test and tune... who does it?

My 454 is broken in now and I am close on the tune but not there yet. I had an old retired racer lined up to help me out with the final carb, ignition, and valve adjusting but he is retired and constantly on vacation. He also doesn't seem to be really "into" it. I thought I had another guy lined up but he's too busy and keeps putting me off.

Where does a guy go for a good old fashioned test and tune shop? I don't really need a dyno since I'm not swapping jets or testing different exhausts... just someone who has the knack for tuning old-school stuff.

Why curtis, you come to AF of course!!

I might suggest to tune it yourself. Other people will not be bothered to do the time consuming trial and error to get it just right, unless you pay them lots for their time. Besidees its easy and fun.

First, I would suggest to do a baseline acceleration run. It is a fair substitute for a dyno.
Any quiet highway will do, where you can go from zero to up to 70 or so.
Do some timed runs from zero to 30, to 40 etc.
Thias will give you a record of the engine's low end and mid-range performance, too.
Keep track of temp and humidity if you can, too.

If your speedo is a bit shakey, use landmarks, ie: accelerate from point A to point B

Next, make any changes to the tuning one at a time, then test it, so you can track the effectiveness of the changes.

For your engine it should be fairly easy to find a published distributor advance curve. Tell me you are using a GM HEI system or an aftermarket type....no points?

I have stacks of car mags in storage, so I am not sure of the specs. Anyways lots of racers have already done the trial and error to set up the optimal curve. Find and use their specs, if you can.

You can get advance tuning kits. Use a timing light and tach to plot the distributor curve, and total distributor advance. You can install a timing decal on the harmonic balancer to provide a more accuate scale of the advance in degrees.

Did you degree the camshaft in, when you installed it? The cam manufacturer should be able to provide specs for the grind you have, a degree wheel and an off-set keyway or adjustable chain and sprocket set. I am sure you know how manufacturing tolerances can throw off the cam timing, even with a new chain set.

As for swapping jets......its easy and likely may be necessary for optimal performance. The carb.......what kind do you have? I know Holleys up, down and sideways, (Q-jets and Autolite's, too) but am a bit shakey on the other brands.

I undrstand that you don't want to spend the time or money at a dyno, but the results can be invaluable. Where are you located, I spend my summers at a shop in kentucky that is known for its results and good attitude.

Why not toss a letter to a magazine such as Hot Rod or Chevy High Performance, maybe that could at least help you.

I'm in L.A.

Well, the carb is a Qjet and its is pretty much "set". It was done by Jet Performance and they've always been dead on. It actually performs quite well by smell (I followed it while a friend put it through its paces) and by feel, but there are all the little nitpicky things. The choke doesn't want to keep the secondaries closed until its warm, so do I tighten up the choke or bend the lockout tang? Each is a viable solution, but which is best? Its questions like that which I can't answer.

The ignition is a Mallory billet HEI. I have the mechanical tuned to be all in at 3000. It provides 22 degrees mechanical, so I have it at about 12 BTDC at idle for 34 total. The vacuum advance is designed for ported vacuum but I'm giving it manifold since I have no ported source, but that should only affect it between 0 and 1/4 throttle.

The valves I have adjusted three different times using two different proven methods and I always get one too tight and one too loose; probably differences in lifter bleed down rates or preload specs. They are PAW's brand so they are rebuilt from various manufacturers. 20/20 hindsight there; should have just bought them from Comp when I got the cam.

I guess what I'm saying is, I've tried now for two months to dial it in and I'm so terrible at it that I'm ready to turn it over to someone pro. I guess it also means that a dyno would be of some help, but the curve and jetting should be spot on, its just the finer points like choke settings, idle mix, and getting the friggin valves to shut up ! :)

Its also getting to the point where I'm taking this car cross country on the first of June and my trial and error ain't working so well. Maybe time for someone else to fumble around :)

I've never needed these services before so I have no idea where to go. I see "tune up" places, but I assume they are smog related and they seem to be more of an O2 sensor/MAF replacement type places. I know there are Hot Rod shops and race shops, but they probably don't want to fuss with a street engine. Where can I go to have this done right?

BTW: After five tanks of gas, she seems to have settled on 10 mpgs :D Ouch !

The choke doesn't want to keep the secondaries closed until its warm, so do I tighten up the choke or bend the lockout tang?

Uh...are you sure??
Q-jets usually have a pesky lock out that stops the secondaries from opening until the choke is warmed and open all the way. Half the time this lock-out linkage is troublesome. A simple tiny piece of fine wire can hold the lock out mecanism out of the way giving you secondaries all the time.

Have you adjusted the secondary air door spring preload? Usually you want to ligten up the load on the spring until it starts to hesitate a bit when the secondaries open, then tighten it up just enough to eliminate the bog.

