here are some of the modifications I plan to make to the supercharger....
The yellow circle is where I plan to press in a freeze plug to seal off the bypass valve passage. This has to be done because the 4.9 distributor is right below this area.
The blue area is where I plan to grind a new hole into the bypass passage... so that the bypass valve will still be functional and allow air to flow from the plenum
The rib in the red circle will be grinded away to allow air to flow from the plenum to the bypass passage
The pink circle is where the pcv valve pulls crank case gas... here I plan to drill a hole in the metal plate where this hole is and weld in a nipple so I can connect a hose and route it to a valve cover on the 4.9
The purple circles are ports that will need to be plugged
The green circles will not be used and will be covered by the metal plate
[This message has been edited by MaxCubes (edited 02-21-2013).]
wouldn't it be easier to adapt it to the stock 4.9 TBI style intake with the injectors in the ports? also can you use a distributorless ignition system on it to save space also?
The Allante intake is what I have... and they say it flows better than the stock 4.9 intake anyway.
In my situation, the supercharger fits under the hood with the stock distributor. It would be easier for me to leave the distributor alone... Plus it is easier to alter ignition timing on a distributor in boosted conditions (with an MSD box #5462)
[This message has been edited by MaxCubes (edited 01-09-2013).]
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02:42 AM
Will Member
Posts: 14252 From: Where you least expect me Registered: Jun 2000
Originally posted by MaxCubes: The four studs for the Allante upper plenum is not sufficient for a supercharger plenum. The supercharger is big and heavy and belt driven and it takes force to drive it... and needs a strong base to hold it
While a wider support base is always better, I wouldn't have said that the Allante mounting studs are inadequate. However, in your shoes, I might enlarge the studs from 8mm to 10mm.
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11:22 AM
81 4.9L X-11 Member
Posts: 129 From: S. FL, err now Philly !! Registered: Sep 2006
Fits 1993 to 1997 Buick Roadmaster, Cadillac Fleetwood, Chevrolet Camaro Caprice Impala, Pontiac Firebird. With 3.4 and 4.3 and 5.7 engines.
Thanx, any chance you can measure the distance between each of the bolt holes? Outside to outside is probably the easiest. Looks like it's close to the size I'm looking for on a project.
Originally posted by 81 4.9L X-11: Thanx, any chance you can measure the distance between each of the bolt holes? Outside to outside is probably the easiest. Looks like it's close to the size I'm looking for on a project.
Cheers
distance between two holes on tensioner is 4 7/8" .... distance between holes on the custom little curved bracket is 1 5/8"
You seem to know lots about Throttle Bodies, FOY says this is the TB from the 94 Northstar motor and it is supposed to use the same Idle Control Motor as the stock 4.9 intake. Do you happen to know the diameter of the stock 4.9 TB vs this Northstar TB?
Here are the pics I copied from FOY's build thread on my car with the custom intake.
------------------ 857GT Part 85GT Part 87GT Part Caddy, 93 Eldorado 4.9, 5spd Dual O2 Custom Chip, Custom Exhaust. MSD Everything Now with Nitrous. Capt Fiero --- My Over View Cadero Pics Yellow 88GT 5spd Full Poly Suspension, Lowered 1/2" in front, Corner Carver.
1999 and older northstar throttle is 73mm .... 75mm for 2000 and newer northstars... throttle on 3800sc is 69mm
I couldn't find any info on 4.9 throttle.... but it looks too small for any decent flow
Is your intake manifold modified to handle the extra flow? .... Because the twin bores on the manifold are the same size as the stock 4.9 throttle bores.
[This message has been edited by MaxCubes (edited 02-21-2013).]
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10:58 AM
Capt Fiero Member
Posts: 7657 From: British Columbia, Canada Registered: Feb 2000
Yes he cut out the holes in the intake, and opened it right up.
------------------ 857GT Part 85GT Part 87GT Part Caddy, 93 Eldorado 4.9, 5spd Dual O2 Custom Chip, Custom Exhaust. MSD Everything Now with Nitrous. Capt Fiero --- My Over View Cadero Pics Yellow 88GT 5spd Full Poly Suspension, Lowered 1/2" in front, Corner Carver.
