Carb or Holley Projection - The 1947 - Present Chevrolet & GMC Truck Message Board Network

5150.4.67 · 09-20-2008, 01:08 AM

I'm building something different from assorted collection of parts. Trying to squeeze 325hp on pump gas out of a 305 with 8.3 DCR, aluminum zz4 heads, Sandersons D ports, etc. My dad has a Projection kit (new) that he is willing to throw in. Just one catch- its the 2 barrel version (650cfm). Is that going to be adequate or should I just use a 600 cfm double pumper and rpm performer? It comes with a Holley 2 barrel manifold that looks, well, like an old 2 barrel. Anyone running Projection? What do you think (other than the fact I'm nuts for building a lil ol 305

)?

Jay

67dragtruck · 09-20-2008, 07:58 AM

I don't remember the power capability of the 2 barrel projection, but just from my first reaction 650 is still bigger than a 600 carb so as long as the injectors are large enough it should work fine. I'm going with an edelbrock pro flo efi on mine. I ran it for a short time on another 406 and the throttle response was amazing. I personally hate carbs.

Tom

chevy_mike · 09-20-2008, 11:26 AM

I agree, 650 CFM equals more the 600 CFM. I would go with the EFI in a heartbeat. So many benefits once you get it dialed in.

FWIW, most people over carb engines all the time. I know the ZZ4 I had was spec'ed to 355 HP with a Holly 650 carb and that's a 350 CI engine. Your 305 will be fine with 650 CFM.

My .02 worth.

5150.4.67 · 09-20-2008, 03:53 PM

Well thanks for the replies. I'll give the injection a try. BTW, it comes will 85# injectors. Literature says its good for 275 hp. I sure like the looks of that 4 barrel inj system though! Yeah, 650 cfm should be plenty.

Jay

PanelDeland · 09-20-2008, 05:16 PM

Actually the 650 is probably good.The idea of a larger carb making more HP is true at the top end but with a carb you get the top end at the cost of lower RPM driveability.A carb guru explained it to me that at WOT you want all the air/fuel mixture you can get.But lower RPM cruising speeds and stop and go around town require better throrttle response in the mid range.Cruising RPM needs a better vacuum signal and flow velocity to run well in those ranges.According to him the 600-650 range was probably about right for all but the wilder street driven cars.So if you want mileage,throttle response and driveability I would say the 650 projection would be a great choice. In this case the 600 cfm carb would probably be a good choice for the 305 also.Sounds like it's a question of which you want to tune.

67dragtruck · 09-20-2008, 07:25 PM

Check into the injectors a bit. Sometimes you can cheat them a bit by running them at a little higher pressure. Edelbrock does this with my kit and get 30 lbs out of 26 lb injectors by running them at 50 psi instead of 45. Just a thought, but it sounds like you need a bit more fuel to support the power level you are after.

Tom

5150.4.67 · 09-20-2008, 11:58 PM

Tom, I think your right. I may run into trouble up on top. The kit does come with adjustable regulator, I guess I'll just have to play with it.
Also, I wonder if I can get away with 0.045 quench without detonation?

Thanks again for everyones input.

Jay

09-20-2008, 01:08 AM	#1
5150.4.67 Registered User Join Date: Dec 2007 Location: Modesto, Ca Posts: 411	Carb or Holley Projection I'm building something different from assorted collection of parts. Trying to squeeze 325hp on pump gas out of a 305 with 8.3 DCR, aluminum zz4 heads, Sandersons D ports, etc. My dad has a Projection kit (new) that he is willing to throw in. Just one catch- its the 2 barrel version (650cfm). Is that going to be adequate or should I just use a 600 cfm double pumper and rpm performer? It comes with a Holley 2 barrel manifold that looks, well, like an old 2 barrel. Anyone running Projection? What do you think (other than the fact I'm nuts for building a lil ol 305)? Jay

09-20-2008, 07:58 AM	#2
67dragtruck Registered User Join Date: May 2001 Location: Bethlehem, GA, USA Posts: 389	Re: Carb or Holley Projection I don't remember the power capability of the 2 barrel projection, but just from my first reaction 650 is still bigger than a 600 carb so as long as the injectors are large enough it should work fine. I'm going with an edelbrock pro flo efi on mine. I ran it for a short time on another 406 and the throttle response was amazing. I personally hate carbs. Tom __________________ No more dragtruck for me. I'm building a new ride though. It's a '71 fleetside, 400 sbc, 700R4. Working on it now, finally. Soon to have Edelbrock Pro Flo EFI, Vintage Air, 1 piece windows, buddy buckets, etc. My new build thread: http://67-72chevytrucks.com/vboard/s...17#post2861817 Best pass with the old dragtruck: 5.32 @ 131.6 mph 1/8 mile w/ a 1.25 60' Fogger/Plate 2003 Best pass with the street 406 hydraulic roller motor w/ mild plate tuneup 5.93 @ 114 mph 1/8 mile w/ a 1.29 60' 2003 or 2004

