CarburetorsCarb discussion and questions. Upgrading a Third Gen carburetor, swapping TBI to carburetor, or TPI to carburetor? Need LG4 or H.O. info? Post it here.
Welcome to ThirdGen.org!
Welcome to ThirdGen.org.
You are currently viewing our forum as a guest, which gives you limited access to view most discussions and access our other features. By joining our community, at no cost, you will have access to post topics, communicate privately with other members (PM), respond to polls, upload content and access many other special features. Registration is free, fast and simple, join the ThirdGen.org community today!
All incremental times improved. Bumped timing to 37 on fastest pass. Launch RPM helped, son was a little distracted. Was not paying close enough attention to launch.
This Friday night, will be doing more testing. Using metering plate in secondary side. 3310 750 Vac. Sec. carb.
Looking at track condition etc. Was fastest average ET/Speed for current tire size/temperature. Around 3 to 4 tenths faster.
Last best of 8.11 was run at 42 degrees with 1 inch shorter tire. If we see cool temps again, I think it will run faster. This was also the night of higher MPH, I atributed the 85+ to the 42 degree weather.
Car does rise through 1st and most of second gear.
Cranking pressure is a little over 220 PSI. Still using pump premium. May also try race gas.
This ad is not displayed to registered members. Register your free account today and become a member on ThirdGen!
Sponsored Links
Registered users do not see this ad. Click here to register for free!
30 degrees difference in ambient temperature is going to make a HUGE difference in performance. Cooler air = denser air = more HP.
You really need an air density guage to stay on top of things. But that's getting ahead of ourselves. Adjsuting jetting and timing to atmospheric changes is a very delicate science. Something to try when you are sure that you have the absolute maximum out of the car.
Might be worthwhile taking a couple of degrees of timing out and seeing if that picks up the top end. If not then you're not running too much timing. Make a run at 37 degrees ...and then try 35 degrees. If the car goes faster great. If the ET is slower but the MPH goes up....then you need a High Gear timing retard system.
Some cars need a lot of timing at the bottom and midrange to build torque...but then they have a bit too much at the top end. The solution is to run a timing retard system that engages in top gear at a specific rpm. MSD makes such a system.
Edit: Then again...you've already proven that the car responds well to 37 degrees of timing so retarding it may prove nothing
As you are finding...the closer you get to the ideal tune ...the harder it is to gain time. The last few hundreths or thousands of a second, can literally have you tearing out both your hair...and your wallet.
EDIT: What are you running for jets? Jet up a couple of sizes with whatever timing gives the best result. If it goes faster continue jetting up till it slows down. Conversley, if jetting up makes it run slower...jet down a notch or too. Be careful though. Watch very carefully for any signs of detonation when jetting down. Little specks like Black Pepper on the plug ceramic is a sure sign of a detonation. So are plugs that turn a " Battleship " gray. Richen the mixture and back off on the timing if you see either of these conditions.
Needless to say...if you pull the plugs and an electrode or two are melted then you've gone waaaaayyyyy too far into the Bad Zone
Last edited by Chickenman35; 01-04-2004 at 02:03 PM.
One other thing to try....you say you installed this cam 4 degrees advanced. Was this 4 degrees advanced from the timing card? If so try it straight up. Should help the top end.
What RPM are you pulling in gears and through traps?
EDIT: Looks like the car is struggling to pull the taller tire. You might need a bit more gear.
Last edited by Chickenman35; 01-04-2004 at 02:05 PM.
What launch RPM are you using now 2,000 or 2,200? I think your slicks should be able to handle a lot more than that. With the taller tire that hurts your gear ratio. You may have to gear down as mentioned.
The advantage to the taller tire is that it absorbs more shock at launch and offers more grip. But unless you get to the point where you can spin the tires loose at launch , then you are not maximising their performance.
Are you still getting the brake creap over 2,000 RPM? If so install an adjustable proportioning valve and crank some more BIAS to the rear.
I would also install a line lock to the rear brakes. Stand on the brakes. engage the line lock. Time to go...click the button and you're off. Makes startline concentration easier and reduces reaction time. Should really drop those 60' times.
I'm thinking max Torque convertor launch ( 2,800RPM + ) should be what you're aiming for.
Last edited by Chickenman35; 01-04-2004 at 02:11 PM.
Last weekend was waste, lost coil. Car breaking up badly. Will test again tomorrow night.
