smoktire

I got a 42 & 35 discharge nozzles and is still got a lean bog when i hammer the pedeal at lower rpm(idle to 2200) ...flot level is ok and fuel pressure too the pump is set at 0.035. What could it be

F-BIRD'88

"-stock convertor--"

some "stock torque converters have a very low stall speed. like 1400rpm.

A cam like the XE268 likes a little higher stall.
A 3000stall would be just right.

Try increasing the intial timing. don;t be shy here.
give it as much as it wants. then recurve the distributor to allow this increased initial timing but the same total mech timing. You want 18 to 25 initial and 32 to 36 total.
So you need to limit the mechanical travel of the advance to about 11 to 14degrees.
Stock is usually 20 to 24degrees.

Then you won;t need a #42 shooter a #25 to #35 should be enough.

" fuel pressure too the pump is set at 0.035." ?????????????????

smoktire

The accelerator pump diafragme to leaver clearance usualy set at .035".For the cam they says(comp cams) that its the bigest cam that fit with the stock torque converter.flash stall is around 1700rpm (stock).The problem is that beafore the head swap it was ok...no bug...

Chickenman35

Make sure that you have Zero clearance between the pump cam and pump lever at idle. Actually give the spring about 1\2 to 3\4's of a turn pre-load. You only need .015" clearance between the diaphram and the pump lever at WOT...not .035".

What pump cam are you running?

smoktire

Ok i will set it at .015".For the pump cam its the red one.

F-BIRD'88

yes the Comp catalog says that about the cam being the biggest for a stock converter.....BUT it will be just acceptable with a stock converter. it will perform a lot better with a high stall converter. A XE268 makes less torque than a smaller cam at and below 2500 to 3000rpm. A 3000stall will really wake it up off the line.

Chickenman35

Gakkk...red cam is Horrible. Weakest profile of al the cams. Try a Blue cam in the #2 hole or a Green cam in the #1 hole. The Red cam has very liitle lift and duration. So you use up it's patthetic little shot of fuel before the mains start to flow.

Go with a #31 or #35 Tube type shooter and one of the above mentioned cams on the Primary side and you should be much better. Leave the Secondary side alone for now.

BTW, I think you are adjusting things wrong. You do not adjust the pump lever spring until you have .015" clearance between the diaphram " Tit" and the pump lever at WOT. You adjust the pump spring untill there is ZERO clearance between the pump cam and the pump lever at idle. Then you should add 1\2 turn of preload to the spring.

Then.... you check to make sure that you have a minimum of .015" clearnace betwenn the pump diaphram and lever. You could have .100" or .050" clearnce...matters not a bit. Thre just must be some clearance left over so you don't bottom things out and bend the pump arm.....but you DO NOT purposely adjust things to " achieve" the .015" figure.

BTW, you usally only run into problems with clearance if using really big cams like the Pink cam or the Brown cam . These are specialty cams ( Race conditions only ) that must be used with 50CC pumps.

SLEEPER 86

the easiest way i have found to adjust pump arm clearance requires two people.have a buddy hold the carb at wot(engine off!)at the same time have him press down hard on the pump arm with a flat bladed screwdriver,when you are sure both are fully depressed,adjust the pump arm clearance to .015(holley spec).if that doesnt help check float level and for vaccum leaks.a #35 squirter should be fine.
Eric

smoktire

My flaot level is ok , my pump clearance is ok...i re-check my pump cams and the rear one is white ,the front one looks to be pink or pale red.??

Chickenman35

Change the front cam to what I mentioned. Looks like it could be a Pink or Red cam...neither of which is suitable in your situation.

Check out these threads as for the reason why. A ton of info here:

https://www.thirdgen.org/techbb2/sho...hreadid=202171

https://www.thirdgen.org/techbb2/sho...hreadid=208836

smoktire

Thanks Chickenman35 i will read this

smoktire

I tried a blue cam in the position 1 with 35 & 32 sqirter with no results exept backfire and bog...i will try the second position and i will tell you back what i got..

Chickenman35

That is bizarre...you should not have got a backfire with the Blue cam...even in the #1 position. The #2 hole gives a more aggressive profile though. Try it in the #2 hole.

FBIRD88 touched on a point...what are you using for initial timing? You should be up around 12 degrees to 14 degrees. With Vortec heads limit total ( mechanical ) advance to around 32 degress...but you still need the initial.

