Quote:
Originally Posted by gmanelan
More questions:
1. Did you do any work to the t heads to take advantage of the mod solex/dc30 cam? John at Dougherty is recommending dc15-102 which he says has slightly more lift than an e. This was based on my aim of a street only car prioritising mid-range. He said DC30 wouldn't give benefit without opening up the heads a bit (hope I'm not misquoting/understanding him). I know he is expert, just trying to understand why so many people seem to run DC30 on stock heads.
2. What alloy did you go for with the JE pistons - I have read people on here saying using the 2618 pistons is not advised due to fact the piston will expand faster than the barrel, and advise 4032 alloy. JE seem to make 4032 pistons but only with 10:1 compression. Will this be too high for my intended platform (ie single plug)?
Thanks
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John @ DC is my go to guy but he generally suggests a "more" conservative route.
10:1 is too high for your application. Mild cams almost always increase dynamic compression so starting with 10:1 will be challenging. That said, it is relatively easy to trim the pistons to a desired dome volume (IE: lower compression).
The formula for milling 4032 pistons is:
Piston dome cc's to gram conversion: 1cc (volume) = 2.71 grams (weight)
You can use additional base gaskets to reduce compression. Additional base gaskets will increase deck height so it has to be considered a compromise.
Ordering a custom piston is always an option.
As for piston alloys: 4032 has a lower expansion rate which would match well with the cast iron or Biral cylinder. Cast iron has a lower expansion rate than Aluminum so you can run a tighter tolerance.
The 2618 expands more consistently with aluminum cylinders so they can be clearanced to take those higher expansion rates into consideration.