New Motor Questions

[71-Super]

I have a few questions about a new motor I am building up. I have allready purchased a 78.4 stroke CW crank from European Motorworks with T1 journals and Scat H beam 5.4 rods. I will be going with 96mm pistons unless I can reliably get away with larger P/C's. It will be a daily driver with a DTM shroud.

1. What Compression Ratio? thinking 8.5 or 9:1... Is that to much for street? I will be using atleast 91 octane, 93 is available here but not everywhere.

2. What cam? I want this to have low to midrange power. This motor will see nothing over 6K RPM.

3. What do I need to do with my heads besides bore for bigger P/C's (They are 1.7L)? P&P??? how big on the valves?

4. What carbs? 44 IDF's?

5. Anything else I may be missing.

6. How much HP will this engine make?

Any thoughts, opinions or help will be greatly appreciated.

thanks for the info.

jeff

[kdanie]

Bore. Most U.S. builders say the 103mm cylinders cause problems with warping and high oil temps (due to low quality). There are ways around these issues...have the cylinders cryogenicly treated to stabalize them (they may need rehoned), then have the fins coated with a high tech heat sheading coating to disipate the heat better. Have the pistons ceramic coated on the tops to insulate them from the combusion heat, allowing less heat to get to the oil and decrease the chances of detonation.

Heads. I would go with 46X38 8mm stem valves, 48mm intakes weigh alot and will require more spring pressures to control them.
Port the heads or have them done by a pro. Keep as much "squish band" as possible around the combustion chamber. Set your deck height at .040" and adjust your combustion chamber volume to get the desired compression ratio.

Compression ratio. I would run 9-1 compression, stockish engines can run this safely. Personally, I like compression. If it were my engine, I would coat the combustion chambers and valves with the Ceramic stuff too and run 10-1.....Hey wait a minute, that's exactly how I set my engine up! (94X71)

Cam. Check the WebCam site or call them for a recomendation. Be sure to use their lifters also. Also get their valve spring recomendation to go with their cam. Some of the German tuner sites have cams listed but their numbers are calculated slightly different than in the U.S. Germans tend to run longer durations that we do in the U.S., but I think they design their cams with more gentle ramps.

Carbs. I would get some Dellorto 45DRLAs or Weber 48IDFs, Weber 44 are equivelent to Dellorto 40s. I don't think the 44s would feed a stout engine at 6000 RPM.

HP. It depends on the cam you choose and the quality of the head work.

There are many ways to configure an engine. Everyone must make their own choices and compromises.
ken

[Oliver Knuf]

As all the points are correct and tested dozens of times, I would only change the deck height to .050" and run 44 IDF's, as the 44's run out the 40mm Dells. They perform 180-190HP on Type 4's here, they do that in the US, too! Even 103mm p&c's would work for a long time, if you rework them correctly. The poor cylinder and ring quality that you get in the US is the main reason.

German cam measurement is different as we have nearly 20° more duration on our cams. A 316° Schleicher runs as an Engle W-120 with 294°, so just subtract 20° and you have a US measurement.

44mm x 38mm valves would do their job, too, if the complete head is p&p correctly!