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I need help with my 998 engine problem
https://www.ausmini.com/forums/viewtopic.php?f=2&t=90605		 Page 1 of 2
Author:  gtreplica [ Wed Sep 23, 2015 6:29 pm ]
Post subject:  I need help with my 998 engine problem
Hi all, I am new to the forum, but I have been restoring my mini for the past seven years.

I need some advice from the mini gurus about an engine problem I am having.

I have a 1977 clubman with the original 998 block which I have extensively worked on. It has twin 1 and 1/4 SU's. 12G295 head skimmed, ported, etc, with double valve springs, hardened seats (run 95 octane), 1:5 roller rockers. LCB extractors, lightened flywheel, double row timing chain, 998 cooper camshaft. Electronic ignition kit on 45d dizzy with vacuum advance (from Minisport)

The engine goes strong, I have no problem sitting on 140kms on the highway, but I have real problems at times. If I am revving the guts out of it, it goes great, but as soon as the revs are low and I put my foot down it struggles, with no power, if I take my foot off and on again once or twice it then takes off. This is especially noticeable when going up a hill and changing up a gear.

I have tried almost everything, including:
Carbs rebuilt. M needles, tried blue and red springs. Correct SU dashpot oil at different amounts - makes no difference. Tuned the carbies with a synchrometer. It idles beautifully. Tried it rich and weak, still does the same thing.
Tried different timing - alot - always has the same issue, and like I said it ticks over nicely and has good power most of the time.
Tried several different coils including Lucas gold, GT40R with a ballast resistor and currently on a GT40.
Put an electronic ignition kit on the dizzy.
Tried different tappet clearances from 0.12 to 0.20.
Compression test showed 110 - 120 across all four cylinders.

Could it be the 998 cooper cam and roller rockers? I think it needs to be a bigger advance curve, and would like a stealth black box or a 123 dizzy. It is already very advanced at idle to get a good tickover, and goes strong at high revs so I'm not sure if this is the problem.

What do you guys think- help please!!!!
Author:  drmini in aust [ Wed Sep 23, 2015 7:43 pm ]
Post subject:  Re: I need help with my 998 engine problem
General comment on your spec:
I would first lose those 1.5 rockers, they really only work on big motors. No good on a 998, you just lose torque, as you have found.
Next, I would change the cam for a modern grind, say an RE266SS, or similar. A 998 Cooper cam is too tame to get decent HP.
If you want roller rockers on a 998, stick to 1.3:1 ratio.

[edit] If this problem is intermittent I would suspect a fuel flow problem. Check that first.
Author:  gtogreen1969 [ Wed Sep 23, 2015 8:18 pm ]
Post subject:  Re: I need help with my 998 engine problem
Talking Dissys
I just recently had a play with my 43D4 dissy and found that it had a slow curve and too much advance.
To get my dissy advancing faster I just took out the heavy spring.
The 43D4 dissy runs either 10deg or 14deg advance weights. Mine had the 14deg and I had to tack a weld to the tip of the stop to make it 10deg.
If you run say a 12deg static advance with the 14deg weights it will have 40deg total - too much advance at high rpms.
Some good reading here. http://mgaguru.com/mgtech/ignition/pdf/ ... s_dist.pdf
The black boxes are the way to go for $200.
Author:  IndigoBlueCooperS [ Wed Sep 23, 2015 8:53 pm ]
Post subject:  Re: I need help with my 998 engine problem
I had a similar concern on my wife's 1275 which had 1.5 rockers and an SW8 cam. No power down low.
Changed the rockers back to 1.3's and made a world of difference down low. Didn't touch anything else, just the rockers.
So change your rockers, it's an easy job, just make sure you drain the coolant first!
Author:  Minicooper4me [ Wed Sep 23, 2015 9:18 pm ]
Post subject:  Re: I need help with my 998 engine problem
I would change just one thing at a time to see what improves. Definitely change the rockers, perhaps to standard with 12 thou clearance then full tune up. Cooper cam is good. The poor little 998 just can't handle the big rockers. All the other stuff is good. Compression is down a bit, how are the valves ? Maybe the overlap of the big rockers is letting a bit of puff out the exhaust valves. Anyway, one at a time starting with the rockers.
Author:  Minicooper4me [ Wed Sep 23, 2015 9:32 pm ]
Post subject:  Re: I need help with my 998 engine problem
My engine is a 1098, twin su's, extractors, Wade 104 cam, slightly bigger valves, port/polish, 3.44 dif, cruises quietly at 100 and pulls like buggery. When on the road 15 years ago it would drag off 253 monaros easily and would give standard 1275's a hard time. Currently the body is under restoration. When I get to the engine it will have the same motor bored 60 thou and balanced, new pistons, same cam, same carbies and extractors, same diff. Will add double row timing gears, electronic dizzy, stage 3 unleaded head, flywheel slightly lightened and balanced. Should suit me.
Author:  gtreplica [ Wed Sep 23, 2015 9:56 pm ]
Post subject:  Re: I need help with my 998 engine problem
Thanks for the advice guys. I think changing out the roller rockers is the way to go, they're not cheap but.

Anyone want to swap some barely used 1.5:1 roller rockers for a 1.3:1 set????? Bought them from minisport in the UK for about $600, I see they are $900 in Oz.

