Fitting hotter plugs Q?

mikeinatruck · Post by **mikeinatruck** » Fri Aug 10, 2007 9:17 pm

My old beast of a Landy has now got a late set of HIF44 carbs fitted to a later type inlet manifold, i.e. it does not have a manifold to water pump coolant outlet. Now I have been tinkering with the jets and it seems to run about right, or as best as I can get with out a rolling road. But when it gets hot it seems to be pinking but not like you would expect.

Going up a hill will not do it, but med throttle loads mean you can hear it just (over the noise!)

It is fitted with BPR5ES NGK plugs I am thinking of going to a number 4 hotter plug. Do you think 1 step is enough or would it still run okay with 3's?
I run on Shell V power only with lead additive, the plugs always appear very clean when I check them.

Anyone any experience with hotter plug set ups?

stevieturbo · Post by **stevieturbo** » Sat Aug 11, 2007 1:14 am

Can you reason why you would even think about fitting hotter plugs ?

This would only make any pinking etc worse !!!!

But with a properly running engine, 5's should be fine. You could try 6's, but I see no real reason that you should need them. Sounds more like fuelling and ignition need sorted first.

Post by **Coops** » Sat Aug 11, 2007 9:35 am

i agree with stevie on this one,

Post by **katanaman** » Sat Aug 11, 2007 10:17 pm

I third, fitting hotter or colder plugs is to stop fouling or melting. Going colder could possibly stop pinking but odds on you have a problem elsewhere.

mikeinatruck · Post by **mikeinatruck** » Sun Aug 12, 2007 11:04 pm

I wish it was that easy!the timing is spot on so is the fueling set up and carb balance. I have even gone as far as using a depth micrometer to ensure the jet height is correct and check for comparative dashpot lift accross the rev range!

I do have one last theory to check and it involves changing the exhaust, so i'll see how that goes.

I have managed to contact a friend who used to build Caterhams and he has suggested I could try going to a colder plug and see what changes. So I guess we'll see next outing.

Thanks for you advice.

stevieturbo · Post by **stevieturbo** » Sun Aug 12, 2007 11:09 pm

So what timing are you running when this pinking etc occurs ? And what sort of AFR's are you seeing ?

mikeinatruck · Post by **mikeinatruck** » Thu Aug 16, 2007 10:38 pm

Its not pinking under load, it just seems to be there at a light throttle. I have tried timing at numerous different settings and with a vacuumless dizzy setup. i am starting to think its not timing related now.

I am busy with work at the moment so the old girl is off the road for a while anyway be a few months before she gets another leg stretch.

I am actually thinking of changing the heads for some with valve inserts in as well. Anyone suggest a good company? I actually have two heads ready to send for pressure testing and machining.

stevieturbo · Post by **stevieturbo** » Thu Aug 16, 2007 11:34 pm

Is it defo pinking ?

what fuel ? what CR ? What AFR's ?

ChrisJC · Post by **ChrisJC** » Fri Aug 17, 2007 6:55 am

Any engine machine shop will do, but make sure they have experience of Rover heads as they can be a bit of a nuisance to change valve guides.

Chris.