The subject may or may not be fully correct about it running 12's now, but it is slower than it was for sure. Help!....

I took my car in to the shop a few months ago, and the car has not seemed as fast since. I bought it at a point when it was running 11.0's @ 122. The shop told me they messed with the timing, and when they were done, just put it back to a point where they felt it was running best. I asked the previous owner about this and after yelling at me for allowing someone else to mess with the timing, he said I should set the timing to 34-36 degrees advanced from the white mark they made. Currently, it is reading about 15 degrees advanced from the white mark. Would this explain me getting beaten in 3rd gear by an ls1 car trapping 114? 1st and 2nd were close, but in 3rd he just pulled away and I was thinking what??? Anyway, another question I have is what all does it take to 'tune' a carb car...what do they do when dyno tuning? Just messing with the timing and adjusting the carb? The previous owner said he had tuned it perfectly while spending all day at the track and best times may not come from perfectly tuning it on a dyno when running in the 1/4 mile. Why is this?

 

I can understand the former owner yelling at you- take it in the right way. He probably spent quite a bit of time dialing in the combo to make it that fast before he sold it to you. By the way you described his reaction I can tell you that the former owner was a sharp cookie- he knew how to get the most out of a combo. And he probablly feels a little "dissed" at having someone else tune it, resulting in a large loss of power, even if he doesn't own it any more. There's still a little pride that he has in making it run as well as it did. Guys who really know their stuff just hate when someone else, not familiar with the combo they screwed together, lays a hand on it. Freaks them out real bad.

Don't take his strong reaction the wrong way. In fact, I suggest you use it to help you in this circumstance. Call him back. Let him know you made a mistake and that you could really use his help. I'll bet you $20 that he would be more than glad to bring it back to it's former glory at little or no charge. He'll at least spend a good bit of time pointing you back in the right direction and trying to help the best he can, even if he's not local. In short, if you come back to him with the right attitude and frame of mind he'll probably bend over backwards to help put it back again. I have been in similar situations (as the former owner of a strong running car) and gotten similar calls from the new owner who, if you'll excuse the expression, "f'd up" all my hard work and ended up running a lot slower!

If you show him my reply here as part of your next communication with him I will almost guarantee he will understand, know that you are sincere about getting the car running well again, and help out. Real gearheads are a brotherhood. They love to help out newcomers or those who aren't yet as expereinced. Trust me, he'll help you.

None of that answers your immediate question: How to set timing? The 34-36* of timing the previous owner refers to is the timing, with the vacuum advance disconnected (if any), with the engine revved up well beyond idle. Typically it will take 3000-3500 RPM to bring in the centrifugal advance FULLY to get to maximum timing advance. You want to set it to this 34-36* BTDC setting with the engine revved up at 3500 and then let the timing fall back to wherever it happens to fall when the engine comes back to idle. That could be 20* or it could be 5*. Depends on how the distributor is curved.

Tuning the carb? That could fill a book. Just geting the jetting right to give an A/F ratio that gives best power is only the beginning. Accelerator pump cams and squirters factor into this as well to make sure you don't bog the motor. And if it's a vacuum secondary carb there are other complications. Specific track tuning could be an encyclopedia.

I would strongly suspec that the majority of your power loss is in the ignition advance/timing. Unless someone really messed up the carb bad vs. where it was before they typically don't cost you the kinda HP that getting the ignition curve wrong does.

Could I eventually get you back to full power again? Yes. I can tune like a madman. Will it take almost forever over the internet trying one thing a week? You bet. Your best bet is the guy who really knew how to build and tun that motor in the first place.

 

Sounds like the shop you let "tune" your car doesn't own a timing light and knows less than yu do about tuning.

Take the above advice. Hard to improve on it.

You should have basic tuning tools for a car like that.
Like a advance timing light and valve lash tools and carb gaskets
and spare new spark plugs.
Did the shop change the jetting in the carb?
Do you know what jets were in the carb? Put it back...LOL
Ask the owner for help.
Find out what plugs the motor should have in it. (from the owner)
get some new ones and gap them properly.
Fouled plugs will never work. Don't get stock plugs or platinum plugs or any with a fork tongue.
Get a advance timing light and reset the timing.
34 to 36 degs advance at high rpm sounds real good for a small block.

