Card]

Gene I prepared a spreadsheet in 2001 to assist me in planning my current TC project. It starts at 1250-cc +0.040" oversize, so does not have +0.030" and smaller, but you will probably be lucky to find a block which will clean up at less than 0.040" The sheet plots the following. a.. oversize [eg +0.040" up to +0.140"] b.. bore in mm c.. cubic capacity cc d.. cubic capacity as a % of 1250-cc e.. compression ratio for standard head f.. compression ratio for "8.6:1" head g.. compression ratio for "9.3:1" head I have emailed it to you off-list. If anyone else would like a copy, contact me off list. Mike Card Surrey,UK TC8233 TC9477

----- Original Message ----- From: Gene Gillam To: mg-tabc@yahoogroups.com Sent: Friday, July 26, 2002 6:30 PM Subject: [mg-tabc] Bore VS Capacity Does anyone have a table which shows what changing the bore does to the capacity of the XPAG? Bore: 66.5mm Stroke: 90mm Capacity: 1250cc In other words, what is the capacity when bored .010, .020, .030., etc., oversize? Also, (1) what is the maximum the XPAG can safely be bored; (2) is it safer to insert a liner and bore that out or just bore the normal cylinder? Thanks all for the responses on the 1 1/4" vs 1 1/2" carburetors. I know now not to bid too much on the MGA carbs - smile. Gene Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/ [Non-text portions of this message have been removed]

[Skip Kelsey]

Gene: .010=1250cc 7.25 comp. .020=1270cc 7.3 .030=1280cc 7.4 .040=1290cc 7.45 .050=1299cc 7.5 .060=1309cc 7.54 .080=1328cc 7.64 .100=1348cc 7.74 .120=1368cc 7.84 Cheers; Skip Kelsey........................................................... At 01:30 PM 7/26/02 -0400, Gene Gillam wrote:

>In other words, what is the capacity when bored .010, .020, .030., etc., >oversize?

[Skip Kelsey]

Gene: .010=1250cc 7.25 comp. .020=1270cc 7.3 .030=1280cc 7.4 .040=1290cc 7.45 .050=1299cc 7.5 .060=1309cc 7.54 .080=1328cc 7.64 .100=1348cc 7.74 .120=1368cc 7.84 Cheers; Skip Kelsey........................................................... At 01:30 PM 7/26/02 -0400, Gene Gillam wrote:

>In other words, what is the capacity when bored .010, .020, .030., etc., >oversize?

[Gene Gillam]

Thanks Skip Any suggestions about the other two questions? Gene

[Sam Suklis]

Good Morning, all: I sort of remember someone a while back making an inquiry about a copy of the MG-T Series Technotes manual, published by the New England MGT Register: For what it's worth, there's a copy for sale right now on e-bay, with a "buy it now" price of 49.95 without having to get into a bidding contest. I don't know if that's a good price or not, but thought it might not be a bad idea to pass the info along. Best, Sam Suklis http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=1846579161&ssP ageName=ADME:B:SS:US:1

[Skip Kelsey]

Gene: Most XPAG engines can be safely bored to .120 without a problem. You can also sleeve it and go out to 1500 CC, but it can be tricky. I like to run this engine at 9.3 comp. ratio. It really makes a difference. Skip........................................................................... At 02:56 PM 7/26/02 -0400, Gene Gillam wrote:

>Any suggestions about the other two questions?

[Mark Andrew]

Mine is indicated on the block as +0.020 which says to me that it is bored out that much. Mark Andrew TC 5146 Skip Kelsey wrote:

> Gene: > > Most XPAG engines can be safely bored to .120 without a problem. You can > also sleeve it and go out to 1500 CC, but it can be tricky. > I like to run this engine at 9.3 comp. ratio. It really makes a difference. > > Skip........................................................................... > > At 02:56 PM 7/26/02 -0400, Gene Gillam wrote: > >> Any suggestions about the other two questions? > > > > > > > > > Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/ > > > >

[Non-text portions of this message have been removed]

[Skip Kelsey]

Mark: Dont be fooled by that stamping. It could have been bored several times after that was put on the block. Mike the bores to be sure. Skip....................................................................... At 05:30 PM 7/26/02 -0400, mark andrew wrote:

>Mine is indicated on the block as +0.020 which says to me that it is >bored out that much.

[Sam Suklis]

Skip: I forwarded this to my friend Chuck Brown in Wisconsin, who bought his TC new in 1948 (second one sold in Oregon) Chuck was one of the pioneer racers/engineers of TC's back in the fifties, and was racing it in SCCA events back then, and still does, in vintage races. He's an extrordinary engineer and received substantial publicity in those days for his many victories and engine innovations. Back then, he was running two blowers on his TC...a 15-lb boost Marschall Nordec (belt-driven), PLUS a 15-lb boost rootes type out on the dumb-irons, linked as a two-stage system. I was aware that he'd bored his TC quite a ways out there, so decided to forward the recent dialogue about overbores to him, and get his reaction. Turns out he's using a TD block these days, (his letter explains) to preserve the original TC engine from potential ruin. I thought I'd pass his reply along for whatever value or interest it might have: Here are his two replies: Sam, The method of calculating the displacement of an overbore in the letter you forwarded is incorrect... After all, just do the math [as everyone says now] bore squared x 3.1416/4 x stroke x number of cylinders Or, [ if squaring a number is a bit too difficult ] , bore x bore x 3.1416/4 x stroke x number of cylinders Sam, my INITIAL overbore was to 0.132 over. Then, as racing progressed, and various rebores were required/&.or/honings , I ended up at an overbore of 0.168 Tsunami Pistons, of Tacoma Washington was able to supply me custom pistons in step-ups of 0.004", by using patterns from the Lincoln V-12 of the '40's. The only big change was when I had a set of magnesium pistons "light-off" in the engine, requiring an Iffy .020 overbore to clean up THAT damage. NOTE: still have 'souvenir pistons from that experience, not to mention the crankshaft that broke, the 5 sets of differential gears, the valve that lost it's head, spark plugs that shed the porcelain tips in heat of battle,.... What I am thinking of now, is to pull the roller-cam, install TF-1500 rods, have new bronze guides made for the Sodium-cooled valves.... which are in the TC block, and have it sleeved back to a useable size for "just driving". Then, put the performance parts into the TD block, install one of the blowers, and have some fun again. Would really shed a tear to damage the TC block, so the TD block is a 'little' more expendable. Chuck.

> Gene: > > Most XPAG engines can be safely bored to .120 without a problem. You can > also sleeve it and go out to 1500 CC, but it can be tricky. > I like to run this engine at 9.3 comp. ratio. It really makes a

difference.

> >

Skip........................................................................ ...

> > At 02:56 PM 7/26/02 -0400, Gene Gillam wrote: > >Any suggestions about the other two questions? > > > > > > > > Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/ > > >