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Thread: Holley Ultra XP 850 vs 950?
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11-21-2017 #1
Holley Ultra XP 850 vs 950?
I have a 67 Camaro with a LSX 454 which has ported heads, LPE GT21 cam (700 lift), 11:1 CR, and a tall intake manifold. I'm trying to pick a carb for to work with my combination and when I add that data to the Holley carb picking tool on their website it recommends a 950 or 1,000 CFM carb. When I use the equation that most hot rodders go by which for me is 454 x 6500 x 1.05 (efficiency correction factor with 243/259 duration and race ported heads)/3456 = 896. This will be a street car with some events and street racing. The 2 tuners I spoke with said the 850 is going to be the best even though the 950 will make a couple more HP up top. Any advice or shared experiences would be greatly appreciated.
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11-21-2017 #2Registered User- Join Date
- Oct 2016
- Posts
- 244
Sorry no advice but I have a 950 not the XP but a custom built carb that I bought and is way too much carb for me. I'll sell it cheaper than an XP if your interested. I could send u the build sheet if interested. Lmk if interested.
11-24-2017 #3does anyone have any experiences with the new XP carbs in 850 or 950 CFM on a modded LS motor?
11-26-2017 #4Registered User- Join Date
- Apr 2017
- Location
- TX
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- 138
I can give you some real world advice that I have learned over the years. A smaller carburetor will give you better throttle response and more torque at a lower RPM. With the smaller carb your car will be more enjoyable to drive and feel faster. With the larger carb it will probably be a couple of hundredths quicker in the 1/4 mile but its not that much. My advise is to go small if it is mostly street driven. I have a SBC 406 with a 750 hp series and it runs awesome even though it could make more power with a 850.
Dan
11-26-2017 #5
11-26-2017 #6Good choice as most folks tend to over carb their engines as has been said to me many times by the Holley engineers.
11-26-2017 #7Registered User- Join Date
- May 2013
- Location
- San Diego, CA
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- 265