Coil was getting hot and misfiring. Was gonna try launching higher. Have parts to add proportioning valve but cannot do because carpal tunnel surgery on rght hand today.
with e-brake and footbrake, converter stalls to 3500.
Originally posted by muggsyjack Last weekend was waste, lost coil. Car breaking up badly. Will test again tomorrow night.
Coil was getting hot and misfiring. Was gonna try launching higher. Have parts to add proportioning valve but cannot do because carpal tunnel surgery on rght hand today.
with e-brake and footbrake, converter stalls to 3500.
I think a line lock for the rear brakes would be a big help.
hate to hijack this thread but i have one question for chickenman or f-bird
i too have 3310-6 with a manual choke that i took off. The plate that bolts to the carb has three screws and then there's a hole in the side of the carb that the plate covered. Will this create a vacumme leak if i don't find a way to cover it ?
Originally posted by MIKE 1985 hate to hijack this thread but i have one question for chickenman or f-bird
i too have 3310-6 with a manual choke that i took off. The plate that bolts to the carb has three screws and then there's a hole in the side of the carb that the plate covered. Will this create a vacumme leak if i don't find a way to cover it ?
thanks
Mike
Hmmm...been along time since I did this. Memory a bit fuzzy...but I do seem to remember having to plug a hole in the side of my carb with epoxy. I can go look...tomorrow.
Easier way to be sure. Start car up...if vacuum from hole ...plug it.
I think that may be a vacuum port for drawing hot air out of the manifold crossover when used with an automatic choke...hot air style not electric.
After last week episode of coil failing, engine now runs normal. Made 11 passes which ranged from 8.12 to 8.21.
8.21 was shifting at 6500 rpm, actual shift took place at 6850 RPM.
Tried multiple shift points from 5000/5200 on up. Appears to make little measurable difference. Car is dead consistent w/same shift point. Tried timing from 34 to 37 fixed, again little change. Even had 4 hole 1' spacer on...no change.
Am wondering if heads are not holding it back. Shift point seems to mean nothing. Currently 5800/actual 6000 RPM seems to work best, but this also was during best 60' runs. Gathering parts to make brake valve change. Holding higher launch rpm will drop 60' time and improve et.
Did one banzai charge off combination foot and emergency brake 3500 rpm launch, 60' dropped into 1.7's even though it was not a clean hit. Ordering second lock soleniod for rear brakes.
May get brakes done this week if hand heals okay. Will update.
Preliminary conclusions: 305 needs very hard launch, lack of low/mid torque hurts et. do not shift too late, waste of time with weak heads. Make sure brakes hold good to give best launch.
Engine may have been hurt minorly with the rattling event last weekend. Notice small amount of smoke out of breathers sooner after startup. Compression tester showed three cylinders down 5 to 15 psi off original readings. Oil pressure is still holding normal.
Shorter slicks would help. Gearing for 1/8th is not optimal w/28 inch tire. Traction is no longer problem. Car hooks after burnout.
Testing last night produced a best of 8.0715 @ 85.05 MPH w/1.77 60' in 1/8th mile.
Replacing proportioning valve with rear only valve improved launch RPM to 3000. 60 foot did not improve as much as expected. All the flares worked on first try. Had problems tightening fitting enough with stitches in right wrist.
Using white spring in carb and blue accellerator pump cam. Was thinking of trying open spacer, tried 4 hole spacer and it seems to drop top end power.
I am also considering swapping manifold back to torker at some point. Current dual plane is consistent but I have a feeling it is restrictive. I cannot pinpoint exactly why, but my intuition tells me it is not as strong mid-range or top end. I know this is not real scientific.
Also tried paper clip trick on secondary, opens about 75% of full travel. No hesitation, sputter, pops or miscue from carb. Throttle response is great. Even tried few passes with cable tyes in slot to pull secondary open a little at hit. No discernable change.
Tried timing fixed at 34, 35, 36 and 37. No real noticable improvement. The rotor is indexed.
Best shift points appear to be 6,000 RPM. Up or down shows very small reduction.
Any ideas? Am trying to aquire shorter tires off ebay but have not got them yet. 26 inch tires will equate to a 4.35 rear ratio.
__________________ 1992 Camaro RS
350 cam, headers, manifold, 750 d/p carburator. Th-350, 5400 stall TC, Moser 9", 430 gears. Boxed LCA's, adjustable panhard bar, air bags.
