Page 1 of 1
cylinder head
Posted: Mon Jul 27, 2009 6:39 pm
by andrew.searston
quick question
can you put a 1098 cylinder head onto a 948 engine?????
what difrence will it make???
Re: cylinder head
Posted: Mon Jul 27, 2009 7:54 pm
by Arnie
andrew.searston wrote:quick question
can you put a 1098 cylinder head onto a 948 engine?????
what difrence will it make???
Yes and none is a quick answer. On the standard heads the combustion chamber is the same shape and cc and the valves are the same size. The are a few heads out there with slightly bigger valves and the 12g295 with its open chamber design but these are few and far between.
Posted: Mon Jul 27, 2009 9:29 pm
by andrew.searston
so the 948 and the 1098 are identical?????????
Posted: Mon Jul 27, 2009 11:05 pm
by bmcecosse
No - they are NOT! The 1098 has the 12G202 head - it has larger inlet valves and larger/better inlet ports. The chambers are slightly bigger - to suit the larger inlets - and so to get the same compression ratio as before - you will need to skim the head by ~ 40 thou. May as well go for 60 thou - and get the benefit of slightly higher Comp Ratio! It IS worth doing - but as hinted already - the 12G 295 head has even larger inlets/larger ports and much better shaped chambers - which are even bigger in volume ! So - it would need skimming by ~ 80 thou to get a decent Compression Ratio on a 948 engine. But is well worth doing! If you can also get/fit the camshaft from the 1098 engine (AEA 630) - that will boost the power further - with either head. Next up - you need a larger carb - and an alloy inlet manifold - ex MG Metro is good!
Posted: Tue Jul 28, 2009 12:18 am
by rayofleamington
or just get hold of a 12G940 head - cheaper than a 12G295 and nice BIG valves.
The valves need to be seated well into the head, or you'll need to get the seats cut deeper, but not hard to find out what's what on here.
Posted: Tue Jul 28, 2009 9:20 am
by andrew.searston
i dont want to go that far into modifying it just wanted a little power increase. want to keep it looking original with the same carb.
can you get away with a 1098 head with a 948 carb??
Posted: Tue Jul 28, 2009 9:26 am
by bmcecosse
The can 'get away' with anything you like ! But to get power increase you really need to lose the dreaded 'hot spot' - and so an alloy inlet manifold and matching carb will pay dividends.
Posted: Tue Jul 28, 2009 9:50 am
by Peetee
As a comparison to guage what results you get, a 12G940 or 12G295 head with alloy inlet and 1.5 carb on a 948 engine will give you a slightly faster car and a much smoother and more pleasant engine than a standard 1098.
Posted: Tue Jul 28, 2009 10:02 am
by andrew.searston
i might just keep it standard. will a decoke help improve the engine????
Posted: Tue Jul 28, 2009 11:48 am
by bmcecosse
Not a decoke as such - but grinding in the valves - if they are not properly seating - will help considerably.