Holley 50cc pump question

Can i replace my holley`s(800 DP)30cc front pump with a 50cc?

Thanks

 

50 cc pump

George
I replaced the 30 cc pump on my 850 BG Mighty Demon( basically the same body as a 800 Holley) with a 50 cc unit for a Holley. The only problem I ran into was that I had to put a spacer under the carb because the pump is deeper than the original 30cc unit. This cured the nasty stumble I had. :TU:

 

How big of a spacer did u have to use?what manifold are you using?what discharge nozzles or squirters are you using?i`m trying to cure my off idle stumble also.

Thank you

 

Spacer

I used the smallest I could find because of hood clearance issues. I used a 1/4 " and its on a T/A SP 1. The squirters are #40 font and rear.
I have heard that the manual trans cars need that extra bit of fuel from the squirter/acc pump because of the clutch not having the cushioning effect of the converter on a automatic trans.

 

I think i`m runnin 37`s on the front,i wanted to go bigger thinkin it might cure my stumble but all these chevy guys around here think i`m nuts going to a big squirter like that,thank you for the info i will try the 50cc pump shot and see from there.

Thank you

 

I installed the 50cc pump yesterday but i tell you it ran really really crappy,it felt like it was loading up so i took it back off and put the 30cc back on and ran normal any thoughts?

Thanks

 

can you be more specific?

 

sure,what would you like to know?

Thanks

 

Hey Guys, George Did You Try Changing Pump Cams Cause It Sounds Like You Had To Much Fuel Going In At The Wrong Time.. Change The Pump Cam And I Think Your Problems Will Go Away, They Come In All Different Colors For Different Pump Shot Curves....

 

Eric,good question about the cam but which colored cam do i switch it to?


Thanks

 

George, It's Trial And Error... Also You May Have To Change Squirters To Get It Just Right.. It Took Awhile For Me To Get It Just Right...

 

I'm with Eric, it's all in the cam. At least they're easy to change.

Good luck

 

On my carb when i installed the 50cc pump was the pink cam,the kit came with a brown and a tan cam?

Thanks

 

Well after trying to cure my off idle stumple for so long i finally decided to take my 800 dp and replace it with a brand new 850 dp and guess what the stumple is no longer there,totally gone and runs a million times better than the 800 did.

Thanks

 

So now I'm curious.....what pump/cam/shooter combo is in the 850 as compared to the 800?

I just started reading this thread today, but I agree with the guys offering advice. I don't think the 'carb change' actually fixed your problem; more likely it just has the right combination of parts in the accelerator pump circuit.

JMHO.

Reid

 

it seems the 850 has bigger venturies than the 800 also.

Thanks

 

Yes, it should, but that won't affect your off-idle stumble. That was the original problem, right?

I think you're still back to accelerator pump tuning. If you can compare them and get the 800 set up the same, maybe it will work okay for you.

 

Pumps and Air bleeds

You can buy a pump cam kit that contains all the pump cams to make all the adjustment you need. You can adjust where and when the extra fuel comes in compaired to throttle position.

As far as the difference between 800 and 850. Holley breaks down there carbs for "general" motor combinations. Ever carb is different and is more than just a airflow difference between the carbs. Therefore the fuel curve may match your motor or it may not. For the same reason a #8896 1050 Dominator runs like crap on a Buick and a #9375 1050 is great out of the box. Holley changes air bleeds and internal emulsification circuits to change how soon the fuel starts to flow out of the main jets. A motor with a hotter cam may not work with a 800 but will work with a 850. That 800 might be much happier on a stock motor that has better signal to the carb. The 850 would probably over-fuel a more stock motor. So a squirter adjustment may just cover a problem if you are having to do excessive adjustment to the pump shot. Just because you got rid of a stuble doesn't mean its right, just not bad enough to stumlbe anymore. So always try to stick with carbs that work well and make good HP on Buick 455's. Does help explain things a little.

Generally loose converters or too tight of converters require carb squirter and pump cam adjustments. Also 1"+ carb spacers need more of a pump shot for the added plenium volume.

 

Thanks for the info Rick,my car is not an automatic its a manual shift,and i`m not using a spacer either just a plate that holds the pressure regulator.

Thanks