Hi again,

The job at the moment is to rebuild a 1098 after the head gasket let go, the bottom end was pretty tired also.

The current plan is to recondition a 12G295 head, get some Russell Engineering +100 flat top pistons. The head is with the machinist now getting checked.
The current external parts are: HS4 SU, minispares alloy manifold, standard bore LCB, and a 1.75" twin box RC40.

Otherwise I plan to get ARP rod bolts, an adjustable timing set and a lightened steel flywheel.

I'm looking to fit a minispares EVOLUTION001 camshaft, that's a slot drive cam.

Is the correct oil pump: OIL PUMP 998cc A PLUS SLOT DRIVE, GLP139?
I think that pump might need work to make fit? Or what is the correct way to convert an A series small bore engine to slot drive?

Any other tips or advice? Do those parts make sense?

I would say an adjustable timing gear isn't really needed as you can measure the timing, then get an offset woodruff key for the cam

I'd pay particular attention to the compression ratio and make sure it's under 10:1 . Starting with an unskimmed 12G295 head is a good starting point, but it might still be a bit high unless the chambers are opened up a bit.

I'm not sure on the cam, but interested to find out!

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I'm waiting to find out if the head tests ok from the machinist.
Then I will wait to get it back from reconditioning to measure the combustion chambers and figure out the final plan for the bottom end.

Bore: 67.08mm
Stroke: 83.72mm
Cylinder Head Volume: 28cc
Effective Dome Volume:0cc
Deck Clearance: 0mm
Compressed Gasket Thickness:1mm
Number of Cylinders: 4
Compression Ratio : 10.36 : 1
Total Displacement cc's : 1184.59
So depending on where my deck heights end up I might need to do some work.
With the 6cc pistons compression is only around 8.7 : 1, so those won't work unless I skim the head lots.

The cam is a bit of a bargain buy, but I'm hoping it'll be a nice 'fast road' cam, sporty but not rough

What are your cam specs?
Have you chatted with GR about his pistons?
Id look at a 1.75 SU/ HIF44

alternatively... 8.7:1 is peeeerfect for forced induction

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Here am I sitting in my tin can far above the Moon
Planet Earth is blue and there's nothing I can do...



“A turbo: exhaust gasses go into the turbocharger and spin it, witchcraft happens and you go faster.” - Jeremy Clarkson

The machine let me know the head is uncracked and good to recondition, it's getting new guides and C-AEA526 double springs.

I'll get in touch with Russell engineering after I get my head back and I have measured the chambers

A HIF44 would probably be a great next step, but I was pretty happy with how the HS4 ran, and budget and time are a factor.
A few years ago I rebuilt the HS4 with new throttle that I thinned down and added a machined bell mouth and K&N filter.

No turbo, I'm having enough trouble keeping this thing in running condition as it is.


Evolution001
Seat duration Inlet 257 Exhaust 252
Cam lift Inlet 264 Exhaust 289
Valve lift Inlet 327 Exhaust 358 (Standard rockers)

for comparison

Kent MD266 (supposedly the MD266 is good for 1,200 to 6,500rpm)
Seat duration Inlet 260 Exhaust 270
Cam lift Inlet 263 Exhaust 270
Valve lift Inlet 320 Exhaust 330 (Standard rockers)

Standard 1100
Seat duration Inlet 246 Exhaust 240
Cam lift Inlet 237 Exhaust 235
Valve lift Inlet 281 Exhaust 279 (Standard rockers)

you don't need to do anything to "convert" to a slot drive cam, you just need to have an oil pump that matches it, so slot drive cam + slot drive oil pump = good, pin drive cam + slot drive oil pump = doesn't work

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did I tell you that I won a trophy?

Depending on what your choice of rockers is and what your compressed spring height is, 526 dual springs might be too heavy for this application on an NA motor. Have a read of this thread if you haven't already.

viewtopic.php?f=5&t=101168&start=15

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-----Better is the enemy of good-----
-1976 Yellow Devil Leyland Clubman-
-1970 Morris Mini Van - Work in progress-

If you’re talking to GR about his pistons then you could chat to him about his 266RE cam and springs to suit at the same time.

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1966 Mini Deluxe - “Gabby” 34 years under restoration and counting...
1970 MGBGT
1959 MGA

I remember there being a different number/spacing for the oil pump bolts? Or do you just use the 2 bolts?

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I put a slot drive 998 A+ pump in Joe's 1108 (68mm bore 998crank) with an A+ cam. It bolted straight in . Can't use the 1275 pump the shaft is too long and holes don't line up.

Karcraft stocks the 998 A+ pump. 3 screw mounting.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

that 2 bolt pump is 1275 - see here: https://minisport.com.au/collections/oi ... slot-drive

edit: or here, where your picture came from: https://www.minispares.com/product/Clas ... LP138.aspx

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did I tell you that I won a trophy?

The machine shop put those springs in and wasn't happy with the seat pressure at 120lbs, they took the inner springs out and that gave a seat pressure of 80lbs.
I probably could have just used the old dual springs, I think they were 60lbs seat pressure.

I went out and checked the lift on the valves, and the spring caps were touching the stem seals at around .300" so I made a tool and pushed the guides down to 14mm above the spring seat, it was at about 16mm. Thanks for pointing me to that thread, saved me some trouble later.



I think that would have been the better way to go, I have already got the other cam and hope it will be good enough for what I want
I' also got a GLP139 oil pump to go with it, it has three holes and the shorter shaft, but I won't test fit these new parts until I get this block a lot cleaner

I've been measuring my crank bearings and came up with the following numbers, not sure what to make of them.
I have a metric micrometer so had to do some conversions

Big ends
1.625"
(.020) 1.605" = 40.767mm
Measured
40.78mm
.013mm clearance
0.51 thou?

Mains
1.75
(.020) 1.73
43.942
Measured
43.95
0.012mm clearance
0.47 thou?

The crank was taken out of an unknown engine that had (0.020) bearings that looked pretty good.
I have some plastigauge to check things on assembly.

I have never done this stuff before so don't know if I am looking at things correctly. It should be more like 2 thou, not half a thou?

Did you measure the inner diameter of the assembled bearings too? From looking at the crankshaft diameters in the workshop manual it seems to me like the bearing tolerance is set with the bearing rather than the crank

Eg:
850 crank spec is 1.7505 to 1.7510”
Running clearance is 0.0005 to 0.0020”

Running clearance on the 998 engines and 1275 S is 0.0010 to 0.0027”

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ah, that explains it, I thought the clearance was set with the shaft and the bearings were made "on size" because that's how ball bearings work. I'm very much learning about putting an engine together.
I don't have an inside Mic, so won't be measuring the assembled bearings, hopefully plastigauge will be good enough

Thanks