The BSA A7-A10 Forum

Technical (Descriptive Topic Titles - Stay on Topic) => A7 & A10 Engine => Topic started by: Russ on 14.05. 2014 11:04

Title: Head restoration
Post by: Russ on 14.05. 2014 11:04

Hi Guys,
I'm in the early stages of a restoration of my 51 A10 Iron "small fin" head. My valves are good but the valve guides need replacing. Cast iron guides will be fine for this engine.
I'm planning on using the (heat the head -  cool the valve stem) method and know I will have to re-seat the valves. Also, should I add expense to the project with new valve springs.
I would appreciate some feedback on this job and what to look-out for.

Thanks in advance Russ.

Title: Re: Head restoration
Post by: KiwiGF on 14.05. 2014 12:08

personally i would get new springs if they are available and reasonably priced, but in any event you should check them for length and replace if under length.

just my 2 cents worth!

As an aside, I am building a B31 from a basket case and someone had fitted the wrong valve springs and the spring pressure was massively too high, so its worth checking every detail if your engine history is unknown.

Title: Re: Head restoration
Post by: Russ on 14.05. 2014 12:57

Thanks KiwiGF, I have the measurements recorded somewhere so will check mine tomorrow. If they are undersize I will be back for more advise.
Russ

Title: Re: Head restoration
Post by: WozzA on 14.05. 2014 14:08

Russ... I suggest you get new hardened valve seats fitted & the head decked also.

Title: Re: Head restoration
Post by: muskrat on 14.05. 2014 21:18

G'day Russ.
Has the head been molested before? Might be worth removing the old guides before ordering new as you might have to go oversize. New springs would be good and check the condition of the collets.
While you've got the guides out give the rockerbox surface a rub on glass and wet&dry.
Cheers

Title: Re: Head restoration
Post by: Russ on 14.05. 2014 23:15

Thanks Muskrat
I'll do that.  I should have the dimensions for the guides somewhere so I will check today. If I haven't I'll be back for more help when I knock the old ones out.
If needed, where do I order oversize guides?
As you suggest I will go for new springs and surface the rocker box faces.
The exhaust guides in my head are different to the inlet in that the inlet guides have a slightly rounded / tapered end, where-as the exhaust guides have square / flat ends.
The inlet ones appear more like those shown on E-bay. Perhaps they have been replaced and the exhaust ones are still the original!
Thanks Russ

Title: Re: Head restoration
Post by: muskrat on 15.05. 2014 11:57

G'day Russ.
0.562" sticks in my head. No new ones here to measure, sorry.
Sounds like the inlets have been changed. CI guides in a CI head need 2 thou" interference.
Modak, Classic Allparts here, Classic Spares in NZ or Draganfly in UK or ebay
Cheers