09-20-2008, 11:26 AM	#3
chevy_mike Never Ending Projects Join Date: Jul 2006 Location: San Diego, CA Posts: 3,836	Re: Carb or Holley Projection I agree, 650 CFM equals more the 600 CFM. I would go with the EFI in a heartbeat. So many benefits once you get it dialed in. FWIW, most people over carb engines all the time. I know the ZZ4 I had was spec'ed to 355 HP with a Holly 650 carb and that's a 350 CI engine. Your 305 will be fine with 650 CFM. My .02 worth. __________________ . 1965 C10 Panel, Tiki Express http://www.67-72chevytrucks.com/vboa...d.php?t=506580 SOLD 1968 Chevy C10, Long, Fleetside, Hot Rod Hauler http://67-72chevytrucks.com/vboard/s...d.php?t=313233 SOLD 1965 Chevy C10, Long, Fleetside, Hot Rod C10 http://67-72chevytrucks.com/vboard/s...d.php?t=415702 SOLD We were given two ears and one mouth for a reason... listen twice as much and speak half as often...

09-20-2008, 03:53 PM	#4
5150.4.67 Registered User Join Date: Dec 2007 Location: Modesto, Ca Posts: 411	Re: Carb or Holley Projection Well thanks for the replies. I'll give the injection a try. BTW, it comes will 85# injectors. Literature says its good for 275 hp. I sure like the looks of that 4 barrel inj system though! Yeah, 650 cfm should be plenty. Jay Last edited by 5150.4.67; 09-20-2008 at 04:03 PM.

09-20-2008, 05:16 PM	#5
PanelDeland I am a Referee of life. Join Date: Jun 2000 Location: Greensboro N.C. Posts: 13,992	Re: Carb or Holley Projection Actually the 650 is probably good.The idea of a larger carb making more HP is true at the top end but with a carb you get the top end at the cost of lower RPM driveability.A carb guru explained it to me that at WOT you want all the air/fuel mixture you can get.But lower RPM cruising speeds and stop and go around town require better throrttle response in the mid range.Cruising RPM needs a better vacuum signal and flow velocity to run well in those ranges.According to him the 600-650 range was probably about right for all but the wilder street driven cars.So if you want mileage,throttle response and driveability I would say the 650 projection would be a great choice. In this case the 600 cfm carb would probably be a good choice for the 305 also.Sounds like it's a question of which you want to tune. __________________ The 47-present Chevrolet and GMC Truck Message Board Network,it's owners,moderators,members,and associates of any type should not be held responsible for my opinion. You can't fix stupid,not even with duct tape. "My appearance is due to the fact that "GOD" does punish you for having too much fun!" Barrett-Jackson has perfected alchemy,they make rust into gold! "You can lead a horse to water but you can't saddle a duck" "Cleverly disguised as a 'Responsible Adult' "Sometimes your Knight in shining armor is just a retard in tinfoil"

09-20-2008, 07:25 PM	#6
67dragtruck Registered User Join Date: May 2001 Location: Bethlehem, GA, USA Posts: 389	Re: Carb or Holley Projection Check into the injectors a bit. Sometimes you can cheat them a bit by running them at a little higher pressure. Edelbrock does this with my kit and get 30 lbs out of 26 lb injectors by running them at 50 psi instead of 45. Just a thought, but it sounds like you need a bit more fuel to support the power level you are after. Tom __________________ No more dragtruck for me. I'm building a new ride though. It's a '71 fleetside, 400 sbc, 700R4. Working on it now, finally. Soon to have Edelbrock Pro Flo EFI, Vintage Air, 1 piece windows, buddy buckets, etc. My new build thread: http://67-72chevytrucks.com/vboard/s...17#post2861817 Best pass with the old dragtruck: 5.32 @ 131.6 mph 1/8 mile w/ a 1.25 60' Fogger/Plate 2003 Best pass with the street 406 hydraulic roller motor w/ mild plate tuneup 5.93 @ 114 mph 1/8 mile w/ a 1.29 60' 2003 or 2004

09-20-2008, 11:58 PM	#7
5150.4.67 Registered User Join Date: Dec 2007 Location: Modesto, Ca Posts: 411	Re: Carb or Holley Projection Tom, I think your right. I may run into trouble up on top. The kit does come with adjustable regulator, I guess I'll just have to play with it. Also, I wonder if I can get away with 0.045 quench without detonation? Thanks again for everyones input. Jay

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