What's in my Conquest DJ252 engine bay?

[HenryC]

When I bought the Conquest Coupe, I knew it was running very rich and was blowing somewhere around the exhaust manifold, so the first job was to take the carbs off for a clean and inspection. Having also loosened the manifolds I noticed there was oil in the inlet manifold . I was prepared to take the head off, so I did that as well.

So what have I found?
Twin Carbs are HD6 (which I knew, they should be HS6) from a 3.5 litre Regency (wihich I didn't)
Cylinder head is iron, therefore from a Conquest saloon. Looks the be in good shape but valve guides might be leaking
Cylinder bores are good with no appreciable wear, Core plug under the exhaust manifold is weeping (glad I did take the manifold off!)
Is it a Century or Conquest block / bottom end?
Compression was even at 120 -125 psi

I assume when the car was restored in Australia, the engine was created from available parts

So what to do?
I have a spare engine which would be correct for the car (Century MK1) but it has stood around for a long time and I have no idea what state it is in.
I have another block (rebored) but not sure if it it Century or Conquest? How can one tell? Is there any external difference between them - is it just the Camshaft and maybe the sump that are different?
Eventually I will build the MK1 engine up but no time at the moment

So if I put the engine back together as it was.................
Is there a modification to the valve guides to fit seals, if they are leaking
Am I ever going to be able to tune the engine satisfactorily with twin carbs, possibly with Regency needles, a Conquest head with small valves and possibly an Conquest, not Century cam.

Has anyone any experience or thoughts on sorting out such a muddle as this. Performance is not critical but good clean running is desirable. I don't want to throw money at the current mix up, as I hope to change the engine to the MK1. I know I could buy different needles for the carbs (Burlen have been helpful so far).

Puzzled, Henry

[Stan Thomas]

Hi Henry,

Firstly, as you say the Century engine should have an aluminium head, although the block is identical to the conquest. The problem is the iron head has smaller valves and a slightly lower compression ratio, so you won't gain much from having a twin carb set-up. Also, the Century camshaft was different as were the pistons I believe (but I don't have a Conquest parts book to check. Standard Century pistons are part number 305195 if someone can check).

Basically, you have either a standard Conquest engine with a twin carb manifold, or a Century engine with a Conquest iron head. If the car has a rev-counter its more likely to be a Century engine - do the registration documents tell you anything - or the engine number will identify which engine it is.

Regarding the carbs, your better off with HD6's as they do not leak and are much easier to set - and was quite an acceptable "mod" in its time. However, you will need to change the needles to T.G. - obtainable from Burlen Carburettors on 01722 334221 - but check which needles you already have they might be correct. No other carb changes are needed.

If the present engine is otherwise sound, I suggest you sort the carbs out (simple job) and use it whilst you look at the "spare" Century engine you have. If you do decide to do anything to the Century engine, it is worth having 2.5mm (0.10") planed off the head, both to ensure it is flat and to increase the compression ratio as it was designed for 80 octane fuel. If you do however, you must make up packing plates of the same thickness under the rocker stauntions to maintain the correct rocker angles.

Stan Thomas.

[Stan Thomas]

Henry,

Forgot to add, regarding valve seals, just pop six seals of anything over the inlet valves just to stop oil being sucked down the (worn) guides on overrun. No seals were fitted standard.

[Christopher Storey]

Stan : I hate to tell you this , but 2.5mm is 100 thou, which is an awful lot to take off a head . Did you really mean 0.25mm which would equate to the 10 thou you stated ?

[Stan Thomas]

Sorry Henry - a typing error - yes 100 thou (a tenth of an inch) that is using the original copper composite gasket.

The standard compression ration was 7:1 for a Conquest, and 7.75: for the Century. Given the mass of the crank and flywheel, the engine quite easily accepts anl increase in c/r but with a resultant ecconomy benefit.

Later after-market gaskets were the embossed shim type which increased the compression slightly.

