Broken Alfa Nord Race Engines

Competition engines and ancillaries - general discussion
rmerrell
Posts: 33
Joined: July 8th, 2011, 11:13 am

Broken Alfa Nord Race Engines

Post by rmerrell »

Hello all - first post - be gentle! I'm looking for guidance.

Over the past couple of years I've been trying to have a race engine built for my 1969 Alfa Giulia GT that will be competitive with the Ford Escorts & Lotus Elans I race against in the Scottish Classics. It's not gone well.

The engine is a classic Alfa "Nord" twincam - 1985cc in standard form

The first engine builder included slightly oversized pistons (85mm rather than 84mm). The very first engine dyno run delivered 190bhp (a very good result) but he cracked a wet liner.

2 rebuilds later and two more cracked liners, he abandoned 85mm pistons and delivered to me a conservative (84mm pistoned) engine delivering 173bhp. He was unable to explain why the liners had cracked.

In an attempt to see if there was more in the engine (and with the builder's blessing), I put the car on the rollers at the beginning of the engine's second season. The rolling road operator was very surprised how sensitive the engine was to ignition advance and couldn't get anything more out of the engine without detonation. In fact the session ended with a blown head gasket. Advance was 42 deg max.

Cutting a long story short, the engine subsequently suffered from a cracked head (at some point through season 2) and at the beginning of season 3 a cracked liner and broken piston. A "sister" engine (same engine, same builder) has had a very similar experience.

I've now had a different builder build a new engine pretty much from scratch (carbs, distributor, cams & exhaust reused). It's just been on the rollers and lost a piston seemingly due to detonation (again). Before it failed, it too was putting out around 170bhp at 42deg max advance. It's back with the builder who will test it on his rollers after rebuild.

The spec of the engine(s) is as follows

1985cc Alfa Nord
Cosworth 11:1 CR pistons (first engine was running JE 12:1 pistons machined to reduce CR)
CR = 11.6:1 (first build was higher than this when measured - over 12:1)
Cams 320deg inlet 300deg exhaust 12mm lift
45 DCOE carbs
Head ported & flowed on flowbench
"123" electronic distributor
NGK B8EVX plugs
4-2-1 Alfaholics StSt exhaust
Fuel - UK Shell VPower 98RON?

I'm trying to get to the bottom of these issues. Nord engines cracking liners is pretty rare apparently.

I believe the issues with the first engine were mostly down to over-optimistic compression ratio. Some people have questioned the 123 distributor (including a German engine builder who delivers 200+bhp from a very similar spec engine).

I'm at a loss to understand this issue and I'm looking for guidance please as to what should be my next steps.


Thank you

Richard
Last edited by rmerrell on July 8th, 2011, 6:51 pm, edited 1 time in total.
Guy Croft
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Re: Broken Alfa Nord Race Engines

Post by Guy Croft »

As for your Alfa a very sorry story. 42 deg of ignition advance I'm not surprised it detonated. Those engines have an outrageously big combustion chamber so to get high CR you need a massive intruder on the piston and attempts to achieve that really only succeed in reducing the burn rate - which in turn means more advance is needed. Follow? Detonation can generate firing pressure 5 times the normal 1200psi + that engines have and the intensity of the event is extreme. The pressure will burst the weakest thing in its way which could well be the liners esp if overbored. Your spark plugs would not help you need to be on B9EGV at that kind of CR. Love the reference to the 'German Engine Builder'. Is there such a thing?


G
rmerrell
Posts: 33
Joined: July 8th, 2011, 11:13 am

Re: Broken Alfa Nord Race Engines

Post by rmerrell »

Thanks for the thoughts on timing and especially on the plugs. I guess what I'm trying to get to the bottom of is how people achieve the 100bhp/litre that some do (The Germans in particular), seemingly reliably, on these engines with the Nord combustion chamber. The spec is, on paper at least, correct yet we're 20-30 bhp short of where we should/could be.
Guy Croft
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Re: Broken Alfa Nord Race Engines

Post by Guy Croft »

I know those engines like an old friend.

