Carb changes (jets, accelerator pump, pump cam, etc)...eval

[Anonymous]

Hey all. I finally got around to making the carb changes that William (and others) have suggested...

dropped my main jets even further. Went from the original 73's running really rich, to 71's last week which were still rich, to 68's tonight. Seem better (upper end of STOICH on the gauge at idle).

changed to the orange pump cam at #2 position

changed to the 30CC pump (from 50cc original). I think i got the pump lever adjustment right. I don't have a feeler gauge, but I just set it so that there is no play between the spring screw and the pump lever at idle position. Sound right?

I left the 8.5 PV in there, but I'm getting a little lean shot right from GO so I may need to bump it up right? I also do get a slight hesitation if I'm cruising at like 25mph and I stomp on it. What do you think? Need to up the jets maybe to 70's? different PV?

I also added a fuel pressure gauge in line. I'm only getting a hair more that 3PSI out of the stock pump. I've read my Holley really wants more like 6, no? Maybe need to invest in an electric pump and regulator setup...what do you think?

I haven't changed the shooters at all. Should I tinker with them? the fuel shot that comes out doesn't seem very atomized...pretty solid shot of fuel. Don't I want it more of a spray?

I checked out a copy of Powertuning Holley Carbs...best read in a while. If you have a Holley and want to tinker and tune it, go find this book. It's the bible of Holleys.

Thanks all.

 

[Anonymous]

ok, was just rerading the part about the pump cam, and I'm confused.

There are two holes on the cam labeled #1 and #2. There are also two holes on the pump lever labeled #1 and #2 as well.

The cam I took (brown) was screwed in through hole #1 on the lever (not sure which hole on the cam itself). When i stuck the orange cam on, I jsut lined up the holes and put the screw into hole #2 (with the numbers on the cam itself facing toward the carb..away from me). IS that cam position #2 though? How would that be any different from sticking the screw into the #1 hole. Both holes lined in the lever lines up with the holes in the cam. I'm missing something here. Unfortunately, my Holley bible doesn't really explain this.

How do you determine cam positions #1 and #2?

 

[wsa111]

Bryce, first get 6-7 # of fuel pressure, second set the float level so the level is right at the lower threads of the fuel level plug, third put in #70 main jets, fourth put in the blue accerator pump cam in the #2 screw hole. fifth with the throttle wide open there should .015 clearance between the accerator pump lever & the adjustable screw on the end of the link, this can be adjusted with a 3/8 box & open end wrench. You have to take a pair of pliers to fully open the accerator pump lever & measure & adjust the proper clearance. Last but not least try the 8.5 or the 7.5 power valve, but i am using a 2 stage power valve to cover the lean hole in the part throttle position. The holley # is 125-210 which starts to open @ 9.0 hg & fully open @ 2.5 hg.
You have an OZ head so you may have to go to a #71 main jet???
I have modified the blue accerator pump cam & rounded the sharp corner at the opening ramp to have the same contour as the top corner of the orange cam. I will do a post on this later.The blue cam has the extra lift to richen up the mixture as needed, but without the 50cc pump.
With these modifications using the 30 cc pump have worked out to perfection. Let us know if this combination works for you.
When you set your idle mixture keep it on the lean
edge side otherwise your idle mixture will be too rich. Use a lean drop in idle of 15-25 rpms so your are not to rich then set the idle speed as needed, you may have to do this several times to get the right combination. You don't need a vacuum guage to do this, after years of experience using an air fuel meter you get the feel. The vacuum guage is old school & will produce a slightly richer mixture than needed.
However don't be afraid to use one to get you in the ballpark, and fine tune from there. William

 

[Anonymous]

My Holley tuning mentor steps up to the plate again. Yeah, when I say 3psi I was not happy.

I'd be very interested in your blue cam adjustment! Did you have a second to read my second post about my cam confusion? I thought I understood...seemed pretty easy...but after thinking about it, I made myself more confused!

How can just moving the screw from one hole to the other change anything unless I should also be changing the position of the cam itself? Are both holes supposed to line up on the lever and cam? the way mine is now, with the numbers facing away from me, hole #1 on the lever aligns with #1 on the cam and #2 on the lever aligns with #2 on the cam. I just don't seem to get it I guess. Sorry... :roll:

 

[wsa111]

