Originally posted by Z28Quetzal:
Basil,
Great forum! I just joined up, and I already have a question!!
I too own a Spitfire. Mine is a '78 with the 4 speed non-overdrive. I currently have the Zenith carb on the engine, however, I am in the process of rebuilding a pair of SU HS2's.
I read your post about your Spitfire, and am curious about the mods you made.
- Are the original pistons flat tops or are they dished?
- I have access to a machine shop, and this winter I plan to remove the head and do some work to it. Clean it up and then take it to have it milled down just a tad. How much did you have yours milled down?
- You mentioned you were going to put a new cam on your engine. Have you decided what you are going to do with the hot cam you already have? I'd be interested if you tell me more about it...
Just some questions, hope you don't mind me asking...
Regards,
joe
Hi Joe, and welcome to the forum.
Activity here is still a bit slow but has been steadily improving the last month or so. As we get more members the activity level will pick up - so hang in there and above all - POST!
Now, as to your questions. The original pistons on my car were dished. This, I presume, was to lower compression for emissions reasons. I put 30 thousandths over-sized flat-top pistons in (Euro spec).
As for the head, I just had it milled enough to make it even β wasnβt trying for anything more than just ensuring the head was flat. I was afraid that if I went too much, in combination with the flat top pistons and the hotter cam (which increases valve lift) I was afraid that I might be in danger of fouling the valves onto the piston tops. I donβt know how much clearance there was to play with, so I decided not to take any undue chances.
My old cam is bad. Two of the lobs are flattened off on the tips. I suspect the problem is that when the machine shop that did the work to put it all back, they used the original springs and those springs did not compress enough to accommodate the increased lift of the new hotter cam. This time, I am buying a set of springs made specifically for the cam I am buying - a Kent cam from British Parts North West in Oregon. $166 if you donβt have a core β less if you do (only a stock cam will work as a core β they will not accept a hotter cam as a core). I would not recommend buying a used cam.
Hope this helps. Let me know if you have any other questions,
Basil