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[knight]

Ok, so I have just bought a 1.7 8v motor form an 89 sud sprint, is fitted with 40mm Dellortos with 32mm chokes, has done about 90,000 miles…….I would like to turn it into a mild/hot street motor for my kit car, and I would like your advice on a few matters:-

Pistons – I would like to fit some 16v pistons in order to raise the compression to 10.8:1…….when I eventually get hold of the 16v pistons and rings, they will highly likely be used secondhand, as I dare say new will cost more than the £150 I paid for the motor!....... do I just install them into my motor, or shall I have the bores re-honed and fit new piston rings, otherwise I’m thinking the used rings wont wear too well with an already used bore…….or is it considered ok ????……what do you think?

What choke size and jet settings would you recommend for such an engine? (Dellorto 40’s don’t forget), I have heard people are fiting 34 and 36mm chokes……..will this be totally undrivable, or should I stick with the standard 32mm chokes and a mild jet change???......

While I have the heads off, I might have them ported and have some bigger valves fitted – any advice on what, and what NOT to do in this area would also be appreciated!

[bobbber]

Hi Knight,

I'm pretty sure the crowns of the pistons have convex cut outs in them to allow for the pistons.

This profile would be different to 8 valve pistons. Therefore, the 8 valves would hit the piston crown for a 16 valve piston.

I'm pretty sure I've got that right.

Bob
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Fiat Bravo 165 Sport

[hugh jinjin]

your best bet would be a complete 16v bottom end. that way you get the pistons matched to the bores already and you get stronger rod bolts.As for heads, a recent rule change in the AROC championship means that 16v engines are now allowed in any 33 shell which means that second hand 8v race heads may be available for reasonable money. These are not big valve heads as the rules do not permit that but they are claiming about 140bhp on standard cams and i think standard compression ratio.
that would be my spec for a good mild street engine, and I certainly wouldn't use 36mm chokes as it will be a dog.

[knight]

interesting note about the alfa racers soon to have a surplus of 8v race heads!......140 sounds just where I want to be......on standard compresion sounds good too!

do you (or anyone) know of a web forum where all the alfa-racers chat?.....and sell stuff!

I dont think I will be getting hold of a 16v bottom end, I'd rather skim the heads and clearance my pistons if its going to be that much grief!

[hugh jinjin]

I don't think that there is anything online yet although there is one due to start on the alfaracer site soon. Get along to Oulton Park on Sat 1st april, or Silverstone on the 15th and have a word with the guys there.

[Edward]

Hi,

Do you know if there is any racing at castle coombe this year and what the date is?
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The faster the better.

[Serpent33]

No, the piston wouldn't touch the valves. But you'll have big time problem with the CR. You won't get 16V cr by using 16V pistons. You fail to factor in the different combustion chamber. Unless you are prepared to run only on very high octane fuel or race fuel.

The diameter of the dish on the 8V pistons doesn't clear the valve head area. Which means the dish of the 8 valve pistons has got nothing to do with valve clearence. In fact 16V pistons will have better valve clearance because it starts it's dish right from the edge.
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Each time I speed I say, "Dear lord, make me fast and accurate..."

[Guest]

i will sell you a 16 v engine if you are interested £150