holley 650 dp on 383

[donpr]

I can get a holley 650 dp, will this be a good choice on 383 1986 silverado.here are engine specs http://www.jasperengines.com/pdf/Cla...20Stroker%2009

[geezer#99]

Might work if....
You have the right high stall convertor and rear gears.
Like 2800 stall and 3.73's.
But...
I prefer a vac sec carb like the holley 3310 750 cfm.
Easier tuned with adjustable secondaries.

[donpr]

Thats what I have now, 3310...Im not sure of gearing . I just got truck 4 weeks ago.

[donpr]

I think 4.10

[donpr]

th 400 trans. from jasper too

[donpr]

geezer, I also have elec. fuel pump regulated to 8 * , then get back from drive and its at 4.5-5*. Is this norm or is pump f****

[geezer#99]

As long as you don't run out of gas at 6 grand, you're good.
Is it a liquid filled gauge?
They're known to do that.

[donpr]

holley guage , not liquid filled , holley regulater too. I noticed it did this when I switched from eddy to holley carb. ??? not before.

[OutlawDrifter]

650cfm will be a better street carb. it will speed up the velocity of the air down low in the rpm range. i agree on a vacuum secondary, especially for an auto trans.

[donpr]

ya, the 650 I can get is mech. secondaries. Ill keep the 3310. at least for now.

[cad]

The 650 DP will be fine. Jet it a couple sizes below factory spec, and run it.
I had one on my 10.5:1 383 and it loved it.

[donpr]

thanks cad, do you remember jet # size ?

[cad]

Here is a good listing of orig specs for all Holleys.
http://www.allcarbs.com/tech.php?art=21
The model # will be on the choke horn (4777-1, etc). These are the baseline jets listed.

[donpr]

thats great ... no trouble with being automatic trans., like Im reading in forums and like Outlaw Drifter pointed
out ?

[Tom]

Regardless if it'll work or not, its not an upgrade from your current 3310. You'll get zero improvment in power, torque or gas mileage.

[MikeB]

Originally Posted by Tom

Regardless if it'll work or not, its not an upgrade from your current 3310. You'll get zero improvment in power, torque or gas mileage.

I disagree. Smaller primaries = higher velocity = better fuel atomization = crisper throttle response AND the potential for better gas mileage.

Of course, that assumes proper jetting and power valve selection, as well as staying out of the secondaries until the engine needs them.

That said, I wouldn't use a DP any bigger than 390-450 on a heavy vehicle with auto trans.

Interesting note: Holley says if you can feel the secondaries kick in, what you're really feeling is a bog.

[68c10owner]

Originally Posted by MikeB

I disagree. Smaller primaries = higher velocity = better fuel atomization = crisper throttle response AND the potential for better gas mileage.

Of course, that assumes proper jetting and power valve selection, as well as staying out of the secondaries until the engine needs them.

That said, I wouldn't use a DP any bigger than 390-450 on a heavy vehicle with auto trans.

Interesting note: Holley says if you can feel the secondaries kick in, what you're really feeling is a bog.

A double pumper is not going to come close to the fuel mileage of a vacuum secondary carb. A 3310 Holley would be ideal or the Quick Fuel Slayer series 750 in a street/strip set up. But this engine is fairly mild and the qjet will more than be enough carb and give great performance as well as decent economy if you can keep your food out of it.

BTW, THe Smallest DP I know of is a 390cfm and next one up is a 600cfm. This type of carb doesnt fit this build at all.

[Tom]

Originally Posted by MikeB

I disagree. Smaller primaries = higher velocity = better fuel atomization = crisper throttle response AND the potential for better gas mileage.

Your not factoring in the massive amount of fuel shot in[doublepump= double shot of gas] every time the accelerator is advanced at all.

[MikeB]

Originally Posted by Tom

Your not factoring in the massive amount of fuel shot in[doublepump= double shot of gas] every time the accelerator is advanced at all.

I didn't consider that. But doesn't the rear pump squirt only when the linkage progresses to the point where the secondaries start to open?

BTW, back around 2002 I ran a 650 VC Holley modified by QFT on a mild 383 with a Crane cam (210/210; .470"/.470" lift with 1.6 rockers), Dart 180 heads, and Performer RPM intake. It worked well and let the engine rev to 5800 RPM or so, which was 600 RPM higher than with a Performer 2101 and Edelbrock 600 carb. However, I probably didn't rev it that high more than twice! To me the beauty of a 383 is low- and mid-range torque. So you don't have to rev it as much as a 350 to go fast.

[68c10owner]

Originally Posted by MikeB

I didn't consider that. But doesn't the rear pump squirt only when the linkage progresses to the point where the secondaries start to open?

BTW, back around 2002 I ran a 650 VC Holley modified by QFT on a mild 383 with a Crane cam (210/210; .470"/.470" lift with 1.6 rockers), Dart 180 heads, and Performer RPM intake. It worked well and let the engine rev to 5800 RPM or so, which was 600 RPM higher than with a Performer 2101 and Edelbrock 600 carb. However, I probably didn't rev it that high more than twice! To me the beauty of a 383 is low- and mid-range torque. So you don't have to rev it as much as a 350 to go fast.

You are correct about the secondaries but they start to open pretty quick because they are set up with the primaries with mechanical linkage where as a vacuum carb relies on engine vacuum or open them.

A 600 cfm carb will starve a 383 if it`s anything more than stock and you are trying to rev it, and 5800rpms isnt high. It all depends on how the engine is built as to what rpm it will need to turn. The same cam in a 350 and a 383 will have 2 different power bands. The bigger engine will be done sooner.

[68c10owner]

That camshaft is fairly mild in a 383. I would say the 650 would not be the best choice in a street application. Im a die hard Holley guy but for this set up I`d actually recommend a q-jet from Sean Murphy Inductions. I think in this application it would out perform the 650 as well as the 3310.

[OutlawDrifter]

A qjet is the best choice period. People are scared of them because they are complicated.

[Tom]

Originally Posted by OutlawDrifter

A qjet is the best choice period.

That's been dyno proven to be un-true, at least for best power.

[OutlawDrifter]

I didn't say it was the best for peak HP numbers. It's a better street carb, plain and simple. I'll give up a few ponies on the top side for better driving manners and set it and forget it maintenance.

[68c10owner]

Originally Posted by Tom

That's been dyno proven to be un-true, at least for best power.

Originally Posted by OutlawDrifter

I didn't say it was the best for peak HP numbers. It's a better street carb, plain and simple. I'll give up a few ponies on the top side for better driving manners and set it and forget it maintenance.

For this mild engine the qjet is perfect. It`s going to be a grunt engine. Dont think it will even see 400hp but should be over 400ftlbs of torque. Besides, unless this is going to hit a dyno I dont think the OP will notice a difference but he should like the throttle response and economy the qjet offers as well as great performance. As I said before, I`m a die hard Holley guy but I`ve seen these custom qjets make the same or more hp over the Holleys in certain situations.