Installing an Offy DP
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Junior User
Joined: Aug 2003
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Installing an Offy DP
I just bought a 79 f-150 with a 300 in it. I have an offy DP and was thinking about putting it on the truck. But I was thinking that it may be a waste to put the manifold on without doing any other modifications. What do you think, would I see a power increase or just a increase in consumption of fuel?
Senior User
Joined: Jan 2003
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I just put offy dp with holley 390. EFI manifolds/ walker downpipe/ magnaflow high flow cat/ flow master 50 series with 2.5" duals.
I haven't driven it much yet. I still haven't got the holley tuned just right, but it will scoot for a 300 I can tell you that. It will hit 70mph real quick.
I haven't driven it much yet. I still haven't got the holley tuned just right, but it will scoot for a 300 I can tell you that. It will hit 70mph real quick.
Senior User
Joined: Jan 2003
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You will need to make a bracket for your throttle cable. I made one that attached to 2 stud on my intake. Mine is an auto, so I used a Lokar kick down cable, and ditched the factory rod.
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Freshman User
Joined: Dec 2003
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From: so cal
Thanx I have a Dolphin motorhome built on a 1982 custom f150 with the 133" wb I have already put clifford long tube headers 2/1/2" pipe and a magnaflow muffler. now for the offy and holley I used to be a drag race in the 1950s but I still have the hot rod urge. Any other tips you can give me will be greatly appreciated
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Senior User
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That thing will really come to life when you get done. I know I have been really happy with mine so far. Don't hold me to it, but I will try to take a pic of my bracket setup. That was my biggest headache in the whole deal.
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Joined: Dec 2003
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From: so cal
Thanx again, does your holley sit sideways or straight ahead? did you use a spacer block? I have a lot of questions. how much is the lokar cable? I have about used up my social security this month but I am eagar to finish this mh.
Senior User
Joined: Jan 2003
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Yes, It sits sideways with the primaries toward the head. I recommend a 2" spacer. At first I had a 1", but I tink the 2" gives better clearance for the throttle cable. I am thinking the lokar is $50. Kind of steep, but it does work slick. I got mine from summit racing.
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Joined: Nov 2003
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From: Kalispell, MT
how do you make your spacer? or do u buy it? also, somebody mentioned at one point to make a divider for the intake manifold, to split the barrels of the carb...how do you do this, as well? also...i'd like some opinions of carb makes/models from anybody that has an opinion?? edelbrock? Holley?? what size? and, yes...another stupid question...what the heck's CFM stand for?
MontanaFord
MontanaFord
Last edited by MontanaFord; Dec 22, 2003 at 11:47 PM.
Elder User
Joined: Nov 2003
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From: Kalispell, MT
also...i'd like some opinions of carb makes/models from anybody that has an opinion?? edelbrock? holley?? what size? and, yes...another stupid question...what the heck's CFM stand for?
MontanaFord
MontanaFord
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From: Colorado
You'll find a lot of opinions on carb types and sizes.
For 2 bbls., the 350 cfm (Cubic Feet per Minute) or 500 are usually recommended. Holley makes both.
For 4 bbls - the Holley 390 is the smallest and some guys report running up to 600 cfm. The 390 is supposed to be the best "fit" of the 4 bbls (for the 300-six). Many are happy with 450, 500 and even 600 cfm 4 bbls. Since you can run on the front 2 bbls a lot, they can fit & function well - even if technically a bit large.
Demon, Edlebrock & Holley seem to be the carbs most often mentioned. A smaller cfm will give you the best driveability and fuel economy . There's a chart in most Holley books recommending a carb size that "fits" best. For the 300 that's around 300cfm @ 4,000 rpm . The choice depends on a realistic assessment of how you will be driving most of the time.
Some also mention using a 600 cfm because they had one (or could get one cheap - they're fairly abundant). While a 600 could supply our 300 ci. sixes with enough fuel to spin 8000rpm it's a bit large (theoretically). Even so, some report satisfactory results using 600 cfm carbs. At $300+, a new "perfect fit" carb isn't always an option.
broncr
For 2 bbls., the 350 cfm (Cubic Feet per Minute) or 500 are usually recommended. Holley makes both.
For 4 bbls - the Holley 390 is the smallest and some guys report running up to 600 cfm. The 390 is supposed to be the best "fit" of the 4 bbls (for the 300-six). Many are happy with 450, 500 and even 600 cfm 4 bbls. Since you can run on the front 2 bbls a lot, they can fit & function well - even if technically a bit large.
Demon, Edlebrock & Holley seem to be the carbs most often mentioned. A smaller cfm will give you the best driveability and fuel economy . There's a chart in most Holley books recommending a carb size that "fits" best. For the 300 that's around 300cfm @ 4,000 rpm . The choice depends on a realistic assessment of how you will be driving most of the time.
Some also mention using a 600 cfm because they had one (or could get one cheap - they're fairly abundant). While a 600 could supply our 300 ci. sixes with enough fuel to spin 8000rpm it's a bit large (theoretically). Even so, some report satisfactory results using 600 cfm carbs. At $300+, a new "perfect fit" carb isn't always an option.
broncr
Last edited by broncr; Dec 23, 2003 at 08:23 AM.
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From: so cal
Broncr; thanks for the input, according to 'vince' at offenhauser the holley works the best it is the one that goes on with the least amount of hassle, also offy makes a linkage kit for this setup, thru jeggs it is about $90.00 I ordered one but haven't got it yet [the 390 cfm] hbarharry [old guy]