2nd 8v build: The search for torque

[London_Alfa]

Hello Alfisti

Recently built a 1.7 twin carb engine. There were 2 mods;

Higher Compression pistons (11:1)
Colombo Bariani ***.112.280S cams with 280 degree and 11.2 lift

I am starting to wish I kept the original cams because that instantaneous torque (from 800 rpm) is now a thing of the past. In fact torque is very poor below 4000 rpm. I have lost the original beauty of the twin carb 1.7 8v engine with its immediate torque and it is now more like a 16v.

I've decided to rethink and rework my heads:


Go back to the original cams
Have the heads gas flowed and ported
Change to 44 idf carbs
Maybe use AH Motorsports big valve race pack

Does any one have experience with this? Will any of the mods i'm thinking of above reduce low end torque just like the cams? It's a street car and hp above 4000 rpm is annoying to use. I want the power from 1000 rpm.

[Serpent33]

I use the above cams and have no problem. Not much torque is lost. Pls chk cam timing. These cams should come marked if for the mechanical tappets. High comp pistons are for ppl that really know what they are doing. Replace stock 8v piston first. You may not have sufficient ignition advance due to your high comp. Resulting in super sluggish engine. I don't think your high end is very impressive either. How's the temperature?

[London_Alfa]

Engine is definitely timed up perfectly. The block and the head were cc'd and the compression ratio is definitely no more than 11:1. Vacuum advance is working fine.

Despite these things the car hasn't been to the rolling road yet so that should make a big difference.

[Spooty22]

If low end torque is all you are chasing, heavily ported heads, 44idfs and big valves are not the way to achieve it! These mods will shift the peak torque further and further up the rev range.

To improve torque, either - increase comp. ratio

- increase displacement

- supercharge or turbocharge

- Port heads for maximum air velocity.
(as opposed to porting for maximum flow)

- try and stay away from hot cams

[75evo]

Have you talked to Adie Hawkins about your predicament. Seems like he is a real pro with the boxer (their 2.0L 16V 33 ....260 bhp??).

Maybe it's not the cam lift, but rather the lobe characteristics (sorry, don't know much about boxers). How about the exhaust manifolds and air intake routing? Possibly at this stage you should make sure the mixture is correct, and ignition advance is suited for your engine, not for a stock engine.

I picked up 8 rwhp while tuning my 75 on the dyno. That came from just with 1.5 degrees of advance added (12V, 10.5:1 pistons, CB cams, programmable efi).

Have you checked out Guy Croft's services? Seems like a really good head specialist.

[Serpent33]

Quote:

Originally Posted by London_Alfa Engine is definitely timed up perfectly. The block and the head were cc'd and the compression ratio is definitely no more than 11:1. Vacuum advance is working fine. Despite these things the car hasn't been to the rolling road yet so that should make a big difference.

[London_Alfa]

Quote:

Originally Posted by Serpent33 I run these 280 dur cams and used standard comp. Running 97 rom petrol. I tried 95 ron and detonation is observed when engine temp is higher than usual, from this I am guessing high comp is not a very good idea. There's some theory bout 8v and non high com friendliness. The car idles very smoothly. No torque lost is observed. My low end is very smooth. I hope you can get it sorted out without too high cost incurred. Good luck.

[London_Alfa]

Quote:

Originally Posted by 75evo Have you talked to Adie Hawkins about your predicament. Seems like he is a real pro with the boxer (their 2.0L 16V 33 ....260 bhp??). Maybe it's not the cam lift, but rather the lobe characteristics (sorry, don't know much about boxers). How about the exhaust manifolds and air intake routing? Possibly at this stage you should make sure the mixture is correct, and ignition advance is suited for your engine, not for a stock engine. I picked up 8 rwhp while tuning my 75 on the dyno. That came from just with 1.5 degrees of advance added (12V, 10.5:1 pistons, CB cams, programmable efi). Have you checked out Guy Croft's services? Seems like a really good head specialist.

[1981sud]

London Alfa if torque is what you are chasing take those bolt on filters off immediately!
I have a highly modified 1.5 t-carb and have tried a few different induction set-ups.

1. Bolt on filters. = no torque at all b4 4000 rpm. And not a pretty, but loud induction noise.

2. Original airbox = great torque even with highly moded motor, slightly poorer top-end power, and very boring induction noise!

3. The set-up I'm using now is a compromise. I'm using the original air-box but I have cut out almost the whole front section. I admit it will now be sucking in hot air from the back of the rad, but the difference in power is amazing! And the sound is the best I have ever heard from a boxer, combined with my big bore exhaust it now crackles nicely.
The main point though is torque is still far superior to that with bolt on filters, and with an improved sound and top end power.

Have fun experimenting, it is the best way to find what is best for you.

[77SudTi]

I think with all the mods you have done you can gain some torque back with a proper induction set-up. Going on what 1981sud was saying about air boxes. Do some research about the Trofeo Sud air horns, they were 90 degree bend tubes and were crazily long, no doubt to give the cars some sort of torque so they could get off the line, 44idfs on 1.3L and 1.5L engines sounds silly, but the obviously worked it out. By changing the length of the intake runners to suit your engine you will be able to improve things vastly.

For my Trofeo induction kit going on my Sud I will be making replica Trofeo style airhorns but tuned to a specific length to suit engine capacity and characteristics, of which Im not sure yet. A fair bit of number crunching and R and D to do...

The bolt on air filters are crap, you need some sort of velocity stack for optimum gain.

Lets us know how you get on.