Solex jetting for a 2.0 914

[Henry Schmidt]

Hi guys
I am deep into a 914-4 DP vintage race car the ran Solex 40 P11
I haven't worked on 4 cylinder Porsche 356, 912 or 914/4 for three decades so I need help with a starting jet formula.
Any help would be greatly appreciated.
Cheers

[stownsen914]

Henry, I'm rebuilding an EP 914 (very slowly). It uses Solex 40s. I'll look to see what it has for jetting, pretty sure it's a more modest engine build though, and 1.8L.

In case it helps, I asked a retired racer what jetting he had in his national champion EP speedster (also Solex 40s). Granted, different engine. For 160 hp, he used 160 mains and 160 air correctors.

[Henry Schmidt]

Originally Posted by stownsen914

Henry, I'm rebuilding an EP 914 (very slowly). It uses Solex 40s. I'll look to see what it has for jetting, pretty sure it's a more modest engine build though, and 1.8L.

In case it helps, I asked a retired racer what jetting he had in his national champion EP speedster (also Solex 40s). Granted, different engine. For 160 hp, he used 160 mains and 160 air correctors.

The jetting on the EP 914 seems like a reasonable place to start.
I'll watch for your results.
The EP 356 is good information as well, thank you.

[Henry Schmidt]

A little history for anyone interested. I've received a few email so I thought this made sense.

This 1976 914 Porsche was purchased by Wanye Baker in 1976.

It was sent to Don Araki for race prep. Wayne tells me he spent $ 40K. A huge number in 1976 dollars for an SCCA DP car. He then raced it in the 77-78 seasons winning the West Coast championship in 78. Later that year he took it to the run offs where he did respectably.

He later sold it to a customer F.A.Jacobs. I don't have any information about what he did with it.

In 2003 Wayne bought it back as a body with most of the original suspension to make a rolling chassis.

It sat at Personalized ******** until I bought it in 2022. It was part of a larger parts purchase.

We [Supertec Performance] embarked on a reconstruction project [not a restoration] to make it complete. It still have most of the original paint.

We put brakes on it, built a race prepped transmission and on we're building an engine to 1977 SCCA DP specs.

I'm hoping someone will restore it to it former glory.

[stownsen914]

@henry just checked the carbs and they have 120 mains and 180 air correctors. A little smaller than I expected, but I think this is in line with a milder build. Which I believe this motor is, judging from the collection of parts that came with the car. For what it's worth, this engine was torn down years ago because it "burned the heads" (per the gentleman who raced it). So the above jetting was probably too lean.

[Henry Schmidt]

Originally Posted by stownsen914

@henry just checked the carbs and they have 120 mains and 180 air correctors. A little smaller than I expected, but I think this is in line with a milder build. Which I believe this motor is, judging from the collection of parts that came with the car. For what it's worth, this engine was torn down years ago because it "burned the heads" (per the gentleman who raced it). So the above jetting was probably too lean.

Thank you. I think your reasoning is spot on.
We started working our way through the problem by simply extrapolating the solution based on total CCs, CFM given our specific head flow and projected volumetric efficiency,
In scientific terms.... a WAG.
We bored the venturis to 35mm, change to main jets to 150, AC to 170 and idles to 60 . Emulsion tubes are still up in the air. It doesn't look like we have much choice.
Now we start to fabricate a linkage. All the after market stuff looks pretty wonky.

[stownsen914]

My pleasure.

Meant to write in my earlier post. I was able to figure out much of the history of my car by contacting SCCA. They have a historian who will look over old race results, membership data, etc. I was able to get a bunch of info. on the car I bought, using only a car number + color and suspicions on where and approx. when it raced. I was able to get the owner/racer's name, and was able to get in touch with him. And importantly, I got the original SCCA logbook. Sounds like Wayne's car is better documented, but it might be interesting to fill in the blanks.

[Dave at Pelican Parts]

If you like cable linkages, Tangerine Racing out of CT sells one that is reported to be excellent.

https://tangerineracing.com/shop/ols/products/tangerine-racing-cable-throttle-linkage

--DD

[Henry Schmidt]

Originally Posted by Dave at Pelican Parts

If you like cable linkages, Tangerine Racing out of CT sells one that is reported to be excellent.

https://tangerineracing.com/shop/ols/products/tangerine-racing-cable-throttle-linkage

--DD

I appreciate the suggestion but I think we'll fabricate something a little more "period correct".