Preamble:
Firstly - No jokes about smoke on the water please
That bands best album is actually 'In Rock' but lets not digress before the thread has even started.... Jees
Right - I aquired a lil 7A head complete with cams as a winter project. The objective to try my hand at some port grinding and whatever other machine operations are required to bring the head up to ABY/ADU spec. My intent is to get the head cleaned up then flowbenched to quantify its performance before I do anything to it... Then I'll bench it again after the portwork is complete and I just hope for some mild gains in flow - I'm going to be quite conservative with this as I dont want to trash the head with ill thought use of a die-grinder.
Due to the scarey amount of funds and time required to do this job properly its going to take along time, but as I'm not in a rush I thought it useful to document the procedure here for posterity.
I'll insert photos when I have more time. Got them here somewhere...
Part 1
When it arrived, on 1st quick inspection all seemed well with no cracks in the obvious places and no signs of wear on the camshafts. I had been told that some valves were bent and sure enough there looked like two or three slightly bendy inlet valves - typical as I was hoping to resuse the inlet valves from 7A as they are common with ABY.
I lined up an old S2 EM to verify that I didn't need any new exhaust studs in the head - apparently some 7A heads need this, some don't - dunno why !
Part 2
Had a closer look the following day to work out how to align the camshafts for bearing removal as per the book as I don't have the cam pulley fitted... Doing it in the wrong order can put the cams under undue strain. Thankfully, the OFRM tells me that the camshaft gears have two little marks that align at TDC.
This would have allowed me to remove the camshafts as per the OFRM - which I'll summarise here later when I look at it again to remind me... BUT cos of the bent valves there was no way to hand crank it round to the correct position - I had to adapt the OFRM procedure so as to gradually remove the inlet cam bearings in such a way as to minimise stress on the cam. Once the inlet cam was out I could crank the EX cam round to TDC and do it by the book.
During this I noticed that the inlet cam bearing nearest the timing end was slightly damaged - looks for all the world like postie dropped the head on its end (or it got doushed in a van somewhere) - one of the studs is slightly bent (easy to change) but the bearing is going to have be TIG welded and redrilled or somthing as these shells are line drilled on the head in the factory and cannot be replaced individually.
Bit annoying but not a showstopper.
All of the cam bearing shells were visually inspected and tucked away in labelled boxes for safe keeping. They are numbered which makes life easy - and keyed to only refit the correct way round.
Part 3
The work started in earnest tonight when I started stripping the valvegear. Diesel Des kindly offered me the loan of his funky valve spring compressor until I remembered how I modified mine in the past with a 22mm 1/2" socket and some insulating tape to get me thru this phase. It required some care to extract the collets in this way - several attempts on some valves, lots of patience and plenty of foul language.
All the exhaust valves out easy enough - bagged and tagged with all springs, retainers and whatnot in Tescos finest small ziplock bags. Haven't told 'er indoors yet that I used the last one but hey
TOPTIP #1 - getting the bottom valve spring seat out of an oily head is a PITA, as they just wanna stick there - even upside down sometimes, unless you use one of those magnetic tipped pickup tools to lift them past the valve stem oil seal (VSOS) - neato !
The good inlet valves also came out easy enough... So did the less bent one, but the two heavily bent ones in cylinder #4 are a real sod to shift - not helped by my makeshift tool. Care is required so as not to force the bent valve into the head in such a way that it might damage the surface of the valve seat. I'll have to wait until Des drops by with the proper tool to give me more access.
This really needs photos to do it justice... I'll do my best to revisit this ASAP with the images from the phone.
I verified that my valves are correct parts for the 7A head - you can just make out part numbers at the top of the valve. I have 10 perfectly good NON sodium filled EX valves which have no use for me. They are actually marked 027 611D which misses the middle three digits from the part number - I need 027 109 611B of course to get zee all important Sodium filling.
I'm unsure whether to reuse the valve springs, retainers and such - I'm torn as I don't want to spend a fortune just for sake of it, but I would like something higher spec or just plain new with things like engine internals. No sweat yet as there is no point in paying for exotic valvegear if my headwork is not that good.
The cost of sourcing new lifters, valve guides and valves x 20 is scarey enough, plus covers, nuts, bolts, studs the machine work and coilpaks to complete the build up
I did a quick tot up at list price for entirely new parts right across the head and it was in the region of £2k so forget that idea ! This project aint on that budget...
