if i use a full race bigbore 1275cc extractors on a 1100 will it burn the valves out ???as there is not enough back pressure in the exhaust system ????

it'll only burn valves if it's running lean

back pressure in any exhaust system is bad no matter what, people confuse back pressure with the need for inertia within the system, and that if you use pipes that are too big then you lose it. Each slug of exhaust creates a vacuum behind it which sucks the exhaust charge from the cylinder. If you use pipes that are too big, then the slug of exhaust doesn't have enough inertia to create the vacuum, so you lose performance. The performance loss is twofold, one is that the exhaust isn't being sucked out, and the other is that the piston has to do more work to push it out

So your big bore 'race' extractors on a standard 1100 will probably leave you with bugger all inertia, and you'll go slower

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did I tell you that I won a trophy?

Thanks Simon so wrong mixture can cause it

How many miles on that cylinder head?

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67 Deluxe
Dry suspension
1293cc, 11:1 comp, RE 282 camshaft, 45 Weber, extractors etc
4 synchro close ratio gbox
Cooper S brakes, no booster
Stealth box, as Doc says "goes harder and idles!"
RH tank cos I needed it crossing the Nullarbor etc..

ummm alot hahah i mean alot bout 160 000 i think

Actually we have no idea how many kms. I would estimate it would be in excess of 200,000 if not. Lose to 200,000 kms...... They haven't been easy kms though it has been given a hiding......

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1964 smooth roof panel van
1967 Mk 1 X-Police cooper s
1970 mini k
1975 leyland

Inlet?

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The bitterness of poor quality (or Crappy Workmanship) remains LONG AFTER the Sweet Taste of Low Price is forgotten.

yep

Valves appear to be pulled into the head, no inserts, spark plug looks shagged, carbon build up, corrosion around water way. You have had a good run out of this head. Appears it needs a full head rebuild. At that mileage, how's the rest of the engine ?

And that looks like an exhaust valve. Inlets are the bigger ones and don't burn out.
I agree the head needs a full rebuild.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

the motor has had a very hard life very hard when i pulled it out and gave it to my brother carter it was using oil but still went very well still and he has put a lot of ks on it so i think its time for the old girl to be pulled apart and rebuilt again

C#$p... It's an exhaust valve ....or someone's done something extremely weird...

Cheers, Ian

my bad inlet even