ausmini :: View topic - 1098 Engine Project + 4 Synchro Gearbox

Can anyone give me some pointers as to compression ratios?

1) What was the C/R of a standard 998 Leyland engine? 8.5:1

2) What was the C/R of a standard 1098 out of a Mini K? 8.5:1

3) What is a good number to aim for? Depends on the cam, the bigger the cam the more you can get away with.
I'd aim for 10.0-10.5 with (say) an RE83 or RE13 cam. I run 11.0 with my RE282 cam.

I've had a go using this calculator: http://mk1-performance-conversions.co.u ... r_calc.xls and it would suggest that using:
1098 crank (83.73mm stroke)
+100 Pistons (67.088 bore)
28cc head volume
0cc piston dish
2.7cc gasket volume
0.6 ring land volume
Gives me a C/R of 10.5, which sounds usable. Hopefully the head doesn't need too much to get it smooth as it has already had a big skim.
Using a 998 crank at 76.2mm stroke gives a C/R of 9.6, which is also not too bad either?

timmy201 wrote:

Can you safely sandblast a crank or will it damage the journals?

Crank will come up fine, give it a degrease and water blast first then hit it seriously with a stiff rotary wire brush.
Followed by another degrease.

Kennomini wrote:

Can you safely sandblast a crank or will it damage the journals?

I used to get them shot blasted back in the 60s for fatigue resistance.. we'd tape the journals up first but leave the radii clear.

I think sand might be a bit aggressive, I'd maybe wrap all the journals good in tape first though and don't overdo it.

A rotary wire brush then angle grinder flap wheel would be safer.

I think you need a 1 5/16 socket. I had the same issue!

Watch those BIG 29.4mm valves clear the bores, most people limit ex valve diameter to 27mm (1-1/16") on small bore heads. It depends on your valve lift and how much the head has been decked, ie how deep the chambers are.
I guess you could notch the block if needed, but I'd fit unleaded seats and smaller valves instead. 27mm exhaust valves are plenty big for a smallbore.

If you get any modern cam grind (apart from GR's new `S clone' one) they generally come with more lift than stock. Sometimes a lot more.
If you don't deck the head much you may get away with it, ditto if you are boring it out to +.100" or so.
All I'm saying is, be aware and check it. If it was a 940 head with these exhausts, and good valve lift you would be pocketing the block to clear.

Author:	timmy201 [ Mon May 26, 2014 4:37 pm ]
Post subject:	Re: 998 and 1098 Engine Projects
Can anyone give me some pointers as to compression ratios? 1) What was the C/R of a standard 998 Leyland engine? 2) What was the C/R of a standard 1098 out of a Mini K? 3) What is a good number to aim for? I've had a go using this calculator: http://mk1-performance-conversions.co.u ... r_calc.xls and it would suggest that using: 1098 crank (83.73mm stroke) +100 Pistons (67.088 bore) 28cc head volume 0cc piston dish 2.7cc gasket volume 0.6 ring land volume Gives me a C/R of 10.5, which sounds usable. Hopefully the head doesn't need too much to get it smooth as it has already had a big skim. Using a 998 crank at 76.2mm stroke gives a C/R of 9.6, which is also not too bad either?

Author:	drmini in aust [ Mon May 26, 2014 6:58 pm ]
Post subject:	Re: 998 and 1098 Engine Projects
timmy201 wrote: Can anyone give me some pointers as to compression ratios? 1) What was the C/R of a standard 998 Leyland engine? 8.5:1 2) What was the C/R of a standard 1098 out of a Mini K? 8.5:1 3) What is a good number to aim for? Depends on the cam, the bigger the cam the more you can get away with. I'd aim for 10.0-10.5 with (say) an RE83 or RE13 cam. I run 11.0 with my RE282 cam. I've had a go using this calculator: http://mk1-performance-conversions.co.u ... r_calc.xls and it would suggest that using: 1098 crank (83.73mm stroke) +100 Pistons (67.088 bore) 28cc head volume 0cc piston dish 2.7cc gasket volume 0.6 ring land volume Gives me a C/R of 10.5, which sounds usable. Hopefully the head doesn't need too much to get it smooth as it has already had a big skim. Using a 998 crank at 76.2mm stroke gives a C/R of 9.6, which is also not too bad either?