Paul
Firstly - No jokes about smoke on the water please
That bands best album is actually 'In Rock' but lets not digress before the thread has even started.... JeesRight - I aquired a lil 7A head complete with cams as a winter project. The objective to try my hand at some port grinding and whatever other machine operations are required to bring the head up to ABY/ADU spec. My intent is to get the head cleaned up then flowbenched to quantify its performance before I do anything to it... Then I'll bench it again after the portwork is complete and I just hope for some mild gains in flow - I'm going to be quite conservative with this as I dont want to trash the head with ill thought use of a die-grinder.
Due to the scarey amount of funds and time required to do this job properly its going to take along time, but as I'm not in a rush I thought it useful to document the procedure here for posterity.
I'll insert photos when I have more time. Got them here somewhere...
Part 1
When it arrived, on 1st quick inspection all seemed well with no cracks in the obvious places and no signs of wear on the camshafts. I had been told that some valves were bent and sure enough there looked like two or three slightly bendy inlet valves - typical as I was hoping to resuse the inlet valves from 7A as they are common with ABY.
I lined up an old S2 EM to verify that I didn't need any new exhaust studs in the head - apparently some 7A heads need this, some don't - dunno why !
Part 2
Had a closer look the following day to work out how to align the camshafts for bearing removal as per the book as I don't have the cam pulley fitted... Doing it in the wrong order can put the cams under undue strain. Thankfully, the OFRM tells me that the camshaft gears have two little marks that align at TDC.
This would have allowed me to remove the camshafts as per the OFRM - which I'll summarise here later when I look at it again to remind me... BUT cos of the bent valves there was no way to hand crank it round to the correct position - I had to adapt the OFRM procedure so as to gradually remove the inlet cam bearings in such a way as to minimise stress on the cam. Once the inlet cam was out I could crank the EX cam round to TDC and do it by the book.
During this I noticed that the inlet cam bearing nearest the timing end was slightly damaged - looks for all the world like postie dropped the head on its end (or it got doushed in a van somewhere) - one of the studs is slightly bent (easy to change) but the bearing is going to have be TIG welded and redrilled or somthing as these shells are line drilled on the head in the factory and cannot be replaced individually.
Bit annoying but not a showstopper.
All of the cam bearing shells were visually inspected and tucked away in labelled boxes for safe keeping. They are numbered which makes life easy - and keyed to only refit the correct way round.
Part 3
The work started in earnest tonight when I started stripping the valvegear. Diesel Des kindly offered me the loan of his funky valve spring compressor until I remembered how I modified mine in the past with a 22mm 1/2" socket and some insulating tape to get me thru this phase. It required some care to extract the collets in this way - several attempts on some valves, lots of patience and plenty of foul language.
All the exhaust valves out easy enough - bagged and tagged with all springs, retainers and whatnot in Tescos finest small ziplock bags. Haven't told 'er indoors yet that I used the last one but hey
TOPTIP #1 - getting the bottom valve spring seat out of an oily head is a PITA, as they just wanna stick there - even upside down sometimes, unless you use one of those magnetic tipped pickup tools to lift them past the valve stem oil seal (VSOS) - neato !
The good inlet valves also came out easy enough... So did the less bent one, but the two heavily bent ones in cylinder #4 are a real sod to shift - not helped by my makeshift tool. Care is required so as not to force the bent valve into the head in such a way that it might damage the surface of the valve seat. I'll have to wait until Des drops by with the proper tool to give me more access.
This really needs photos to do it justice... I'll do my best to revisit this ASAP with the images from the phone.
I verified that my valves are correct parts for the 7A head - you can just make out part numbers at the top of the valve. I have 10 perfectly good NON sodium filled EX valves which have no use for me. They are actually marked 027 611D which misses the middle three digits from the part number - I need 027 109 611B of course to get zee all important Sodium filling.
I'm unsure whether to reuse the valve springs, retainers and such - I'm torn as I don't want to spend a fortune just for sake of it, but I would like something higher spec or just plain new with things like engine internals. No sweat yet as there is no point in paying for exotic valvegear if my headwork is not that good.
The cost of sourcing new lifters, valve guides and valves x 20 is scarey enough, plus covers, nuts, bolts, studs the machine work and coilpaks to complete the build up
I did a quick tot up at list price for entirely new parts right across the head and it was in the region of £2k so forget that idea ! This project aint on that budget...Paul
Comment