need help with sbc

3

383rookie

Member
ok , here is the deal. i built a sb 350 for my airboat 93 model with vortec heads, 9.5/1 flat tops ,aluminum intake,holley 650 and the cam is flat tappet melling 22210 (specs .450/.461 lift, 224 duration @.50 114 lobe center) i just recently upgraded to procomp alum heads with 210cc runner, 2.02 valves and the same 64cc combustion chamber, also used a lt-4 hot cam kit( .525/.525 lift 218/228 duration @.50 112 lsa). with the original vortec heads i could turn it to 5000 rpms and now i can only get around 47-4800. but ways i was running 34 deg total timing. my question is why, does anyone think that i have too little carb or do i just need to jet it up or did i just go the wrong way with my setup?
 
383rookie said:
...
the cam is flat tappet melling 22210 (specs .450/.461 lift, 224 duration @.50 114 lobe center)

.... also used a lt-4 hot cam kit( .525/.525 lift 218/228 duration @.50 112 lsa)......


first which cam and type of lifters are you useing
Click to expand...
 
grumpyvette said:
383rookie said:
...
the cam is flat tappet melling 22210 (specs .450/.461 lift, 224 duration @.50 114 lobe center)

.... also used a lt-4 hot cam kit( .525/.525 lift 218/228 duration @.50 112 lsa)......


first which cam and type of lifters are you useing
Click to expand...
Click to expand...
i was using the melling with the vortec heads flat tappet, now i am using the lt-4 with the alum heads and roller lifters and 1.6 roller rockers
 
if the carbs PROPERLY adjusting is MORE than big enough for the application, max torque is generally found at about a 12.8:1 FUEL/AIR RATIO
READING YOUR PLUGS OR HAVING A WIDE BAND A/F GAUGE WILL MAKE GETTING THE RATIO CLOSER TO IDEAL FAR EASIER

viewtopic.php?f=55&t=109

did you degree in the new cam?
if its been installed several degrees retarded/advanced it may have less effective torque
 
grumpyvette said:
if the carbs PROPERLY adjusting is MORE than big enough for the application, max torque is generally found at about a 12.8:1 FUEL/AIR RATIO
READING YOUR PLUGS OR HAVING A WIDE BAND A/F GAUGE WILL MAKE GETTING THE RATIO CLOSER TO IDEAL FAR EASIER

viewtopic.php?f=55&t=109

did you degree in the new cam?
if its been installed several degrees retarded/advanced it may have less effective torque
Click to expand...
i installed straight up. i have a vacuum gauge and will try to get some readings this weekend, should i hook it above or below the butterfly?
 
Under the butterflies - non-ported.

A vacuum gauge will help you dial in your idle. It will not help you with anything above that I am afraid.
 
viewtopic.php?f=55&t=2994&p=7857&hilit=+vacuum+gauge#p7857
vacuum1.gif

use manifold vacuum

keep in mind your previous vortec heads had significantly smaller port cross sectional area, and the lower duration cam you replaced, had a lower lift, both factors would tend to reduce the average rpm of the power band and increase the torque produced at a lower rpm, your current combo with the larger port heads and longer duration cam should produce a bit better upper rpm power at the cost of a bit less off idle torque, but only if the rest of the components match that higher rpm power band, now your carb size is not an issue, but the carbs tune and fuel systems ability to feed the increased air flow rates, an exhaust that's restrictive, or failure verifying the cam is installed correctly and ignition timing is correct, all might be factors holding you back if not correct.
obviously youll want to drop back to basics and verify EVERYTHING like fuel pressure, ignition timing curve, total timing ,fuel air ratio etc.
BTW what exhaust are you running on that air boat?
if its zommies
hemi_zoomie_headers.JPG

your giving away torque that properly designed headers , with a long collector would get you back

ex101200.jpg

http://www.airboatfl.com/eshopprod_cat_ ... eaders.htm
SCH-SO53046.jpg
 
grumpyvette said:
http://forum.grumpysperformance.com/viewtopic.php?f=55&t=2994&p=7857&hilit=+vacuum+gauge#p7857
vacuum1.gif

use manifold vacuum

keep in mind your previous vortec heads had significantly smaller port cross sectional area, and the lower duration cam you replaced, had a lower lift, both factors would tend to reduce the average rpm of the power band and increase the torque produced at a lower rpm, your current combo with the larger port heads and longer duration cam should produce a bit better upper rpm power at the cost of a bit less off idle torque, but only if the rest of the components match that higher rpm power band, now your carb size is not an issue, but the carbs tune and fuel systems ability to feed the increased air flow rates, an exhaust that's restrictive, or failure verifying the cam is installed correctly and ignition timing is correct, all might be factors holding you back if not correct.
obviously youll want to drop back to basics and verify EVERYTHING like fuel pressure, ignition timing curve, total timing ,fuel air ratio etc.
Click to expand...
 
