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Blower engine

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easydean View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote easydean Quote  Post ReplyReply Direct Link To This Post Topic: Blower engine
    Posted: Nov/05/2016 at 6:35pm
So, a 6-71 blower showed up at my place.  I have a 401 to put it on.  Now I need a bit of help on what's best to do when building it.  Compression, good cam (street)?? My 401 has 502 match ported heads, o-ringed block, everything studded, MSD, etc. and was running high 10's in the quarter with a 3200 lb. car (74 back halved Javelin).  I plan on using this as a street engine, not drag engine. Anyone have experience with a blower motor?  Thanks, Dean  cell 701-205-6906
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Green AMX Quote  Post ReplyReply Direct Link To This Post Posted: Nov/05/2016 at 8:15pm
I love when cool parts or cars just show up
69 AMX 390 4speed go pack
72 Javelin 360 auto(sons)
82 Spirit (wife's 1st car)still not done
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Post Options Post Options   Thanks (0) Thanks(0)   Quote AMoCoLite Quote  Post ReplyReply Direct Link To This Post Posted: Nov/05/2016 at 9:13pm
Originally posted by Green AMX Green AMX wrote:

I love when cool parts or cars just show up


This seems to be a regular occurrence for Dean. *ijs*
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shootist View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote shootist Quote  Post ReplyReply Direct Link To This Post Posted: Nov/16/2016 at 9:01pm
Dean try dropping this in the motor thread. I am running a centrifugal supercharger on mine and others are also running superchargers or turbo setups which are not much different than the roots/screw blowers with the exception of external intercooler capability. Anyway, the main factors are going to be fuel selection, boost level and compression. I would keep compression at or below 9.5:1 but again too many factors to make any solid recommendations without knowing more about your expected results.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jpnjim Quote  Post ReplyReply Direct Link To This Post Posted: Nov/17/2016 at 1:54pm
Hi Dean,
For a cam,
blowers usually do better with a wider lobe centerline,
like 112 or 114.
That cuts overlap (overlap isn't desirable with forced induction),
and a wide lobe centers also cuts dynamic compression.
(it seems like excessive overlap would cut dynamic compression , but the opposite is actually true)

Its also a good idea to go with a little more exhaust duration than intake,
since the exhaust needs more help than the intake does on a blower engine.

Depending on how crazy you were going to get, I'd like to find a nice 390 or 401 with thickest cylinder walls you can get your hands on to plop it on, 
or better yet an AMC 327 Smile


71 P-code 4spd Javelin/AMX
some Jeeps and some Fords
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 401MATCOUPE Quote  Post ReplyReply Direct Link To This Post Posted: Nov/18/2016 at 5:44am
Dean...What was your motor setup with before to run high 10's.....sounds like you probably ran big on compression.  Forced induction (Supercharger or Turbo) on a Street Engine, compression is critical.  Like "shootist" is saying 9.5 to 1 is really pushing it....almost everyone I know running a Street Engine that is Supercharged is running 8.5 to 9.0 to 1....I run 9.0 in my Supercharged Avanti, with 10 psi blower pressure.  It is very sensitive to fuels.  I had John Erb former Chief Engineer at Kieth Black Piston help me put together a Hyper-eutectic Piston, Special Ring Package and Custom Grind Cam to match the set up.  One of the biggest mistakes he told me that builders make is in converting engines from Normally Aspirated to a Turbo or Supercharger is the Ring Package.  The end gaps have to change for the different inductions, which change the internal temps.  I had to file fit every ring.....the gaps are not the normal .004 per inch bore.  I think you can get some great advise on here, but need more details of the original build.  Hope this helps.
Ross K. Peterson
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69X,GoPac,390,4sp,64A
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Post Options Post Options   Thanks (0) Thanks(0)   Quote easydean Quote  Post ReplyReply Direct Link To This Post Posted: Nov/18/2016 at 7:53am
My original idea was to put it in my Gremlin.  I now am looking at a couple of Rambler Americans instead.  I would use it on the street and occasional drag race.  I know I need lower compression-not sure if I should have a cam ground or if a good aftermarket cam will be adequate.  I will buy forged pistons-my block is already o-ringed, which is a plus (previously had nitrous) The block is also fully studded.  The end result looks to be a blown, straight axle American gasser, at least at this point.  Thanks to all responding!!!  Any info helps!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote amcglass Quote  Post ReplyReply Direct Link To This Post Posted: Nov/18/2016 at 8:40am
wish parts like that would just SHOW UP here....LOL
Javmanpres

BBG Mark Donohue 401

74 Jav/AMX
71 Matador 2dr sedan delivery wagon
1902 Rambler Runabout   
70 T/A Javelin
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Post Options Post Options   Thanks (0) Thanks(0)   Quote shootist Quote  Post ReplyReply Direct Link To This Post Posted: Nov/18/2016 at 1:13pm
Ok, so if you are going to keep it street with respectable numbers capability at the track but with survivability and longevity at the top I would go something like this.

Roller cam  and rockers(hydraulic for low maintenance solid if you don't mind adjusting lash often)
Keep the LSA at 112-114 like jim said with more lift and duration on the exhaust side
(My cam is a custom grind 282/288 adv. .544/.555 lift 230/236 @ .050")
Edelbrock aluminum heads or ported steel is fine focusing more on exhaust flow
Biggest headers you can manage 1 3/4" primaries minimum 1 7/8" or larger preferred
X or H pipe to help even more on the exhaust flow and balance
Forged pistons that will give you about 8.5 to 9.5:1 compression lower is better with the 671 and I would personally try keeping the compression closer to 8.5 unless you use a chemical or other type of intercooler. Fuel options are critical on a blown motor. I run E85 so I don't need an intercooler because of the higher octane and cooler intake but keep in mind you will need to flow 30% more fuel.
Try keeping your boost below 7-8 lbs for longevity. Watch out if you overbore, some 401 blown motors have blown out cylinder walls at high boost levels so it is worth sonic testing to ensure you have enough meat there. Rings as stated must be gapped larger than a typical stock setup, make sure you follow the piston manufacturers recommendation and gap accordingly. 4 bolt mains if money allows but not really necessary. Extra head bolts added for additional clamping force. O-ringing the heads/block is optional but with extra bolts should not be too bad. Some sort of timing control to take out timing when the boost climbs. MSD ignition box for added zap. If you decide to go E85 make sure all fuel system parts are compatible. E85 while not corosive it is a solvent and will dissolve rubber and any old varnish so keep that in mind. I really like the FiTech EFI system I put on mine because it has tons of features built in so take a look at them for fuel. I think in a boosted applicatioin fuel management is even more important so I would rather have EFI that automatically adjusts the AFR accoring to environmental conditions ensuring the best possibility of detonation resistance.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote bcsideshow Quote  Post ReplyReply Direct Link To This Post Posted: Nov/19/2016 at 5:36am
Great info guys!  I too have been contemplating a pro charger.
1969 SCRambler "B"
1970 AMX 390 Auto
1968 AMX 390 Auto
1970 Rebel Machine Project
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1969 AMX 390 Auto Project
1969 Javelin 390 project
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