I wouldn't mess with the combustion chambers - only a CNC will get them consistent and that's not cost effective. If you do any head work, porting the runners to gasket match is worth the effort and something you can do yourself. The compression ratio will be more of a factor as you increase boost, which is why I asked about the inner cooler - not required but helps a lot.
There's another 4.9L supercharge thread that posted the flow rates of the 4.9 and the supercharger - don't know the specifics but it seemed to me that it wouldn't build too much boost rather just really help the 49s low flow design.
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03:46 AM
dratts Member
Posts: 8373 From: Coeur d' alene Idaho USA Registered: Apr 2001
Mine is not a 4.9 but my boosted engine is intercooled and alcohol/water injected (windshield washer fluid) for knock control. Just another option for boosting high compression engines.
I wouldn't mess with the combustion chambers - only a CNC will get them consistent and that's not cost effective. If you do any head work, porting the runners to gasket match is worth the effort and something you can do yourself. The compression ratio will be more of a factor as you increase boost, which is why I asked about the inner cooler - not required but helps a lot.
There's another 4.9L supercharge thread that posted the flow rates of the 4.9 and the supercharger - don't know the specifics but it seemed to me that it wouldn't build too much boost rather just really help the 49s low flow design.
Have you done this kind of work on heads with success? I ask because of the horror stories I've heard on the other threads about removing the heads for modification... .... and after reinstallation there are soon failures with head bolt threads and blown head gaskets.
Mine is not a 4.9 but my boosted engine is intercooled and alcohol/water injected (windshield washer fluid) for knock control. Just another option for boosting high compression engines.
Yea I wish I could sandwich a decent intercooler under the supercharger... But the supercharger barely fits under the hood without an intercooler.
....One advantage I have (versus other 4.9s in fieros) .... is that I am using a 7730 ecm to run the 4.9 (1991 camaro 305 TPI prom) .... which uses a knock sensor unlike the 4.9 ecm. This knock sensor may save me from blowing the engine!
[This message has been edited by MaxCubes (edited 01-24-2013).]
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01:30 AM
81 4.9L X-11 Member
Posts: 129 From: S. FL, err now Philly !! Registered: Sep 2006
Have you done this kind of work on heads with success? I ask because of the horror stories I've heard on the other threads about removing the heads for modification... .... and after reinstallation there are soon failures with head bolt threads and blown head gaskets.
Yea I wish I could sandwich a decent intercooler under the supercharger... But the supercharger barely fits under the hood without an intercooler.
....One advantage I have (versus other 4.9s in fieros) .... is that I am using a 7730 ecm to run the 4.9 (1991 camaro 305 TPI prom) .... which uses a knock sensor unlike the 4.9 ecm. This knock sensor may save me from blowing the engine!
I guess I should have thought a bit before I made that post. My alcohol injection point is after the turbo and before the intake. None of which works on a supercharger mounted on the top of your engine. Sorry about that.
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06:07 PM
Jan 29th, 2013
81 4.9L X-11 Member
Posts: 129 From: S. FL, err now Philly !! Registered: Sep 2006
OK... got some more progress done today... I am determined to get this done and running... still have more work to do... but I am almost finished with the plenum box...I have finished welding it all together ....need to do some more drilling and porting for the intake runners
....I have also done some research on the GEN5 supercharger (found on 2004 and newer Grand Prix's) A newer, more efficient and cooler running supercharger.... would fit easily on my new plenum.... would just need to open up the plenum lid a bit more.
Of course I will not use the 'fly by wire' throttle that came with this gen 5 supercharger ... I will fabricate an adapter to use either a northstar or LT1 throttle... not sure which one yet
I am finally almost done with this "box" ... It may look easy to make this... but it has taken me many hours of measuring, cutting, welding and test fitting.
...that is the newer 5th generation supercharger I will be running now
...and it now sits on the completed plenum that took me many hours of hard work to finish.
The major fabrication work is done...Still need to acquire some more hardware to get this thing on the road... MSD timing box, rising rate regulator, undersize pulley, northstart throttle and adapter, longer belt, etc etc