Red Car (mine)
Best 350 ET: 7.18 1/8th mile 95.0 MPH. 1.52 60'
Best 305 ET: 8.01 1/8th mile. 85.45 MPH. 1.72 60'
Black Car (son)
6.88 1/8th mile 98.5 MPH 1.44 60'
6.41 1/8th 107.6 MPH 1.41 60' (125 N2O)
Originally posted by muggsyjack Testing last night produced a best of 8.0715 @ 85.05 MPH w/1.77 60' in 1/8th mile.
Replacing proportioning valve with rear only valve improved launch RPM to 3000. 60 foot did not improve as much as expected. All the flares worked on first try. Had problems tightening fitting enough with stitches in right wrist.
Using white spring in carb and blue accellerator pump cam. Was thinking of trying open spacer, tried 4 hole spacer and it seems to drop top end power.
I am also considering swapping manifold back to torker at some point. Current dual plane is consistent but I have a feeling it is restrictive. I cannot pinpoint exactly why, but my intuition tells me it is not as strong mid-range or top end. I know this is not real scientific.
Also tried paper clip trick on secondary, opens about 75% of full travel. No hesitation, sputter, pops or miscue from carb. Throttle response is great. Even tried few passes with cable tyes in slot to pull secondary open a little at hit. No discernable change.
Tried timing fixed at 34, 35, 36 and 37. No real noticable improvement. The rotor is indexed.
Best shift points appear to be 6,000 RPM. Up or down shows very small reduction.
Any ideas? Am trying to aquire shorter tires off ebay but have not got them yet. 26 inch tires will equate to a 4.35 rear ratio.
One question that I asked earlier that has not been answered. You stated that you installed the cam 2 degrees advanced. Now most SBC cams are ground with a 4 deg advance ground in. ( Number crunching your cam specs shows that your Crane cam is already ground with 4 degrees advance built in ). Did you add an additional 2 degrees when you installed the cam? If so this could be hurting the top end. Try installing straight up or retarding 2 deg.
Trying the Torker again might not be a bad idea. I was thinking of suggesting that myself. But first try the RPM with an open spacer and with no spacer ( or a very thin one just to isolate heat ). Performer RPM's are sensitive to spacers.
Have you done any jet changes yet? What are you running currently?
I'd play with the following in order:
1) No spacer.
2) 1" open spacer.
3) Don't know if you've played with jets already...but you've changed the combo so you have to baseline again.
Set timing at 35 deg. Go up two jet sizes from what you have now ( on Primaries since you can't change Secondaries easily ). If car gets faster, keep going up two jets at a time till it slows. If car does not improve, jet down two sizes and see if MPH picks up. Be carefull jetting down. You don't want to run into detonation. That's why I suggested that you back off the timing a couple of degrees. Always go with the minimal timing that produces the best MPH. I'm thinking you're pretty darned close on jetting from what you've described though. May not be much gain...but easy to find out.
4) Retard cam to straight up if you advanced it over and above specs. If car picks up speed retard another 2 deg. The RPM probably doesn't need the extra torque that advancing the cam will give. Retarding cam picks up top end.
5) Try the Torker again. Restricted heads may need the larger runner volume. You may have to play with cam advance again if you changed it in step #4.
Did you ever try a cut down K&N Stub stack inside your velocity stack? The K&N Stub stack will really smooth the airflow into the body. Can be worth 25 to 30 CFM.
Alternately you can mill or die grind off the choke horn. Look at some Holley HP's to see the effect that you want. Replace the throttle blade screws with some "Allen Head Button Screws" and RED Loctite in place. File off any exposed threads. This can add another 15 CFM all by itself.
These last two items are really nit picky items but they can add some HP. Not uncommon for a 350 to pick up 12 to 15HP with just these mods alone.
I'd leave them to the absolute last...although I would be tempted to try a K&N Stubstack all by itself...without the velocity stack. Better yet..If you have, or can borrow a Moroso 14" drop base air cleaner with a minimum of 4" element ( preferably 5" high ) and the Stub Stack. It would be interesting to see how that goes. I wouldn't spend a great deal of money on it...but if you've got the parts hanging about or can borrow them.....