Bryce, the # 2 setting depending on the pump produces more pump shot rather than the #1 position.
When you install the screw to fasten the pump cam, use the bottom hole which is the # 2 position. The # 2 position is the lower hole in the plastic cam line them up & install the screw in that position. Then check your full pump travel adjustment as described in the holley manual.
You need an electric fuel pump & a better mechanical pump to. Use both the electric pump as a pusher to the mechanical pump & then the mechanical pump to the carburetor.
When you look at the blue cam, you can see the sharp edge at the opening of the contour, match that contour to the orange cam & it worked great for me. I did not try the orange cam with a .031 nozzle, i may try that also???? My next carb to fine tune is the 7448 350 cfm to see if it performs as well as the 500 & the better fuel miliage with the smaller venturi. Let me know you almost have this engine tuned to perfection. William

 

[Anonymous]

Maybe it's just late, but I still don't understand the difference putting the screw in one hole vs the other would make. i Understand the theory on different cams and positions, but here is what I'm stuck on:

when I stick the cam in place BOTH the #1 and the #2 holes line up...so what's the difference which one gets the screw? I could understand if I had to shift the cam one way or another or flip it over or something to get the holes to align, but the holes match perfectly.

This to me does not alter the position of the cam in reference to the holes.

Does the screw go through the #2 hole in the lever AND the #2 hole in the cam? Should the numbers on the cam be facing out (away from the throttle body) or inward (toward the throttle body)?

Man this sounds dumb, but it IS my first cam and pump change

As is, should I change nozzles? What is stock in my 500CFM 2300? If I read correctly, upping the nozzle size will only shorten the duration at which fuel is flowing into the venturi not the volume...right? BUt going too small can restrict the flow so much that the pump springs gets compressed and you lose flow...sound right? With my hesitation at 25mph, should I change main jets or try changin the nozzels first and in which direction do you think?

I did go to 71's from the 73's but it still seemed quite rich. Maybe the little hesitation says go to the 70's, eh?

What are my "better" mechanical pump options? The stock Ford one isn't cutting it. Does Holley or someone make a mechanical for the '68 200? I don't remember seeing one listed. What would be the problem with just going to an electric vs using both?

Again, thanks tons for your suggestions!

 

[Anonymous]

OK, forget what I said...I jsut got in closer to look at the cam holes and #1 and #2 don't QUITE line up exactly at the same time. I was expecting they would be offset a little more dramatically, that's why they just seemed to be in line.

I guess when you are transalting such small motions anyway, a little difference can go a long way.

I'll need to see pics of the blue cam work you are doing..not sure I inderstand where to grind.

 

[wsa111]

Bryce, just install the blue cam in the #2 position. I will get a chance tomorrow to show you how to round off the blue cam for our application. In the mean time put the cam in to cover up the lean area on quick acceleration.
If you hold the orange cam in front of the blue cam you will see the sharp acceration of the blue cam compared to the orange cam. Bring the orange cam exactally over the blue cam & round off the sharp corner to match the contour of the orange cam. When done the blue cam has the extra lift to supply our engines with the correct amount of fuel using the 30 cc accerator pump. My 500 carb is now very crisp in throttle response & with no flat spots even on full throttle acceration. The holley is a very adjustable carburetor you just have to find the right combination.
I put a sanding disc in my drill press & rounded off the sharp acceration ramp on the blue cam. William

 

[Anonymous]

Cool. I'll give it a try tomorrow.
Thanks William

 

[wsa111]

Bryce, just give a shout if you need further assistance or pictures of the accerator pump cam modification, try the blue cam as supplied, you might need that extra shot of fuel cause you are using the OZ head. William

 

[Anonymous]

I pulled the orange cam and compared it to the blue one. I see the edge you were talking about. I ground it down just slightly to be more curved like the orange one. It DID make a difference. That hesitation when matting it at midrange RPMs is gone and the offline throttle is more responsive.

I did seem to have a little surging at cruise speeds. Slight, but there. My A/F gauge showed it pretty clearly. I may need to bump the 68 jets up. Should I go to 69's or 70's (the 71's seemed too rich).

My mixture adjustments still seem odd to my untrained hand. I'm only backed out about 1.25 turns. Any more than that and i'm reading overly rich. Doesn't that seem like not enough turns out to be right? I've always read that 2.5 is the place to start.

Anywho, thanks again William for the help. This cam, pump, and jet setup is working out really nicely. I still wonder if I should do anything with the squirters. I've still got the stock ones on. Any thoughts? How do I know if I need to change them?

 

[wsa111]

Bryce, i have the 70 main jet with the .028 accerator pump & the blue cam. Yes i would go to the 70 jet.
You can try the .031 accerator pump nozzle, but if all hesitation is gone, it may be too rich. Its easy to change with a phillips screwdriver, just don't drop it down the throttle bore.
try a carter fuel pump to get your pressure closer to 6#. you may have to add an electric pump as a pusher to the mechanical pump. With out proper fuel pressure or volume your top end will suffer. I run both pumps & have 7# & it shows no signs of leanout, pulls strong to 6000. William