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1967 400/400
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Discussion Starter · #1 ·
Okay... 1967, 400, 670 heads, Dougs Headers, 2.5 duals, Flowmaster 40's, no crossover.

My exhaust is embarrassing. It's a beautiful car so so it draws a ton of attention... and then I have ZERO oomph to back it up. Im on my 3rd set of mufflers, 3rd crossover, and now my last ditch effort was to swap the cam, which I did, and I got no where.

I don't want turn downs because I like the look of tail pipes exiting the rear, and I think that exhaust gas ahead of the axle isn't the best idea for me or the car.

I'm perplexed... My 70 vette with a 275 hp 350 and Turbo mufflers sounds like the hammers of Hell. My 67 GTO sounds like a 280z. Now to add insult to injury, it looks like I may have a stripped manifold bolt and it's leaking enough to blow out the gasket. If I have to remove the header to fix it, I would not put them back on.

Are the Ram Air manifolds available yet and can they be put on with the engine in?
 

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Yes, RA manifolds are available and they can be installed with the engine in the car. It'll be harder to get the headers out than it will be to put them in.

When you say it has no "oomph" --- are you talking about how it sounds or that it doesn't have the power/performance it should?

BUT - I highly doubt that your exhaust is the source of the problem, if I understand you correctly that it's lacking power? Have you tried driving it "uncorked" (headers open) to see if that makes a difference? That's a whole lot easier than rebuilding your whole exhaust system, especially when you're not sure it's the cause of the problem.

Bear
 

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Discussion Starter · #3 ·
Mostly referring to "sound", but I do firmly believe that power is still down.

The original can was a 4/7 swap and I spent weeks going back and forth with Butler about a replacement, which would be a dramatic improvement. Their selection "helped", by eliminating the 4/7 swap and increasing duration, but the LSA moved the power band up, which isn't the best for an auto without a stall.

My old 67 used to sound extremely aggressive and the car whipped you back in your seat... This car spins the posi without power-braking, chirps 2nd, and even chirps 3rd... but it just feels soft... and I really have to work it to get it to do that. Most times I mash the throttle and it just sighs and dumps gas... if the kickdown doesnt occur, it's very uneventful. Off the line in dual gate, it goes like a rocket, but I can't see me ever putting up a fight against any modern muscle car.

If this makes sense, it's fast, but it's not "it looks like the passenger just soiled himself" fast.

No Ive never un corked it but Ive been considering trying that.

Im dreading the thought of trying to tap the head with the header on... of course, it's the 4th bolt back on the driver side, so the brake lines and steering are in the way.
 

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If I do go with Ram Air manifolds, are there aluminum ones? What's the best brand/ style?
There are differences and quality matters. I have no direct personal experience with any of them, but I hear that the ones from Ram Air Restorations are the best quality. BUT, converting to manifolds isn't going to make it sound louder or more aggressive. If anything, doing that will tone it down even more.

Most times I mash the throttle and it just sighs and dumps gas
THAT sounds more like a tuning problem than anything else. By any chance, have you run a leakdown test on the engine to see how well the cylinders are sealing?

If I were to come into this problem "cold", here's the approach I'd take, in order:
  1. Run a leakdown test. This will tell me how well the cylinders and valves are sealing. Anything more than 6%-10% is cause for concern. The lower the better.
  2. (Maybe) run a compression test - just to get a ballpark idea of how much cylinder pressure it's making, because I'm curious. It won't really tell me anything important that I didn't already know from the leakdown test though.
  3. Make SURE it doesn't have any vacuum leaks. Intake, brake booster, all hoses and fittings, carb base plate, throttle shafts, etc.
  4. Spark plugs. Clean? Gapped correctly? Ignition wires in good shape (observe it running in the dark and look for arcing/sparking where there shouldn't be any). Cap and rotor in good shape?
  5. Ignition timing and advance curve. With 670 heads I'd start with 37 degrees total mechanical all in by 2500 rpm (initial + distributor but no vacuum can) and play with it from there, and probably find that it wants more. With those heads, it'd be on a steady diet of -at least- 93 octane 100% of the time.
  6. Carburetor. If I get even a hint of a bog when I stomp on the pedal from about 6 inches away, work it until I don't. Use a reliable air/fuel meter to check mixtures "every where else". I want at least low to mid 14's at idle, mid 13's to low 14's at part throttle cruise (all speeds), and 12-12.5 at WOT.
I might have to revisit-redo steps 5 and 6 multiple times until they're both optimized, because changing one can affect the other.

