A series budget engine rebuild

[garellikatia]

So curiosity got the better of me and whilst I'm waiting to sort pistons, the block machined etc... I decided to trial fit a 1275 head to my 998 engine currently in the car

My DTI was measuring valve lift on the exhaust valves

and I compared that to the valve to head surface depth on the 1275 head and there's enough clearance.

I'm going to dry fit the head without a head gasket and turn it over manually first to make sure. 😯  😂  ill stick some of my kids playdough in there to see if the valves clearance 

It will probably lose me some torque due to less port velocity bottom end but give me a bit more top end as its better flowed ports etc... 

[Stinkwheel]

Whats that inlet manifold you have there? Look slike a fancy aftermarket jobbie

[Merryck]

I haven't been able to find those pistons. I did some from the Midget, but if you're going oversize those won't be of any use to you I assume? If they could be useful I'll dig the rest out and take photos.

Really don't know where my other set have gone, I recall them being oversize. Fuck knows how I've lost them.

Too much shite I guess.

[MiniMinorMk3]

1 hour ago, garellikatia said:

I'm going to dry fit the head without a head gasket and turn it over manually first to make sure. 😯  😂  ill stick some of my kids playdough in there to see if the valves clearance 

It will probably lose me some torque due to less port velocity bottom end but give me a bit more top end as its better flowed ports etc... 

 

 

But how often do you think you will be reving the engine to the max? If you building for road use then low down torque is far better than all out power as this is where you will be using the engine most. There's nothing worse than having an A-series that's all top end power and no bottom end torque. You'll be riding the clutch trying to get away from the lights and everyone will look at you going "Look at that boy racer thinking he is Paddy Hopkirk". 

1 hour ago, Stinkwheel said:

Whats that inlet manifold you have there? Look slike a fancy aftermarket jobbie

That inlet manifold is an old Mitchum Motors one. They were a shop based in Mitchum back in the olden days. It is one of the worst after market single carb manifolds you can get because of it's log type design. It has right angled bands in it which do not help flow.

Here's what David Vizard found out when he flow tested a bunch of manifolds for his Tuning BLs A-Series Engine book.

The ones sold by MiniSpares and Mini Sport today are very similar the the Howley manifolds.

[garellikatia]

On 05/11/2024 at 12:28, Merryck said:

I haven't been able to find those pistons. I did some from the Midget, but if you're going oversize those won't be of any use to you I assume? If they could be useful I'll dig the rest out and take photos.

Really don't know where my other set have gone, I recall them being oversize. Fuck knows how I've lost them.

Too much shite I guess.

Ahh thanks for looking I appreciate that. I've bought some oversize 0.040 ones from Greece. Hopefully as I've already paid vat and its under £139 I shouldn't get nailed with any extra charges.

[garellikatia]

On 05/11/2024 at 13:02, MiniMinorMk3 said:

But how often do you think you will be reving the engine to the max? If you building for road use then low down torque is far better than all out power as this is where you will be using the engine most. There's nothing worse than having an A-series that's all top end power and no bottom end torque. You'll be riding the clutch trying to get away from the lights and everyone will look at you going "Look at that boy racer thinking he is Paddy Hopkirk". 

That inlet manifold is an old Mitchum Motors one. They were a shop based in Mitchum back in the olden days. It is one of the worst after market single carb manifolds you can get because of it's log type design. It has right angled bands in it which do not help flow.

Here's what David Vizard found out when he flow tested a bunch of manifolds for his Tuning BLs A-Series Engine book.

The ones sold by MiniSpares and Mini Sport today are very similar the the Howley manifolds.

Thanks for that info, I've actually been meaning to change it for a while. Luckily I picked up  one for £15 posted On FB. 

Just going to clean it up a bit 

[garellikatia]

As much as I'm inclined to agree with the above statements,  I'm still keen to Try the 1275 head. If it's really bad, I'll pocket the block and change the cam. 

I have chucked the 1275 head on after my calculations. But the valves still glanced the block without a head gasket. This was with my worn 998 rocker set. I then changed the rockers for less worn ones. 

