Listers - just ran some tests on my Spitfire 1296 cc engine (FK252234 UE)
and am looking for some feedback as I'm kind of new to this.
Engine Symptoms:
- ran well, good power
- quite a lot of noise from the cylinder head area which valve adjustments
didn't seem to help
- would smoke a bit when taking off from the lights after idling for a
minute or two.
Compression Test (psi)
Cylinder Dry Wet
1 155 167
2 170 178
3 180 185
4 122 125
Cylinder 4 was noticeably slow to produce compression when cranking (over
five cranks on the starter) - all the others reached over 100 psi on the
first crank and max'd after 3-4.
I'm thinking I probably need a valve job but am looking for some advice
here.
I then measured the cam lift with a dial gauge at the top of each pushrod
(rocker gear removed) and got the following (inches):
Valve Lift
1Exh 0.2122
1Int 0.2130
2Int 0.2125
2Exh 0.2133
3Exh 0.2123
3Int 0.2137
4Int 0.2138
4Exh 0.2139
All the measurements were repeatable within about 0.0005.
The max difference is 0.0017 - can anyone tell me if this is significant?
I couldn't find any specs on stock cam lift but this doesn't seem
especially high. If I need to replace it or get a regrind I was thinking of
going with a mild street cam but if it's fine I'll probably leave it as is.
Following all this I removed the head. The tappet-to-valve contact surface
seem fairly worn although the pushrods and cam lifters looked pretty good
(although I'm not too sure what to look for).
There is a lot of carbon buildup in the combustion chambers but I was able
to measure the cylinder bore diameters just below the lip I think
reasonably accurately.
The diameters were (inches):
Cylinder Perpindicular Parallel
1 2.919 2.917
2 2.916 2.915
3 2.917 2.915
4 2.913 2.917
The stock bore is 2.9 and I know the engine was rebuilt at least once
previously. I guess I'm looking at wear of 0.003-0.009 on a bore of 2.910.
The main questions on my mind are:
- do I need a rebore or can I just put in new rings?
- what bore size should I order for?
- do I need to remove the pistons and measure the diameters?
- do I need to remove the crank and measure the bore at the bottom of the
cylinder to be sure?
The cylinder head height is somewhere around 2.99 to 3.00 inches. I
couldn't find a spec on this (I think maybe my Haynes isn't quite detailed
enough here!) so I'm not sure if this is stock or not. I seem to remember
seeing something on the list about cylinder head height vs. compression
ratio a while ago - did anyone save this or care to comment.
All comments/input greatly appreciated.
Mark Sinclair
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