Are you using a vacuum advance? What do you have it hooked up to? Ported or manifold advance?

smoktire

I tried the number 2 hole with a 32 discharge nozzle wayyy bether no backfire but does not have a clean crisp response.(now i can nail it whithout stalling)For the timing i got 8 deg. initial (before tdc) and 17 mecanical =25 deg total i am not running any vaccum advance. If i get more than 25deg it start to ping even with 94 octane gas **i got vortec heads with fast burn chamber and around 10.3:1 CR**

Chickenman35

At what RPM is your total advance all in? You may have to slow up the curve. Many people make the mistake of bringing it in too quick. With Vortec heads, I would set the distributor up so that your mechanical advance does not start before 1,000 to 1,200 RPM. Total mechanical advance should not be in till 3,500.

You should be able to run 30 to 32 degrees of mechanical advance without pinging on pump gas with your combo. I'm thinking that your timing curve is too quick.....or possibly your Primary jetting is a bit on the lean side.

Do run a vacuum advance, it will increase full milage and drivabilty. You should purchase a Crane adjsutable vaccuum advance though, as it will need to be tuned.

Get back to us with your timing curve info and jetting info.

BTW, what pump gas are you running? IE: What brand? Some like Shell are horrible. Try and find a brand that uses an Ethonal ( Alchohol) blend of about 10%. This will greatly reduce pinging and dieseling. Car will run smoother as well. My car will diesel with 94 Octane Chevron at 13 to 14 degrees initial. With Mohawk 94 [ 10% Ethonal blend...only in Canada eh ] I can easily run 16 degrees with no dieseling or run on. Car runs noticably smotther on the Mohawk. Canadian gas generally of higher quality than US gas...even for the same so called Octane rating.

One other thing. You have a spacer under the carb. Is it a four hole spacer or an open spacer? Performer RPM's don't seem to like open spacers. A four hole spacer gives better throttle response and on most combo's, more power.

smoktire

My mecanical advance goes in at about 1300rpm and got full advance at around 2500rpm so you think that i should strech this to 3500 and add 7 deg to my 17 deg to end up with 32deg.

For the main jets its 70...(71 on the rear)on my A/R guage at part throttle it seams to be a little lean so i buy 73 one but theres not in yet(Some person at my local track say that A/R guage gives false reading....
I will try the 73 today(Note:when i am WOT the A/R indicate the same ratio that i get at part throttle )

For the vaccum advance i alredy got a accel ajustable unit(not using it).I does not have any vaccum provision on my carb pn:O-80541-1 should i add advance over my"32deg"and how many?
I will have to connect it to my intake directly.

My fuel pressure regulator is pn:12-501 set at 7psi and my fuel pump is edelbrock victor pn:1711 (1/2 reduce to 3/8 line)

Was running 91 octane from Ultramar but even with only 25deg it ping.At my local track i was told to run 94 octane from Petro Canada and i stops my ping but i could not put more initial advance...i tried and got ping...

For the spacer its an open 1" nitrous plate Cant remove this

After a series of little test i found the primary blue cam and 32 dis.noz. are right on(half throttle before the secondaries open)...it seams to be that the secondaries that are not good

Should i fix the timing first or goes with bigger jets on my primary(73) and secondaries(??75??)

Thanks :hail:

Chickenman35

Fix the timing first.

Full mechanical advance by 2,500 is way, waaayyyy too fast. No wonder it pings. Slow it down so that the total mechanical is in no sooner than 3,500. You're going to have to play with things a bit as your start point is a little high ( 1,300 rpm ) and the finish is too low ( 2,500) rpm. Try and get the mechanical advance to start at 1,000 to 1,100 rpm and stretch it out so that full mechanical advance does not occur until a minimum of 3,500 rpm. Beleieve it or not you can actually stretch the total mechanical to finish by 4,000 rpm.....so you're way too quick on the curve.

Try going with some lighter weights and a slightly lighter spring. The lighter weights will stretch the top part of the curve and the lighter spring should let things start a bit sooner. May take some fiddling.

Didn't notice that you were in Quebec. Can you get Mohawk or Husky ( same thing )? Petro-Can gas is goat ****!! My car refuses to run on it. Even my 1984 Chevy Cavalier Wagon ( Winter beater ) hates PetroCan gas!!

With your CR you will have to run 92+ or 94+...no if's ands or buts. Mohawk\Husky the best....Chevron 94 a distant second best.