If the previous owner won't help with the tune, repost and we'll help get it back. But we'll need certain info on the parts that make up the combo.

 

Thanks for the help guys, and I fully agree that I need to learn this stuff - I am too, just very sloooowly. Let me clarify something that came out wrong. The owner didn't 'yell' at me, but was a little upset in his tone when he emailed me after I told him. Quite frankly so was I because I didn't 'let' the shop mess with the timing. They just went ahead and did it anyway. The shop owner's dad was dying and so customer service was waaay out the window so they didn't consult with me before doing things. Kind of a bummer. I bought the car from the previous owner probably almost a half a year ago, and feel that I have wore out my welcome as far as asking questions goes. That is why I wanted to ask for some help on here. I will not be really attempting to do this on my own. I will most likely take it to a performance shop, but I felt it would be to my advantage to lear nas much as I could before I went. Thanks again guys and anymore knowledge you can spill on me as far as carb tuning/timing/dyno tuning vs. track timing etc would be appreciated!

 

Going to need a lot more specific info on the motor and the parts that make it up.
The more info that you can squeeze out of the previous owner/ builder, the better.

Carb model# jetting now
cylinder heads
compression ratio
Intake manifold
camshaft grind # Solid lifter? hydraulic? recommended valve lash?
Ignition, timing at idle and at high rpm.
etc etc
The more specific the better.
Is this car nitrous oxide injected?

You need to know where you are before you can plot a course to maximum performance.
But you have an advantage, you know the car was "right before"
The shop who messed with it probabily didn;'t farqk it up too much.
The difference between a cars tune on a dyno and at the track
is basicly the difference in temperatures and airflow over the carb
while running.
Generaly when a car or motor is "dyno tuned" You want to
start ("baseline") your "track tuning" (which is the real world) with richer jetting (about 4 to 6 jet numbers) and less ignition timing.
then work leaner in jetting and creep up the timing all while watching the Track MPH. Generally a small block with flat top pistons will want 32 to 36 deg total timing for maximum performance. If the motor wants 42or 47 degs to run the fastest its likely too lean. (slow fuel burn)
The MPH is a the best indicator of horsepower.
the ET and 60ft times indicate traction, driving skill and accelerator pump tuning gains or losses.
Starting with a slightly rich jetting and less than optimum timing
and working up to the "lean best power" ( maximum horsepower)setting is the safe way to get the most out of it. Being too lean or over advanced
is bad (can damage the motor) being alittle too rich and a little shy on timing is ok (safe) and will only slow you down a little.
generally carbs need about 4 to 6 jet sizes at the track than on the dyno.
The exhaust system can/will affect the cars performance and
carb jetting. What works " thru the mufflers" may need something different when "uncapped).
Start rich and retarded say 30/32 deg total and work leaner and
up in timing. Watch the MPH on the time ticket.
Only change one thing at a time.
When you get the best MPH jetting and timing, then work on accelerator pump tuning and traction ( tire pressure, launch rpm etc)
Takes patience and only change one thing at a time.
Let the car tell you what it likes.
if you tune the car for cool clear dry days then on a hot humid day it will want less jetting.
Less air density.
if you tune it in for a hot humid day the the jetting will be too lean on another cool, clear day air day.
When in doubt always go back to the cool clear day tune to avoid
being too lean.
This time of year is a good time to track tune a car.
The air is good (good for making horsepower) and the local tracks tend to not be busy.
Write down your tuning changes. its easy to forget what jets are in the carb over a week.

Use high octane gas. Cheap low octane gas will not get you maximum performance. Detonation ( spark knock) will destroy your motor and ruin your day real quick.

If the motor needs 110 octane to avoid spark knock cause its a high compression motor, Fill the tank with 110octane race gas.
throwing a gallon in the tank to spike it up won;t get you there.
If the motor has around 10:1 compression it will need 92+ octane gas. get the best street gas you can. Like 94 octane.
Octane booster is snake oil. Don't use it. If you need high octane buy race gas. its cheaper. There is no little can of miracle
mix that will get you 100octane out of 92 octane gas.
You will never ever see a pro racer/ engine builder/tuner in any professional racing using octane booster out of little cans. Take the hint.
If the car is nitous injected, get the tune right "on the motor"
before you attempt tuning in the nitrous power.
the method is the same start rich/ retarded and work leaner.
Watch the plugs for danger signs. (leanness, overheating, detonation)
The color of the plugs is almost meaningless.
Doesn't show maximum performance but will show you danger signs. As long as the plugs look ok believe the MPH gains when jetting etc.

