18 replies to this topic

[Bacon]

Hello.

I'm going to bulid a fast road 998 engine over the next few months and could really do with some advice.

My buget is around the 300 mark.

My plan is to build a sreamer.

What i had in mind was.

Block pocketed to suit a 1275 head.
MG metro unleaded head,skimmed to suit.(10.1 cr)
Lightened flywheel.
SW5 cam.
1.5 su carb
Stage 1 kit.

Does this sound like a good set up,I'm not 100% sure if the cam is the right one.As I want it to be quite a high revving engine and I've been told this cam is for good for touque through the range till about 5000 rpm.

If anyone has any other ideas or can surgest any other route to go I'd really appreciate it.

Thanks,Bacon.

[Jammy]

My buget is around the 300 mark.

My plan is to build a screamer.

Something doesn't sound right there! lol

What I'd do for £300 is this:

Second hand HI38 with manifold - £30
2nd 12G295 (will give you decent rockers and double valve springs) - £50
SW5 cam (very good cam!) - dunno!
RC40 exhaust with freeflow manifold - £80ish?
Rolling road session at mini friendly garage - £60-80
Gaskets and other lil bits - £20

If you have enough left for a lightweight flywheel then thats a bonus! This will make a nice revvy, torquey 998 on a low cost. I expect Dan to comment later since he has a very similar (or did have) spec 998. Or PM him!

[Guess-Works.com]

You have got to be lucky with your purchases doing it within 300...

If you strip the engine, you may find you need new mains/bigends, possibly a crank regrind timing gear oil pump etc etc..

No point trying to build a performance engine if you are unsure of the bottom end condition.

[Bacon]

My buget is around the 300 mark.

My plan is to build a screamer.

Something doesn't sound right there! lol

What I'd do for £300 is this:

Second hand HI38 with manifold - £30
2nd 12G295 (will give you decent rockers and double valve springs) - £50
SW5 cam (very good cam!) - dunno!
RC40 exhaust with freeflow manifold - £80ish?
Rolling road session at mini friendly garage - £60-80
Gaskets and other lil bits - £20

If you have enough left for a lightweight flywheel then thats a bonus! This will make a nice revvy, torquey 998 on a low cost. I expect Dan to comment later since he has a very similar (or did have) spec 998. Or PM him!

Thanks,the only thing with that is I really want it unleaded,hence going for the MG head.I no I have to get the block pocketed but it works out cheaper doing that than getting a 12g295 head converted ,which is what i was going to do.As for performance do either of them outway each other?Also when putting a 12g295 head on do you need to skim it as it has a larger chamber size?as to bring the cr up.

I've got a stage 1 kit with a freeflow manifold knocking about so theres no cost needed for that.I also have the carb sorted.

Yeah GW. I do agree with that.I'm building up out of 2 998 engines and I have a 3rd to hand incase of any trouble I come up against.The one I'm using came out of a very low milage car and I drove the car before I removed the engine so hoping that everything bottom end and below inc gearbox will be ok.Also can you recomend a good suitable final drive.The gearbox that I was thinking of using came from a 998 early 70s car running on 10' wheels,as I want to run 10' I thought this would be suitable to use.Would I be correct in thinking this or due to an increase in performance should I change it?

Thanks again.

[stormduck]

To refurbish a 998 to completely fresh standard, without a re-bore, you're looking at nearing £150 in parts: piston rings, big end shells, main shells, gasket set, core plugs, cam followers, head gasket set, engine lube, engine paint, degreaser. Plus a flywheel puller or you'll not be getting anywhere! Add a new clutch at £60. Hopefully if the bores are okay the cam bearings will be too, otherwise that's another £30 at the engineers to get replacements fitted. After all this your £300 budget is gone!

You might be able to pick up parts 2nd hand on the cheap, but the most important thing is getting the 998 refurbished up to a good standard before thinking about improvements.

ah, i missed you're reply. In that case you've saved yourself a lot of cash as the bearings and rings should all be fine! just a new gasket set and engine lube!

