Gday all... I've got a bit of a problem (possibly with my cam or carb setup) and i'm not sure whats best to do about it. We had a club dyno day last weekend and mine really failed to impress. Its a 1330 with 290 duration (wade 446b) cam (.350 valve lift on std rockers), mk1 S spec head (1.4 inlets 1.2 exhausts and ported), lightened flywheel, balanced, maniflow lcb and 45mm DCOE weber (36mm chokes, 155 main jets, can't remember the others). anyway it feels very stong and torquey at low revs and is heaps of fun to drive and all that, but it gave one of the lowest power output readings of all the 1275's in the club. supposedly this particular dyno (an MDXdyno) gives fairly low readings anyway (the dyno owner put his VY SS Crewman on there and got only 195 rwhp - should do at least 220), but anyway i got 52hp at 5200 rpm and it pretty much just died after that. for comparison, one guy with a fairly standard 1310 in his moke, with single 1 1/2 SU got 48hp. and it won't do more than 92 MPH at about 5400rpm either... (3.44 diff)
Wade say to dial in the cam at about 105*-107* but with the intention of making it more torquey it was set to 101.5*. They reckon at the recommended setting it should pull very strongly from 3000 to at least 6500rpm.
also its running a bit lean (14.7:1 through the whole rev range)
do you think getting the mixture a bit richer will help much or at all and would the fuel economy suffer much? If I retard the cam a bit will i lose much low-end drivability? I'm told that setting them up for max torque rather than max power makes them quicker on the street, but i get the feeling that with a few more revs i might not get roasted quite so easily by my mates 1.8 laser ...
any ideas?
Thanks
Geoff

1. I think it might be a bit lean- I'm now running 160 mains & 170 air correctors with 36mm chokes (in Dellorto 45).

2. What max advance are you running? Don't be afraid to play with it. Most motors with decent cams in need a fair bit of advance. I started at 32*, kept going up, and up... it's at 42* (at 4000 rpm) now! (OK- I'm running flat top pistons and scooped chambers). Yours would need less with dished pistons. If you go too far it will ping and run rough- if so back it off a bit.

3. Your valve lift is pretty low- I'd stick some 1.5:1 rockers in it.

Mine pulls like a train up to 5000 then gets the hell out of Dodge to 7500+, FAST!

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

What CR are you running? Hard to compare one capacity engine performance to another without the CR as well.

Can you post a copy of the dyno sheet? if you can't get over 5400 rpm in top, that kind of indicates that is where your peak power is. Does the dyno sheet agree? From what the Dr said, it seems like everything is happening a bit low in the rev range. if you get the revs up, you'll get more power, since power=torque x revs

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the world is a book, and those who do not travel read only a page
66 Mini Minor sponsored by http://www.lifeonthehedge.com.au/ The Dog Harness Specialists
It was a pleasure ausmini. I'll miss all you misfits and reprobates

When i was putting the engine together i put a mark at 30* on the harmonic balancer and from memory it doesn't quite get there. probably about 28* i'll have to check again. is that best fixed by increasing the static advance (doesn't that make it harder to start?), or should i look at modifying or changing the dizzy? how much difference might the advance make?
I'd like some 1.5 rockers but they seem to be very expensive, at least for the roller or roller tipped ones. can you get standard (not roller) 1.5 rockers cheap and are they any good?
It seems to go ok-ish as it is. i timed it 0-100kmh in 10.8 secs revving it to 6000rpm, before i realised that it was doing nothing after 5200, so i could probably improve on that with changing a bit earlier. and if i can get the revs working higher hopefully it will be better again...

i spose what i'm asking is can i fix the low rev limit problem with jets and timing (and maybe rockers) without redialing the cam (which i'm guessing would be a pain to do without getting the engine back out). 5200rpm seems VERY low... even my big slugger 4.0L Ford pulls pretty well to 5500...

<edit> I don't actually know what CR it has... I meant to work it out properly before putting it all back together but i didn't... will a compression test give some indication? Also, the dyno sheet shows max 52hp at 5200, then had a wavy line about 48-51hp through to about 5700rpm where they backed off

Compression test will give a vague indication, but you can't beat working it all out on paper for the static CR. Dynamic effects come into play with the test, and these are determined by more than just the swept volume.

But i have heard some of the guys here say anywhere between 140 and 170 psi for 1275-1380cc engines, but i have no idea what CR they were running. My 850 is currently about 100 psi on each cylinder, but i forgot to throw a few slugs of oil in the plug hole to make sure the rings were not stuffed. Don't think that will be a problem with yours though.