I then adjusted the valve clearances and now they clear. I turned it over by hand and it doesn't sound like it's hitting. 

I also turned it over on the starter and it's spinning freely and all the valves seem to be moving fine. 

Unsure how that happened.  Maybe a stroke of luck ,pardon the pun. I will add a head gasket too so that should give me a bit more safety margin.

 

 

I'm just waiting for my pistons to turn up now so I can get the 1098 rebored by 0.040. As thats all i could get my hands on. 

 

I'm not promoting this business but look how cheap these prices are for machine work. It would still work out cheaper to drive there and back from Hull. 

 

http://www.specialisedengines.co.uk/machining-services

 

[Stinkwheel]

Those machine shop prices are RIDICULOUSLY cheap - as you say, almost worth driving up there

[garellikatia]

1 hour ago, Stinkwheel said:

Those machine shop prices are RIDICULOUSLY cheap - as you say, almost worth driving up there

Exactly. My old man goes down there frequently too. It's almost too good to be true. 

 

[garellikatia]

So as I fit the 1275 head I had to file a little bit off the water pump. Fit  a smaller water pump pulley and radiator bracket. 

I also had to pocket the block ever so slightly as the valves just glanced the block and I was worried they'd hit  hard when warm and expanded. 

It was a lot of messing about but in hindsight I've flushed out the coolant system and tended to some rust behind the radiator. So if it's all in vain at least I've done something productive in that sense. 

I know the reliefs are very crude but compression is fine and the top rings don't catch or are exposed. So I'm happy. 

I certainly wouldn't have done it if I didn't have a spare block. 😂 

 

[garellikatia]

So I've had a nightmare haha. On reassembling I'm not getting fuel to the cylinders now. I guess this could be a number things but now the carb is off ready to see what it could be. 

 

The floats getting fuel but just not the cylinders so they must be either a blockage or an air leak. 

Compression is also on the low side now around 80-100 PSI. 

Damn it. Spoke too soon haha

[Stinkwheel]

17 hours ago, garellikatia said:

So I've had a nightmare haha. On reassembling I'm not getting fuel to the cylinders now. I guess this could be a number things but now the carb is off ready to see what it could be. 

 

The floats getting fuel but just not the cylinders so they must be either a blockage or an air leak. 

Compression is also on the low side now around 80-100 PSI. 

Damn it. Spoke too soon haha

Its all a learning process mate and at least you have a spare block etc

[garellikatia]

3 hours ago, Stinkwheel said:

Its all a learning process mate and at least you have a spare block etc

Thanks mate, I have learnt a lot.

 

I'm going to chuck a small bit of fuel down the carb throat to see if that solves anything, and I'll have a little fettled here and there. 

 

I'm not losing any sleep over it though. I will probably just concentrate on getting the spare engine sorted.

[garellikatia]

Quick update.

So I've sorted the head and got it running. Not sure what it was exactly. But had to:

Refit head and all gaskets

Strip and clean carb. 

Adjust timing.

 

I still feel its running a tad too rich and is juddering subtly when driving. Almost like a slight miss fire. 

Going to adjust valve clearances and go from there. But it does run and picks up well with no flat spots. 

To conclude the car pulls slightly better in 1st then the same In 2nd. In 3rd around 2500 rpm it pulls a lot better and feels as though it hits a real sweet spot, then in 4th it really opens up and can easily power through to 60, 70 smoothly. 

 

Would I recommend the head on a 998? 

Possibly with a better cam but with a 998 standard cam, the increase in the mid to top end doesn't seem worth the effort as mentioned by     @MiniMinorMk3

So   unless you spend a lot of time on A roads. Might be nice when commuting to work along then A15, but it remains to be seen haha.

Was still worth the experiment and glad I did it. 

[garellikatia]

In other news I removed the oil core plugs on the 1098, something I neglected to do. Drilled an m8 hole then pushed a rod through to knock the other one out. 