[Fossil]

Henry

I appreciate the above responses to your situation because I once fitted twin HD6 SUs together with their matching inlet and exhaust manifolds to a strict Mk I Conquest iron head engine; to do so I had to elongate all the manifold stud holes with round files because the studs are further apart than on the iron head. Otherwise it was a simple conversion and worked well with the standard Century SU needles, which were as easy to tune as on a similarly equipped Century engine. I'd therefore expect the manifolds from your engine to show signs of similar adjustment; if they don't I'll be extremely puzzled. If I recall the performance of the car did improve significantly together with the fuel consumption, but these impressions were mostly subjective.

Re the findings with your car I wonder whether the original head was badly damaged in some way and the only available replacement that could be found was the iron one; alternatively the original whole engine was seriously damaged and the only available replacement was the Conquest unit. But why not swap the alloy head unless it wouldn't fit? And why the HD6 SUs unless they had been already fitted earlier?? Very mysterious and intriguing.

I don't know for sure whether there are any differences between the two blocks, but in your situation I'd be inclined to see if the alloy head from your Century engine will fit the block in the coupe, and if it does please let me know. Alternatively if you don't mind swapping the engines then do so, far better to have the complete 100 bhp engine that was originally specified than an uncertain combination of parts from both variants. Alternatively check whether the cam in the block is Century or not, and fit the correct one if not.

Of course the DJ252 had the Conquest style dash with no rev counter although I know of one example that has had the MkI Century dash fitted, and that is one mod which I think is desirable unless you are a stickler for total originality.

As far as I'm aware the sumps were the same on both Conquest and Century, although some engines have a sump with a detachable steel basechamber. I don't know whether this was a mod made a late Century engines but it may have been. I've had several Mk I Centuries over the years and a couple of Mk IIs, all of which had the standard whole alloy sump. However the engine in my current DJ256 is a factory reconditioned unit fitted in the 1970s I think, and it has the steel basechamber. It's a very convenient modification since it enables access to the main part of the sump for cleaning and inspection and to the oil pump without having to remove the entire thing. I hope these comments help, the car is fortunate to have found such a knowledgable and concerned new owner.

Does anyone know whether the alloy Century cylinder head will fit a strict Conquest engine block? Are the head stud positions the same? Also are the camshafts interchangeable? I'd like to find out in connection with the upgrade of another Conquest engined car.

Best regards

Geoff

[Pendle]

Henry,

I am away from home so I can't check this, but i believe that the Conquest Service Manual contains information which relates engine numbers to model types. If I am correct, you should be able to find the engine number on the petrol pump boss, and look up which model (strict conquest or century) that the block was installed in.

[HenryC]

Thank you for such comprehensive replies.

Stan - I too only have only the Century parts manuals. The block and iron head that were on the car appear to be in good condition. The head appears to have been ground flat fairly recently as it is still shiny in places. I think I will take your advice and reassemble the engine as it was. I will then rebuild the Century engine and fit that when I have the resources to get the engine out of the car.

Geoff - you are correct about the manifold stud holes, I wouldn't have noticed and I will bear this in mind when choosing which manifold to use when rebuilding the Century engine. I have a another spare alloy head which needs a bit of welding on the waterways. I will check this evening to see if it fits the block in the car, and that the head stud lengths are suitable. If I can get the welding done quickly, I may be tempted to fit this head but I am not sure if the existing rocker arms (from the iron head) will line up (the valves in the alloy head are separated by a bit more to allow for the bigger valve heads). Looking in the parts book, it appears that the detachable sump was available in both alloy and steel.

Chris - I know that the service manual gives engines numbers at which design changes were made but I'm not sure if Daimler allocated engine numbers in 'blocks' to different engine specs. I'm going to start another topic on this tonight.

Thanks again, I'll let you know how I get on.

[weddingcartim]

hi guys i have a spare ally head if needed

[HenryC]

Geoff,

Both the alloy head and the iron head fit onto the block in the car, so stud centres are the same. I will have a closer look at the waterway passages to see if there is an obvious difference.

The alloy head is thicker at 3.285",the iron head is 3.207". Both have been skimmed / ground, by how much I don't know.