[Fot] Compression

Tue Dec 7 10:15:50 MST 2021

Glad to hear it!

Sent from my iPhone

> On Dec 7, 2021, at 11:45 AM, DAVE HOGYE <dlhogye at comcast.net> wrote:
> 
> 
> Phil, 
> Greg Solow provided me with TR3-4 chamber volume numbers and their related compression ratios while I was building my TR3 engine.  49.6cc is what I ended up with, an approximate ratio of 10.8:1.  Your numbers coincide.  I had .125" milled off before shaping and opening the chamber to 49.6.  
> Good stuff.
> Dave H. 
>>> On 12/07/2021 5:31 AM Phil Gott via Fot <fot at autox.team.net> wrote:
>>> 
>>> 
>>> If it helps, please find attached an Excel spreadsheet that calculates both the current compression ratio as well as the head volume needed to get the compression ratio you want.  Just put the dimensions in the yellow highlighted cells.  If running a pop up piston, you will need to determine the volume of the pup up above the normal piston crown surface.  The spreadsheet as attached has dimensions for a slightly modified TR4 with flat top pistons.  I hope this is self explanatory.
>>> 
>>> Regards,
>>> 
>>> Phil Gott 
>>> 
>>> 
>>> -----Original Message----- 
>>> From: Chuck Gee via Fot <fot at autox.team.net> 
>>> To: Bob Bownes -Seiri <bownes at seiri.com> 
>>> Cc: 'Friends of Triumph' Triumph <fot at autox.team.net> 
>>> Sent: Mon, Dec 6, 2021 10:51 pm 
>>> Subject: Re: [Fot] Compression 
>>> 
>>> Yes they will, but that isn’t really the problem.  The extra stroke of the TR6 motor makes building compression easy.  The 2L motor is a little more challenging because of the shorter stroke.  You just can’t shave enough off the head to get really high compression without getting into the water passages.  Pop ups are necessary to maximize compression. 
>>> 
>>> Chuck
>>> 
>>> On Dec 6, 2021, at 6:40 PM, Bob Bownes -Seiri via Fot <fot at autox.team.net> wrote: 
>>> 
>> 
>>> 
>> 
>> 
>> Hmm,
>> 
>> Will a TR6 head fit? There is plenty of meat on those to get Ludicrous Compression. 
>> 
>> Bob
>> 
>>> On Dec 6, 2021, at 20:58, Scott Janzen via Fot <fot at autox.team.net> wrote: 
>>> 
>>> 
>> 
>> I’ve found the GT6 head has some thin spots and depending on the casting can’t take milling too much more than 11.5 to 1, maybe 12 if you get lucky with the right casting.  As to the lore that circle B heads are the best, I have not found that to be correct in this respect.  Seems like they are all over the map.
>> The rest has to come from domed pistons, which I have not yet tried, so there’s probably some more HP to be found.  
>> Before you mill a head, find a shop that can “xray” it for you to tell you how thick the metal is above the cooling passages.  When I had this done, they just marked the thickness directly on the head with a market.  If memory serves, one of the thinnest spots is not quite outside the fire ring on the head gasket near #1.  I had one fail there that got milled 50/thousandths too much.
>> 
>> 
>> 
>> On Dec 6, 2021, at 1:36 PM, McKearn McKearn via Fot <fot at autox.team.net> wrote:
>> 
>> Now that we have the crank and rods figured out, how about we discuss making compression?
>>  I know this can be a sore subject and everyone has an opinion as to how much is enough or too much so where do we start?
>>  I have built a couple TR6 engines that were in the 13:1 range thanks to much head milling and pop up pistons. Will the 2.0 litre engine be the same ?
>>                                       Thanks.  P.J.
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