More Horses

[teddy bear]

My wife and I have, for the past two weeks, been the proud owner of a very nice red 1300 AGK 158S. I had no intention of buying a Dolomite and had gone to see another car at this dealer near to where we live but the Dolomite stood out and was in our price range. After a short test drive, we decided to buy and it has been very much admired where we live in south Lincolnshire. Comfortable, with nice handling, gearbox and brakes makes for a desirable car apart from the lack of power. Some might want to avert their eyes at this stage but we also have a 1966 Riley Kestrel 1300 which in standard form puts out a respectable 72 gee-gees. The performance difference is very marked even allowing for the lower weight of the Kestrel. I am not after a hot motor just about another 12/15 hp and propose obtaining a spare head to port with twin carbs and possibly the twin exhaust. I have the chance of a 1500 head with carbs and manifold and would like to know if the 1500 head will fit the 1300 block with no mods? I assume it will as the bores are the same on the two engines. Any comments please from the many knowledgeable members out there. I do not wish to have the car off the road for more than a month so nothing drastic such as engine changes.

[Triumph1300]

The 1500 head will fit, but I suspect you will need to skim it significantly to get a decent compression ratio.

I can't remember the combustion chamber volumes off the top of my head.

[Jod Clark]

Skim the head until the face is level with the machined surface where the manifold gasket fits against the head. Hard to explain it but with the head on the bench you will see what I mean. That will give a compression ratio of 10.25:1 or very close, which should run nicely and still leaves enough meat around the water channels in the head. I've long maintained that the compression ratio is artificially low on the 1300, possibly to de-tune the engine and give the 1500 a reason for being.

[teddy bear]

Thanks, both for your replies. Obviously, I am on a steep learning curve and although I know lots about our 1966 Riley Kestrel and 1936 Riley Merlin I know nothing about Triumphs. It now turns out that the heads I have been offered are from Mk3 Spitfires so my question is are these any good? Jod mentions a c/r of over 10-1, is this not a bit on the high side for an every day road car? All and any advice gratefully received.
Graham Martin

[GTS290N]

pm sent.

[Triumph1300]

They're the head used on the 1300tc, so yes they're good.
You would also gain with a matching cam change

[cliftyhanger]

A spitfire mk3 produced 75bhp (but remember the power was measured in a different way then so probably nearer 70bhp)

To get that you would need the head and cam, but watch cam journals, I suspect the 1300 needs a large cam journal with no cam bearings, but the cams re available with that size journal from Canleys etc.

The single 1 1/2" SU will make almost as much power as a pair on a 1500, so I think the situation would be the same on the 1300. However.....If you look to use the 1500 twin cast manifold and downpipe, you cannot fit the single carb inlet manifold. Not sure about the club 4 branch manifold.

Don't be tempted to get a cam that is "too hot" as it moves the power band up the rev range and makes life hard work.

[teddy bear]

Thanks Clive.
The question of camshaft journals is obviously something I was unaware of, hence the undoubted value of Forums such as this. Would anyone know what type I have from the engine No which is DH80488HE? My initial intention is to fettle and smooth ports on the Spitfire head, leave the single carb and exhaust as it is and change camshaft for either a Spitfire one or one similar. As you say nothing too fierce! Always best not to change too many things at one time as you can easily lose your way if things do not work out. If this goes well then carbs/exhaust would be next.
Graham Martin

1978 1300 Dolomite ( now club member)
1966 1300 Riley Kestrel
1936 9HP Riley Merlin

[cliftyhanger]

Pretty sure you have a large journal camshaft. You could fit cambearings and use a genuine mk3 cam, or get one on a large journal blank. Newman cams seem to be very good, or try canley classics. The DH engine is essentially the same as a mkIV spitfire.

[teddy bear]

Thank you Clive. Have a spitfire head coming tomorrow and have ordered a Newman camshaft. Going to be busy!!!
Graham Martin

[cliftyhanger]

Excellent. You will need to do a needle swap, I am sure somebody can recommend something suitable. Afraid I have no experience, but I am sure plenty of others have. Worth asking (in a separate thread is your best bet)