I plan on putting a holley 390 on my 300, I notice there are atleast 3 different models 4208, 6299 and 8007 what is the difference and which one do I want
thanks

 

I searched SummitRacing for Holley 4208 and it is a fuel injector. There was no Holley 6299.

There are two versions of the 390 that I know of. The 0-8007 is the one you want.

The other version, the 0-80507-1, has no choke and has mechanical secondaries. It is meant for racing applications using two of them on top of a tunnel ram or other dual 4 bbl manifold.

 

I'm not sure what the differences between the models are. My guess is that the 4208 and the 6299 are custom tailored to specific engines.

The 8007 is the 'generic' model and is the only one that you can purchase new. When you go to Holley (or any other retailer) and purchase a new Holley 390, you get the 8007.

 

I did a google search for them, and they do exist. They're just not purchasable new.

 

I have a 390 on mine and you want to make sure you have a good alum intake and headers with duels. With out this you will be running to rich. For your secondaries do not use the lightest spring as your four barrel will open up almost effortlessly.I have the medium spring in mine and it still opens a bit early I believe. I would also reccomend you use a K&N air filter as well.
With this setup you will be able to pull about anything you want to. I am very impressed with this setup. The 300 is a work horse in itself but with these mods it increases torque significantly. I would love to put it on a dyno for numbers. I have hauled 2.25 tons of gravel and can maintain highway speed even going up hill. If this is what your looking for you will be happy with this setup!!!!

 

I would definitely recommend a high flowing exhaust, (although headers and duals aren't necessary). However, running rich has more to do with the carb's jetting and which jets it currently has in it.

It definitely wakes the motor up though! Night and day from stock.

 

thanks guys, there is a 6299, 4208 on ebay right now so just wondering what the difference is? contemplating between offy DP, C or cliffy?
I want it to pull hard all the way up to at least 4500rpm. truck is a 77 f-100 c-6 dana 44 rear, not sure what gear. the engine in it now has 5 psi. oil pressure and knocks real bad. I have a 91 300 I'm putting in with efi manifolds, single exhaust 2.5"
with flowmaster 40 all the way back. 260 comp cam at a later date

 

The 6299 and 4208 may simply be the same carb as the 8007 but have slight adjustments or variations to them for different emissions purposes. It's difficult to say, since they're not very common.
Give Holley tech a call or email and ask them, and see if they can provide extra information. Or do some google research.

The Offy DP is a good choice for the low end. The Offy C and Clifford are very similar but are more for higher RPMs and higher performance engines. That said, I have both a DP and a C on two different 300s and I like both. The C doesn't have the grunt, but makes for a very smooth power curve that's, for a lack of a better term, luxurious.

Keep in mind that the EFI engine is slightly different. There's no port for the fuel pump, so you'll need to run a different setup, such as an aftermarket regulated electric pump.

Also, the head on the EFI engine is designed for fuel injection and has fast burn characteristics in the combustion chambers. It'll work with the carb, but may throw things off a little.

 

Thanks, I been reading alot of stuff on here about the swap the combustion chamber, fuel pump and the like. you have alot of good stuff to say I value your opinion thank you!! I have seen your replies on alot of threads you seem to have alot of knowledge
on the big six!!!!!!

 

I'm not sure about the 4208 - couldn't find any info in my holley book on it. The 6299 doesn't have a removable power valve in the primary metering block. Which means it would make trying to tune the holley more difficult. You would be stuck with what ever was built into the carb. If you want something you can tune and adjust to your vehicle then you should stick with the 8007. They are more expensive but you can adjust a lot more on them to make your motor run the way you want it.

 

I wouldn't know a fraction of what I do if others on here and other places hadn't been willing to help me when I didn't know a thing.

Glad to help.

That's some good info to know. A non-removable power valve would really hinder quality tuning.