Nothing essentially wrong with the spec except the CR is too high and 11 is perfectly adequate & the reason you are so down on power is your engine is almost certainly detonating to an extent. Non-terminal detonation saps power in case you did not know.

(Though I would just add you don't quote the carb choke size or cam FL timing which would have a bearing on peak power).

There are as many causes as the day is long - to start with search this site by the keyword 'detonation' and start reading. I have written more on this than almost anything/anyone. You will find 13 pages available.

G
rmerrell
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Joined: July 8th, 2011, 11:13 am

Re: Broken Alfa Nord Race Engines

Post by rmerrell »

Thanks again, Guy.

Carb details
Venturi dia. (mm): 36
Main jet/air jet/emulsion tube: 165/77727.7/175
Idle jet/idle tube: 50/7850.1

104 degress peak lift timing. And there's a typo above - it's 320deg duration inlet.

I'll go hunting the detonation info, thanks. I read up on it quite a bit but I've plenty to learn. The original engine builder didn't detect any detonation on his engine dyno but I'm guessing that's not to say it didn't exist. Detonation was the only mechanism we could come up with to generate the necessary forces.
rmerrell
Posts: 33
Joined: July 8th, 2011, 11:13 am

Re: Broken Alfa Nord Race Engines

Post by rmerrell »

Just a bit more information - the head gasket from an earlier failure and the power curve from the dyno run on the last failure.
Attachments
The dyno run just ahead of failure. Torque looks nice and flat
The dyno run just ahead of failure. Torque looks nice and flat
RGouldPowerCurve.jpg (64.53 KiB) Viewed 16685 times
One of the earlier headgasket failures which is clearly detonation
One of the earlier headgasket failures which is clearly detonation
gasket.jpg (137.47 KiB) Viewed 16685 times
Guy Croft
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Re: Broken Alfa Nord Race Engines

Post by Guy Croft »

You need to go up on choke size to 38 or 40mm, this is what's holding back the top-end power. Small chokes tend to give more bottom-end & mid range.

A good engine builder would have briefed you on this.

G
rmerrell
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Joined: July 8th, 2011, 11:13 am

Re: Broken Alfa Nord Race Engines

Post by rmerrell »

Great input, Guy - thanks.

Finding a good engine builder (believe it or not, I only heard about you yesterday) is easier said than done. I asked around all of my Alfa contacts (I've been driving Alfas - and a couple of Fiats - my entire driving career) and there was absolutely no concensus. The usual 105-series parts specialist weren't prepared to recommend anybody. My choice for my first race engine was based upon the recommendation of a friend & 105-series restorer. This builder is an Alfa racer himself and an automotive drivetrain consultant. My second engine has been built by a builder who has done a number of other engines of friends and has done a good job. Where we went wrong on this build was to not have the time to have the engine set-up by the builder. Living north of Inverness and managing a son who (I hope) is recovering from very serious cancer has made all of this just a shade more complicated. You live and, hopefully, learn.
WhizzMan
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Re: Broken Alfa Nord Race Engines

Post by WhizzMan »

What 123 are you using exactly? If you are using one that is not "freely programmable" you will see the 42 degrees advance at partial throttle. I don't think that is what is killing your engine, but most likely it's the pre-programmed curves in it. The 123 ignitions with the 8 selectable curves are very nice for street and "sports" engines, but if you want this much power out of a nord, I personally would use the programmable one, or not use the vacuum advance on a mechanical timer with an optical pickup system.
Book #348
rmerrell
Posts: 33
Joined: July 8th, 2011, 11:13 am

Re: Broken Alfa Nord Race Engines

Post by rmerrell »

I'm using (or was using...) the standard Nord version of the 123. Race regs only let me get away with this version because it's pre-programmed and confers no real advantage over the individual distributors it replicates. I couldn't get away with the programmable version - they are strictly banned. The 123 was the choice of the original engine builder. It's a shame that this original version came with so few curves.

