Port size on 2.3

[Seppo]

Planing to build the follow for my 67.
This is a street car and the Torque is more important then HP

85mm cylinder with JE piston 10.5:1
66 stroke
Solex camshaft

The cylinders heads from a 2.4T with 30mm intake port.
I am thinking to enlarge to 32 or 34 mm.
What is you recommendation?

[Henry Schmidt]

Originally Posted by Seppo

Planing to build the follow for my 67.
This is a street car and the Torque is more important then HP

85mm cylinder with JE piston 10.5:1
66 stroke
Solex camshaft

The cylinders heads from a 2.4T with 30mm intake port.
I am thinking to enlarge to 32 or 34 mm.
What is you recommendation?

10.5: 1 on a street motor is too much even with twin plug. Lean closer to 9.5:1 and get the snap back with ignition timing.
36 intake is a nice size intake with 40 Webers
I today's world the Mod Solex is a nice compromise and can be ground on your Solex cores.

[Seppo]

Originally Posted by Henry Schmidt

10.5: 1 on a street motor is too much even with twin plug. Lean closer to 9.5:1 and get the snap back with ignition timing.
36 intake is a nice size intake with 40 Webers
I today's world the Mod Solex is a nice compromise and can be ground on your Solex cores.

Thank you Henry!
In Europe not so easy to find a workshop to regrind a camshaft
Maybe a "E" camshaft will work as well?

[Walt Fricke]

I had one of these - great motor. But it was a race motor with '40s, and Elgin 310s. Me, I'd go for S cams, but Henry has built a lot more motors than I have. Got a now defunct race shop to get Cosworth to make the 85s - this before the day when there were a number of manufacturers who would make a custom piston for not much extra.

I had 10.3:1 with twin plug on US pump premium, 91 ron/mon. It idled around the paddock just fine. Bogged coming out of some corners initially, but by cranking way down on the accelerator pump I cured that.

[Henry Schmidt]

Originally Posted by Seppo

Thank you Henry!
In Europe not so easy to find a workshop to regrind a camshaft
Maybe a "E" camshaft will work as well?

S cams are spirited but the lobe center and overlap challenge low end.
Although E cams were the rage back in the 70s-80s they really are pretty lame cams on a small engine.
The Solex or Mod Solex would be worth the shipping. I can have some cams ground for you (I might have cores) and ship them.
If you have E cams, they cam be ground to Mod Solex grind.

[horizontallyopp]

Originally Posted by Walt Fricke

I had 10.3:1 with twin plug on US pump premium, 91 ron/mon. It idled around the paddock just fine. Bogged coming out of some corners initially, but by cranking way down on the accelerator pump I cured that.

Walt was that running at elevation in Colorado?

[Seppo]

Originally Posted by Henry Schmidt

S cams are spirited but the lobe center and overlap challenge low end.
Although E cams were the rage back in the 70s-80s they really are pretty lame cams on a small engine.
The Solex or Mod Solex would be worth the shipping. I can have some cams ground for you (I might have cores) and ship them.
If you have E cams, they cam be ground to Mod Solex grind.

I would love to ship the cams to you Henry, but the shipping cost too high just not worth it

[Walt Fricke]

Keith - yes, a mile high. I never ran that motor out of Colorado. Back then there were no aftermarket super rod bolts, and a stock bolt eventually gave out, as I would spin it up to 8,000 RPM. If it warms up some maybe I'll dig out one of the heads and measure ports.

[Seppo]

Just measured the dome volume of the piston 40cc and heads 68cc.
That makes the static compression 13:1......
I confused if the European gasoline can handle this?

[Neven911]

Originally Posted by Seppo

Planing to build the follow for my 67.
This is a street car and the Torque is more important then HP

85mm cylinder with JE piston 10.5:1
66 stroke
Solex camshaft

The cylinders heads from a 2.4T with 30mm intake port.
I am thinking to enlarge to 32 or 34 mm.
What is you recommendation?

Hi, This similar to what I'd like to do with my 914-6, May I ask where did you get 85mm cylinders? are they 84mm bored? Did you consider the 86mm kits?

Thanks Neven

[Seppo]

Originally Posted by Neven911

Hi, This similar to what I'd like to do with my 914-6, May I ask where did you get 85mm cylinders? are they 84mm bored? Did you consider the 86mm kits?

Thanks Neven

The 84mm cylinder was overbored to 85mm. I have got the pistons from a friend some years ago, So I wanted to use it.

[stownsen914]

13:1 is aggressive even for a twin plug race engine running 110 octane fuel. Single plug on pump gas - recipe for engine damage. This could be even worse on a 67 which would have 2.0L heads which have a steeper combustion chamber and I believe have a reputation for being more detonation prone.

[Henry Schmidt]

85 bore x 66 stroke....1.0 mm deck, 40cc dome and 68cc chamber calculates to 12:1.
I could be wrong but I ran the numbers twice.
Still too high for street gas even with twin plug.

[Seppo]

I have rechecked the deck height with the solder method and have only 0.4mm
I will increase it to 1.5 as recommended in a book..make the compression 11.4

[stownsen914]

Let's see if Henry or others chime in, but I believe 1.5mm is considered a bit high and can encourage detonation which could be risky for a high compression engine. At the compression ratios you're talking about, you'll need to run 100+ octane.

[356RS]

Time to change out the pistons for a lower compression or if you have a good machine shop that can maybe mill the tops of the pistons down if there's enough meat on the piston dome.

[Henry Schmidt]

Originally Posted by stownsen914

Let's see if Henry or others chime in, but I believe 1.5mm is considered a bit high and can encourage detonation which could be risky for a high compression engine. At the compression ratios you're talking about, you'll need to run 100+ octane.

This theoretical 1.5mm deck height being detonation prone is generally a consideration when discussing larger bore engines.
I think Seppo is confusing piston clearance with deck height. Deck height will affect piston clearance but is not the same.
Piston clearance should be at least .070".
The term "deck height" as I understand it is the measurement from the cylinder deck to the piston deck. 1/2 stroke plus wrist pin height will determine piston deck.
(Crank center to cylinder deck) minus (1/2 stroke plus pin height) equals deck height.
Generally just measuring from the cylinder deck to piston deck with a caliper will suffice.

[stownsen914]

@Henry - always good to have your expertise. By piston clearance, you are referring to distance from piston dome to head?

[Seppo]

Here is how I measure the deck height 0.48mm
@Henry - I really appreciate your help

[Seppo]

I get another set of pistons.
Now the compression is 9.8:1 with deck height 1.32mm