James Johnston

New to Working on British Cars:  Although I have been working on cars and engines for over 15 years, including 2 years in an automotive machine shop, I have only recently gained any experience in the British field.  My 1974 Triumph Spitfire underwent a complete engine rebuild last winter, and I have a spare block which I am going to build as a race-prepped engine. 

The Block:  All my machine work has been performed by A-1 Machine on Greg St. in Sparks, Nevada.

What I Had to Work With:  To begin, my research has yielded the following information.  My engine was originally rated at 53 horsepower.  You should be able to obtain 80 to 90 horsepower with a street engine.  While power can be boosted above 120 horsepower in full race trim, you will lose any long term reliability.

Compression:  In addition to the head work mentioned by Gene deRuelle, a vital item in the Spitfire 1500 is the compression ratio.  The stock compression ratio for all years but ‘76 was an anemic 7.5 to 1.  If you are on a budget, you can substitute flat-top pistons from a ‘76 for your dished pistons.  (See below for a note on pistons)  This will bring your compression ratio to 9 to 1.  All 1500 engines had the same bore, stroke, and pin height (including Midget 1500’s) so you can interchange them without worries. 

If you have the head at a machine shop, you may want to have it surfaced, both for reliability and performance.  The following figures are estimates, you will need to perform the calculations yourself to be sure.  Surfacing the head .050 inch with flat top pistons will result in a compression ratio of about 9.8 to 1.  This is about the limit if you want to run straight premium unleaded.  I have heard of heads being surfaced .100 inch with no problems. 

A warning….although a good idea anytime you assemble an engine, it is especially important when you change any clearances (or add a cam) to turn the assembled engine over by hand to be sure no valve to piston contact occurs.  If you don’t, all your hard work may be ruined in a few short minutes.

Intake Valves:  Another note about cylinder heads is that Triumph went to slightly smaller intake valves in 1975.  The difference may not be big enough to make a noticeable difference, but if you are after budget horsepower, it will help to obtain an earlier head.

Pistons & Rods:  A note on pistons…1500’s originally had split skirt pistons which MUST be replaced if you are going to build any sizable amount of horsepower.  They simply won’t hold up.  Solid skirt pistons are available from true performance houses.  Also, it is highly recommended that you upgrade the rod bolts, if not the entire rods.  The crankshafts in 1500’s are steel rather than cast iron, and as such are the one reciprocating part with a decent performance potential.

External Oil Supply to the Rocker Shaft:  Many sources have cited the need to provide an external oil feed to the rocker shaft, however I have not done so and have had no problems yet.  While simply my opinion, this should not be necessary on an engine which is truly clean upon assembly and receives regular oil changes.  If in doubt, be sure that the oil gallery in the head is not obstructed by the head gasket.  For those of you who really want one, they are available from Max’s MG Service (Vic Auletta) - http://www.rockerarmkit.com/ - for about $155.

A Cam Source:  Another company which regrinds British cams is TS Imported Automotive - tsimportedautomotive.com  - I ran across them during an extensive Google search and cannot offer any insight on their service.  As they are in Ohio, they may not be your first choice.

Help on the Internet:  For an extremely in depth and informative look at building a Spitfire for performance, go to Totally Triumph at http://www.totallytriumph.net/spitfire/engine_building.shtml#Head

Performance Parts & Services Suppliers:  As far as I can tell, Moss and Victoria British do not sell any performance internal engine parts for Spitfires.  Some very helpful members of the Bakersfield MG Club suggested APT (Advanced Performance Technologies) in Riverside, CA. www.aptfast.com   While their website and catalog are both extremely out of date, you can call and talk to someone who actually works on British cars and knows what part you need (or can help you decide what part you need).  They sell parts for nearly any British make.  They also offer machine shop services. 

While not really a performance supplier, Rimmer Brothers - www.rimmerbros.co.uk - does supply any replacement part you could ever need, up to reconditioned engines and transmissions.  Their prices on large items are good, if you are willing to pay the shipping from Britain. 

Another British company that supplies true performance parts is Moss Europe - www.moss-europe.co.uk//MossUK

Jamess Johnston- April 2006