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Old 07-23-2012, 05:14 PM
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You do not need to fill the gas tank with race gas to test.
I do all my testing with a under hood 2 gallon fuel cell.
allow buying small quanties of high octane unleaded race gas and allows easy blending with pump gas
to get the right fuel octane blend to protect the engine from detonation.

You do not need to use the AFR meter or a gas probe etc.
Its probabily reading wrong any ways, using a tail pipe probe.
Start tuning pig rich and work leaner from there.
Start with high octane gas.

You will have this motor smoked before one of the tanks is empty, using 89 octane junk gas. I bet money on it.....

you want to be as rich @WOT under boost as required. 12:1 or richer 10.5:1 afr is not too rich at all under high boost.
Put the exhaust probe away.

A $80 baseball radar gun and a $30 detonation listener amp and headphones is much more usefull to dlialing in this motor.

Then go to the hardware store and get a length of dryer hose and rig up a fresh air ram air set up so the blower sees nice cool air.

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Old 07-23-2012, 06:57 PM
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Plugs made real no difference. The primary jet was changed to .101 the secondary was and is .104 there was a error in my post.

Contacted edelbrock, and they say that the timing should be retarded about 10 degrees. That would place me around 24-26 total at 3000 if the MSD boost retard was installed to auto correct the timing. Setting the mechanical total to that number does not give the stellar performance it is capable of.

This engine wants the advance, but cannot handle what it wants. The sound is detonation. I can twist the distributor and get it rattling like rocks in a can.

Poor fuel is a concern I never had to deal with. My method of building 9:1 engines that spin to 5500rpm make 89 octane pretty safe. Nothing is wrong really, I need to tune it using what is avalible.

My options seem clear, buy the boost retard or run race gas. I will get back to you when I figure out more. Thanks to all. Your experience Fbird is appreciated. I am not going to blow up anything. These engines are tough, and Im not beating it up. Only playing with a new peice of technology.
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Old 07-23-2012, 10:32 PM
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l press to cause you to have to retard the timing

Congrats on your build. I often think a small motor supercharged would be a good combo. I had a T-bird SC with a 3.8 supercharged for over 200k miles. I even ran it on 87 for a while.

I think your cam is just a little too light. It probably builds just enough cylinder pressure to cause you to have to retard the timing. I run 34 deg total at 2100 and let the initial fall where it may....just so it doesn't kick back on the starter. I use an RPM cam which has a bit more timing so cyl press is a bit lower. I also run vac adv however the cam causes the idle vac to be a bit low so I only get about 4 deg additional at idle. Cruising I have enough vac for the full 10 deg extra. This allows me to lean the cruise mix to 14.8-15.2. I've been all up and down the scale. I have over $100 in main jets alone. I can go leaner however I reached a very slight lean surge and a loss of mpg so I backed off just a little and mpg came backup and surge went away. I get 12.0 12.4 wot and 6-8 psi boost but I have throttle stopped the carbs to about 1/4 of secondary opening and have all the power I can use on the street.
I up to 16-17 mpg now and getting better all the time....I've been running 87 for 2 years now and approaching 20k miles.

I do use Holley 750 dp's however. They are far more adjustable in the idle and just off idle in my opinion. I would guess that better than 90% of my driving is on the idle and transition circuits.

I would suggest moving your AFR sensor up the pipe to about 24 in from the heads. Way back at the tail pipe leaves you open to air leaks which will quickly destroy accuracy. When you are playing with fire you need all the help you can get.

Cool air to the carb is a very good idea. I've measured my blower temp as high as 200 deg F even though it has lots of air going over it. I've also measured polished blowers at over 50 deg hotter than my sandcast blower...which is why I chose to go this route years ago.

I also would suggest you investigate water /alcohol injection. This will help a lot to safeguard your motor. It's pretty easy with a single carb.
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Old 07-24-2012, 12:25 AM
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Are you sure the timing is not advancing further once at 5000+rpm?
More than intended.

Where on the engine is the vacuum advance hose connected to?.
is it possible you got the small 305 performer cam version with the shorter intake duration? 195 214.
or the cam is over advanced.

Fuel octane is never a problem right up to the point its a problem, then its a big problem. (like when you supercharge a 9.xx:1 engine.)

