wanted douglas cylinder head

[vicplummer]

Hi im Vic i live at the goldcoast qld Aust and im chasing a 1928 or 1929 dt douglas type 1 front cylinder head any condition.you can contact me on 0402310578 or 0432060459 or email me using the email or PM links to the left anytime thanks

[Dave]

Hi Vic and welcome to the forum. I modified your email address to refer to the links underneath your name to the left. There are "bots" that scan web pages looking for email links. When they find one, the address is added to a list and deluged with spam. Using the links to the left helps reduce this problem as they are only visible to members. Hope you are successful in your search for a head.

Dave

[Alan Cun]

Hello Vic, After a quick look in the shed at my DT heads I do have a surplus of front heads however they are for the 600 DT. Is it a 500 cc or 600 cc you are after. I will have a closer look when I get a chance as I know there was a 500 and a 350 barrel. If I have what you want I will be down for the Pine Rivers Motor Cycle only Swap at the end of June.        regards Alan

PS you could also take a trip out to Nerang and see my old mate Ray Owen who is doing a DT (however he does spend a lot of time in Victoria chasing Gold

[Alan Cun]

Hello All, Hope I can be excused if I appear to be replying to my own submission however I have been contacted by Vic by personal email and will be able to set him up with the required head and maybe other items.

The reason also for this response is to clarify what I got wrong. The 500 and 600 heads are the same. A quick trip out to the shed proved that the copper head gasket does in fact fit the heads and 500 barrels.    Alan

[Doug]

Alan,

Something does not sound right there. The 62mm bore barrels (500cc) should have a head gasket 2.75" diameter to the inner edge of the ring groove. The 68mm bore barrels (600cc) should have a 3.156" diameter to the inner edge of the ring groove. Visually a quick check is the 600cc barrels/heads have the ring groove right out adjacent to the holes for the cylinder hold down studs, and the 500cc the groove is well inboard (all shared the same cylinder stud pattern.)

I have seen a number of 500cc heads and barrels with two sets of grooves; quite a number to suggest more than just an individual or two modifying 500cc parts to use on a 600. While I have only seen 500cc DT heads, I have compared the combustion chambers and ports to the later 600cc heads with enclosed valve gear. They are identical, except that the 600cc heads were more circular, and the assumption would be the 600cc DT was the same. The 500cc combustion chamber is slightly elliptical, as greater width was needed in the one axis to accommodate the valves.

-Doug

[Alan Cun]

Yes Doug, Once again you are right. I went to bed last night running my statement through my brain, and it occurred then that the hemisperical combustion chamber on the 600 must have a 68 diamter compared to the 62 of the 500. Another trip to the shed and yes the 600 valve seats go almost to the sealing ring. So a 600 head on a 500 barrell would certainly result in the valve strking the top of the bore. Back to my original statement A500 head would be needed. I did notice however in the past I have bored out 500 barrells to 66.Being a through bolted motor the thinness of the barrell base wouldn't be a problem. Anyway this would probably allow the use of 600 heads. I did this many years ago and never used. My 600 DT motors have all been bored out to 70 to take Kawasaki pistons as have my 600 EW and E 29. I also noticed on OC OB heads the valves dont come as close to the sealing gasket. regards Alan

[Doug]

Alan,

The 500 barrels are relieved (cut-away) ever so slightly at two points to clear the valves, where as the 68mm bore of the 600cc does not need this. After a re-bore or two, this valve relief on the 500cc barrel disappears.

The OC heads have a included valve angle of 90 degrees, where as the DT has an included angle of 82 degrees (and I have seen one or two at 80.) Nominally this would place the valves of the earlier engine closer to the cylinder wall. BUT, the valves of the earlier engines intersect at the head joint surface, whereas the DT and ilk the point of intersection is down in the cylinder itself. I can not recall the exact amount off the top of my head, but it is something a little over a quarter of an inch. So that makes the later heads with the narrower included angles between the valves, the ones that are a close fit in the 62.25mm bore of the long-stroke DT 500.

-Doug