I've got some cloth roll I will push through on a threaded rod like a "pull through" similar to how we clean a rifle barrels. 

My pistons will be arriving from Greece on Wednesday so hopefully I will get them and the block to the machine shop on Thursday to be bored +0.040 taking the displacement to 1115cc 

 

Measured the crank journals and they're within the tolerances and not needing a grind. With advice from theminiforum. Which is nearly £200 saved. 

 

[MiniMinorMk3]

36 minutes ago, garellikatia said:

 

I still feel its running a tad too rich and is juddering subtly when driving. Almost like a slight miss fire. 

 

Have you adjusted the mixture on both idle and fast idle?

24 minutes ago, garellikatia said:

 

My pistons will be arriving from Greece on Wednesday so hopefully I will get them and the block to the machine shop on Thursday to be bored +0.040 taking the displacement to 1115cc 

 

+0.040 on an 1098cc will take the displacement to 1132cc. Standard bore is 2.543 in and stroke is 3.30 in. 

 

[garellikatia]

On 18/11/2024 at 14:44, MiniMinorMk3 said:

Have you adjusted the mixture on both idle and fast idle?

+0.040 on an 1098cc will take the displacement to 1132cc. Standard bore is 2.543 in and stroke is 3.30 in. 

 

 

ah yes of course,  haha 1115 for +0.020  1132 for +0.040

I was half way through doing so with my colourtune (setting idle at least) when it seemed to pack up.

I've bought a wideband gauge which will be coming next week so I'll get that fitted to give me an accurate reading especially under load where a colour tune couldn't do. 

My timing light also fell apart so I need to get another one of those sorted. Guess I've not used them in that long so they've suddenly given up haha. 

I'm also contemplating the ABY needle as the AAA needle I have atm will be far too rich as its ordinary more akin to big bore engines. 

Looking at the profile it seems Leanish low end then richens up nicely top end which would probably suit. 

All a load of experimentation at the minute but just glad to be getting stuck back into the mini and tinkering. 

[MiniMinorMk3]

There's a good needle comparison chart here

Mintylamb SU Needle Compare-o-rama

[2flags]

Fettling and tinkering is how to get the best from these. Swop out needles, adjust the timing slightly, adjust the mixture.  Keep at it, I'm sure you'll soon have her running sweetly. 

[garellikatia]

2 hours ago, MiniMinorMk3 said:

There's a good needle comparison chart here

Mintylamb SU Needle Compare-o-rama

Excellent thanks, I'll probably end up buying a few and seeing what works best 

[garellikatia]

1 hour ago, 2flags said:

Fettling and tinkering is how to get the best from these. Swop out needles, adjust the timing slightly, adjust the mixture.  Keep at it, I'm sure you'll soon have her running sweetly. 

Absolutely, I find that bit quite rewarding too. When it actually runs nice! Worth the  cold nights In the garage hehe

[garellikatia]

As the winter snap is coming I decided to try out the indoor car bubble I got cheap from demon tweeks.

Really impressed and perfect size. Although I was rushing as I needed to take the kids to swimming so it's all lop sided haha

I'm going to build a pvc tubed frame to hold it up so I can drive in and out and keep it up. When I need to work on it I'll just have to pull it out and store it in the bag it came in.  It looks too tight but that's just how I drove on to it. 

[garellikatia]

Pistons arrived from Greece today. 

Spoke to the machine shop and they've now said as it's +0.0040" rebore, it will be £25+  VAT per cylinder and then a bit more on top of that because they will have to do a second cut.

I'll drop the block off tomorrow and work out the price worst case scenario because I'm not keen on just guessing what the end price will be. 

 

[High Jetter]

4 thou is tiny tho?

[Mr Pastry]

4 minutes ago, High Jetter said:

4 thou is tiny tho?

I think it's 40 thou. 

[garellikatia]

Oh yea 40 thou hahaha can you  tell I'm a metric kid. 1.016 millimetres roughly.... 😂 

[High Jetter]

11 minutes ago, Mr Pastry said:

I think it's 40 thou. 

Yep, major fail here.