Much like screwing the top on a pipe bomb is no problem right up till the top is on a lair too tight, then its a big problem.

The carb main jetting may need to go further richer. bigger jets yet.
The air fuel ratio @wot under boost just may not be rich enough.

A good fat AFR @wot should quench all detonation at a mild 5-6psi.

The car may be starving for fuel at high rpm.
(common with mechanical fuel pumps) (right angle fuel fittings, inlet side fuel hose collapse, fuel pump pivot arm float, fuel pump hot etc etc.)
You should be using a electric fuel pump. Fuel delivery is much more critical on a supercharged motor.

Either the fuel is really crappy and or the WOT AFR is still too lean or is leaning out at high rpm or the timing is more advanced at high rpm than you say.
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Old 07-24-2012, 09:17 PM
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II think the 650 is set pretty rich. It is the timing. The vacuum advance connects to the back of the e force unit at a corrected manifold source.

Cold air system is on.

It is much better.

The cam is possibly too small, and not bleeding off enough compression. Hard to believe but true.

Recalibrating the govenor shifts to 4,500 rpm with timing at 32 it is fine.

This E curve is a trip. You set the total then dial it back with 2 dials. The manual/instructions contradict themself. Telling me to set it at 2 and 9 and it is supposed to idle at 12 and total at 32. It does not. Even the chart in the back differs. I set it with the dial back light and it seems better. You cannot trust anything new anymore. Should have stuck with the old springs and weights.
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Old 07-25-2012, 01:52 AM
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Good to hear it is now coming around.

What is your pri and sec jetting and pri metering rod now?

I recomend using a balancer timing tape or mark the balancer at 30-32-36deg yourself so the effect of a dial back timing light is removed from the pic.
(Some are good , some not so good) Its easy to mark the balancer yourself.

Yup the cold air/ram air induction works good. cold air is better.

I'd like to see you try a .107" secondary jet.

This should allow you to rev it to 5000+ rpm without detonation.

Then,,,, you should/may be able to tame...lean down the primary cruise circuit
(primary metering rod change) as the cruise on the primarys at part throttle
(before boost builds) may be quite rich. (need to know the boost at part throttle and throttle position. % and engine rpm.

I believe you should be able to now change to a .068"x.037" or .070" x .037" primary rod
keep the .101" pri jet.

With this you may need to go up on the pri power step spring to the 8" or 10" spring. (stiffer spring)

This will clean up the part throttle cruise.... low or no boost
The power step up spring choice is very critical now.

Use a .107" secondary jet with this.

Tell me how this specific change works. (my and other readers benefit and info)

May need to go to 31deg timing under boost.

How do all the plugs look after a WOT power run? now after the change.
any black or silver peppering on the plug porcelins?
ground strap appearance?

the cold air /ram air looks good.

Do you have a vacuum gauge?

Last edited by F-BIRD'88; 07-25-2012 at 02:22 AM.
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Old 07-25-2012, 02:11 AM
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A boost timing master should be on your shopping list now.

will allow more driving flexability... better mileage
more engine reliability and the ability to retune for different levels/quality of fuel octane use.

will allow a generous 12 to 14 initial 34 to 36deg at max "centriifical advance"
while not under boost (throttle closed or near closed)
and generous vacuum advance for when boost is 0 and there is vacuum in the intake manifold.

and roll back the timing as boost and rpm builds 31-32ish on good 93+ gas

-29 30-31-32 on 81-91 gas. as required.

When you want to run it on the edge you need to be able to detune it when you get a tank of bad gas or encounter harsh operating conditions or both.

A boost retard like the Crane unit with the dial on the dash that you can easily adjust on the fly is real nice. especialy for varying fuels.

you really should consider giving the 800cfm AVS carb a second chance. Its has the best chance of giving the right
total fuel curve once properly dialed in correctly. idle / low cruise/ mid cruise-low boost/heavy throttle big boost power mode
and WOT full power and boost.

I believe it will return better fuel mileage too. (If you can keep off the throttle and boost) I'd rather not have to type the 3 pages of yada yada yada to explain.

A Crane HMV272-2 cam would be sweet in that motor, now. possibily with a 1.6in/1.5 ex rocker combo.
.484" in and .480" net valve lift. This is a sweet running camshaft.