Cam is still two degrees advanced, same as before. I will reposition straight up or 2 degrees retarded. When I added open spacer last night, we picked up a small improvement in MPH. This is based on same 60' and shift point for 3 8.12 passes w/o spacer and 2 w/1" spacer.
Carb. has original jetting/plate system, #35 nozzle and blue pump cam in position #2. Both last night and Friday night, cool weather, plugs looked new after passes. Very small dot of tan/brown on insulator. Electrode and ground strap did not show any major sign of overheat. Is it possible we need more fuel from the primary side? I have not done plate changeover on secondary side yet. Since we rely on primary so heavily, maybe an increase in jet size will help 60' as well. This may be why we seem to be up against wall on 60' time, not enough fuel.
The best 60' of 1.77 is with 3200 RPM launch. I had expected a thousand RPM improvement to impact 60' more. I honestly did not think about the primary doing so much work. Should this situation exist the plug readings would be masked by the rest of the run. In discussion with son and notes taken, the best improvements noticed came after accellerator pump nozzle and cam change. Next improvement came after slicks were changed.
We did try to drop nozzle size from 35 to 31 and throttle response suffered. Could this be an indication of a lean condition? Would a lean primary main circuit restrict 60' performance? Wouldn't there be a stumble/bog or something?
Engine temp is running 190 at end of 1/8th mile. Cools quickly on return road. Do not expect this is an issue although prior temps were 180 at end in warmer ambient before cam/manifold change.
Still running velocity stack, removed complete choke assembly. No stub stack yet. Maybe pick one up this week. Will also be sealing carb to scoop with base and foam. Still running on a tight budget, out of work due to layoff. Limiting cash outlay untill hands heal and start new job.
I did try running no air cleaner for a few passes on Friday night. No real change.
Going to run 1/4 mile next Saturday night. 1/8th mile has IHRA pro-am event.
Last edited by muggsyjack; 01-26-2004 at 12:12 AM.
Originally posted by muggsyjack Cam is still two degrees advanced, same as before. I will reposition straight up or 2 degrees retarded. When I added open spacer last night, we picked up a small improvement in MPH. This is based on same 60' and shift point for 3 8.12 passes w/o spacer and 2 w/1" spacer.
Carb. has original jetting/plate system, #35 nozzle and blue pump cam in position #2. Both last night and Friday night, cool weather, plugs looked new after passes. Very small dot of tan/brown on insulator. Electrode and ground strap did not show any major sign of overheat. Is it possible we need more fuel from the primary side? I have not done plate changeover on secondary side yet. Since we rely on primary so heavily, maybe an increase in jet size will help 60' as well. This may be why we seem to be up against wall on 60' time, not enough fuel.
The best 60' of 1.77 is with 3200 RPM launch. I had expected a thousand RPM improvement to impact 60' more. I honestly did not think about the primary doing so much work. Should this situation exist the plug readings would be masked by the rest of the run. In discussion with son and notes taken, the best improvements noticed came after accellerator pump nozzle and cam change. Next improvement came after slicks were changed.
We did try to drop nozzle size from 35 to 31 and throttle response suffered. Could this be an indication of a lean condition? Would a lean primary main circuit restrict 60' performance? Wouldn't there be a stumble/bog or something?
Engine temp is running 190 at end of 1/8th mile. Cools quickly on return road. Do not expect this is an issue although prior temps were 180 at end in warmer ambient before cam/manifold change.
Still running velocity stack, removed complete choke assembly. No stub stack yet. Maybe pick one up this week. Will also be sealing carb to scoop with base and foam. Still running on a tight budget, out of work due to layoff. Limiting cash outlay untill hands heal and start new job.
I did try running no air cleaner for a few passes on Friday night. No real change.
Going to run 1/4 mile next Saturday night. 1/8th mile has IHRA pro-am event.
Think you should be getting a bit more color on the plugs than that. Sounds a bit lean. Lean mixtures take a long time to color plugs.
I generally like to see a light chocolate brown on my insulators. Road Racing and Hillclimbs require a tad richer mixture than Drag Racing to prevent detonation...we're under load for so much longer.
Pump shot will carry through any noticable bog...but a lean mixture will bring torque and HP down. I'd jet up a couple of sizes on the Primaries. What do you have in now?
EDIT: Looking at some of my Dyno sheets...I had a flat spot in my Torque\HP curve between 3,000 RPM and 3,750 RPM with my street jetting. I picked up from 5 to 12 ft\lbs of Torque and HP just by jetting up two sizes on the Primary for the track. You could not feel this flat spot driving the car. Only the Dyno showed it.
