670cfm projection unit on a 250? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

shelby987 · 02-10-2008, 10:39 PM

Is anyone familiar with this product from holley, I can't seem to find any information that tells me whether or not it can be used on 6cyl. applications.

myoldchevytruck · 02-10-2008, 11:02 PM

I am running a 670 but I,m not sure about a 6 cyl. I'll check back in a few.

myoldchevytruck · 02-10-2008, 11:11 PM

Shelby987,

Just called my local speed shop (where I bought my 670) and he asked motor size of the 6 cyl. He said if it's a 292 or larger it would be fine. He said the 570 would be his 1st choice but the 670 would work.

Good Luck

67shortie · 02-11-2008, 01:31 AM

Projection unit?

I have never heard that lingo before....

500cfm would do fine, heck Holley has a 390cfm 4bbl too that would be nice on a 250 as well.

68Stepbed · 02-11-2008, 02:15 AM

That 670 would be way too much on a six. I would look into a 390 4-bbl or a 350 2-bbl. If the engine is hotter than stock, the 500 2-bbl might work well for you too. I beleive the 570 would still be a bit much, but could made to work easier than the 670.

I'm gonna assume that the application is your 70 K20. The 350 2-bbl or 390 4-bbl will give you the best driveability and throttle response. If you do any pulling or towing, it would also help with low end torque than a larger carb.

shelby987 · 02-11-2008, 04:25 AM

just to clear up some confusion, the 670 projection unit from holley is a TBI unit, it is not a carb.
Is the Max CFM of a TBI unit really an issue? I figured I could get away with a larger cfm rating on fuel injection?

02-10-2008, 10:39 PM	#1
shelby987 Registered User Join Date: Mar 2005 Location: Just outside Durham, NC Posts: 894	670cfm projection unit on a 250? Is anyone familiar with this product from holley, I can't seem to find any information that tells me whether or not it can be used on 6cyl. applications. __________________ 1969 SS 350 Camaro Sold 2008 1970 3/4T K20, stock height with 33's, 250 I6, 3 on the tree, and locked front and rear 4.10's 1980 Chevy Malibu 2 dr Sold 2007 1993 Olds. Cutlass Ciera Wagon Traded 2006 2003 Saturn L200 w/5pd. D/D My list spans 5 decades with One common thread.....GM!

02-10-2008, 11:02 PM	#2
myoldchevytruck Retired Air Force Veteran Join Date: Aug 2007 Location: Pembroke Pines, Florida 33024 Posts: 1,808	Re: 670cfm projection unit on a 250? I am running a 670 but I,m not sure about a 6 cyl. I'll check back in a few. __________________ Harry 69' SWB Step Side 1/2 Ton w/68' Front Clip Swap from Leafs to Trailing Arms (Complete) Swap 6 Lug to 5 Lug (w/ Disk Brakes in Front) 3/6 Drop Help Support The Board Click Here For Information On How To Subscribe Krue's FAQ Page Vendors

02-10-2008, 11:11 PM	#3
myoldchevytruck Retired Air Force Veteran Join Date: Aug 2007 Location: Pembroke Pines, Florida 33024 Posts: 1,808	Re: 670cfm projection unit on a 250? Shelby987, Just called my local speed shop (where I bought my 670) and he asked motor size of the 6 cyl. He said if it's a 292 or larger it would be fine. He said the 570 would be his 1st choice but the 670 would work. Good Luck __________________ Harry 69' SWB Step Side 1/2 Ton w/68' Front Clip Swap from Leafs to Trailing Arms (Complete) Swap 6 Lug to 5 Lug (w/ Disk Brakes in Front) 3/6 Drop Help Support The Board Click Here For Information On How To Subscribe Krue's FAQ Page Vendors

02-11-2008, 01:31 AM	#4
67shortie Green club Join Date: May 2002 Location: Central CA Posts: 1,059	Re: 670cfm projection unit on a 250? Projection unit? I have never heard that lingo before.... 500cfm would do fine, heck Holley has a 390cfm 4bbl too that would be nice on a 250 as well. __________________ 71 short/fleet ECE 4/6 drop, LQ4/700r4/3.42 gears 70 SS396 Chevelle 427/200-4R/3.73posi 61 Lincoln Continental, black on black Son you are going to drive me to drinkin if you don't stop drivin that hot rod lincoln

02-11-2008, 02:15 AM	#5
68Stepbed Registered User Join Date: Mar 2005 Location: 10-Uh-See Posts: 5,609	Re: 670cfm projection unit on a 250? That 670 would be way too much on a six. I would look into a 390 4-bbl or a 350 2-bbl. If the engine is hotter than stock, the 500 2-bbl might work well for you too. I beleive the 570 would still be a bit much, but could made to work easier than the 670. I'm gonna assume that the application is your 70 K20. The 350 2-bbl or 390 4-bbl will give you the best driveability and throttle response. If you do any pulling or towing, it would also help with low end torque than a larger carb. __________________ Matt 68 C10 stepside, LS1/700R4, TCI Engineering suspension system Last edited by 68Stepbed; 02-11-2008 at 02:19 AM.

02-11-2008, 04:25 AM	#6
shelby987 Registered User Join Date: Mar 2005 Location: Just outside Durham, NC Posts: 894	Re: 670cfm projection unit on a 250? just to clear up some confusion, the 670 projection unit from holley is a TBI unit, it is not a carb. Is the Max CFM of a TBI unit really an issue? I figured I could get away with a larger cfm rating on fuel injection? __________________ 1969 SS 350 Camaro Sold 2008 1970 3/4T K20, stock height with 33's, 250 I6, 3 on the tree, and locked front and rear 4.10's 1980 Chevy Malibu 2 dr Sold 2007 1993 Olds. Cutlass Ciera Wagon Traded 2006 2003 Saturn L200 w/5pd. D/D My list spans 5 decades with One common thread.....GM!

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