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990 Cylinder Head

Posted: Sun Jan 12, 2020 7:20 pm
by Moose
Hi all,

I have acquired a 990 selectamatic with a victor cab. When I got it the engine was weather seized. Having free'd the engine and got the tractor running the next task is to replace the cracked cylinder head (see picture). The current cylinder heads part number is F906760 from what I can make out. The question is will a spare cylinder head part number F921438 be a straight swap when i atempt this repair next week? Also while I head off is there anything else I should look for?
IMG_2306.JPG
IMG_2306.JPG (30.68 KiB) Viewed 650 times
Thanks as always.

Re: 990 Cylinder Head

Posted: Mon Jan 13, 2020 5:14 am
by ollek
There are no part numbers starting with a letter F, all David Brown part numbers starts with the letter K. I think you are reading the casting numbers off the cylinder head, The head number can not be found from the head itself, you need to look in the parts catalogu. Please see the following link https://partstore.caseih.com/us/parts-s ... 6ar1246807 The head is the same in Selectamatic tractors from 1971 to 1976 and models 990, 995, 996, 1210 and 1212, all with AD 4/55 engine

Re: 990 Cylinder Head

Posted: Mon Jan 13, 2020 7:06 am
by GeoffDEAL
Hi be sure to replace the valves original ones have a habit of heads breaking off have had two motors do it but replacement valves have never done it yet, a 1200 head also fits a 1494 no difference.

Re: 990 Cylinder Head

Posted: Mon Jan 13, 2020 9:15 am
by Moose
Thanks for the replies. Sorry about the cast numbers. I believe the engine in the 990 is an AD4/49 so the question is will a head from an AD4/55 engine be a straight swap?
Thanks.

Re: 990 Cylinder Head

Posted: Mon Jan 13, 2020 10:54 am
by ollek
Earlier 990:s had a 4/49 engine and later a 4/55 engine. Please check the engine model and serial numbers. There can ber a difference in the connection betwen the water pump and the cylindr gead. A short rubber pipe or a flat O-ring.

Re: 990 Cylinder Head

Posted: Mon Jan 13, 2020 4:50 pm
by Moose
I do not have access to the tractor until the weekend but I do know that the serial number is 990A/489166 which suggests it is an early one. I know what you are saying about the water pumps. As seen in the picture above the connection is a short rubber pipe. If I understand correctly I may need to swap the waterpump to one with a flat O ring connection. Thanks for all the help I shall attempt the repair next week.

Re: 990 Cylinder Head

Posted: Mon Jan 13, 2020 6:27 pm
by TEZB
early 990's had 4/47 engine's latter one's had 4/49 engine's

Re: 990 Cylinder Head

Posted: Mon Jan 13, 2020 8:28 pm
by Scooby
Your tractor went down the track around May-June 1968. If it still has it's original engine it is a 4/47 engine.

Re: 990 Cylinder Head

Posted: Mon Jan 13, 2020 9:27 pm
by Moose
Thanks for the feedback guys. I will get some pictures at the weekend and post them.

Re: 990 Cylinder Head

Posted: Fri Jan 17, 2020 4:58 pm
by Moose
As promised.

Re: 990 Cylinder Head

Posted: Sat Jan 18, 2020 2:26 pm
by Moose
Got a picture of the ‘block’ below the alternator it appears to be blank! Although towards the circle there seems to be two overlapping zeros.

Re: 990 Cylinder Head

Posted: Wed Jan 22, 2020 5:22 pm
by Moose
Hi all just thought I would bring this to an end. Have replaced the cylinder head and got the tractor running again. I also had to replace the water pump as stated. I have attached some pictures of the cracked cylinder head. Thanks to all who helped.

Re: 990 Cylinder Head

Posted: Wed Jan 22, 2020 11:20 pm
by mc
Interesting photographs.
The original cylinder head, timing case, main frame, oil filler & serial number are correct for a 990 with AD4/47 engine. However the cylinder block has been replaced with a later type as fitted to the AD4/49 (990) & 4/55 (995/6, 1210/12). This would probably explain the lack of an engine serial number stamped into the block. This was the correct replacement as recommended by DB when the supplies of the original AD4/47 cylinder block were used up. If this is the scenario then the engine will be the same cubic capacity as the AD4/55 (100 mm bore x 4-1/2 inch stroke), but retains its original crankshaft, connecting rods & most other components.

Re: 990 Cylinder Head

Posted: Fri Jan 24, 2020 9:39 pm
by db2d
When replacing cylinder heads on early 990 and 1200 tractors with the later 962268 assembly new pistons are required because the larger valves may foul the original pistons.