As for the valves....you are using a method where you can adjust all the valves by just moving the crankshaft twice, right? That is always a bit risky. Remove all the plugs and both valve covers. Ease piston #1 up to TDC with the valves closed and adjust the valves for that one cylinder only. Then move the crank enough to do cyl#2. Sure you have to shift the crank a bit eight times, but this method is very accurate and fool proof.

Also......fix the vaccuum advance. Manifold vacuum is simply not suitable. It prevents proper advance just when you need it most - when you are into the throttle. If you have ever driven with a vacuum gauge hooked up to a ported source you would see how well suited it is to provide advance.
Also your distributor was designed for ported vacuum.

I cannot stress this enough. All your other tuning is largely a waste of time until you get that ported source fixed....Until then you are wasting fuel and not geting all the HP you paid for.

I agree with your ported vacuum advice, however there are two problems; 1) there is no ported vacuum source on the truck Qjet I have. I can pull the TB and add one but there really isn't a decent place to drill for it. 2) Without the vacuum hooked up (while adjusting initial timing) This cam doesn't allow for anything vaguely resembling a smooth idle. This simulates using a ported vacuum source. As it is now, I set my initial to 12 BTDC, then hook up the manifold vacuum and I have about a lot of advance and the idle smooths out incredibly (of course).

I'm afraid that with ported vacuum at idle I'd have to raise the idle so far that I'd be off the transition slots. Thoughts? Another question on that topic; at what throttle position does manifold=ported? I guess what I was thinking was that vacuum from both sources would be equal past about 1/8 throttle, so the only points where the vacuum advance would be different is at idle. Is my thinking correct? If so, I wouldn't mind keeping the manifold vacuum. If I'm wrong, I'll look into modifying the TB to have a ported source.

When I adjusted the valves first it was when I was assembling the engine. I used "turn over once" method that you say is tricky. The book said it works on stock-type cams. Although my cam is not stock, it is much milder than many of the muscle car era cams. The first engine I built worked fine this way. This time it made one valve too tight (got the rocking in the engine) and at least one valve that ticks like mad. I pulled the valve covers again and used the method where you adjust the exhaust when the intake valve is half closed, and you do the intake valve when the exhaust starts moving. Same exact problem; one tight, one loose. I adjusted them a third time using that second method and same exact problem. I think what's happening is that I used PAW lifters. They are a good quality rebuilt lifter, but you can tell they aren't all the same. Some might have been chevy originals, some might be comp, some crane, some erson... who knows. I think they just have different preloads and different leakdowns. I was afraid I had some bum lifters, but the thing that gets me is that they make the same amount of noise regardless of RPMs. If it was a leaky lifter, it would pump up at higher RPMs or at least change its noise. I think the best way to solve the problem is to do a running adjustment. If I still have problems after that, I'm pulling the intake and putting 16 NEW lifters in there.

Youre right about the choke tang. The funny part is, the choke is adjusted properly. I checked the vacuum brake and was going to adjust it so it didn't pull it off too much, and its adjusted almost to the extent of its travel. I think I'll try to find a middle ground by tightening up the choke a little. I don't mind if the choke stays on a touch too long, but right now if I start it and touch the throttle it drops down. Seems odd for a properly adjusted choke.

I told you, I suck at dialing in an engine :) Wanna come to L.A. and help me? :D

Hey, help pay the airfare and I'm there !! I'll even bring some snow with me as a souvenier! :smile:

Some thoughts, if your idle smooths out that much when you hook up the vacuum advance, maybe 12 BTDC is not enough advance. On several engines I have built, with aftermarket cams. they produce the best power with 14 to 17 BTDC. Of course, keep an ear out for detonation.

Manifold vacuum is horrible for providing advance. It gives you advance at all the wrong times. Manifold vacuum is highest at idle, then as soon as you crack the throttle, it disappears, only to reappear at cruising speed at very light throttle.
But as soon as you NEED the power, when you step into the throttle, it disappears, retards the timing and makes the car run very sluggish. Try driving with a vacuum gauge installed in the car and you will see what I mean.

Ported vacuum provides all the advance at precicely the right time, when the airflow into the engine increases. Ported and manifold vacuum do not equal each other at any predicutable time, because they function independently based on throtle position and revs.
Trust me, curtis. Get rid of the manifold advance. At this point, this is the most important tuning change you can make. Even if you have to take the carb back to the shop and pay for further mods, you should do so. You will be amazed at the improvement the proper vacuum will give you.
I'll post a bit more later. Let me do a bit of research on the valve specs.

