Abarth engine upgrades

[wmausbach]

Depending on the rules a 1608 will produce about 160 hp with 12.5 Cr, Webers, and full race cams, likewise an 1756 will produce about 180 hp with a 2 liter about 200 hp. I seen various dyno sheets with these numbers on various race engines. This is about 100 hp per liter which is a good bench mark for two valve engines non-supercharged. Most of the SCCA-NASA engines
exceed these numbers now.

All the discussions have been for street engines.
Wayne

[MrJD]

Wayne:

some of the higher "race" hp numbers are using the Uber rare Abarth 16 valve heads though right? I was under the impression 150-180 was about all Abarth ever coaxed from the 8 valve head.

I'm not trying to be a pain here, just trying to learn more about these engines, so bear with me... trying to establish the winning formula for a good long lived yet hot street engine.

2ltr block and
2ltr head (less shrouding) with larger valves and a bit of porting/polishing (my understanding is that no other head is better, thought I did read the 1.6 has some benefits)
Cams (upper level "stage 2" or "street/strip" style) (~$400)
10.5:1 compression pistons (~$350)
Stock rods, maybe shot peened (shot peening is never a bad idea, i've even seen guys go so far as cryo treating also to keep from paying up for forged units)
Good free flowing exhaust system (2.5" was preferred on the toyotas I am familiar with... being 1.6-2.0 engines. We also went with 4-1 long tube headers over the 4-2-1 variants. I'd assume this is also applicable to these engines?)

and on to my main question:

Intake: for a carb, dual IDF's... but 40 vs 44? Clearly the 44's will breath better at 6k+, but i doubt they will run as well around town. Also, is a 2.0 with stock rods going to behave itself at 6k+ (my guess is you'd really have to take your time balancing the crank)? I'd think the 40's would actually make more useable power (better low end torque) at normal RPM due to their slightly higher velocity charge.

[djape1977]

stock konrods will do the job

[Daniel]

and on to my main question:

Intake: for a carb, dual IDF's... but 40 vs 44? Clearly the 44's will breath better at 6k+, but i doubt they will run as well around town. Also, is a 2.0 with stock rods going to behave itself at 6k+ (my guess is you'd really have to take your time balancing the crank)? I'd think the 40's would actually make more useable power (better low end torque) at normal RPM due to their slightly higher velocity charge.
MrJD

If your running an 1800 or 2L with mild to maybe larger street cams good flow on both ends I'd say
44s all the way, the notion that they can't be tuned to be streetable is all myth. 44s arent overly
big and you can run 34-36mm Chokes which would be perfect for a good street engine. The Cams
will be more of a RPM vs Torque output at low speeds deal breaker.

[sptcoupe]

I agree 100%. There are zero disadvantages going with 44s. The coupe, with GC 3A cams and 44s plus all the other tricks has a ton of torque and HP, runs perfectly smoothly. 44s are the right choice for a fully developed 2.0L full house street motor. You can also get a lot of tuning flexibility because you can use an F9 emulsion tube with better results on the 44s, and if you want more low end torque, you can use 34mm chokes. If you are going to spend the money to let it breath to the max, then get the most out of your carbs, as well. Remember, the stock euro 1608s with a mild cam came with 40s. Your 2.0L is 25% larger and will breath way better if you do what you are contemplating. Go for the 44s.

[131]

I couldn't find a copy of the chart I was looking for, but it's Fig. 32 on this page:
http://www.webercarburatori.com/?p=handbook&s=2
A 1600 at 6k/rpm lands on the chart with 32mm venturies, which is what the factory fitted. A 2 litre at 6k/rpm has a 37mm venturi indicated, which you can't fit to 40mm carbs. If you're going to the trouble of making the head breathe, you may as well fit carbs that will do it justice. If you're not going to drive it passed 4k/rpm, don't bother, fit 40s.

[MrJD]

So what diameter exhaust tubing is recommended for such a preparation? I assume 2.25" or 2.5" but I saw 2" mentioned elsewhere... though that sounds restrictive for a 2.0ltr car.

[131]

So what diameter exhaust tubing is recommended for such a preparation?

I've got 2" on mine, I wish I'd gone 2.25".

[divace73]

So what diameter exhaust tubing is recommended for such a preparation?

I've got 2" on mine, I wish I'd gone 2.25".

I had 2" with straight muffler and resonator on mine and found it too loud (for the road anyway), what mufflers / resonators will you be running, I have to look at mine soon again don't know if I should increase it?

[131]

The bloke that did mine initially put a 16" oval at the front, but it was too loud, so he put a hotdog after the rearaxle to tone it down a bit. It's still loud, but I like it, the kids reckon they can hear me before I turn in to our street, our house is 400m from the corner. When I got the new car, my neighbour complained that his alarm clock had stopped, the exhaust on the other car would wake him every weekday at 6:35 as I left for work. Hopefully the weather is favourable this weekend so I can get the head, cams, carbs and exhaust swapped over, all on the pretext to management that I have to cure an oil leak.

[wmausbach]

MrJD,
We have gotten off subject alittle bit. I'll try to answer all your questions as you appear to be new to the wonderful world of the Lampredi 124 motor with documentmended facts and then throw in my opinions. I have over thirty years with owning, racing and building these engines but I do not consider myself an expert but I'll quote those that are.

First to give a little history as you have a lot of the data mixed up. All the hp numbers I have been quoting are for the Two Valve 124 engine designed by Aurelio Lampredi not the 4 valve. However to clarify I will give a brief history of both.
Fiat started getting interested in ralling in the late 60's early 70's. The competion numbers are from the factory racing teams. These are the racing history
Year Model Engine size Valves Fuel Del HP
1970 124 spider 1608 8 valve Carb 160 hp
1972 124 Abarth Rally 1756 8 Valve Carb 176 hp
1974 Lancia Beta Cpe 1756 8 valve Carb 180 hp
1975 124 Abarth Rally 1850 16 Valve Carb 190 hp
1976 124 Abarth Rally 1850 16 Valve F.I. 210 hp
1976 131 Abarth Rally 1995 16 Valve Carb 210 hp
1978 131 Abarth Rally 1995 16 Valve F.I. 230 hp
This is all the naturally aspirated engines as Fiat went the route of supercharging and then turbcharging. The current issue of "Auto Italia" English magazine has a good article on an 124 Abarth Rally that has been raced it's whole life. It was recently given a Abarth 4 valve head prepared by Guy Croft (One of the experts). (Issue 214-December 2013)

For general info the Abarth Strada 130TC had 130hp with a 2liter NA but the 1988 Lancia Intergrale had 185hp with a
intercooled Turbo 2 liter for the highest hp factory street car with two valve head design. In competion this was bumped to 270hp.
The highest dynoed hp NA is Bill McDanial's NASA sanctioned spider at 205 hp. This car has 48 mm Webers, 46 mm valves and 13.5 compression ratio. He is now going the VX path.

This info comes from two books, Twin-cam Italia by Phil Ward and The Guy Croft Workshop manual (first edition)
Both should be bought for the serious student. Next will be answers to your build questions. Enough for tonight.
Wayne