big valve 940 head on a 1098...

Post by **callyspoy** » Sun May 17, 2009 2:04 pm

can it be done?? i know the standard 940 head can be put on, but can the big valve ones? this is for my dad as he is rebuilding and playing with a 1098...he has both "small" valve 940 and big valve, so not an issue, but he would like to fit the big one!

Post by **Peetee** » Sun May 17, 2009 2:28 pm

Can't see the bigger valves would make that much difference given the state of tune. I would recommend selling the big valve head on ebay and with the proceeds getting a 1.5 carb and manifold to suite the other head - without them it's about as effective as half a pair of scissors.

Post by **callyspoy** » Sun May 17, 2009 2:40 pm

half a pair of scissors can be used as a stanley blade! but i see what you mean!
anywho, dad has a 1275 in the car. he wants to take it out to "in the long run" rebuild it.
we have a 1098 that he is going to rebuild, bigger head, cam, possible rebore, duplex chain and all the other little bits. he already has an LCB and 1.75 carb on the car so the fear of the head being wasted with small carb/exhaust is not valid.
before any one says, yes, we/he knows that it would make more sense to do all this on the 1275 engine, but where's the fun in that!!
oh yes, also, it's going to be mated to a toyota 5 speed too...one day...

Post by **bmcecosse** » Sun May 17, 2009 9:16 pm

It can certainly be done - the inlet valves go down the bores ok - but you must check the exhaust valve clearances from the block. Some heads seem to be ok as they are - I had to sink my exhaust valves into the head by 40 thou to get sufficient clearance. The 1.75 carb is a bit too big anyway - and as you well know - this would all go better on the 1275! The 1098 is longer stroke - don't run it beyond 6000 rpm - even then - be sure to fit a proper crankshaft damper - not just the steel lump sold by ESM and maybe others - that has no 'damping' characteristics. But it will certainly work ok.

Post by **callyspoy** » Sun May 17, 2009 9:58 pm

cheers folks, i just looked back and realised i had already asked the same question, i do apologise, that's what happens when you have too many things going on and then your asks you to check something!

Post by **bmcecosse** » Sun May 17, 2009 10:16 pm

Hope you got the same answer!