Ported vacuum it shall be :) Thanks for the clear description. I can do it since the guy at Jet told me exactly where to drill and what sizes to use, but I'll probably just take it back to him. I'd hate to muck it up. Or... I could maybe trade the TB off my Caddy 500's Qjet. That car is laid up for several months in preparation for an ecid dip, and its probably getting EFI with its own spark control, so it won't need vacuum advance at all. The idea juices are flowing now :)

Thoughts? Another question on that topic; at what throttle position does manifold=ported?

Never. Assuming any airflow at all. There will always be a pressure drop. At WOT of course it is negligible.

Use a couple vacuum gauges and test. BTW, You should be able to accomplish most of what you want to do in the driveway or on the street. But to get it really correct you will need a dyno. (Preferably one with inertia and brake capability.

Jim
SR Racing

I can do it since the guy at Jet told me exactly where to drill and what sizes to use, but I'll probably just take it back to him. I'd hate to muck it up.

A vacuum port going to a v/a unit has no "flow", so the size is not important. The position of course is.

Jim
SR Racing

I think you should take it back to the people at Jet.
IMHO even though you supplied them with the carb to rebuild they should have recognised this deficiency in the design and informed you of it (if they really know their stuff). At the very least, they should modify it for you at no charge, since you are a repeat customer.

The way he spoke of it, he seemed to be very willing to add one for free. It should take about 10 minutes with the proper drill bits and know-how.

So, to revive an old thread...

I swapped out TB from another refurbed Qjet. It was identical except it had a ported vacuum source. So, I hooked the HEI up to the ported source. I grabbed the cap and gave it a little more advance and it started right up. I warmed it up and set the initial to about 15, and at that I had to crank the idle setting way up just to get it to run. It now idles terribly rough at about 900 rpms, the idle vacuum is between 10 and 12" and there is way too much mechanical advance causing detonation everywhere in the load and RPM band.

Its like I either have enough advance to get it to idle and have terrible detonation, or I can't get it to idle with the proper setting. How do I get around this?

Your aftermarket distributor body likely has an adjuster to reduce the amount of vacuum advance.

Usually the adjustment screw is accessable with a small allen wrench placed through the vacuum port on the distributor body. Yours might be adjusted differently.
You should be able to reduce the total amount of vacuum advance.

Failing that, the centrifugal advance springs may be too light, allowing advance to occur too soon, or too much overall advance. A kit with a variety of spring tensions is easy to get so you can mix and match different ones until its just right.

If that fails to work, you can get this vacuum source switch valve that automatically supplies either ported or manifold vacuum, depending on which is higher. That way you have manifold vacuum for a smooth idle and ported vacuum for max power.

At WOT, the engine pings so much that I only ever did it once. Terrible; no power, sounded like hammers in the cylinders. You would think that there is almost no vacuum at WOT from a standstill, so evidently, the mechanical is just way too advanced.

The mechanical offers 22 total, not sure about the vacuum. The springs are tuned to have all advance in by 3000 rpms and I verified that with a timing light.

I tried it later and disconnected the vacuum advance entirely and got the same thing.

The 22 mechanical suggests 14-16 initial for a total of 36-38, but at 16 the car dies. I can get it to run by cranking the idle stop way up, but it sounds like junk and runs so rich that it burns my throat.

I've gone over everything. The carb has been apart three times, the ignition curve is spot on, the engine runs strong otherwise.

At this point, I'm running out of time. This car goes cross country sooner than I care to think about and I'm making things worse. What kind of shop am I looking for? Who does it? What do I look for in the yellow pages? Its very much not like me to take a car to a shop (I literally haven't done that for over 10 years) but I need it done now, done right, and just done. :)

I can understand your frustration.
IMHO your distributor is defective or not suitable for the application. I have encountered similar problems where supposedly high quality aftermarket performance parts have ended up being a bag of sh*t............immediatly what comes to mind is my experinence with expensive Crane electronic ignitions, those big yellow Accel coils and Moroso plug wires (all of which I bought new). I have had far better luck using properly set-up stock ignition parts.

I don't want to suggest your Mallory (?) distributor is poor quality, but I suspect its the source of your problems. Perhaps it is intended for a race-only application, perhaps it has an otherwise undetectable defect. Did you buy it new??
I have encountered troublesome performance parts that get sold off as used because someone encounteres just the same frustration and problems as you have.

My last suggestion is to throw in a regular, decent stock GM HEI distributor. So long as it works well, and is not worn out etc, give it a try.

Otherwise:
You would need a shop with experience in setting up race cars and custom performance cars.

Ask at the carb shop you went to.
Get out the yellow pages and call up some performance auto parts places and performance engine builders. Just very briefly and nicely explain your situation and ask if they know of anyone who can do this kind of work.

Anyone in the performance auto industry develops contacts and gets feedback about who is good and not.

Thanks so much for all of your help. I take back some of the bad things I said about you :)