Bear
 

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‘65 GTO, 400, 4spd, Tri-Power
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Dosent make sense, I have almost the same setup on my '65, Flowmaster Delta 50's (which I changed out from the 40's as they were too loud), Hooker headers, 2.5" duals, no crossover, and it sets off car alarms in my parkade. Maybe your definition of aggressive is different then mine?
 

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If I do go with Ram Air manifolds, are there aluminum ones? What's the best brand/ style?
I haven't seen aluminum ones but I got mine from Butler on a black Friday sale and they came in a Pypes box, I love them and went on the motor while on the stand and the motor just fell in the engine compartment. I did blast them and sent for color samples of high temp paint from KBS and painted them like a tungsten color because they came with only 500 degree paint.
Motor vehicle Hood Bumper Automotive exterior Auto part
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Discussion Starter · #9 ·
Dosent make sense, I have almost the same setup on my '65, Flowmaster Delta 50's (which I changed out from the 40's as they were too loud), Hooker headers, 2.5" duals, no crossover, and it sets off car alarms in my parkade. Maybe your definition of aggressive is different then mine?
Like I said, my mild vette is much louder/ more aggressive.
 

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Mostly referring to "sound", but I do firmly believe that power is still down.

The original can was a 4/7 swap and I spent weeks going back and forth with Butler about a replacement, which would be a dramatic improvement. Their selection "helped", by eliminating the 4/7 swap and increasing duration, but the LSA moved the power band up, which isn't the best for an auto without a stall.

My old 67 used to sound extremely aggressive and the car whipped you back in your seat... This car spins the posi without power-braking, chirps 2nd, and even chirps 3rd... but it just feels soft... and I really have to work it to get it to do that. Most times I mash the throttle and it just sighs and dumps gas... if the kickdown doesnt occur, it's very uneventful. Off the line in dual gate, it goes like a rocket, but I can't see me ever putting up a fight against any modern muscle car.

If this makes sense, it's fast, but it's not "it looks like the passenger just soiled himself" fast.

No Ive never un corked it but Ive been considering trying that.

Im dreading the thought of trying to tap the head with the header on... of course, it's the 4th bolt back on the driver side, so the brake lines and steering are in the way.
Have you looked at Pypes mufflers I have the Race pros with a cross pipe and it sounds good I think and you can still hear your passenger with no droning but I haven't had anyone do a drive by to see how they sound as a bystander but my wife heard me a mile away open it up with our windows open so that made feel good, you might like the Violator muffler, lots of sound videos out there but it's still hard to choose.
 

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Discussion Starter · #12 ·
Have you looked at Pypes mufflers I have the Race pros with a cross pipe and it sounds good I think and you can still hear your passenger with no droning but I haven't had anyone do a drive by to see how they sound as a bystander but my wife heard me a mile away open it up with our windows open so that made feel good, you might like the Violator muffler, lots of sound videos out there but it's still hard to choose.
Yes, they were way too quiet. Thats what was on there originally.
 

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Discussion Starter · #13 ·
There are differences and quality matters. I have no direct personal experience with any of them, but I hear that the ones from Ram Air Restorations are the best quality. BUT, converting to manifolds isn't going to make it sound louder or more aggressive. If anything, doing that will tone it down even more.



THAT sounds more like a tuning problem than anything else. By any chance, have you run a leakdown test on the engine to see how well the cylinders are sealing?