Last edited by Chickenman35; 01-26-2004 at 02:59 AM.
Originally posted by muggsyjack 72 on primary and #21 plate in secondary (equals 75 jet). Gonna pickup jet kit and plate conversion today.
Drill out the jet holes on the secondary metering plate with a 3/32th drill bit. equal to a #82secondary jet.
Fuel is what makes power. give it t all the primary jetting it wants.
Usually a car will need more jet than what makes best power on the dyno.
73-74-75-76 what ever makes it go the fastest.
Ignore the color of the plugs as long as it goes faster.
Once it has enough jet, it may want less timing.
No good news other than nothing hurt. Track was very cool, only 25 - 30 cars in staging lanes total. Track never got heated up, 60 foot times all over the place. Could not make any determination on changes.
Faster cars all over track, most ended up swapping lanes. One guy in a Camaro left with wheels in air and lost traction at top of first gear and nearly rolled when it slammed down. Another lost its driveshaft just off line.
Will probably run on Wednesday or Friday then points race Saturday.
Originally posted by muggsyjack Going to track tonight. Put 76 primary jets and 79 secondary jets. Will see if engine responds. Temperature should be in 40's after dark.
Ummmm...one thing I'd be carefull about is making more than one change at a time. You've changed both the Primary and Secondary jetting at the same time.
I would have stayed with the 72 Primaries and baselined the new Secondary block jetting until you got the same ET and MPH as before. Otherwise you can lose the tune in a hurry. You really don't know at thsi point if the Secondary block with #75's in it equals the fuel curve of the Secondary plate with #75's. ( Differences in air bleeds and emulsion tubes as I mentioned ). That is your baseline and that is what you have to establish.
#72's in the Primary are pretty rich, particularily for a 305. Fattenning the Primary any further may make the car lazy off the launch and affect the 60' times.
I'd go more for a combo like #72 Primaries and #80 Secondaries. The real problem is figuring out if that Secondary block gives the same fuel curve as the plate, as I've mentioned. I think #80's in the Secondaries should be a safe starting point....just put in a fresh set of plugs and watch for any signs of detonation. I'd then jet up tp #82's and see what the MPH and ET do. Then try #74's and watch what the 60' time does in addition to the MPH and ET.
The Primary jetting will afect your 60' times. The Secondary should not. If you find that the 60' times slow with a fatter Primary jet....but the MPH goes up then that means that you should lean the Primary down a tad and richen the Secondary by the same amount.
Just some more food for thought
Last edited by Chickenman35; 02-03-2004 at 01:35 AM.
Will try 72 and 80 on Friday night. Best pass on last Wednesday was 1.79 60' and 8.14 ET, first pass of trailer. From there it was all downhill. Got on son about taking stock 305 to 7000 RPM on burnouts. The only upgrades in bottom end is ARP rod bolts, High pressure/high volume pump and new bearings.
Checked out fuel system. Running stock TBI intank pump w/Mallory regulator. Checked volume output to feed line. With sintered filter in place, pump emptied tank into two 5 gallon jugs with heavy bias (more) toward jug closest to inlet. Put gas back in car (7 gallons) and removed sintered filter. Emptied tank in half the time and jugs were near equal in amount of fuel. It is possible that pump may not have been keeping up at high demand. Now it may be better.
Another question, I generally run pressure just before point of lifting needles off seats, 5.75 to 6 PSI. I read in Mallory literature that the boost port can be used to drop pressure at high manifold vacuum. It may be worthwhile to use manifold vacuum to drop pressure at idle to prevent flooding and run higher pressure setting overall. I tested in driveway and at idle w/pressure set to 7.5 PSI, vacuum added drops it to 3.5 PSI. When the throttle is hit, the pressure jumps back up.
At higher RPM the engine will not develop high manifold pressure? I have always been under impression that manifold vacuum at full throttle stays low like >3" unless there are restrictions before carb. Is this correct?
Another concern is a diaphragm failure, I would hate to have fuel dumping out of vacuum fitting into engine compartment or released near any wheel. Porting this the engine would flood motor and give driver indication of problem. What do you think?