grumpyvette said:
http://forum.grumpysperformance.com/viewtopic.php?f=55&t=2994&p=7857&hilit=+vacuum+gauge#p7857
vacuum1.gif

use manifold vacuum

keep in mind your previous vortec heads had significantly smaller port cross sectional area, and the lower duration cam you replaced, had a lower lift, both factors would tend to reduce the average rpm of the power band and increase the torque produced at a lower rpm, your current combo with the larger port heads and longer duration cam should produce a bit better upper rpm power at the cost of a bit less off idle torque, but only if the rest of the components match that higher rpm power band, now your carb size is not an issue, but the carbs tune and fuel systems ability to feed the increased air flow rates, an exhaust that's restrictive, or failure verifying the cam is installed correctly and ignition timing is correct, all might be factors holding you back if not correct.
obviously youll want to drop back to basics and verify EVERYTHING like fuel pressure, ignition timing curve, total timing ,fuel air ratio etc.
BTW what exhaust are you running on that air boat?
if its zommies
hemi_zoomie_headers.JPG

your giving away torque that properly designed headers , with a long collector would get you back

ex101200.jpg

http://www.airboatfl.com/eshopprod_cat_ ... eaders.htm
SCH-SO53046.jpg
Click to expand...
i am running the regular airboat headers like the ones in the last 2 pics, what size jets should i start with and what is an a/f gauge
 
i did a small test this pm before dark and it seems that around 3000 rpms the exhaust will quickly turn red, i double checked the total timing and it was on 35 deg so i turned it back to 33 and it still does the same thing. waht should i be able to get away with for my timing?
 
Id try 37 degrees and see what the results are and if you can pull the plugs and post CLEAR DETAILED PICTURES, and( hopefully label each plug with its cylinder number) I can tell a good deal about both timing and your fuel air ratio,
example ( this picture is not really crystal clear but it is barely usable)
2078.jpg




Id suggest jumping up a couple jet sizes, if the plugs look lean while your at it.
if the headers quickly turn red its sometimes related to the timing being a bit retarded or the mix on the lean edge
 
just run it until the headers get hot, at about 3100rpm, so your fully advanced on the ignition curve,cut the ignition, wait for it to cool so you don,t get burnt, and pull label and photo the plugs.
Ideally I need a clear look at the center electrode, and curved ground strap and insulating porcelain


fairly new plugs are ideal, but as long as they don,t have mega mileage you can get some info on RECENT combustion chamber conditions
http://www.4secondsflat.com/plug_chart.html

http://www.4secondsflat.com/Spark_plug_reading.html

http://www.google.com/search?ie=UTF-8&o ... park+plugs
 
ok your obviously running a bit richer, in the fuel/air ratio and cooler in the combustion chamber, on average than ideal and the cause is most likely at least in part due to being RETARDED in the current ignition timing, that retarded ignition timing allows a good deal of what should be combustion chamber heat to exit into the headers.
because the plugs look sooty and dry/black and the ground electrode shows LIMITED exposure to heat, so step one is to gap the plugs at .045 thousands and advance the timing a few degrees to lets say at this point 37 degrees all in at 3100rpm,and run the engine long enough to get the plugs to clearly indicate the , new temps, (for 15 minutes) then re-post the plug results

you may want to read thru these links as theres good info

http://www.4secondsflat.com/plug_chart.html

http://www.4secondsflat.com/Spark_plug_reading.html

http://www.google.com/search?ie=UTF-8&o ... park+plugs
 
timing at 37, ran it for a little while and didnt see the exhaust get red at all and was able to remove plugs immediatly with my hands( after breaking loose)
 

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the cylinder heats almost correct, or at least better, but theres things you can do to get a more consistent burn,we can get back to ignition timing later or you can try adding a degree to 38 degrees total, and you may want to go to a one heat range hotter spark plug, that will help clean up those readings and get a more consistent burn, but remember as the mixture gets leaner the heat increases so the ignition timing required may change again as the jetting changes are made. now work on jetting the carb and power valve selection
what are the current jets?
what is your current power valve number?
have you set the float levels?
whats your current fuel pressure at idle?...3000 rpm?

viewtopic.php?f=50&t=1853&p=4848&hilit=+air+fuel+meter#p4848

viewtopic.php?f=50&t=2891&p=9279&hilit=plugs+ratio#p9279

viewtopic.php?f=55&t=109

viewtopic.php?f=44&t=773

viewtopic.php?f=50&t=383&p=2301&hilit=+power+valve+vacuum#p2301

viewtopic.php?f=44&t=777&p=4546&hilit=+power+valve+vacuum#p4546

viewtopic.php?f=55&t=1790&p=4544&hilit=+holley+cam+pump#p4544

viewtopic.php?f=55&t=1639&p=4545&hilit=+power+valve+vacuum#p4545

THESE THREADS SHOULD HELP
 
power valve is 6 or 9, (i think 9) the jets are 68, (i have a set of 72) i have set the floats and dont have anyway to tell fuel pressure yet. i will try to get something tomorrow.
 
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