The 1275 mg head will have larger valves than the 12g295 so will be a better option providing it's in good nick and not in need of refurbishing (new seats, guides etc), providing pocketing the block doesn't cost many pennies up the engineers.

How old are the engines because they may all be verto clutches, in which case a lightened flywheel with one of these won't be worth the pennies....you may have an older pre-verto with the long arm in one of them, which will be excellent if you have!

There's a book called power tuning the 998, which will be very good for you to read, i have it here but intend on selling it as i'm no longer using a 998!

[Bacon]

To refurbish a 998 to completely fresh standard, without a re-bore, you're looking at nearing £150 in parts: piston rings, big end shells, main shells, gasket set, core plugs, cam followers, head gasket set, engine lube, engine paint, degreaser. Plus a flywheel puller or you'll not be getting anywhere! Add a new clutch at £60. Hopefully if the bores are okay the cam bearings will be too, otherwise that's another £30 at the engineers to get replacements fitted. After all this your £300 budget is gone!

You might be able to pick up parts 2nd hand on the cheap, but the most important thing is getting the 998 refurbished up to a good standard before thinking about improvements.

ah, i missed you're reply. In that case you've saved yourself a lot of cash as the bearings and rings should all be fine! just a new gasket set and engine lube!

The 1275 mg head will have larger valves than the 12g295 so will be a better option providing it's in good nick and not in need of refurbishing (new seats, guides etc), providing pocketing the block doesn't cost many pennies up the engineers.

How old are the engines because they may all be verto clutches, in which case a lightened flywheel with one of these won't be worth the pennies....you may have an older pre-verto with the long arm in one of them, which will be excellent if you have!

There's a book called power tuning the 998, which will be very good for you to read, i have it here but intend on selling it as i'm no longer using a 998!

The main basis of the engine is out of an early 70s mini,with a non verto clutch.So hopefully that should fit the bill.

I've been in touch with minispeed and they will pocket the block for 75 pounds.They also said to me that they would supply a recon MG head slightly skimmed to bring the cr up to 10.1 (as needed I'm told when fitting to a 998) and pocket the block all for 225,does that sound reasonable???They said they need a head for surcharge but I have an old leaded 1275 head that I can give them.

I'm tempted to go that way as I'll no it's all be worked to suit.I can see this going over buget but I'd prefer to spend a bit more and have it wright than to cut corners and waste money in the long run.

I'd be interested in the tuning book.If you want to sell it pm me.

[Jammy]

It seems like the Metro head will be just as cheap then! And yea, unless your running domed pistons with the 12G192 I believe you'd have to get it skimmed, unless its already been done.

If your rebuilding the box then fit a competition diff pin, I wouldn't worry about doing more than that for the power you'll see.

Also, are you fitting the cam yourself?

[Guess-Works.com]

Note* if it's an original unleaded MG head, it will be the same as the 12G940 you already have, only UNLEADED MG heads had bigger valves, or those which have been converted from unleaded.

However, any 12g940 head will be a better than the std 998 head..

Also, slightly off topic, have you consulted your insurance company as per the increase of insurance, also ask them how much the upgrade to a 1275 unit will cost, you may find it to be cheaper

[miniboo]

also have a look at morspeed for engine work.

[minidaves]

Been to minispeed, well if it wsas me i would not pocket the block, and sure as hell not use an early 70's 998. YOu need to get yourself a high comp 998 kinda 88 on as these rods are suited to reving better, then basically, spend about 1k on sorting the rest out as in new pistons rebore new bearings crank polish and bearings, cam bearings (they are always knackered) a recon gearbox with uprated diff pin and a kent 256 cam, mg metro cam, and a little bit of head grinding. get either an unleaded 998 head a 12g295 or 202 and convert to unleaded and run a little less comprestion like 9,5:1.

making/building fast reliable engines costs money, and if the budget is £300 the a stage one kit is almost going to have half of that before you start

dave

[Jammy]

Hmm, think you may of missed the point slight Dave. And he said he already had a Stage 1 kit knocking around, so bar the cost of an RR session its not going to cost him anything.