Last edited by F-BIRD'88; 07-25-2012 at 02:19 AM.
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Old 07-25-2012, 03:19 AM
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From this point a Water methanol injection system would allow
a custom blower pulley swap for more boost and timing and more power
while keeping the motor out of trouble Especially on hot days.
Magnuson has other pulleys for this blower.

Then you 'd see just how a blown 305 rocks.
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Old 07-25-2012, 04:07 PM
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Quote:
Originally Posted by spinn View Post
My 305 had a supercharger installed the begining of the month. There have been a few hurdles to deal with. My fuel pump went after changing the pump outlets 90's. The fuel pressure is now stable after replacement. I have been recurving my distributor every few days. There is power, but at higher rpms it seems like power is not ramping up.

build
305 rebulit short 8.9:1
peformer cam
Ls6 beehives little retainers
vortec 906 heads 60cc
E force 122 eaton supercharger
650 cfm AVS
E curve MSD no box
3000 stall
3.73 8.5 rear 28" tire

The manual explains that timing should be reduced 2 degrees for every one lbs of boost. It also recomends a MSD retard boost timing box which I really dont want for 5-6 psi . My curve has been 12 intial 20 more at 3000 rpm for 32 . 8 in the can at 10 " vacuum. After the supercharger locked out at 20 works surprisingly well. The faster the charger spins the more power it makes all the way up. At 10 intial plus 15 at 3000 works good too. Anymore than 25 total after 3000 doesnt work well. The gas is 89 octane.

I do not want to use the MSD box and boost retard. What is the normal acceptable timing curve for a supercharged mild engine? 20 and 25 sound a little short for totals. This also affects normal cruising. Has almost brutal throttle response cruising without the higher timing.

If I go down in plug heat range more will that allow higher total numbers?

Good news, mpg has not changed much.
As the charge density (molecules of fuel and air) inside the cylinder goes up so does the speed of the burn. This also has a dependency upon turbulence of the mixture inside the cylinder.

An unsupercharged engine with a moderate cam from idle to legal cruise speeds has low charge density and turbulence. Therefore, in order to get the burn to occur so as to place the maximum cylinder pressure at the optimum piston position in its bore travel to extract the best power in moderate conditions it takes quite a bit of advance. However, as engine speed picks up and the throttle is opened the density and turbulence within the cylinder substantially increase which speeds the burn rate such that the optimum advance is achieved around 3000 RPM where no further advance is needed in spite of the significant reduction in burn time. For a normally aspirated engine running at atmospheric pressure the needed advance is about 32 to 38 degrees this depends a lot on cam timing, compression ratio, combustion chamber shape, spark plug location and heat range.

When supercharging is introduced the mixture density and turbulence inside the cylinder is increased which reduces burn time thus reducing the need for as much advance as an unboosted engine. The super charger manufacturer in your case recommends removing 2 degrees per pound of boost. Detonation is the limiting factor as to how much boost and how much advance the engine will accept before blowing some expensive part to pieces (usually a piston often taking other things with it). The boundary can be pushed around with changing mixtures rich tend to cool the cylinder by the energy it takes to phase change the extra fuel from liquid to vapor and physically interferes with the flame travel forcing the fire around large molecules adding distance and time. Adding alcohol and or water injection does a similar thing where the phase change absorbs energy (heat) and adds burn time by physically adding distance to the flame front as it tries to get around the globules of liquid. This should not be confused with burning alcohol as a fuel which brings what appears to greater octane resistance, this is a function of the previous descriptions of interference with the cylinder temps and flame front speeds but goes much further into the heat energy difference lesser of alcohol against equal weights of gasoline. So pure alcohol takes a lot more compression to extract its heat energy in the burn.

All of this is to say that while you have instructions from the manufacturer, you do have a unique combination and will have to tease out what set up will work with the engine configuration you've built and the fuel you wish to use. Frankly I much prefer the MSD retard device as electronic control of the advance/retard system is a lot more discrete and reliable than the old vacuum and centrifugal systems.

Bogie
As the charge density (molecules of fuel and air) inside the cylinder goes up so does the speed of the burn. This also has a dependency upon turbulance of the mixture inside the cylinder.