Originally posted by muggsyjack Will try 72 and 80 on Friday night. Best pass on last Wednesday was 1.79 60' and 8.14 ET, first pass of trailer. From there it was all downhill. Got on son about taking stock 305 to 7000 RPM on burnouts. The only upgrades in bottom end is ARP rod bolts, High pressure/high volume pump and new bearings.
Checked out fuel system. Running stock TBI intank pump w/Mallory regulator. Checked volume output to feed line. With sintered filter in place, pump emptied tank into two 5 gallon jugs with heavy bias (more) toward jug closest to inlet. Put gas back in car (7 gallons) and removed sintered filter. Emptied tank in half the time and jugs were near equal in amount of fuel. It is possible that pump may not have been keeping up at high demand. Now it may be better.
Another question, I generally run pressure just before point of lifting needles off seats, 5.75 to 6 PSI. I read in Mallory literature that the boost port can be used to drop pressure at high manifold vacuum. It may be worthwhile to use manifold vacuum to drop pressure at idle to prevent flooding and run higher pressure setting overall. I tested in driveway and at idle w/pressure set to 7.5 PSI, vacuum added drops it to 3.5 PSI. When the throttle is hit, the pressure jumps back up.
At higher RPM the engine will not develop high manifold pressure? I have always been under impression that manifold vacuum at full throttle stays low like >3" unless there are restrictions before carb. Is this correct?
Another concern is a diaphragm failure, I would hate to have fuel dumping out of vacuum fitting into engine compartment or released near any wheel. Porting this the engine would flood motor and give driver indication of problem. What do you think?
I knew that regulators could be boost referenced when using forced induction , but I never thought of doing it the other way around.
Started looking through some of my Barry Grant literature and it made note of exactly this situation. However, it is used usually only with alcohol motors that need 4 to 5PSI at idle and 9 to 12 PSI at WOT. For a gasoline motor you should not need to do this at all.
With the Mallory regulator, return line to tank and the Stock TBI injection Fuel Pump, I would think you should be OK.
Regarding volume. Barry Grant recommends for a Large Displacement, High horsepower motor....that the fuel system can fill a 1 gallon container in 20 seconds. We're probably talking Big Block 500+ HP here. I don't think that you'll need anywhere near that amount of fuel.
Volume is the key, not pressure. As it is difficult to measure volume however ( unless you have inline flow meters ), pressure is usually what we have to go by.
One way to be sure that you're not running out of fuel is to rig up a video Camera so that it is focused on the fuel guage as you make a run. Then you can replay the guage readings back in the pits. Kinda like a poor man's Data logging. Works great. If all your guages are clustered together you can also see what the oil pressure and water temp are doing.
As long as the pressure stays reasonable, I would think no less than 4.5 PSI at the end of top gear, I would not worry about it too much. As you found out, the sintered carb filters are a big restriction to fuel flow.
Regarding plug colors. I just learnt something new today.
According to Barry Grant....Drag Motors with modern High Energy ignitions will take a very long time to color plugs. So always go by ET and MPH...not plug color, with a Drag Motor. F'Bird 88 mentioned this. Apparently the plugs can stay almost " Bone White " even with a correct mixture. Has to do with the short duration of runs, the High Spark output and the lack of lead in Pump fuels.
Now Circle Track Motors and Road Race motors are a different animal. Those will color plugs ( with or without lead ), and it is still an essential part of tuning those types of motors.
Now I'm a Road Racer and Hillclimber. We're always checking plug color and for good reason. You can't afford to let a Hill Climb motor run lean for an instant. Instant holes in pistons. When I run a Hillclimb my plugs will color after one run. In fact I've taken a plug wrench and socket up with me in the car to " Read " a plug after a run, when I'm playing with mixtures. But we're running at 3\4 to full throttle up grades averaging 7 to 10 percent, for over two minutes in a run. That probably equal's about 20 runs at the strip.
Just goes to show that you can learn something new ever day.
PS: You should still read the plugs on a Drag Motor though. I think you know why Muggsy...but for General information for those who may not.
If you find black specks like Pepper on the insulator, or if the insulator has turned a " Battleship " grey....Back off on the timing and richen the fuel mixture immediatley!!! The " Black Pepper specks" are deposits of melted aluminium from the pistons. An insulator that has turned a " Battle ship " grey has been exposed to extreme detonation. Holes in pistons will follow very shortly. With open pipes you sometimes cannot even hear this " Death Rattle ".
