blower question

[Camaro crazy]

hello everyone..im a newbie..here great site!..im here in Cali. i have a boat but its used for fishing..:) ....i have a question on my blower though, its in my Camaro.. if anyone can give me some pointers..that would be great, im running a sm 350 low comp. with a 6-71 blower and two 600 Holley double pumpers, the jets are at 73 all the way around, that it came with the problem im having is i was running 2 1/2" exh. and the Car ran perfect..well i changed to 3" with a H pipe and now at high RPM's it stumbles..i thought if i go a little bit bigger on the primaries about 3 sizes up it would help, well the car dosnt stumble as much but it feels like i lost a lot of power..so should i put the 73's back on primaries and only mess with secondaries? and how much should i go up? thanks for any input on this, i also had changed plugs,wires,fuel filters,air cleaners, timings good, to rule out anything else.

[TIMINATOR]

Air bleeds are too large. Go back to the jets you had and drop the airbleed size by .003 to start. See what it does. You may have to go smaller yet. Jets affect the entire range of rpm from as soon as the fuel flows from the boosters. The air bleeds made smaller will start the main circuit slightly sooner, but will progressively richen the mixture as the rpm and airflow increases. This is but 1 difference of blower carbs, the most important being boost referenced power valves. They will prevent leanout as you "pedal it" to get traction. The lack of this deal is the #1 reason we see bearing issues on a blown deal. ***boat the magazine had an article on the conversion last year. TIMINATOR

[Camaro crazy]

Air bleeds are too large. Go back to the jets you had and drop the airbleed size by .003 to start. See what it does. You may have to go smaller yet. Jets affect the entire range of rpm from as soon as the fuel flows from the boosters. The air bleeds made smaller will start the main circuit slightly sooner, but will progressively richen the mixture as the rpm and airflow increases. This is but 1 difference of blower carbs, the most important being boost referenced power valves. They will prevent leanout as you "pedal it" to get traction. The lack of this deal is the #1 reason we see bearing issues on a blown deal. ***boat the magazine had an article on the conversion last year. TIMINATOR
ill change it back to 73 and see about ordering the smaller air bleeds, Thanks! this has been driving me bananas..:) how would you adjust the carbs..a turn and a half out to start? and would you just go to where i can find the highest rpm..?Thanks again, chris

[TIMINATOR]

Check and set fuel pressure and then fuel level. Lock out the dist advance, set it at about 32 to start with. Remove one end of the linkage to one carb, then back out the idle speed screws until the butterflies just close, turn them in one turn, then reinstall the linkage. They are now syncronized, when adjusting them, turn them the same amount and direction. Turn the idle mixture screws in until seated, then back them out the same amount, 1/2 turn if 4 corner idle, 1 turn if not. Start and warm up the engine then set the speed (same amount on both screws), then mixture, keep all mixture screws even. This will get you set up for idle. Then do the bleeds. TIMINATOR

[Camaro crazy]

here is a pic:
http://i27.photobucket.com/albums/c155/69camarofast/6-71.jpg?t=1181769933
it seems like when my engine is warm my fuel pressure drops from 6 to 3 lbs. looking at my hoses i may have to move them farther from my headers?..ok so ill go 1 turn out..on air mix screws? (4) per carb.does that mean 4 corner idle?--im also running a mallory comp 9000 elect.ign. i did put the 73 jets back in yesterday but i still have the 75's in the secondaries..so maybe i should put the 73's back in the secondaries also? like it was original? it seems to miss at idle and a little at take off..but when on the gas it doesnt seem to miss..it runs fairly well.

[Camaro crazy]

..i am running an electric Summit fuel pump, my jets are all 73 front and back, i changed the primaries at first and it didn't clear the problem so then i did the secondaries and it made it worst..so im not sure if maybe my fuel pump isnt big enough now? whats wierd is that it seems to run ok when its cold still misses a little but runs good when i take off and run through the gears..then after the engine warms up it starts spluttering and stumbles more after the engine is warm, but im still at the right temperture..so i almost thought about laser cutting some spacers with a 2 1/2" hole and mounting it beteewn my collectors, to see if back pressure is the problem? im not sure what else i can do? i was thinking maybe my power valves were blown or exceleration pumps were messed up? the carbs are only 1 year old, but before i tear down the carbs..i was thinking back pressure? but then again does that mean blower motors can't run straieght headers? cause they would stumble also?

[Daytona100]

Fix your fuel pressure issue and see what happens. Mike:D

[T-Bag'n]

3 lbs of fuel psi is'nt enough especially on a blown deal if it goes lean it will melt down. I would make sure that under a load when it sputters that you have sufficient fuel psi....

[RumRunner]

Can't tell from your picture, but if you're using a liquid filled fuel pressure gauge. This will give you a false reading. As the gauge gets hotter it will read less pressure.

[cfm]

Listen to Rum, it's no joke. In a certain application that we make a fuel psi adapter for we found the liquid filled would read wrong (2-4 pis less on a 13-14psi system) when engine was hot. Liquid (glycerin I believe?) will push gainst mechanism as it expands and offset psi reading. Took us along time but we finally figured it out. Doh.
Also, are reading fuel psi at the rpm/load this is happening ?
Lastly, yes, your fuel could be getting too hot. While running slow/idling/cruising it takes a lot longer for 2 carbs/ 4 float bowls / etc to need replenishing.
I'd check the fuel pump/regulator first, even if it was nice high dollar stuff.
Unfortunately, this sympton can be one of a bunch of things. Repair obvious or more obvious things first.

[Camaro crazy]

i am running a liquid filled fuel pressure gauge, so i will have to change that out and look when it stumbles if my pressure drops, also im still running 3/8" fuel line which had worked before so im not sure if i should also go up on that, thanks guys for your input as this problem has been driving me bananas,..Thanks again Chris

[Camaro crazy]

update, i laser cut some spacers to go inbetween the collectors, and ran it..it runs better, i have a lot better bottom end, and lauches pretty good i still have a surge at high rpms, so i may look at the excelerator pumps or power valves..i know engines like to run rich when cold, so im thinking maybe differant power valve..not sure yet. but i seem to be going in the right direction.