If I were to come into this problem "cold", here's the approach I'd take, in order:
  1. Run a leakdown test. This will tell me how well the cylinders and valves are sealing. Anything more than 6%-10% is cause for concern. The lower the better.
  2. (Maybe) run a compression test - just to get a ballpark idea of how much cylinder pressure it's making, because I'm curious. It won't really tell me anything important that I didn't already know from the leakdown test though.
  3. Make SURE it doesn't have any vacuum leaks. Intake, brake booster, all hoses and fittings, carb base plate, throttle shafts, etc.
  4. Spark plugs. Clean? Gapped correctly? Ignition wires in good shape (observe it running in the dark and look for arcing/sparking where there shouldn't be any). Cap and rotor in good shape?
  5. Ignition timing and advance curve. With 670 heads I'd start with 37 degrees total mechanical all in by 2500 rpm (initial + distributor but no vacuum can) and play with it from there, and probably find that it wants more. With those heads, it'd be on a steady diet of -at least- 93 octane 100% of the time.
  6. Carburetor. If I get even a hint of a bog when I stomp on the pedal from about 6 inches away, work it until I don't. Use a reliable air/fuel meter to check mixtures "every where else". I want at least low to mid 14's at idle, mid 13's to low 14's at part throttle cruise (all speeds), and 12-12.5 at WOT.
I might have to revisit-redo steps 5 and 6 multiple times until they're both optimized, because changing one can affect the other.

Bear
  1. Never did a leak down test. It seems healthy and only has 4000 miles on it... plus I didn't want to know! But I guess I should.
  2. Wires are MSD 8.5 an less than a year old, however I had them in metal separators and I just noticed that they were arcing like crazy during my cam install last week. So, I took them out of the metal sleeves and ordered new wires, but I dont have them yet.
  3. Plugs are new. Were gapped at 45 for my ignition, but when I saw the plug wires arcing, I swapped in new ones at 35 again.
  4. Dizzy is a pro billet which Ive painstakingly spent a year curving. LARS vac corrector, etc.
  5. Carb is a new Edelbrock AVS2 800, which Ive also spent a year meticulously jetting, using a vaccuum gauge and AEM AFR gauge.
More than anything, when you mash the gas at cruise, it rarely kicks down the TH400, so it just labors uneventfully... untill it catches up. Shifting manually is fine. Also, as I mentioned, off the line performance is spinning the posi for 10-20 feet and then chirping 2nd and 3rd... I just feel like it should all be a little more violent/ aggressive/ in your face.
 

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More than anything, when you mash the gas at cruise, it rarely kicks down the TH400, so it just labors uneventfully... untill it catches up.
That's a big clue.

Suspect a couple possibilities: trans vacuum modulator problem and/or trans kickdown solenoid problem.

The way it's supposed to work, is when you hit the throttle, the switch should "pull" a valve in the transmission to energize the kickdown valving. The modulator is there to "read" engine vacuum and from that, infer the amount of load on the engine, and delay upshifts accordingly. Under light load conditions when there's a lot of vacuum, the modulator is what allows the "early" upshifts to happen. Without it working at all, the transmission would always shift like it was running at WOT, the upshift points being controlled by the mechanical governor that's gear driven off the output shaft.
The modulator is nothing more than a vacuum actuated diaphragm that moves a valve in the valve body. The most common way it can fail is for the diaphragm to rupture or there to be a leak in the line going to it. That usually will cause it to act like it's at WOT all the time AND also be the source of a maddening vacuum leak that really messes with fuel mixtures, that you may not hear because it's down under the car. If it's really bad, it will allow the engine to suck transmission fluid up the line and into the intake, giving you symptoms of bad rings and blue smoke out the exhaust. But, that's not the only way it can fail. Personally I've not heard of this happening, but in theory it might also be possible for the modulator plunger to get jammed in the housing - maybe causing the opposite effect - the transmission might always shift "early" - even under heavy throttle.

Shifting manually is fine. Also, as I mentioned, off the line performance is spinning the posi for 10-20 feet and then chirping 2nd and 3rd... I just feel like it should all be a little more violent/ aggressive/ in your face.
Shifting manually causes the fluid path through the valve body to be different in 1st and 2nd. That takes the modulator and the kickdown solenoid mostly out of the picture in 1st, somewhat in 2nd, until you get up into 3rd/Drive. If you leave the trans in Drive and hammer it from a stop, how does it shift? Does it "wind out" each gear or does it seem to shift way early? If it holds each gear for a "long time" like it should, but shifts early when driving sedately, then the modulator is probably OK - I'd still check for line leaks though.