I'm swapping the 123 for a standard Bosch distributor (Pertronix equipped) and resprung for race engines that we can tweek if it's too far from ideal.
Guy Croft
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Re: Broken Alfa Nord Race Engines

Post by Guy Croft »

I strongly recommend you talk to Lee at H&H Ignition about type & calibration - they are a very good & reliable supplier to GCRE about this before anything else which is by way of saying they know more than me, though it would be unreasonable ot assume they know the best curve for every engine and I always specify what I want at point of order. They are truly expert on this subject.

FWIW I cannot imagine this unit needs a curve any different from a Fiat 8V TC which is 10 deg static +/- 2 deg and peak advance anywhere from 3500 to 5500 (I would go for 3500) of 34-36 deg total (static + centrifugal). Part-throttle advance is another matter altogether those curves can look really freaky with up to 45deg at some load sites but that applies ONLY to mappable units which are calibrated off the throttle position and no way do you need one of them. Fact is during racing the thing is going want 35 deg all the time - unless you race below 3500 which I don't imagine you do. You can even lock up the distr at peak though 24v starting would likely be needed.

The amount of advance depends entirely on the burn rate. 8V units like this burn rather badly and need this amount but VERY unlikely more. Fast burn units like 4-valve heads and some 8V (like the SOHC Fiat X19 type with swirl ports) need a lot less. I am past telling folk to buy my new book but I figure you should because I explain these critical & interlocking things in the kind of detail you want and in a readable way.

{{ Agreed, Homme? (Whizzman) - you've got it haven't you?}}

G
rmerrell
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Joined: July 8th, 2011, 11:13 am

Re: Broken Alfa Nord Race Engines

Post by rmerrell »

Thanks (yet again), Guy. Don't worry - I'll be voting with my wallet and ordering your book (only found out about it and you yesterday). During my extensive & wildly varied (steelmaking, Fairy Liquid production, beer widget moulding, intranets, Rolls Royce steam-raising boilers, $40m hi-rise warehouses, blood glucose monitoring etc), I've found that problems is where you learn most. I'm really keen to learn.
WhizzMan
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Joined: August 13th, 2010, 8:05 pm
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Re: Broken Alfa Nord Race Engines

Post by WhizzMan »

I have the book, if that is what you're asking Guy.

If you're not allowed the programmable 123, probably the best alternative would be to use a simple mechanical advance mechanism. If you are allowed some form of electronic ignition to replace at least the points, you would most likely benefit from that. Guy's advice to go to H&H to get it sorted out, sounds like a good idea, if you're not looking abroad. Until then, you could just not connect the vacuum advance tube on your 123, so it won't go to extreme ignition advance angles on part throttle. You'll most likely will need to readjust your mechanical advance if you do so.
Book #348
rmerrell
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Re: Broken Alfa Nord Race Engines

Post by rmerrell »

No vacuum advance on 105-series Alfas so that's not an issue.

To Guy's point about race revs, here's a trace from a couple of years back of my (then) new race (170bhp) engine in RED versus my previous trackday/fast road (150bhp) engine in BLACK - you'll see that I ddon't run as low as 3500rpm
Attachments
Trace showing revs & accelerations (Red 09 Black 08) (see text)
Trace showing revs & accelerations (Red 09 Black 08) (see text)
08to09Comparison.jpg (170.32 KiB) Viewed 16584 times
rmerrell
Posts: 33
Joined: July 8th, 2011, 11:13 am

Re: Broken Alfa Nord Race Engines

Post by rmerrell »

I heard today from my friend/neighbour (who also has his engine from the same builder) that they've discovered "dirt in the carb" on #2 today which probably points to it running lean and detting ahead of the other cylinders.
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