An unsupercharged engine with a moderate cam from idle to legal cruise speeds has low charge density and turbulance. Therefore, in order to get the burn to occur so as to place the maximium cylinder pressure at the optimium piston position in its bore travel to extract the best power in moderate conditions it takes quite a bit of advance. However, as engine speed picks up and the throttle is opened the density and turbulance within the cylinder substantially increase which speeds the burn rate such that the optimium advance is achieved around 3000 RPM where no further advance is needed inspite of the significant reduction in burn time. For a normally aispirated engine running at atmospheric pressure the needed advance is about 32 to 38 degrees this depends a lot on cam timing, compression ratio, combustion chamber shape and spark plug location.

When supercharging is introduced the mixture density and turbulance inside the cylinder is increased which reduces burn time thus reducing the need for as much advance as an unboosted engine. The super charger manufacturer in your case recommends removing 2 degrees per pound of boost. Detonation is the limiting factor as to how much boost and how much advance the engine will accept before blowing some expensive part to pieces (usually a piston often taking other things with it). The boundry can be pushed around with changing mixtures rich tend to cool the cylinder by the energy it takes to phase change the extra fuel from liquid to vapor and physially interfers with the flame travel forcing the fire around large molecules adding distance and time. Adding alcohol and or water injection does a similar thing where the phase change absorbes energy (heat) and adds burn time by physiaclly adding distance to the flame front as it tries to get around the globules of liquid. This should not be confused with burning alcohol as a fuel which brings what appears to greater octane resistance, this is a function of the previous descritons of interferance with the cylinder temps and flame front speeds but goes much further into the heat energy difference lessor of alcohol against equal weights of gasoline. So pure alcohol takes a lot more compression to extract it's heat energy in the burn.

All of this is to say that while you have instructions from the manufacturer, you do have a unique combination and will have to tease out what set up will work with the engine configuation you've built and the fuel you wish to use. Frankly I much prefer the MSD retard device as electronic control of the advance/retard system is a lot more descrete and reliable than the old vacuum and centrifugal systems.

Bogie
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Old 07-25-2012, 04:14 PM
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If the cruise control vacuum accumulator is connected in the same Tee as the vacuum advance, will it provide vacuum to the distributor once vacuum lowers at wide open throttle? There is no vacuum leaks in the advance lines, and no one way valve there, but they connect to multiple places. If so, this could be why locked out timing and no vacuum advance worked without problems.

They need to make a timing display device that shows what the exact timing is at operation. I am too old to ride the fenders.

It is a competitve build. It will challenge any NA $2000 combo. It is no space shuttle, but a monster of a 305.

I heard about the statin finish blower housing too. They disipate the heat via the grainy surface. For a cooler charge, low temp.

Thanks bogie, makes perfect sense. At least the second time.

My cam could be alright, but the springs are not really well. The beehives were grabbed from a GM series II v6. At .420 sqeeze they had around 260 lbs of open and 300 at .500. For seat they were in the 90's at installed height. This could be valve float and the blower is increasing the stress on the seat causing preignition.

The cam could be small and out of power range after 4500 , and go lean based on duration and lift for the ammount of power it is making.

I am not in my element, and beyond my knowledge a little bit.

Last edited by spinn; 07-25-2012 at 04:28 PM.
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Old 07-25-2012, 04:51 PM
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F bird - I will try the .107 sec jet and recalibrate to 5200 shifts again. Also get some boost and vacuum numbers for you.

Another thing those timing numbers were not correct. The e curve has a inital then you add that to your inital. The manual does not go into detail about this. If it curves 10+ 25 and you set it with 10 inital of your own , you have 45 mechanical. That is detonation territory. I even contacted MSD and they suggested buying the retard and MSD wires, also they explainrd to start out with timing locked and just setting the total. That worked.

Last edited by spinn; 07-25-2012 at 05:00 PM.
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Old 07-25-2012, 06:49 PM
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E curve distributor:

I don't have any experience with this specific distributor
so your info on how it really works is all welcome.

So by what you are saying it may have a start cranking retard function of 10deg.

Ya you have to rev it right up and check the actual timing at high rpm
"centrifical" may not max out at 3000 rpm.
May keep advancing further with more rpm,,,5000+rpm.

Remember the vacuum advance distributor hase does not connect to the carb base.

