Carb tuning questions??

[Gus68]

Het guys! Been a while since I've posted on here, I've had kind of a crazy year, but I have been lurking. Anyway I have some questions on tuning my Holley. My car is a 68 chevelle with a 406, AFR 210 heads and victor jr. I have a 4500 stall in my turbo 350, and I am running 3.73 rear end gears. Anyway..... I have an older Holley 830 double pumper and everything works great.... but only AFTER the engine warms up and the thermostat opens. If I try to mash the throttle from a dead stop or even rolling I get a big BLA, So what I usually do when I go racing is drive around in the pits for a few minutes and watch my temp gauge when it gets just a little over 190 it comes down just a touch so I know my thermastat is open, then I pull into the staging lanes and everything is fine, if I don't do this then I get the big BLA!. So just recently I got a 1 inch spacer an thought I'd try it. Now it seems like I have made my little problem worse!! My plugs have always looked nice and tan, but I am wondering if I need to jet up and go alittle richer??? Or am I way off here???? Does anyone ave any advice??? I am not known for my vast knowlage of the Holley carb!!!! Thanks!

[supernova]

Man it seems we had that problem years ago with a 406 I built for a friend. We put a choke carb on it and it fixxed it. The motor was cold natured and need help to warm up. After it warmed it was fine. If i'm no mistaken the 400 has heat transfers in the stock heads and intake to help with that very same problem. After market intakes and heads are not set up like that. If the plugs look good and it runs good when it's warmed up, it might not have anything wrong with it. You could try a newer carb that has more features to help overcome the issue.

Maybe someone else here has an idea of something better to try.

[Speedster]

just a couple thoughts? have you checked your power valve? have you checked accelerator pump to make sure your getting a good squirt? i was having issues with mine and it turned out to be the diaphram had dried up and cracked from sitting and was getting a full squirt. Changed it and problem solved?

[jaspermaggie]

I say go up in pump shot. I would start with 5 up and go up or down.

[want-a-be]

I say go up in pump shot. I would start with 5 up and go up or down.

Yes,...this is a pump shot issue. Pump shot doesn't have much influence in coloring of the spark plug. Well usually. But it does greatly influence throttle response. To me, it sounds like you have need more pump shot proven to me by how the combination reacted to the spacer being added to it. The throttle response actually got worse. If you had too much pump shot before the spacer was added then the throttle response should have improved with the addition of the spacer.

A possible wrinkle in my way of thinking here might be if the spacer is a 4 hole instead of an open. But I would think the plug color would be darker if it was too much pump shot and a 4 hole was added. But I still think it's not enough.

What squirter size are you running? It is stamped on its side. How are you adjusting your pump shot? What pump cam are you running and what setting is it at? When you slowly open your throttle,...do you ever run out of pump shot before you get to wide open throttle? When you very first bump the throttle, ever so slightly, do you have fuel comming out of the squirter?

Don

[Craig W.]

I've also seen ignition timing effect this. You might try adding more initial advance.

[want-a-be]

I've also seen ignition timing effect this. You might try adding more initial advance.

What timing are you running?. Is it locked out or are you running any mech/vac advance. If so,...what is the initial, how much does the distributor advance, and when is it all in by?

Don

[Gus68]

Hey, thanks for the responses!!!! Sorry I haven't gotten back to this, I have been remodeling a bath room Anyway I got a chance to get my carb off and both squirters are 37s. I'm nt sure on the pump cam, but it is kind of a white color (little faded looking) My jets are 77 in the front and 82 in the rear, fronts a little small? My timing is at 36* and all in at 3000. Sorry if I seem a little dumb when it comes to Holleys, I have run AFB style carbs in the past, and got to know them pretty well, but I don't speak fluent Holley. I used to have a 750 AFB and after recieving much crap from my friends, a buddy of mine gave me this 830 and I picked up about 2 tenths, so I want to make this work!!!! Thanks again!

[want-a-be]

Try locking the timing out, and running at it at 36° of timing.

Did you look into the carb and try running the throttle all the way through it's motion? If so, while moving the throttle to wide open, did the fuel stop squirting into your carb? If so then you are running out of pump shot and it is needing adjusted. Front jets aren't too lean if you are running a power valve. If you are running a P-V, then what vacuum is it rated at?

Don

[Gus68]

I can see how timing could cause this problem, and it could be, but why does it get better once the car is warmed up? And I did not have this problem with the AFB. As far as the power valve goes, there are 3 numbers on them, front has a 3 on the left 6 on the right and a 5 on the bottom, the rear has a 5 on the left 6 on the right and a 5 on the bottom. Please explain these numbers to me. Sorry for sounding so dumb but this really is my first holley.

[sc racing]

Power valves stay closed until the vacuum drops to a certain value. The 6/5 on yours indicates that it will open when engine vacuum drops to 6.5". The best way to test for proper p/v is put a vacuum gauge on direct vac source with the car at idle in gear read the vacuum gauge and select a p/v 2 " less than your vac reading. Example: if you have 8.5" of vacuum your 6.5 should be ok if you have only 7" get the closest p/v which will be a 4.5, or if you have 11" get an 8.5 and so on.

[want-a-be]

I don't like power valves myself actually. I don't even run them in my street stuff. If you decide to just take it out and run a block off in its place then just jet up from where your at about 10 jet sizes and tune from there.

if you feel like you'd like to talk about this some on the phone, then PM me and I'd be glad to send you my contact information so you could call. Cost you the price of the call only.

Don

[Gus68]

Just an update. I jetted up a little in the fronts (77 to 80s), I put in a pair of 42 squirters, and put the carb back together. I also bought an assortment of cams although I have not installed any yet, just gonna try what I did first. I haven't got a chance to run the car yet, hopefully this weekend. I will let you guys know what happens. Thanks again!!!

[spib]

I would block off that back powervalve and run 6-10 jets bigger then front, and to me front jet seems to big
I would try a 72-74 jet in front
with no power valve in rear with a 80-84 jet in rear

[grandville455]

I would Put the 50 c.c Pump on front and give it a nice big shot! U runnign the hollow pump screws?, What kind of linkage does it have on it? The nascar style?and yes that does seem kinda rich on the primary side. If this is race only i would get rid of the power valves all together and jet accordingly