Cheers......
Author:  Minicooper4me [ Wed Sep 23, 2015 10:23 pm ]
Post subject:  Re: I need help with my 998 engine problem
While waiting to get rid of the rollers, I betcha if you changed them out to standard rockers right now, you will have instant success. A hour's work is all it takes.
Author:  gtreplica [ Sun Oct 04, 2015 2:45 pm ]
Post subject:  Re: I need help with my 998 engine problem
Hi all, I want to thank you guys for your advice.

I changed the 1.5:1 roller rockers for a standard set of cooper s forged rockers, and although I did get a power increase down low - it seems a bit more torqey, I spun the wheels a few times off the lights - I still have the same problem and have developed more issues.

Problem 1:

The same thing is still happening with the throttle response, if I am at mid range revs and I put my foot down, it does not accelerate, it just sputters, when I take my foot off and on again, it will take off. It's like something gets stuck, then gives. It runs fine when revving it's guts out, and if I gradually increase the throttle it seems ok - but who wants that.

Problem 2:

The revs are now surging. When it is warm, and at idle, the revs run at about 1000rpm for 5 seconds, then down to 500rpm for 5 seconds, then up to 1000, etc. I've tried all sorts of timing, and it always does the same thing. I noticed when I was driving it on the highway today at 110kms, it felt like it was surging back and forth.

The carbies seem good, I have synched them, and the mixture seems good, but are they the problem? I have an electric fuel pump, so it should be getting ample fuel.

The dizzy seems to get extremely hot, could there be a problem with it? electonic ignition?

What timing should it be? there are no timing marks on my aftermarket flywheel, I adjust it by ear to get the best revs at idle usually, but i have tried lots of other timing. There are markers on the crankshaft pulley (see picture) but I haven't been able to fing anything to say what they represent. Someone told me that they are 4 degrees eack mark, but if that is the case then I am running close to 20 degrees at idle (timing light). This seems way too much, but if I run it at the 5 - 10 degrees recommended for 998 cooper - standard 998 clubman, then it splutters and dies.

HELP
Author:  winabbey [ Sun Oct 04, 2015 2:53 pm ]
Post subject:  Re: I need help with my 998 engine problem
Below is the late 1977 Technical Bulletin that advises the new location for the timing marks on the A Series engines.

Sorry, I don't have the knowledge to help with a diagnosis of your issues.

Attachment:
C 35_77 p1.jpg
Author:  gtreplica [ Sun Oct 04, 2015 3:42 pm ]
Post subject:  Re: I need help with my 998 engine problem
Here's some pics of my mini if anyone is interested.
Author:  Minicooper4me [ Sun Oct 04, 2015 7:07 pm ]
Post subject:  Re: I need help with my 998 engine problem
I'd go back and check a few basic items one at a time then take it for a run.
- Oil in dash pots - too thin or not enough will have them bouncing. Maybe they are sticking. Test by removing the air filters, put your finger in the hole and see if they rise steadily without sticking. Sometimes if they are sticking, loosen the 2 screws, give the dash pot a jiggle then retighten evenly then retest to see if the pots are sticking. If they are sticking, you can give the inside of the pots a rub with very fine wet and dry sandpaper in a circular motion, not up and down, then clean before reassemble. It only takes one little nick to make them stick.
- Loose or misaligned inlet manifold, could be sucking in air.
- May be over carburetted. Needles need to be as lean as possible. Try standard springs as well.
- Maybe go back to standard dizzy to test if the electronic is not up to scratch.
- Tappet clearance to around 12 thou.
- Is valve timing correct.
There are plenty of things you can do but only do one as a time as a process of elimination. Do the easy stuff first. I'm sure it will be pretty simple so solve.
Author:  drmini in aust [ Sun Oct 04, 2015 9:19 pm ]
Post subject:  Re: I need help with my 998 engine problem
I'm wondering why the dizzy is getting hot? What coil are you using? If you have points and a resistor (1.5 ohm) coil, the points will burn out faster and the coil will overheat. This gives intermittent problems like you have.
If it has points and no ballast resistor, you want a 3 ohm coil marked `12V'. Not a `use with resistor' one.
Could also be a crook condenser, it's hard to buy good ones now.

Personally I'd fling the points & condenser, and fit an electronic module; contact `convertible mini' on here. You don't need to buy a new `electronic distributor' for more $$$.
Author:  Aussie Brian [ Sun Oct 04, 2015 9:25 pm ]
Post subject:  Re: I need help with my 998 engine problem
have you tried taking it for a run without the air filter?
Author:  gtreplica [ Sun Oct 04, 2015 9:42 pm ]
Post subject:  Re: I need help with my 998 engine problem
Hi drmini, thanks for the reply. I have already fitted an electronic ignition kit to my dizzy (minisport).

With the coil, I have had lots of problems with this, I bought a Lucas gold which I figured was faulty because it misfired like crazy, there was only intermittent spark from the plugs. Then I bought a GT40R, after a while I realised it should have a ballast resistor so I bought one and when I plugged it in it misfired like crazy. So I bought a GT40 a couple of weeks ago, it seems fine, but runs extremely hot as well as the dizzy.

Do any minis have the ballast resistor wire already there? Why would it run worse with a ballast resistor on a GT40R?

Do you think that the dizzy might have been damaged by the "faulty" coils, or incorrect coils?

What would your recommendation be for coil and dizzy combination.

To Aussie Brian, I will try it without the air filter tomorrow and see if there is a difference.
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