Will watch plug colors carefully for detonation. going to use 72/80 jetting and we will see what happens.
I have 26" tall slicks coming and also have added alternator cutout since engine idles 300 RPM higher when Alt. is not connected. Will not use cutout until later in evening on Friday. Need to baseline jetting and fuel pressure first. Slicks may not be used for couple of weeks, got good deal on them used.
Still looking for a 7.9X second 1/8th mile pass. I think it is there waiting, we could not have been that close on tuning.
With brake mod in place, can hold 3200 RPM erratically. Brakes bled again and again untill no air. Replaced everything including drums, whl. cyls and master. Linings are Bendix premium. Driver sometimes pushes through lights. Is this normal or do shoes need to bed? Does anyone make sticky rear shoes for camaros?
Originally posted by muggsyjack Will be testing on friday night.
Will watch plug colors carefully for detonation. going to use 72/80 jetting and we will see what happens.
I have 26" tall slicks coming and also have added alternator cutout since engine idles 300 RPM higher when Alt. is not connected. Will not use cutout until later in evening on Friday. Need to baseline jetting and fuel pressure first. Slicks may not be used for couple of weeks, got good deal on them used.
Still looking for a 7.9X second 1/8th mile pass. I think it is there waiting, we could not have been that close on tuning.
With brake mod in place, can hold 3200 RPM erratically. Brakes bled again and again untill no air. Replaced everything including drums, whl. cyls and master. Linings are Bendix premium. Driver sometimes pushes through lights. Is this normal or do shoes need to bed? Does anyone make sticky rear shoes for camaros?
Yep...shoes do need bedding. Normally takes about a hundred miles of stop and go driving to bed them. Will get better with time.
EDIT: Slightly larger rear wheel cylinders would help increase rear braking force further if needed.
Stock rear size is 3\4". Raybestos Part # WC37647 ( With Metric inlet threads M10 x 1) or #WC37625 ( With SAE threads 3\8" x 24 ). From what I can gather, 82 to 88 diffs had cylinders with SAE threads and 89 to 92 diffs had cylinders with Metric threads. Changing fittiings is no big deal.
EDIT: Raybestos makes a 7\8 rear cylinder #WC37644 ( With SAE threads 3\8" x 24 ). That would help rear brakes.
I think that 7.9 is waiting also. I think the 26 inch slicks will do it. You've made some pretty good progress . 8.6795 81+ MPH w/1.8936 60' time, to a 8.0715 @ 85.05 MPH w/1.77 60' in 1/8th mile. More to come I'm sure
Last edited by Chickenman35; 02-04-2004 at 01:20 AM.
Went ahead and put 26" tires on......New problem, developed stumble at launch. One pass it almost lifted wheels and died. Just enough to kill 60' time. Overall car is slower on MPH by a considerable degree. I changed shooter and am now using 42 tube type. The stumble stopped. At least it has not come back yet. It did this when we tried banzai launches at 3500 RPM off comb. e-brake and footbrake a couple of weeks ago.
Best pass was only 8.30 @ 82.2 MPH. Last pass after jetting up to 73/82. Is it possible that the metering plate was that much richer? Car has lost MPH primarly since change to block instead of metering plate.
Thinking of putting plate back on for tomorrow bracket race and see if MPH returns.
Originally posted by muggsyjack Went ahead and put 26" tires on......New problem, developed stumble at launch. One pass it almost lifted wheels and died. Just enough to kill 60' time. Overall car is slower on MPH by a considerable degree. I changed shooter and am now using 42 tube type. The stumble stopped. At least it has not come back yet. It did this when we tried banzai launches at 3500 RPM off comb. e-brake and footbrake a couple of weeks ago.
Best pass was only 8.30 @ 82.2 MPH. Last pass after jetting up to 73/82. Is it possible that the metering plate was that much richer? Car has lost MPH primarly since change to block instead of metering plate.
Thinking of putting plate back on for tomorrow bracket race and see if MPH returns.
As mentioned in PM...do a compression check. You may have a couple of hurt cylinders due to the "Detonation" that your driver " forgot " to mention.
Valve springs may also be losing pressure due to those 7,000 rpm burnouts.
Going back to old combo is a good idea. That's what notes are for. Metering block just may require the exact same jetting as plate. IE: 75's.