A few months back I put together a 998 and lightly tuned it with the view to have a cheap engine that was bit faster and 'perkier' than standard that I could use while I was getting my other project sorted.

I don't know what Bacons situation is, but Dave is right, if you want the engine to last, you need to spend the money you have on making sure the existing internals are tip-top.

[Bacon]

Note* if it's an original unleaded MG head, it will be the same as the 12G940 you already have, only UNLEADED MG heads had bigger valves, or those which have been converted from unleaded.

However, any 12g940 head will be a better than the std 998 head..

Also, slightly off topic, have you consulted your insurance company as per the increase of insurance, also ask them how much the upgrade to a 1275 unit will cost, you may find it to be cheaper

I don't quite understand your reply.When you say 'an original unleaded MG head will be the same as a 12g940',but then you say an 'UNLEADED MG head had bigger valves or those which have been converted from unleaded'.Is there not conflict there?If an unleaded MG head is the same as a 12g940 (do you mean valve size?)then does that not mean your saying they all have large valves,which I'm sure they don't.Also in the second quote,do you mean you can't go to large valves in a leaded head and have an unleaded head conversion.I might be reading it wrong,but could you please explain.

As for the insurance,I had a 1275 a few years back on the road.But due to unforseen circumstances I wont be able to run one again for a while.I will get in contact with my my insurance company but I have a feeling they'll prefer me driving a 998.

Thanks,Bacon.

[miniboo]

yeah an original leaded mg head has bigger valves as standard so if you convert it to unleaded then it will still have the bigger valves as standard.

look in the FAQ for a guide on head valve sizes

[Bacon]

Been to minispeed, well if it wsas me i would not pocket the block, and sure as hell not use an early 70's 998. YOu need to get yourself a high comp 998 kinda 88 on as these rods are suited to reving better, then basically, spend about 1k on sorting the rest out as in new pistons rebore new bearings crank polish and bearings, cam bearings (they are always knackered) a recon gearbox with uprated diff pin and a kent 256 cam, mg metro cam, and a little bit of head grinding. get either an unleaded 998 head a 12g295 or 202 and convert to unleaded and run a little less comprestion like 9,5:1.

making/building fast reliable engines costs money, and if the budget is £300 the a stage one kit is almost going to have half of that before you start

dave

Why is pocketing the block a bad idea?

I would of liked to have gone the 12g295 route but after buying one and having it converted I just can't see it waying out.

I don't understand about paying out 1K on refurbing the rest of the engine.I understand your making a point of 'theres no point tuning a tierd engine' but I do intend in a refurd as in followers,big end shells etc.But this was never going to be a money pit engine,just a bit of a fun build really.

I agree with the 9.5to1 cr.In my old 1275 I was running 10to1 and I had alot of heating problems and I would really like this to be as reliable as possible.

yeah an original leaded mg head has bigger valves as standard so if you convert it to unleaded then it will still have the bigger valves as standard.

look in the FAQ for a guide on head valve sizes

Thanks for that.I'll have a look.

[stormduck]

I've just finished reading a keith calver article in mini world a couple of months back about fitting the large bore head to a 998. He didn't pocket the block! But instead used a different process involving re-cutting the exhaust valve seats to slightly recess the valves into the head. I can scan it in for you if you want? It seems like a cheaper option as to refurb a head you would ideally need to re-cut the seats, so then you wouldn't need the block machined at all. It should be cheaper this way. The photos show that it's the exhaust valves that would foul on the block, but by doing some work on the valves and seats, the extra clearance can be gained so that nothing hits. But your engineering place would need to do a few measurements of the head first......let me know and i'll scan it in, looks good. Also shows flow test results showing how much better the large bore head is. And you won't need to skim the head as the extra clearance between valve face and head face is needed. The compression ratio shouldn't be bad at all.......standard 998 heads have about 24cc, whereas 1275 heads have 21cc.....less space, higher compression, don't skim the head and still run 95RON and should be looking high 9s, but it would have to be worked out with measurements. I have the formula to do it in Vizard's book, jsut needs the right measurements.

oh, and the older mg heads have 35.7mm inlet valves, newer ones have 33.3mm.