jakeflyer

Looking at one of Dempsey’s horsepower charts, raises some questions about the earlier SC engines with an 8.5:1 vs the later 9.3:1 pistons. Horsepower is shown to be the same @ 5500 rpm. The earlier engine has the smog pump and I understand it has different porting. The Euro or RoW engine has 9:8:1 with 400 more RPM and produces 24 more horse power. I did not look up cam changes. Here is a trident question. 1. Can the 8:5:1 run on a good regular grade fuel? 2. Can later Mahle pistons go into the earlier engine and what kind of bump will it give? 3. Are Euro pistons along with higher RPM a doable deal with stock injection on the U.S. engine? -------- I am going to look at a couple of earlier SC cars this week and have new interest in them with the cost of fuel going up and the prospect or running regular.

Steve Weiner-Rennsport Systems

Jake,

Euro engines make more power due to CR, cam timing, exhaust differences, and ignition timing.

Mahle pistons can only be used in Niksail cylinders and some SC's had Alusils. Of course, one must also check piston-to-cylinder clearances to be sure even if they are the same materials.

Raising CR requires more fuel and many US-spec fuel distributors cannot adequately do that. Caution is strongly advised.

8.5:1 can be used with good fuel, but there is far more to the story than that. When Porsche specified fuel grades for SC's here in the US, the quality and composition of gasolines were very different from today as that was a long time ago. Add the carbon buildup after X-number of driving miles and the static compression is oftentimes more than stated CR.

I don't know what your local climate is so I cannot help you further, but I can offer some sound advice; Be VERY careful about using regular (87) or even mid-grade (89) fuels if your car has some miles on it. The consequences of running cheaper gas are far more expensive,.........

Peter Zimmermann

I not only use Premium grade gasoline, I only use Chevron Premium, which is time-tested to be the absolute best for the street. The only car in my garage that gets 87 is my F 150, which was specifically designed to use Regular grade gas.

Brads911sc

If you are worried about the price of gas, id buy a honda civic or accord... and run cheap gas... I wouldnt run cheap gas in my PCar... or upgrade the engine to get a few mpg extra... Seems that if you cant afford good gas... probably also cant afford the maintenance on the car... just my .02 cents...

flatsixnut

I'll second the use of Chevron gas, (Even though my word is not as golden as Pete's is.) I have always ran the 93 octane from Chevron, as well as all my other P-car buddies.

Pete..I run 93 in my F150 also, but it is not a stock truck.

Amber Gramps

I have been called a nutcase over and over for my love of high octane. The use of low octane is a zero sum gain. You spend less and you get less. It's that simple. I have not even pumped "regular" into my lawnmower in 20 years. I bet you could get greater performance out of a well tuned 3.0 on a good octane fuel than a 3.2 on crappy 87. My chevy gets the good stuff, but my 3.2 gets the really good stuff.

My secret blend is $40.00 in 91 octane at chevron @$3.50/gallon and $40.00 in 100 octane pump gas @$7.00/gallon at VP Racing right across the street.

I could do this for years and never spend as much as getting that kind of return from motor mods alone.

jakeflyer

I remember the last fuel crunch with long lines and fuel shortages. The 8.5:1 seemed a logical reason to buy another SC, giving me drivability with all fuels. However, I am saved again by you guys, the voice of reason. ----------Steve, good reminders, thanks. Stock is good.

Amber Gramps

Jake, what is the octane of the fuel for the plane? Now that would make the old SC purrrrr.

Is that a Piper Cub?

Peter Zimmermann

I poked around under the hood of mine, smiled with the knowledge that it's got 300 hp, didn't have the foggiest idea how to get more, and gave up right then and there! That said, I'd appreciate knowing who has good prices on Bilstein shocks for the beast!

Mike Murphy

+1 This is true for all engines. It is why engine builders have to consider the carbon buildup variable when deciding on compression ratio. On Chevy V8 smallblocks, we used to figure about 1/2 point. So if you wanted a 10:1 engine, you would build a 9.5:1 engine!

jakeflyer

Douglas, the compression ratio on the Cub is 6.5:1--Regular is overkill. . 1944, WW2 they went easy on the little planes that would be away from central bases and flying on anything they could find. The good stuff went for the big radials with the blowers, Lindberg was a shaker and mover in development of the high octane avgas in the 30s. As with Porsche, racing improves the breed. Porsche was involved in some of the engine aircraft design of WW2 and Porsche has made some efforts at the present small plane engine market without success. The oil/air cooled boxer engines of the 1930s and 1940s small a/c design and the Porsche/VW engines are very similar. However, you can change rod bearings on the Continental engines with the cyls off and the cases not split.

flatsixnut

I just went with simple bolt ons. The truck is a 5.4. BBK shorty headers (keeps the cats), custom exhaust, intake, and I run the Superchips Tuner on the high performance 93 octane program.