Author:	timmy201 [ Tue May 27, 2014 9:31 am ]
Post subject:	Re: 998 and 1098 Engine Projects
drmini in aust wrote: timmy201 wrote: Can anyone give me some pointers as to compression ratios? 1) What was the C/R of a standard 998 Leyland engine? 8.5:1 2) What was the C/R of a standard 1098 out of a Mini K? 8.5:1 3) What is a good number to aim for? Depends on the cam, the bigger the cam the more you can get away with. I'd aim for 10.0-10.5 with (say) an RE83 or RE13 cam. I run 11.0 with my RE282 cam. Ok thanks. I haven't put any thoughts into a cam choice yet. I don't want it too lumpy, and seeing as I shouldn't be revving an 1100 too much, I'd like to get more low down grunt than high end revs. I had a little time in the shed this morning and I got all the pistons out of the 1098. They came out very easily, and best of all the big end bearing shells were in good nick, and the crank still had a polish on it. I can't get the crankshaft bolt undone to take off the timing cover as I don't have the right size socket.. It's bigger than 1 1/4 and smaller than 1 1/2. You can see the high tide mark on the crank Attachment: 14091699978_2be073f5c2_o.jpg But it might be ok? Attachment: 14091687938_e30c2b6d73_o.jpg I also had a bit of time to give the gearbox a quick scrub. It started off like this Attachment: 14187800525_539d8181bb_o.jpg And after. It turns over and all the teeth look fine, although there is a bit of gunk in the diff at the moment and it can be hard to turn the driveshafts occasionally. There is a lovely oil sludge at the bottom that needs a bit of a soak with degreaser to shift out Attachment: 14277916734_b203ef6056_o.jpg I was pleasantly surprised by how well the gearbox came up, as most of the orange wiped straight off. Hopefully when I get the crank out it scrubs up ok too...

Author:	drmini in aust [ Tue May 27, 2014 11:19 am ]
Post subject:	Re: 998 and 1098 Engine Projects
Crank will come up fine, give it a degrease and water blast first then hit it seriously with a stiff rotary wire brush. Followed by another degrease.

Author:	Kennomini [ Tue May 27, 2014 1:00 pm ]
Post subject:	Re: 998 and 1098 Engine Projects
Can you safely sandblast a crank or will it damage the journals?

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Author:	drmini in aust [ Tue May 27, 2014 2:22 pm ]
Post subject:	Re: 998 and 1098 Engine Projects
Kennomini wrote: Can you safely sandblast a crank or will it damage the journals? I used to get them shot blasted back in the 60s for fatigue resistance.. we'd tape the journals up first but leave the radii clear. I think sand might be a bit aggressive, I'd maybe wrap all the journals good in tape first though and don't overdo it. A rotary wire brush then angle grinder flap wheel would be safer.

Author:	Scoop [ Tue May 27, 2014 6:23 pm ]
Post subject:	Re: 998 and 1098 Engine Projects
I think you need a 1 5/16 socket. I had the same issue!

Author:	timmy201 [ Wed May 28, 2014 5:01 pm ]
Post subject:	Re: 998 and 1098 Engine Projects
drmini in aust wrote: Crank will come up fine, give it a degrease and water blast first then hit it seriously with a stiff rotary wire brush. Followed by another degrease. Yep you were right. I just need to get some more degreaser as I've used up my last batch! drmini in aust wrote: Kennomini wrote: Can you safely sandblast a crank or will it damage the journals? I used to get them shot blasted back in the 60s for fatigue resistance.. we'd tape the journals up first but leave the radii clear. I think sand might be a bit aggressive, I'd maybe wrap all the journals good in tape first though and don't overdo it. A rotary wire brush then angle grinder flap wheel would be safer. I think I might just stick with the wire brush rather than sand blasting. I'd tape the old bearings over the journals to protect the crank Scoop wrote: I think you need a 1 5/16 socket. I had the same issue! Yes I do! Luckily I was able to borrow a socket to get the crank out today. I needed a pretty long breaker bar to get it undone... Thankfully the crank ended up ok. It will probably need to be taken a size under, but I need to confirm what size it is now. The 1098 one is on the right and 998 on the left. It had +40 pistons in it already The last 998 engine was in good condition internally, and had been stored with oil in it. Unfortunately the bores have a bit of rust in them. It had definitely been apart at some stage, the lock tabs on the big ends were a bit dinged, and there were new style gaskets throughout. It was in a similar condition to the other 998, if they had been stored indoors it would have been as easy job to get them going again. At this stage I'm still not sure of the next plans for them. There is an option to pick up another 1098 for spares, which might be good even if that just yields another crank...

