Bore VS Capacity

[Skip Kelsey]

Gene: THis guy sounds like my kinda guy. Very interesting background. Skip........................................ At 04:33 PM 7/26/02 -0700, Sam Suklis wrote:

>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/ > > > > > >

[Gene Gillam]

Skip, I think he sounds like everybody's kinda guy. Gene -----Original Message----- From: Skip Kelsey [mailto:kelsey@shadetreemotors.com] Sent: Friday, July 26, 2002 7:54 PM To: Sam Suklis; Gene Gillam; mg-tabc@yahoogroups.com Subject: Re: Re: [mg-tabc] Bore VS Capacity Gene: THis guy sounds like my kinda guy. Very interesting background. Skip........................................ At 04:33 PM 7/26/02 -0700, Sam Suklis wrote:

>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/ > > > > > >

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[Donald Wilkinson]

See Mike Sherrell's book (TC's Forever) page 135. Answers both questions. I ran a TC block bored .1475" (70.3 mm) which gave 1390 cc displacement, but eventually a dime sized hole appeared in one bore, letting in water, which extinguished the fire in that bore. Some well equipped shops have a sonic device for measuring cylinder wall thickness. Don TC 7993

>From: Gene Gillam anngene@bellsouth.net> >To: mg-tabc@yahoogroups.com >Subject: [mg-tabc] Bore VS Capacity >Date: Fri, 26 Jul 2002 13:30:56 -0400 > >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/ > >

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