Technical > Matt Shaff's Engine Shop

Adding a blower to a 13:1 engine

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wideopen231:
I ran 13:1 on blown alky hemi with 14-71 at 54%/42lbss.droped back to 12:1 ran faster and hurt less parts.
 Also think about bottom end designs. Hemi not really better at making power but its better at handling it. Alan Starr ran nitor chevy way into 70's.He said stupid pride made him do it he should have went to hemi way sooner.

 If your running mild OD.Why not drop compression. If need more power throw cpl percent more at it.Easy,quick and better tunablity.Your winner ,winner chicken dinner thing. Only draw back to OD changes is it does effect distribution, small but note worthy.

 As for gasket question. I agree 100% that only copper gasket belong in blown engine.Hey if it works for T/F guys it should hold up for you right. I will tell you that I had lot less gasket problem once I started torque from out to in instead of norm in to out. Was billet heads and was told it would stop blowing gaskets and pretty much did.

IMO milder compression and more OD with slightly rich starting line,then leaning thru mid track  with riching valve for last 300 to 500 feet of track is great setup.Used if for last cpl years we ran funny. Car was quick top qualifier always a contender and for style racing and rpm we ran at not bad on parts.Even with outdated heads we should have chnaged years before.This was before timer systems allowed in alky cars.

Big Rhino:
Thanks a lot for all the great info, tips, and experience.  As I said earlier, this is kind of an experiment for me.  The reason for the big blower (10-71 W/ teflon strips) is 'cause I am in the beginning stages of building a 582, (Callies bottom end) and was going to use the same blower (hopefully using the 412 as a learning bench).  I had initially planned to go with 8-port injectors, but have always been intrigued by the blowers.  I'm just trying to learn as much as I can about them first.  Most tracks down here are only 1/8th mile, so my goal is to get into the high 4s.  Probably not too realistic with my little Pinto (92" w/b and 2200 lbs), but I am looking at a couple FED's, hoping to make a move by Christmas. Great Website here!  Thanks again for all y'alls input!

wideopen231:
8 port w/8 hats is standard setup.Very easy to tune and work with.One thing to remember with teflon stripped blower is to keep check on condition. Even if your not trying for max power every run. If you want consistent runs its even more important.Remember that fuel thru top of blower will help teflon live longer,keeps it cool and lubed.

  Tip I got from Swearinger was to check vaccum at idle .All you need is one extra nozzle hole(1/8 pipe) thats pulgged,pull plug idle will go up then stick end of vaccum gauge into it let it idle back to norm.If this number stays the same and Idle rpm are the same you are good to go. Maybe hard to believe but 1" differance will make change in performance. YOU HAVE TO HAVE SAME RPM and not be messing with air gap in butterflys.

    Have cpl extra holes in bottom of hat that are normally plugged,If idle drops pull a plug about 250 rpm increase.If idles high plug one.Very quick very simple and you are not screwing with barrle valve all the time.

Big Rhino:
Once again, great information.  Thanks!
 I am seeing a trend here of recomendations to go with the Hemi block for the extra strength in the bottom end?  Is it a significant difference from a Bowtie or Dart block?

wideopen231:
All depends om how hard you are going to push it. On decent setup with medium OD BBC works fine.If you are going to go after max power.All I can say is there is reason Top Alcohol ,Pro mod and extreme blower class cars run hemi blocks for the most part. If you are going this route you can make BBC work but IMO you are way a head starting with Hemi style motor. Look at the two block.With BBC the crank is knd of hang out like dead weight.With hemi the mains have way more support and stength. Parts being readily available is huge benifit.With mild setup you can shop and buy used parts that are more than ready for you needs.I would stay away from stuff like used rod or cranks from fuel teams. Heads,cams, blocks ,alky car cranks( have checked) Intakes and few others can save you lots of money.

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