Author:	timmy201 [ Sat May 31, 2014 9:31 pm ]
Post subject:	Re: 998 and 1098 Engine Projects
I did some measuring today. First up was the 12G202. It was a little rusty on the bottom. It had standard 1 5/32" intake and 1" exhaust valves. It was 2.75" thick, so it hadn't been skimmed before and was completely standard. I haven't got a valve spring compressor so I couldn't get it apart. I'd already measured the 12G295 head and it was 2.67" thick, which is skimmed a fair amount. The intake valves are 1 9/32" (32.5mm), which are up from the standard 1 7/32 (31mm) The exhaust valves were 1 5/32" (29.4mm), which is up from the standard 1" (25.4mm) The valves should clean up ok Can't fit much bigger valves in there! Intake ports. Not sure if these are standard Middle exhaust port. Not sure if this is standard The oversize 295 valves compared to the standard 202 And the port size comparison. I've got them both soaking in a vinegar bath overnight so I'll be able to see how well they scrub up.

Author:	drmini in aust [ Sun Jun 01, 2014 8:06 am ]
Post subject:	Re: 998 and 1098 Engine Projects
Watch those BIG 29.4mm valves clear the bores, most people limit ex valve diameter to 27mm (1-1/16") on small bore heads. It depends on your valve lift and how much the head has been decked, ie how deep the chambers are. I guess you could notch the block if needed, but I'd fit unleaded seats and smaller valves instead. 27mm exhaust valves are plenty big for a smallbore.

Author:	timmy201 [ Sun Jun 01, 2014 8:36 pm ]
Post subject:	Re: 998 and 1098 Engine Projects
drmini in aust wrote: Watch those BIG 29.4mm valves clear the bores, most people limit ex valve diameter to 27mm (1-1/16") on small bore heads. It depends on your valve lift and how much the head has been decked, ie how deep the chambers are. I guess you could notch the block if needed, but I'd fit unleaded seats and smaller valves instead. 27mm exhaust valves are plenty big for a smallbore. Yep, I'll have to check it will all work. The head wasn't properly attached to the engine when I got it, and I have no idea if it actually ran when it was together. It's missing the valve train and most of the pushrods so I might pinch a set from the other engine to do a dry fit. Am I right in thinking that having oversize valves will mean that I don't need any extra valve lift? The chambers are still fairly deep. I hadn't thought about unleaded valve seats and putting in some smaller valves, I'll have to look into that. The heads had a soak overnight in vinegar. I gave one of the chambers a quick scrub and the gunk came right off... Port face cleaned up nicely too on the other one

Author:	drmini in aust [ Mon Jun 02, 2014 8:03 am ]
Post subject:	Re: 998 and 1098 Engine Projects
If you get any modern cam grind (apart from GR's new `S clone' one) they generally come with more lift than stock. Sometimes a lot more. If you don't deck the head much you may get away with it, ditto if you are boring it out to +.100" or so. All I'm saying is, be aware and check it. If it was a 940 head with these exhausts, and good valve lift you would be pocketing the block to clear.

Author:	timmy201 [ Tue Jun 03, 2014 10:20 pm ]
Post subject:	Re: 998 and 1098 Engine Projects
drmini in aust wrote: If you get any modern cam grind (apart from GR's new `S clone' one) they generally come with more lift than stock. Sometimes a lot more. If you don't deck the head much you may get away with it, ditto if you are boring it out to +.100" or so. All I'm saying is, be aware and check it. If it was a 940 head with these exhausts, and good valve lift you would be pocketing the block to clear. Thanks for the heads up The 295 head cleaned up nicely after another few days soaking. Most of the rust and scale came straight off with a little scrub. Top Bottom Exhaust port Intake Centre exhaust Intake Exhaust port The Red 202 cleaned up alright too. The dark bits are pitted, but would come good with a skim. The next 202 was sitting bare out in the elements. Looks like it came from the bottom of the ocean! I thought this one would only be good for scrap. After. I'm surprised by how well the head has held up! Chamber After I haven't seen many 202 heads with the cut outs on the port face? After Once I've finished cleaning and organising what I've got and what I need and I'll be able to formulate a plan... I really enjoy bringing unwanted junkyard scrap back into something presentable.

Author:	timmy201 [ Fri Jun 06, 2014 8:30 am ]
Post subject:	Re: 998 and 1098 Engine Projects
The 998 cranks are both on standard bearings. The 1098 is on +010 for big end bearings and +020 for main bearings.

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Author:	drmini in aust [ Fri Jun 06, 2014 3:55 pm ]
Post subject:	Re: 998 and 1098 Engine Projects
I'd be tempted to use a 998 crank and bore the bugger to 68mm. This will give you about 1107cc and you can rev the tits orf it, unlike any 1098. 998 cranks are pretty sturdy.