_________________
the world is a book, and those who do not travel read only a page
66 Mini Minor sponsored by http://www.lifeonthehedge.com.au/ The Dog Harness Specialists
It was a pleasure ausmini. I'll miss all you misfits and reprobates

I did a comp test before i rebuilt the engine, and the readings were 250,250,200,250 and it used to ping an awful lot - chambers were very carboned-up too. the head was all redone, so i don't know how much the chamber volume has changed, the block was faced about .005 too which might affect it.

whats the proper way to do a comp test? all plugs out or just the one being tested? full throttle? need to disconnect the fuel line?

I don't think having the plugs in or out effects the cylinder under test so much as the starters ability to turn the motor over fast enough. So given the high pressures you mentioned, three cylinders less resistance will make the starters job much easier. I was not advised to remove the others as a matter of course, so i am not entirely sure.

I have been told that you need to open the throttle fully as you turn the motor over to ensure that you don't starve the inlet side.

If you get good even compression on all cylinders, then everything appears to be fine. In your case, you had one cylinder that was low. To determine if this is because of rings, you throw a couple of slugs of oil in the plug hole to help seal the rings. If the pressure jumps back up then its the rings. If it stays low then it is a valve. If it is a pair of cylinders next to each other, it could be head gasket, but there are other more obvious signs of this.

I would expect the pressures to be around the 250 psi mark still, because unless you specified for a certain amount to be machined off the face of the head to increase compression, then the most they would give it is a light skim to ensure it is flat. Because it is a cast iron head, even that may not get done unless you specify.

Did you touch the rings at all or was it just the head?

_________________
the world is a book, and those who do not travel read only a page
66 Mini Minor sponsored by http://www.lifeonthehedge.com.au/ The Dog Harness Specialists
It was a pleasure ausmini. I'll miss all you misfits and reprobates

I don't know what advance plate is in your dizzy but mine is now running about 18* static advance, with a Pulsar D4R85 dizzy which has a 12* mech advance plate (=24* at crank). I'm running 10.4:1 C/R.
My full advance point (42*) is 44mm around the crank balancer from TDC...
Sounds a lot, but if I retard it the performance falls off a bit, all the way up.

I'm not saying yours is the same as mine, but play with it until you're happy. 3* static advance like a stock S just won't work...

<edit> re the 1.5 rockers- there are alternatives to `bling bling' anodised rollers which you can't see anyhow:-
I run the 1.5 forged ones, cost me 90 quid from MiniSpares UK a while back.
You can also use RWD Corolla forged rockers if you make some rocker posts to suit, or butcher the Corolla ones. I rebuilt a 1380 race motor that had them.
Or fit offset bushes to some pressed steel or S rockers- gives around 1.4:1. Probably need to make the bushes though- MiniSpares don't stock them now.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

it was a full rebuild, just used the old pistons since they were almost new anyway. The head was completely done over as i mentioned, including reshaping the chambers a bit so it may be changed??? also as i was saying the chambers had a thick layer of carbon everywhere, so i would imagine that would decrease the overall volume in there and raise compression, maybe???
the rebuild included improvements on just about everything, cam, carb, head, exhaust, flywheel etc so i'd have thought it would be making more power than it is... but i spose if i fix the low rev limit, the power output might fix itself...


I can 't remember what we set the static advance to, but I'll see what its like with some advancing... then with some bigger jets (aim at around 13:1 like i've read?) we might be getting somewhere. I'm wondering if it may not be worth worrying about getting too high in the revs (retarding the cam) before i look at the bigger rockers anyway. that .350 lift probably isn't good enough for big revs is it?
The other thing is i'm still using the original exhaust after the maniflow lcb. 1 5/8" pipe and i have no idea what sort of muffler it is, so maybe a 1 3/4" with a decent straight-through muffler might help too...

here it is... its an MDXdyno (i haven't heard of them before). Its a little bit strange in that you have to figure out where the 'real' readings start... i'm guessing its about 62kmh on this graph, also the torque figure they quote on the bottom is the torque being produced at max power, which i wouldn't have thought was very useful information, max torque would be better

You will find the 1.5 rockers help breathing a lot on a 1380. They made a hell of a difference to my 1310.
Just remember to open up the valve clearace by .003" when you fit them, unless your cam is designed for 1.5 rockers. I'm running .020" on mine with a Graham Russell RE13 cam.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.