30 CC ACCELERATOR PUMP ON A 500 CFM 2300 HOLLEY??

[wsa111]

Has anyone out there gone from the 50 cc accerator pump to the 30 cc pump on a 500 cfm 2300 holley on a log manifold. The same throttle bore & venturi diameter of 1 3/8 is used on a 750 cfm 4bbl using the 30 cc pump on the primary throttle. Just wondered if anyone had tried to down size the huge pump shot from the 50 cc pump shot. The 4bbl carb uses the white cam in #1 pump position which is the least amount of pump shot.
The 500 cfm 2300 holley was designed for a certain type of usage on large v-8's, which would require a large accerator pump shot.
Are we over shooting with the smaller engines such as a 200 or a 250 six??? Any thoughts or experience would be appreciated. : William

 

[Anonymous]

My old 250 liked an aggressive shot off idle from the Holley 500, but not a lot of volume past 1/2 throttle. I used an orange cam in the #2 slot. It also responded noticeably better than a "1.21" Autolite 2100 that it replaced. I doubt the Autolites have that big of a pump. The 30cc is typically for marine applications where throttle response is far less crucial and throttle applied slowly.

Before changing the pump/diaphram, I would try a smaller cam and different mounting slots/positions. Even with a 50cc pump, a small cam may only use 25 ccs.

 

[xctasy]

Sounds right enough.

The time of concentration for fuel to travel from the pump squirters to number 6 and 1 is longer than from number 1 to 8 on a V8. Sotck 25, 28 or 31's are often too small to give a good transition with the leaner 63 to 69 jets most 500 punters run.

The deal is that a six needs more squirter jet than a V8. The stock I6 manifold has many 90 degree drop outs, and lots of wetted port area to drop fuel out of suspension. The old plain Jane V8 two plane manifold is not that bad. That's my sum up from what I've seen with Chrylser 265's and Ford X-flows. It's certainly something I have calculated from runner length with the small Ford Log I6's.


I think your real question may be this:-

"does the 50 cc ever run out of fuel on transition with the ideal jets for a healty six". I'd say no. Even with 31 and 34 jets commonly used here.

It's probably worth getting a 34 squirter set up with a 30cc pump on the more savage plastic cam position, and see if it runs out of gas in the 40 to 60 range in 2nd.

(This is from 3000 to almost 5000 rpm on most engines. It shouldn't run out of fuel when accelerating savagely).

 

[wsa111]

John & Deano, thanks for the feedback. Would you believe i must read your mind cause i would start out with the orange cam in the #2 position as my first choice. I have already changed to the 30 cc pump, but in hindsite i should have just left the 50 cc pump in there & just change cams. The pump will only pump what ever the cam rate of lift & total lift regardless of potential pump capacity. as far as main jet size i just need to get this head & camshaft upgrade installed along with header & the transistion to dual exhausts via a x-pipe.
Gentleman again thanks for the info. william

 

[Anonymous]

Bill,

Never tried it myself

I've swapped 50cc pumps in place of 30cc pumps on 4 bbls before but never vice versa.

Just a FYI. I swapped back to a .028 center squirter (per your advice) and it works great!!

I'm done tinkering with the carb so heres what it is;

.028 squirter
6.5 power valve
#72 jets

Thanks for the advice!!

Doug

 

[wsa111]

Doug, you have nothing to lose. try an orange accerator cam in the #2 position with your present setup. Set your present accerator to holley specs .015 at full throttle between the lever & the pump arm???
give it a shot & let us know the results. As john said it will cut down on pump discharge past 3/4 throttle,either you will have a flat spot or it will crispen your throttle response & fuel mileage. Keep in touch, bill