It goes to the intake manifold under the blower.
So does any accessory vacuum ( cruise control transd modulator etc)
All these should have a 1 way vacuum check valve inline too

If the PCV is going to tbe carb base, it must not draw oil from the valve cover any time, especially under boost. Something to check.
Oil getting in with combustion is a no no, especially suprcharged combustion. Many valve cover PCV/breather baffling sucks. Especcially all aftermarket covers.

These are all the little things you have to work out to make it all happen.

Tell us more about how the E curve distributor actually works as you get it figured out more. Your real world experience is all good here.
Benefits all. How do you adjust the amount of vacuum advance ? and the slope rate of vac advance.?

May need to use a mechanics hand vacuum pump to apply vacuum to the distributor to test and adjust the vacuum advance
rate / per vacuum.
Valve springs: the GM LS6 springs should be a straight swap. Must shim to desired installed height, installed and open pressure.
375# per inch. good for hyd's hyd rollers and street solids.
GM number 12499224 16pc set.

100-110 seat and 290-310 open for that mild cam. That cam don't rev up that high anyways.

Last edited by F-BIRD'88; 07-25-2012 at 07:03 PM.
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Old 07-25-2012, 07:49 PM
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A quick run through on the e curve. It has solid state circuitry, no springs and weights. 2 dials to select the curve one for the rev limit. All curves A-T start advancing at 1200rpm and finish at 2000 - 3500 , that way you are not adding over timing as rpm climbs after. What you have to watch is were the iniatial from the e curve starts. If you lock it out with "T" at 25 and give 10 with the dial back light , yes it is a total of 35. The other curves have 25 total but come in at different initals. If you set up a curve that starts at 0 with zero inital, then dial a curve that starts at 10 or 15 defrees at zero, you have to add that to the total. Because if it starts at zero and you place 15 mechanically twisting you are going to start 0 rpm with 20+ degrees and end over 40+ total . Depending how it is set. Makes no sense trying to explain. Ill include a link. If it works the figure 3 diagram shows the curves.

The cruise control accumulator can supply vacuum to the vacuum advance then?



http://www.msdignition.com/WorkArea/...id=15032386286

Last edited by spinn; 07-25-2012 at 07:58 PM.
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Old 07-25-2012, 08:18 PM
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The cruise control accumulator can supply vacuum to the vacuum advance then?

i am not enjoying that...
vacuum advance should go directly to a vacuum port on the intake manifold below the blower and should not be shared , twinned or effected by any other vacuum device.

And should include a 1 way check valve inline to avoid manifold boost pressure acting on the distributor or creating a leak.

Do not twin with any other vacuum device on the same source.
Use separate vacuum source ports on the intake manifold.


From what I get from the instructions. The whole thing is based on a total advance sweep of 34 degrees. Of the 34degress you can divided that up for use as vacuum advance+ mechanical centrifical advance and start retard.

Choosing more of one effects the amount of the other.
(When using a centrifical advance curve do not assume the timing actually maxes out as they say, at high rpm. You must rev up the motor and watch the timing curve and verify high rpm timing.

ya I would start by using locked out timing.
From what I gather, when using locked out timing and the 4 choices of start retard. Each choice of start retard also has an effect on the amount of vacuum advance available. eg: less start say 5 deg retard allows more vacuum advance

travel to be available.

I think a mechanics hand vacuum test pump and vac gauge needs to be used to watch the actual vacuum advance amount and slop based on vacuum applied to the hose.



Is the carbs accelerator pump volume and shot rate timing correct for the blower? good smooth throttle response with small and larger throttle changes.

blower motors as a rule tend to like a lot of idle timing so "locked out advance" should work very well.

The key will in getting the vacuum part throttle cruise advance slop just right.
let us know what you end up with. for timing and jetting.

Cannot stress enough the need for good 92+ octane gas thou.
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Old 07-25-2012, 08:29 PM
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You can buy the little plastic in line vacuum check valves from NAPA etc.
Commonly used on Fords on emissions era cars with carburators and emission controls, (egr, AIR, TCS), cruise control and air conditioning that were controlled by vacuum EG 1975 to 1986 years.

Junk yard is another good source. The more under hood snake's nest of vacuum lines the better chance you will find the little inline check valves on that car.
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