Do run the vacuum advance. Set it up for about 10 degrees. Once you have slowed the mechanical curve down and sort out the Fuel quality issue the engine should be happy. Vaccuum advance is only used for part load and cruise conditions. It has no bearing on the timing curve at WOT. It will, however, result in better fuel economy, driveabilty and a cooler running engine ( IE: in stop and go traffic ) .... once you have a proper Mechanical curve set up.

The 80541-1, being a Race carb should be pretty much spot on as far as jetting. 70"s in the Primary sound about right. What are the plugs looking like and what heat range are you running?

If a plug cut looks like the engine is a bit lean, then I'm thinking you should go up about 2 sizes on the Secondary. You should be able to show full rich ( 12.5 to 1 or 12 to 1 ) at WOT on the A\F meter...if it's working correctly. I like to run a tad rich on the top end because I Road Race. An engine that is a tad rich may lose a couple of horsepower ....but it will run cooler and not be in danger of blowing HOLES in the pistons ( as compared to an engine that is jetted for slightly lean ). Food for thought. Especially with NO2.

A\F meters are good for getting a baseline. While not 100% accurate ( exception being Wide Band O2 sensors...expensive!! ), especially at full lean and full rich... they are a good tuning tool as long as you recognise their limitations. I use mine for a basic calibration....call it a "coarse" adjustment. Then I fine tune by plug color and Dyno runs. Whatever the engine wants after the " coarse" setting....that's what you give it...regardless of the A\F meter reading. Go up a couple of sizes on the Secondary jets. If the ET goes down and the MPH goes up...then the engine obviously wanted the extra fuel.

One important factor is age and condition of the O2 sensor. If this gets contaminated with fuel ( excessively rich running or fllooding of carb ) or just plain " old", it will usually indicate a leaner mixture than what the engine is actually receiving. Always double check settings by doing a plug check ( New plugs ) after a run.

Secondary pump cam. Again go with a Blue cam in #2 hole. Try a #31 shooter. I prefer the tube type shooters as they direct the shot more accurately to the center of the carb venturi. I think that will perk things up. You may be able to get away with even a #28 shooter on the Secondary side, once you make the Secondary pump cam change.

smoktire

Until i get a new timing tape (the one i had disepear) i mess with my shooter i had a 32 on the rear
i tried a 28 and replace the white cam by a green on the first hole (about the same profile).Now the secondaries looks
exellent but the primary side (32 shooter with blue cam in the second hole) still weird...i tried a orange cam in the second
hole and got a big improvement but i was testing in a wet road.For now it seam to be near perfect for me.I got my
mecanical advance kit:2 light spring 2 medium and 2 hard ones should i use the wheits from the kit or the stock ones?

For the spark plugs i was using AC R44LTS but they were verry light brown near white i was thinking that they were too hot
so i change them for AC R42LTS now they are black.I think i should get AC R43LTS

For the O2 its a brand new (60 days) BOSH piece.

No mohawck or husky neither chevron here.We got ESSO-SHELL-PETRO CAN-MR GAS-SONOCO-ULTRAMAR-CANADIAN TIRE-
and all the small ones.But they all stop at 91 octane exept petro can for the 94.

I will tell you as soon as i fix my timing

THANKS

smoktire

I put back my AC r44LTS cause the 42's were too cold and found one old AC R42LTS with melted ground electode (cylinder 4).Change my primary jets for 73 and secondaries ones for 75.Put my advance wheight kit with medium spring and the adjustable vaccum advance thing...waiting for my degreed proform damper cover to check the timing curve

smoktire

I finally got my degreed damper cover i set the timing to ...12deg initial advance and 35 total all in by 3000 and rejets the carb to 71 primary & 73 secondary.....Orange cam in the second hole with 35 disch.nozzle for the front & for the rear green cam with 28 disch.nozzle ...Works like new I got a new best ET 13.17@104 instead of 13.35@103

Thanks evryone for your help

scottland

I don't feel like reading the whole thread to find out whether you already know,

But the accelerater pump cam in that picture is upside down. The weights should act upon the rounded part of the cam. Check your total timing, i doubt your getting much mechanical advance.

don't know if that helps your problem or not, but it always helps to have things right

smoktire

For the accelerator pump in the picture it came like this from holley in the box... anyway i change it for a orange one.The timing advance wheits i got 40 deg of total timing with the moroso kit (12 initial) so i went back to the stock one and got 35 total (12 initial)

Chickenman35

Ummmm....I think you mean the distributor advance cam. And you're right...it is in upside down.