Re the core plugs please note what Bystander said. I would judge whether it's needed or not based on the condition of the bits you can see.
If running a 2 bearing crank general practice is to allow say 20 thou gap between piston crown and the top face of the block at tdc, stops pistons hitting the head at high rpm. With a 3- bearing crank you can cut it a bit finer. If things are a bit tight you can normally skim 10 or 20 thou off the piston crowns to make the clearance. It is also possible to put a spacer under the block, but you don't want anything interfering with the base of the piston skirts. All I'm saying really is do some measuring (or trial assembly) & understand what you're in for before taking metal off - you can't easily put it back on!
(22-05-2018, 08:47 PM)Andy Bennett Wrote: I have made a somewhat speculative purchase of a block and would appreciate some guidance on what my options are.
With my engine chewing a head gasket once a year (1000 miles) due to various breaks across the gasket caused i suspect by less than perfect surfaces on the block/head, and there being a lot of exhaust fumes from the tappet cover (with cord rings having been fitted by a previous owner to ‘cure it’) I have for some time been planning a top end upgrade/rebuild/repair.
Well, the opportunity has come to fruition. I have purchased a block with the following identification: 7521, 31 8 29. Now call me Sherlock, but I take it from this that it is a 1929 block.
My box is a 1933 model.
The block at first look appears basically sound. It needs some helicoils etc and some surface refinishing, but hopefully nothing too problematic from what I can see so far.
So to my questions:
The bore sizes are 2.235 to 2.237 inches. Is it safe to take it that this means that it has been bored to +30, rather than +40?
The block is ‘naked’ so no guides, valves, studs etc. I cannot see any significant changes from the 1929 to 1933 block design, so can I use this 1929 block on my 1933 engine? If so should I use the earlier flanged guide etc as on the pre 31 engines or can I just use the later plain guide etc in this block and so basically build it up as a 1933 spec block?
One of the water inlet manifold stud threads has suffered somewhat, as in below picture. Clearly this is going to be an area which suffers from corrosion. However, it also doesn’t take pressure. There doesn’t look like a great deal of material to take a helicoil and there is a decent amount of thread present, so recommendations appreciated, should I just use as is or attempt helicoil?
edit: there is more material than the close up image suggests, the shadow makes it look worse than it is.
Thanks all
Andy
In addition to all the useful replies you already have, I make a point of loctiting all studs into the block to fill any spaces in the the thread so that rusting will be minimised. Also for water joints I use stainless steel studs, with fibre washers under dome nuts on the outside, which eliminates any sealing problems.
Robert Leigh
The side water inlet can be repaired by using a stainless steel repair plate from John Barlow supplied with fixings, for fitting information see BA7C technical website.
Thanks all.
I feel a shopping list coming on, but think I have pushed the A7 budget a little in the last few weeks so may hold off for little while. I am sure I will find more questions as the refurb progresses.
(23-05-2018, 07:18 PM)Andy Bennett Wrote: Thanks all.
I feel a shopping list coming on, but think I have pushed the A7 budget a little in the last few weeks so may hold off for little while. I am sure I will find more questions as the refurb progresses.
Andy
Not sure what manifolding you are using but note that the earlier block has valve chest cover studs set higher than the later block so the largish knurled nuts are trapped behind the later combined manifold .
Also as discussed previously it is an idea to drill out the brass plugs to the gallery above the manifold and replace with screw in plugs after cleaning the waterway.
I'm in the process of syncro-seat grinding my valve seats in my block after having new K-liner valve guide inserts fitted.
At the same time as this was done by one of the local motor re-conditioners, I had the block put in their "hot bath" for several days. I had removed the core plugs first.
This solution ( I think it is caustic) loosens and dissolves the build up of mud and ferric oxides in the water galleries. I then followed this up with an extensive water blast on the highest pressure I could get the blaster on.
I have recently sectioned my early 90's UK trip initial high performance block and was surprised at the amount of rust that was significantly blocking the water galleries. I highly recommend getting your block into a "hot bath" for some time. Even with the core plugs out, it is not possible to poke a wire around all the galleries. The rust is also so hard that the wire would not dislodge the crud.
I will attempt to post some photos showing this later.
I guess the dreaed brown spots in cyl wall the main worry. A brief hone with a fine re ringing hone would likely show. If no mates have one, these hones can be purchsed cheap 2nd hand as many had them but little use for on moderns
Thanks again.
for the chest cover I did take a look following the earlier comment. I also checked using the usual books as it looked to me like the later chest cover would fit as the threads are in the middle, and it seems that I have the slightly later of these blocks with the screw in core plugs but with the later chest cover, so shouldn't be a problem manifold wise.
Also appreciate the other bits and bobs, lots to think about but forewarned is definitely forearmed and I want to make sure I don't ignore anything whilst I have the luxury of time to get it right.
