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Triumph 1500 engines with Spitfire Mk3 Camshaft


French Midget

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Hello,

I have on my MG Midget a Triumph 1500 engines which previous owner has got rebuild and modified, in particular with a Spitfire Mk 3 camshaft, which sounds to be not so unusual in Triumph world.

Has somebody any idea of adjustments specific to this engine configuration :
- idle speeds,
- ignition timing (initial advance setting),
- centrifugal advance curves,
- ... ?

More details about my engine configuration and installation :
- K&N air filters,
- 4-2-1 exhaust,
- NGK BPR6ES spark plugs,
- 25/65 Mk 3 camshaft, timing 110° ATDC,
- 36.4 mm inlet valves and 31.3 mm exhaust valves.

Thanks in advance for your help, best regards
Thierry

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Welcome Thierry, sounds like you've got a good engine - those are some of the most cost effective modifications to the 1500 and are very highly thought of, so it sounds like you've got a good engine there.

I would've thought you should get an idle speed pretty comparable with the standard 1500 cam, maybe a little higher but both were designed for road use. Under the bonnet of my 1500 Spitfire the BL sticker recommends an idle speed of 650-850, which is about what I tend to get (depending on how the carbs feel that day), though I'd aim for the upper end of that. You don't want it too low or else the alternator might not put out enough charge.

Ignition timing is 10 degrees b.t.d.c at idle for the standard engine, but the best way to do it is keep turning the dizzy until the revs stop rising, then back it off a bit. Or do it by vacuum if you have a vacuum gauge, and set it just a bit off max vacuum.

Dont have any centrifugal advance curves handy but others running megajolt and upgrades are probably far more qualified than me to give advice on your engine in that department.

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I have a 1500 in my car with a mk3 profile cam and the same filters and exhaust mods you have and it runs pretty nicely on AAQ needles. It  idles at the standard rpm and I have it set up with the standard timing. I had a good mess around with the timing before the RBRR last year and tried all sorts of settings but ended up back at the book figure!

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At the moment - standard.

But before that I used a ported and polished head with standard valves (three angle cut). At that time my car had carbs that were knackered and didn't run well. Unfortunately, by the time I got my new carbs, I'd taken the head off for some more work so I never got to fine tune the new carbs to the modified head!

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If it helps I have a modified head 10:1 compression, 3 angle valve cut, ported and polished +40 thou overbore, crank stroked and a piper 270 cam in a 1500 along with 4-2-1 manifold, straight through lrge-bore exhaust, 8oz yellow carb springs, HS4 carbs, k&n air filters and run AAU very nicely. AAQ/AAT are popular choices as will says.

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CharlieB wrote:

Increased or decreased? Increased sounds like a recipe for disaster, 1700 anyone?  :(


A very minor increase, along with the cam choice (thanks to Marcus) and a few other mods has lead to a very well behaved engine with good low, mid and high end torque and good gains in hp. The bearings if anything will as per most 1500's be the first failure point if my 'experiment' goes awry.

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