 

Sorry this doesnt relate to the topic, but Damon, u said u tune like a mad man, well im going to college in PA anyway we could meet and u could help me with my car. Maybe at a nearby track or something when spring hits?

 

Hey!! No hijacking my thread!!

I have lots of good info on the car from the previous owner saved in my emails. Here are the answers:

Carb model - AED Modified Holley 750 double pumper
cylinder heads - AFR 210's with exhaust side slightly ported
compression ratio - 11.25:1
Intake manifold - victor jr
camshaft grind - hydraulic crane 234/242 @ 050. 539/558 lift w/comp cams pro magnum roller rocker arms 1.6/1.52
Ignition, timing at idle and at high rpm. - not sure about this
Is this car nitrous oxide injected? - nope

This is a pump gas motor. Does this help a little more?

 

The AED modded Holley will be a bit of an unknown thing cause it will depend a lot of what they modded.
The metering block emulsion tubes and air bleeds calibration are usually different from the holley they are based on.
The right jetting can be real different than a stock holley.
You're going to need some specific jetting sizes info to base line it. Start rich , work down>
***This motor is real border line on being a real TRUE PUMP gas motor.***

For maximum performance you want about 100 octane on a 11.25:1 motor. even with aluminum heads.

You can fudge it around with retarded timing and rich jetting and get away with 92 octane under mild street driving but for maximum performance with sharp (lean) jetting and (max) timing I'd start at a true 100 octane.
Gas , even race gas is cheap compared with new pistons and a rebuild.
Start there and tune it in and then work back down in octane or you may damage the motor.
A 50/50mix of pump 92 and 110 unleaded race gas will get you 100 octane.
It just does not pay to short the motor on octane when tuning it.
Detonation will kill the power and ruin the motor in a hurry.
You cannot hear high speed detonation. You'll never know it till its too late.

If you don't believe me I'll mail you the broken piston ring lands to prove it.


Find out what plugs ( heat range) and jets the previous owner used.
Get a timing light start at 30 deg total and work up.
if you get beyond 37 or 38 degs something is not right.
Again the AED custom carb will be the unknown factor here.
Cause they are all custom tweeked.
If the Shop pulled the fuel bowls off to check the jetting and saw what appear to be nonstandard jetting, they may have swapped in what they thought were the right jets (for a stock holley)..

 

actually, the pump gas was on orders from the original owner. He built it to be a pump gas motor. It currently has about 16k miles without tasting a drop of high octane fuel. Should I try it anyway and see what she does?

 

My best advice is yes start with 100octane.
A little extra will not slow you down.
Too little octane will cost you BIG trust me.

Don't want to get into a big theroretical an pratical argument about octane and what a 11.25:1 motor needs for maximum performance and what you can get away with while cruising and
playing around of the street.
The laws of physics are the same here as there.
It is easier to work within them than against physics.
( unless you're $$ pig rich$$)

You may have actually already damaged the motor ( scuffed the rings and killed the ring seal) by running less octane than you should be.
A cast piston motor will break the ring land under detonation
a forged pistoned motor will just loose the ring seal.
and be down on power. The only cure is a rebuild.
Like I said , It does not pay to fight physics. Physics will always win.
Start with a full tank of 100 octane.

An 11.25:1 motor will need more than 92 octane.

 

On a recent project I built a 12.65:1 motor.
Nice and radical.
ran like a champ on 94 octane gas for months right up until a ring land land go.
Never heard a hint of detonation or preignition.
Never showed a hint of trouble on the plugs.

was driving it to the track to test it on 110 octane and 94 octane.
Went WOT to pass a car and .......
Took out a piston, the cylinder head (custom ported), and most of the valves are bent (debris though the motor)

ran the same on 110 octane as 94 octane right till it come unglued.
Luckily it won't be too heavy on the pocket to rebuild it.

But loosing the cylinder head hurt. It was a lot of work.

Rode the edge good for a while ..........Physics won.



Your parts are going to be a lot more expensive than mine were.

 

F-Bird: Thanks so much for your concern. I don't have much more to say in this reply other than that.

 

Stupid4901- shoot me an email.