First order of business: get your kickdown working. Check the switch and wiring connections - which you should find on the driver's side of the transmission just above the pan, about midway. Make sure the fuse isn't blown, make sure the switch on the go-fast pedal is there, working, and adjusted. Check out the modulator on the passenger side of the trans and the vacuum line going to it - make sure you don't have any leaks there. I haven't personally tried what I'm about to suggest, just because I haven't needed to - but something you might try: Unplug the solenoid connector at the transmission, take some jumper leads and apply 12 volts to the solenoid connector on the side, and listen - see if you can hear anything clicking/moving inside the transmission. If you can hear "something happening" inside when you apply the voltage, then probably the solenoid and circuit itself is working. Like I said, I haven't tried this myself on my car, which I know is working, so I'm not sure if you should be able to hear anything or not, but it's worth a try.

Good luck!

Bear
 

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Discussion Starter · #15 ·
Yes, hammer down in drive will wind out and shift hard... roll on WOT is where it seems to fart out.

I did check the solenoid and replaced the KD switch, but it's still very inconsistent at best. The modulator had a bad diaphram, so I replaced it, and I cutom bent a steel line, so there's not much rubber there... I do have a quality onboard vac gauge and I'm in the 18 range, power brakes work like a dream, with the new cam, so I'll assume vac is good.

The car only has 336's and I'd love to swap em out for 355's, but Im already taching 3000 at 70, and I prefer to cruise at closer to 80. No stall eaither, but Im about to put a TKX in the car, so that should solve all of this and give me control of the power band.

I do use 93 or better, at all times.
 

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I wouldn't waste time on the TH400 and get that TKX in there :D and if you get the wide ratio it has a 3:27 first gear so you won't have to change the rear, it will get out the hole like a bullet out of a barrel (y)...again jealous of all you aluminum head and five speed guys :cautious:
 

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I know you don't want turndowns, but that is what I have on my car and it is LOUD (to the point I created a post a while back asking about side exhaust in front of the wheels).

Mild 400, Hedman long tube headers, standard H crossover, 2 chamber flowmasters, turndowns right in front of axle. LOUD as F. What I'm missing is the nasty lope you probably just got from your cam swap.
 

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Mostly referring to "sound", but I do firmly believe that power is still down.

The original can was a 4/7 swap and I spent weeks going back and forth with Butler about a replacement, which would be a dramatic improvement. Their selection "helped", by eliminating the 4/7 swap and increasing duration, but the LSA moved the power band up, which isn't the best for an auto without a stall.

My old 67 used to sound extremely aggressive and the car whipped you back in your seat... This car spins the posi without power-braking, chirps 2nd, and even chirps 3rd... but it just feels soft... and I really have to work it to get it to do that. Most times I mash the throttle and it just sighs and dumps gas... if the kickdown doesnt occur, it's very uneventful. Off the line in dual gate, it goes like a rocket, but I can't see me ever putting up a fight against any modern muscle car.

If this makes sense, it's fast, but it's not "it looks like the passenger just soiled himself" fast.

No Ive never un corked it but Ive been considering trying that.

Im dreading the thought of trying to tap the head with the header on... of course, it's the 4th bolt back on the driver side, so the brake lines and steering are in the way.
You did the cam swap? You don't like it?

You can get a 2,500 stall converter for cheap. You could have the larger full size converter in that trans which will make it soggy/slow. Unless you know the trans is the born with TH-400 and it still has its original converter, you might want to just swap for a better converter until you can do the TKO or 4-speed swap.


Put one in my brother's car - worked great. Just fill out the form. $325.00 for the TH-400. Of course TCI and B & M are good converters as well. I have said this before, my boat of a '73 Fury & 360CI 2 Bbl, 180 HP/2.71 rear gear has a factory "loose" 2,500 stall converter. You would be impressed when I mashed the gas. Puts the engine up into its lower power range and out of the gate I go. If I ran an automatic, I would have to have a 2,400-2,500 stall converter just for the smiles.

But, you may have more power than you realize as a broader torque curve can be deceiving because the power comes on very smooth rather than explosive and track results do prove this.
 
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