sd1 heads info please

thamesroverp6

thamesroverp6

Member
i have a set of sd1 heads laying around and once i get the p6b up and running, i may look at fitting them to the block later on.
can someone please tell me:
can i remove existing heads and fit sd1 heads without the need to replace/fit anything else?
Apart from tin gaskets, will i need new head bolts?
thankyou
 
Not going to get into a head bolt debate on here.
But from what I understand if the tightening sequence involves a torque setting then the bolts can be re used. If the tightening sequence involves an initial low torque setting and then further tightening by degrees, then the bolts cannot be re used.
The P6 has a torque setting.
There is always other stuff to replace, eg exhaust manifold gaskets, coolant hoses that you find iffy when removed, rocker cover gaskets, dirty fuel filter, dirty breather......................................................................

Remember you will lower the compression ratio fitting SD1 heads, but you will gain on slightly larger valves. Ideally you want the SDI heads skimmed to keep the 10.5 :1 CR, fit shorter bulleted guides with seals, get a nice 3 angled valve seat job done and a clean up of the bowls and ports - then you will see some gains.
 
cobraboy said:
There is always other stuff to replace, eg exhaust manifold gaskets,
Click to expand...

P5B/P6B/SD1 don't have exhaust manifold gaskets.


cobraboy said:
Remember you will lower the compression ratio fitting SD1 heads, but you will gain on slightly larger valves. Ideally you want the SDI heads skimmed to keep the 10.5 :1 CR,
Click to expand...

Just fitting the SD1 heads won't alter the cr. You only need to skim the heads to maintain the cr if you use composite head gaskets.
 
Ah ha
Well they have them if they are fitted ;) and quite often with headers it is the only way to get a seal.
I must admit I have not cc'd P6 against SD1 so am thinking that the pistons are the way in which the P6 gets its higher CR ? in which case the bigger valved SD1 heads would be even more attractive.
Thanks Harvey
 
I'm not actually a real mechanic, just an enthusiast, so feel free to ignore my tuppence worth, which is to use a nice new set of head bolts for peace of mind! Rimmer Bros do 'em.
 
I did some research back in the day, and I believe the SD1 heads breathe 12% more air than the P6 ones. Don't know why I remember that bit, but I changed them back on the 80s and do remember I had to change the needles to AAA, although, I did have some tubular headers as well from a chap called Mike the Pipe.

I never changed the head bolts tbh, and don't try to fit P6 spark plugs :)
 
Hi, I remember Mike the pipe at Croydon, I bought some headers for the Ford Essex V6 I'd put in an Avenger. He was considerably cheaper than an alternative from Howe exhausts, not a very presupposing premises but I couldn't fault the quality of the work. Thanks for the trip down memory lane.;)

Colin
 
thanks guys i am happy to give it a whirl when the time comes, i accumulated the gaskets (even the exhaust manifold gaskets) from work ages ago,
whats the best way to remove the bolts to the exhaust manifold bolts from the block? i think i have to attach them to the sd1 heads.
 
Sorry to jump on This thread but does anyone know the amount of skimming required to keep the compression ratio at 10.5 1 ?
 
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