Launch stumble...You could definately be getting fuel slosh . Are you running float bowl vent whistles? If not, try the old trick of a fuel hose connecting the Primary and Secondary vent tubes together. Cut a hole in the top side middle to allow air to vent ...but keep fuel out of air horn.
You might want to start running jet extensions on the Secondary jets....you could be uncovering the jets at launch now.
In brackets today, car ran best of 8.27 @ 82.6 w/1.83 60 foot time. Was 10 -15 degrees warmer than 8.07 pass. MPH still down at least 2 MPH.
This is with metering plate instead of jet block. Slosh preventer tube in place, traction was poor. Even put in new set of plugs on final pass, no net improvement.
Need to do compression check and also want to check to be certain we have not lost cam lobe or a chunk of one. When changing plugs, noticed some mixup in cylinders. Fuel distribution not perfect, or varied efficiency among cylinders. Everything sounds good, no lifter tick indicating too much lash. Valve springs are possibility, valve bounce could be happening in the upper rev range.
Even pushed car to be certain nothing is dragging like brakes or sticky e-brake cable.
When I changed bearings and rod bolts during initial build phase, I only did light hone on cylinders to reseat original rings. There was bore wear as there was a ridge at top of cylinder. Maybe we have pushed rings/walls too hard. When originally assembled, there was never any smoke/steam from valve cover breathers until after a hard charge. Now it happens upon startup, cold.
We now have 154 passes on car at minimum of 5000 RPM to a Maximum of 6500 RPm shift points. Motor has seen 7000 RPM during burnouts. Ring seal is probably declining.
The good news is the car appears to run quicker at less MPH, indicating that shift points and launches are sorted better.
Last edited by muggsyjack; 02-08-2004 at 09:35 AM.
Originally posted by muggsyjack In brackets today, car ran best of 8.27 @ 82.6 w/1.83 60 foot time. Was 10 -15 degrees warmer than 8.07 pass. MPH still down at least 2 MPH.
This is with metering plate instead of jet block. Slosh preventer tube in place, traction was poor. Even put in new set of plugs on final pass, no net improvement.
Need to do compression check and also want to check to be certain we have not lost cam lobe or a chunk of one. When changing plugs, noticed some mixup in cylinders. Fuel distribution not perfect, or varied efficiency among cylinders. Everything sounds good, no lifter tick indicating too much lash. Valve springs are possibility, valve bounce could be happening in the upper rev range.
Even pushed car to be certain nothing is dragging like brakes or sticky e-brake cable.
When I changed bearings and rod bolts during initial build phase, I only did light hone on cylinders to reseat original rings. There was bore wear as there was a ridge at top of cylinder. Maybe we have pushed rings/walls too hard. When originally assembled, there was never any smoke/steam from valve cover breathers until after a hard charge. Now it happens upon startup, cold.
We now have 154 passes on car at minimum of 5000 RPM to a Maximum of 8500 RPm shift points. Motor has seen 7000 RPM during burnouts. Ring seal is probably declining.
The good news is the car appears to run quicker at less MPH, indicating that shift points and launches are sorted better.
8,500 RPM shift point????? Yikes!!! I hope that is a misprint. After 154 passes
I think the motors getting tired. Fresh rings and valve springs hopefully would perk it up.
Something to try when you get the new motor built, or the re-bore on the 305.
RE: Launch stumble reappearing. This may be due to the increased launch rpm's that you are now running. While the old setup was optimised for launches at between 2,000 to 2,200 RPM's...with the launch RPM's in the 3,500 RPM range, you are likely using so much throttle that you have used up most of the pump shot.
Note where accelerator pum arm is contacting the pump cam ramp at idle ( Entry ramp ).
Use the " Paper Clip " trick on the throttle cable to see how much throttle you use at launch. Now, rotate throttle to the amount shown by the Paper clip. Note position of cam in realtion to accelerator arm. I'll bet a lot of the " Ramp " is used up.
Solution is to rotate the cam and drill an extra hole, so that when the throttle is opened to " Launch RPM". the accelerator pump lever is now contacting the cam at the " Entry ramp" position or just slightly off. This of course will mean that you will have a huge amount of slop in the system at idle....but that doesn't really matter.
You could of course try the " Pink " cam, which has a later timing curve built in specifically for High RPM launches..... but the Pink cam also has a lot of shot. You may run into the Black smoke on launch problem again.
