small Gull Blocks & Heads

[blackdoggie]

Hi all, probably another dumb question but I haven't found what I was looking for by searching...and my Clymer has no answers... so once again I want to tap into your collective (or individual) wisdom

Are there two types of block and head for small seagulls (40 series)? The reason I ask is that I've come across a small seagull block that seems to have the correct bore length and diameter (piston fits), exhaust and water ways in the same place but the carb mounting flange/induction bracket on the block body is not in the centre of the block as it is on my other 3 40+ gulls, its towards the edge/side. It looks if anything 'younger'. Did Seagull alter the 40+ block over time?

Also, did some gulls have screws rather than bolts securing the head? I'm trying to work out if these are original features or something that has been buggered about with? (that is more buggered about with than is desirable)

confused

Ken

[blackdoggie]

OK I spent my lunch hour searching through old threadz without any luck so I've been into the garage to carry out further investigation..... the block is clearly a 64cc block and appears totally interchangeable with the other 40 series I have but it differs insofar as:-
1) the induction port enters to the side of the cylinder rather than in the middle. This may be to get gases to swirl or vortex into the crankcase. Would this seem to be an attempt to improve aspiration?
2) the exhaust port has a divider so it is split into two. this may be common but I haven't got similar on my other blocks which have just a single wide port.
3) the waterway prior to exiting the block is one long channel whereas on my other blocks there is a bridge halfway along the channel.
4) the block base has studs with nuts to mate with the crankcase instead of bolts as my others have

Can anyone advise if this is either an older type of block or a more recent type? Its in pretty good nick and once I get the waterways and the mating faces cleaned up I'll use it in my rebuild but I'm just curious about why the design altered and if one type was found to be more efficient that the other?

Ken

[blackdoggie]

OK, not getting far...........maybe photos will help

piston crowns

as you can see two almost identical pistons but the crowns are markedly different. Its the one on the right that is different from those I am used to seeing. In addition the ring locators are differently aligned

Blocks

Two almost identical blocks but the exhaust porting is different, the flange that mates with the crankcase is longer on the right hand block, the inlet port is located so as to enter the cylinder at the side (see below) and the waterways are slightly different on the right hand block

inlet port

OK, here we have 3 blocks, the two on the left are identical and have BRITISH SEAGULL in raised letters on the block, the right hand block doesn't

logo

incidently, the right hand piston goes with the right hand block, it looks seagull, they seem interchangeble and fit, but are different from what I am used to seeing. Can someone please tell me if the right hand block and piston are seagull and if so, more or less when would they have been in production?
Ken

[charlesp]

Yes it's a Seagull block. Nobody as far as I know made copies or even anything similar.

Can you give us serial numbers from the actual engines?

As a general rule British Seagull did try to improve things after the first introduction of a motor. Sadly that improvement seems usually to have been about a reduction in production costs, right up until the latter days when a genuine search for efficiency was the order of the day.

[blackdoggie]

thanks Charlesp, can't be sure about engine no's - the leftmost block was from a bitsa job that had a seized 40+ gearbox and a seized block/piston but had a 40- crankcase so it could have been anything really (well it was free!). The crankcase no was FI954D0 which made it 1970. The middle block came off a 40+ FP433KK5 which made it 1975, it appeared OK but the waterways were totally concreted up and it was many a year since water had flowed. It was in poorish condition. The right hand block I bought as a 40+ but have no idea of the engine no or year of manufacture.

I have one reasonably sound gull FP616N9 and have been trying to put together one really good gull from all the best bits and I'm just about ready to put it all together now.

inlet ports

this shows the differing port alignment and also that the port is smaller in diameter on the right hand block

water channels

this pic also shows damage (a chip) to the leftmost block around the nearside of the cylinder lip that sits inside the head. That damage is the reason I looked for a 'good' block since when I put it together I want it to work well for a long time.

Ken

[Charles uk]

Ken I have not done any research work on the permutations of 40 series cylinders as I have never considered "improving" one.

The bridged exhaust version looks to be the earliest one of the three, as it probably had the highest scrap factor during production. An unwelcome attribute for any component!

The piston ring locating pin locations will relate to the port positions to prevent the ring ends entering the ports.

As you've started this quest perhaps you should buy & strip at least one of every 64cc model & measure all the changes,
Port duration in degrees,
Port height, width, corner radius,
Bridged,
Inlet port location.

There's a year's work & a heap of spending & maybe 10 people will be interested, & you wonder why no one's done it before!

[blackdoggie]

Oh My God, thanks Charles uk....I think
Interesting that you do not indicate any surprise at there being quite a variation on the blocks. I erroneously had thought that they would all be just about the same as I (again erroneously) thought that they would all be interchangeable but clearly if ports are different and piston ring locators have to match the ports then that is not quite the case. Glad you've put me right on that matter
That you think the bridged right hand block is earlier is also very interesting as I had thought it might have been an evolution. That block also has the narrower diametered inlet port to the side and the deeper crankcase flange. I had thought that this might be a revision but equally it also could have been an earlier experiment that for good reason (presently unknown) that came to nothing. What surprised me most was that the name was omitted from the side of the block.
The block and piston look perfectly fine but if the design was dropped for a design flaw reason I'd love to know before I include it in my rebuild.
I'm not sure I'd be technically able to compile the sort of detailed analysis of the block as you noted and I'm certainly sure I couldn't afford to get an example of every 64cc model, I take it then that Seagull were relaxed in their specifications and record keeping?
My interest was not in 'improving' the seagull engine, but merely to understand better, put together a very good clean example that will outlive me with care and in so doing learn how to maintain it properly. It does rather take over though!

Ken