A little more Horsepower

[DAVID GAGNARD]

Fast;

again just .02 cents worth.......

My old 600 DP is the plain Jane variety and it works great, I have a 650 DP Demon Race carb on my race car (331cu. in. right at 500hp) and I have tried it on my 351-W "street' engine and didn't really find enough difference to justify the extra $$$$..


I would also suggest the 650 DP over the 600 DP, not that much difference in performance and price, but gives you a little extra "wiggle room" for future upgrades, again JMHO.......

If money is not a problem, go with the HP "race series" carb, otherwise on a light car with your engine the "Classic DP" for almost half the price will suit your needs just fine....
The other $300.00 bucks or so could be used for a cam upgrade later or other "bolt-on" upgrades..........

If it were my call, I'd go with the Classic 650 DP Holley and put the additional money to other upgrades and/or your exhaust system.

Also on my old 600 DP, I spent about all of 20 minutes with a hack saw and hand file and cut off the choke horn myself, don't know if you gain much, but it looks cool and costs me nothing but a little time........

David

[fastd]

Reality check: how much time do any of you spend over 6000 rpms?

[patrickt]

Originally Posted by fastd

Reality check: how much time do any of you spend over 6000 rpms?

My peak shifting points are basically at 6000. I have my rev limiter set at 6400. So to answer your question, "only when I'm getting on it and screw up my revs."

[RodKnock]

Originally Posted by fastd

Reality check: how much time do any of you spend over 6000 rpms?

Did the Holley tech say that it doesn't help at all in the lower RPM ranges? I mean no benefit?

[fastd]

I have a 6000 rev limiter (that seems to kick in around 6300 rpms)

The Holley tech said that 600 cfm will be better at the lower RPM ranges than the 650...

[patrickt]

If all the planets align just right, here is where I shift. I have never made that 4th to 5th shift though at the suggested RPM.

[fastd]

Spoke with my tuner again; we are going to go with the 600; he says that this carb is so adjustable that I will have no problem if I want to go bigger later; and as the engine is now, it is the best choice.

FYI, I won't have it installed until the week after next (Thanksgiving), so all of you are just going to have to wait for the dyno results.

[patrickt]

... and he likes the more expensive HP version, yes?

[fastd]

Patrickt,

Of course...

[olddog]

Originally Posted by fastd

All,

My tuner came back to me and said he thought the 600 cfm dp would be a better fit than the 650 dp; based on David G's and olddog's post, you guys would probably agree...?

Fastd

I'm a little late, but yes. I would think the 600 would be just fine. I don't think head and cam changes are going to need more carb unless you rev much higher, which I doubt your bottom end is good for.

In my puppy days, I liked the spread bore carbs for engines that ran through a large rpm range. The smaller bores were more tunable at idle, and the big bores breathed better in the 8000+ range. I don't think you would need one.

I don't think I ever ran into a hot rodder with a small block that was't over carbed, or a big block that was under carbed. You might be the first.

[fastd]

Olddog,

I agree with everything you said. "You might be the first" - Wow; nice.

I am hoping to get it just right.

I asked a lot of questions and found out that my 750 hp with vacuum secondaries found out really isn't working right; if I were to keep the 750 hp I would have to change the springs and add a metering block. I found out that the stock spring that came with carb is the heaviest - the "black" spring - and for my size engine, the spring doesn't start opening until 2700 rpm, and never fully opens! I would have go down to a yellow spring I think. And since it runs lean at the top, I would need to add the metering block that would provide the ability to changes the secondary jets. After I did all of that though, I would still have too much carb. So, going with the 600.

[patrickt]

I think you're going to get the horsepower improvement you want. It might not be the absolute most you can get, but all you have to do is hit the throttle once on the street and have the rear break loose unexpectedly and then you'll say "well, maybe I do have enough horsepower now."

[fastd]

I think that is exactly what I am looking for...don't really care about the numbers so much.

[fastd]

Dyno Results are in!

Previously best real run was 301 hp and about 292 lb torque.

Change the carb to 600 dp (with a 1" carb lifter plate) and changed to 2.5" exhaust (from stock ERA 2");

New numbers: hp was up 50 to 351.1 @ 5250 rpm and torque was up about 70 to 361.7 @4750.

Very satisfied (although couldn't take a test drive due to snow) and the guys at DG Performance at Wake Forest/Franklinton were absolutely fantastic. Highly recommend for anyone in the area. The guys treated my car like it was their own.

[Stentor]

Congratulations on the increase in HP and TQ. I am sure you are eager to take her for a drive.

[*13*]

Just install a line lock & do burnouts in the garage.

[MaSnaka]

FastD,
Those changes in HP and TQ were about what I got from a muffler change (double chamber restricted to 2 1/2" open), an intake manifold upgrade (performer 390 to rpm performer) and proper carb tuning (770 Holley street avenger). The difference is quite noticeable but not over the top. Just feels like the engine woke up. Sounds better too. You will be happy.

John

[fastd]

Took my car out for a test drive (31 degrees in North Carolina, roads still a little wet) after the power increase - WOW!!!