I am putting together a street and strip motor, mostly strip. I hear that you want to keep these motors below 6000 rpm for reliability. It will be a 10.5 to 1 comp. A lot of port work by a reputable machinist. Will also be supercharged at max. 6 lbs. of boost. I know it seems strange but it is a proven combo for 250 c.i. small blocks. Make the motor run hard naturally aspirated and the give it a little help. Has set land speed records.
My questions is what duration combination keeps you below 6000 rpm.

6000 RPM is a good limit with stock rods, balanced lower end, and good pistons.

You can run a pretty agressive cam for this redline. For that comp and a NA motor, I just designed a cam (custom regrind from Oregon Cams): 250 @ 0.050" INT, 243 @ 0.050" EXH, 105 LSA, 0.494"/0.480" lift int/exh. Yes, you read that right, more intake than exh duration.

I am no expert on blower cams, but I would guess you want a bit less overlap?? You could go with an even duration cam of 240 @ 0.050" and 108 LSA? I have though a lot about NA cams and some about turbo cams, but not at all about blower cams...

Lou

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Home of Slant6-powered fun machines since 1988

Thanks Lou. I didn't think that the manufacturers recommendations were correct. By their recommendations a anything over 270 deg. duration would put me over 6500 rpm. With the long stroke of a 225, it just didn't compute in my head. Again, thank you.

My pleasure. You should do a search for modifications to cams for blowers and let us know what you come up with. I have an M90 blower on the shelf I'd like to try at 5-8 psi sometime, so I'll be interested.

I have a turbo project (starting with 6psi) in the works already, due to be assembled later this spring...

Lou

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Home of Slant6-powered fun machines since 1988

Thanks again. I am using a M90 for my project. I plan to get the motor out this week. I have most everything. I just lack rings, bearings, rod bolts and head studs. We will be oringing the block and using a copper head gasket. This all will be going into a 71 Duster with all the street trim. In other words, it won't be extra light. I wil be using a full manual 904 with 3800 stall converter to be reasonably streetable. I'm not trying to set the world on fire, just have fun.

Rat
Keep us posted. I have a FED that will use the M90. The blower manifolds from Aussie Speed are ready if you need one.
Frank

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Scrapple: Because a mind is a terrible thing to waste.
73 Duster - Race Car
66 Dart Wagon - DD
178" FED
82 D150
All Slant powered

Will you Please come to Irwindale on a Thurs nite and run it?I have been going every other Thus nite for a year now and havent seen anouther slant.Sick of beating 5.0s.Pm me if ya wanna come out and watch and pick my brain,VERY willing too help.Guzzi Mark

Mark has got it goin' on - meet him...

Lou

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Home of Slant6-powered fun machines since 1988

That would give me a good reason to go to irwindale. I am a horrible spectator. I do not have a car to run now and nobody to help. I was helping on a couple of cars running at PSCA races but money got short and everyone stayed home. It would be great to get out and see what you are doing. I have a feeling that tackling one ofthese motors is going to be humbling. It would be great to get off the ground with the experience that you guys have.

I am definately going a week from this thursday to check out my lastest changes.Hopefully can get it below 8.07 with the old motor.Come check it out,it will be th only flat black chopped top 62 Valiant there.Guzzi Mark

And its BAD AZZ TOO. Ive seen it in person.
Frank

_________________
Scrapple: Because a mind is a terrible thing to waste.
73 Duster - Race Car
66 Dart Wagon - DD
178" FED
82 D150
All Slant powered

Thanks Frank.Mark

Look for this:

See you there.

Planning on going Thursday,if I get my tubs done.Cut one out today and spent 5 hours mocking up aluminum panels,probably 20 hours away from happiness...
Ya might want to call me Weds to make sure I can make it. 562-986 0070 Mark