Many years ago one of our local club members did this type of porting work on a 2.5 GTV6 with great results. He opened up the runners, carefully matched them to the heads, cleaned up the ports, and removed the little stacks cast inside the V6 plenum. Everything else on the car was left as it was.

End result was around 10bhp at the wheels on the Beninca dyno. Just for a few hours and a few dremel bits. Even if that 10bhp was "hopeful" it was well worth it. And as an added bonus the car ran sweet as.....

 

Yes, I will be port matching everything. And getting a baseline dyno run before and after.

Good to hear that similar work has been done with good results. My reasoning is that this work certainly can only help the breathing of the engine.

It is interesting to compare the finish of the ports of the twinspark head to the old Nord. The Nord has much smoother ports than the T-S head. But the runners of the manifold are quite frankly.... ****e!

 

wouldnt extrudahone take care of those rought casting blemishes?

 

Yes. But that's not as much fun as doing it yourself!

And, like the reason I do all my own seat cutting by hand: I will do a better job.

 

This is was I do to my Nord 3 years ago, runners were increased from 36-37mm to 41mm in diameter. It was weld and polished, so as you can see it is impossible to detect the difference from outside, also any problem with reliability.

 

This is was I do to my Nord 3 years ago, runners were increased from 36-37mm to 41mm in diameter. It was weld and polished, so as you can see it is impossible to detect the difference from outside, also any problem with reliability.

Yes, I remember you did this. And I admit, inspired me to do the same. The finish you did on the outside was very nice. Did you ever dyno this engine before and after?

I am not going to go to those lengths, just weld it back together. I am not going to enlarge the tracts with this engine as I am just staying with the standard cams. The twin spark runners do lend themselves to this process as they are very curved. I am currently waiting for an extension piece to get right down the runner.

 

No I do not Dyno the engine neither before or after, I bought the car in non running conditions so I cannot say if it has now more or less power, but friends with the same car say mine feels with a little more torque over all the rpm band, but IMO if so, it has to be very little because the engine still maintain the original cams and motronic inj/ign system.

Now I'm preparing a 2.0 TS engine for my Spider, but starting from a 155 engine, it would have 12:1 compression ratio, I have the head ported and a little modified, but maintaining internal diameter of the runners from the valve guide area upwards (38mm approx.) what is being custom made is the "intake manifold" (4 slightly curved independent tracts), the 2+2 barrel throttle bodies, the individual trumpets, and a common atmospheric pressure plenum. Then will come a custom made exhaust system, and then probably a set of cams.

Speaking again about the inlet diameters IMO going over 38-40mm is a mistake, because a lot of kinetic flow energy is lost, reducing the gains that could be obtained from the resonance effects of a well tuned intake/exhaust system, so you are right letting the internal diameter as it is and cleaning the cast irregularities.

 

Now I'm preparing a 2.0 TS engine for my Spider, but starting from a 155 engine, it would have 12:1 compression ratio, I have the head ported and a little modified, but maintaining internal diameter of the runners from the valve guide area upwards (38mm approx.) what is being custom made is the "intake manifold" (4 slightly curved independent tracts), the 2+2 barrel throttle bodies, the individual trumpets, and a common atmospheric pressure plenum. Then will come a custom made exhaust system, and then probably a set of cams.

You are pretty much describing the sort of "proper" engine I plan to build as time and $ permit. I would love to base it on a 155 engine, but they were never imported here to Australia. The last 2.0 8V (155 and 164) engines had a 90 mm stoke, and when combined with an 85 mm bore gives about 2043 cc engine (a 70 cc capacity increase). I am in Italy in September near Milan, so i am going to sniff around some breaking yards while my wife is off shoe shopping (shudder!:crying. Maybe I can locate a crank and rods to slip into her bags and bring home with me....

The 155 head of course is better with respect to the port entry angles. But then you have to deal with the cooling passage issues when installing in a RWD. Maybe it is just better to use the 75 head, perform some welding, and make a new manifold. The curved runners would be necesary to clear the bonnet and get reasonable length.

BTW: Pics Please!?

 

Guys, also deep in a 155 8V implant... mine into a 68 Junior, only with a turbo as well. Custom sump and engine placement seem to be the key, but I suspect I have slightly more height than you do with the spider. The other forum:

1968 GT 1300 Junior - Alfa Romeo Forum

 

Progress

Progress has been a bit slow. The onset of winter meant that I had to finish the insulation under the house... And I am finishing off a mild 1750 engine for a friend.

The combustion chamber... usual stuff: hard to take a good picture down the ports from the inlet manifold side. Inlet valve pockets opened up. Used Jim K's dimension to ensure no penetration through the oil drain gallery. If this was a real performance engine, I would weld do some welding and sleeve the port like I have done before on Nord heads.

The chamber and port bowls

Head

Inside plenum

Runners (not perfect as they are really ROUGH, but huge improvement

Welded together

 

Some progress

I have decided to use some Nord rods lying around. I checked the two sets of rods out of interest against each other.... No more than 1 gram difference overall. Of course this is not as you would do it for a real race engine, but shows that Alfa did match their rods well. It also confirms what I was told years ago when I paid to have Alfa cranks and rods balanced after I had left the engine reco business.... That it was barely worth the time and effort unlike American rubbish (but engine shops will still happily take your $$).

TS rod top

TS rod on left chunkier in the beam

And weight

37 grams more than the nord

 

More

I marked the pulley at 25 degrees BTDC and while the crank was at this, set the inlet cam at the timing mark. This simulates the cam while advanced (worst case for valve interference). Then with bluetac on the valve recesses (where do you buy plasticine these days at night???) cranked it over.

Crank pulley (rightmost mark is 25 degrees... should get a degree wheel).

This is the camshaft cap marked for advanced mode

Squashed Bluetac

1.65 mm clearance, Exhaust was about 2.0 mm.

Not exactly sure off the top of my head what a standard TS head thickness is, but this was 134.9, Nord rods and standard cams running stock timing there is plenty of piston/valve clearance.

 

Fast work...

Head shot

Bottom shot

Screw in crank plugs

Done

 

Good job!!!, with the Nord rods you should be getting 10.9 to 1 compression ratio, if the rest remains standard.

 

Hey Luke - so how is it running? happy in the end? can you estimate the power you have?

I was looking at your rod comparison today when performing the same TS -> Nord switch as you did. I see you had no valve clearance issues, but did you otherwise leave the TS pistons stock standard? do you recall their position at the top of the stroke? flush to the deck, or higher?

cheers - andy

 

Well... Can you ever have enough power??? I am guestimating that the engine has ~160 bhp. Everyone who has driven the car comments on the torque.

I never had this engine on the dyno, but my feeling is that the it probably had 10 bhp at the flywheel more than the standard engine with BBR chip. Shown in this post:

Link.

The increase is most noticable between 3000 to 5500 rpm. I feel the top end is restricted by the flappy AFM. Problem also is you get used to the power and want more.

The pistons are stock and from memory and the image here, they were pretty much level with the top of the liners.