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Frnknsteen

Frnknsteen

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Spencer, IN
Hi Guys,

I posted on this yesterday in my restoration thread, but thought it might make more sense to post here.

I have a '67 Barracuda I am working on. My restoration thread will show what all I have done to it, so I won't repeat here. Basically, the motor was in it and running good when I bought it. I put the transmission back in and got the suspension and steering back in line. I took it to a local shop and had them put it on the chassis dyno and look for best carb and timing settings.

Outcome was that I am getting 254hp and 340+ft/lbs to the wheels. It drives pretty good, but it just seems a little lazy and needs woken up a bit. I hate to say it, but I have no idea what is in the motor. Like I said. It was in the car, ran good, and I got it for what I believe to be a good price after looking at others. Previous owner couldn't find his folder of receipts, and could just tell me they "Did some work to the motor and put a Competition Cam in it".

Specs I know:
1977 400, 906 heads, Speed Demon 750, Tri-Y headers, Magnaflow 2 1/4" exhaust
A833 4spd, 8 3/4 Suregrip 3:23 - 245/60R14 Radial T/A's in back (25.6" Diameter from what I've seen on tire charts)

I really have nothing to compare to determine if I should be happy with the output for this cruiser, or if there are some little things I could do to wake it up a bit. This is a "For Fun" car that I'm driving and enjoying while most of my money goes into the rebuilding of my Charger. That means I've got SOME budget, but somewhat limited.

I'm planning to do a compression check of all the cylinders. I know that won't tell me the compression ratio, but it will tell me how even the motor is from cylinder to cylinder, and tell me how much air I'm moving and if I'm low, like 110psi or doing ok, like 150 - 160psi. It wouldn't hurt to pull the heads off and see where the top of the piston is from the top of the block so we can look at CR, but that's hard to justify when it is running good. Maybe a good winter project though!.

Wondering where you guys would go with this car? Leave it where it is and just enjoy it while redoing my Charger (Then build it up more)? Or is there things I could do that would immediately help perk it up. I do have a set of 915 heads I could swap in to get a bit of a CR boost.

Mark
 
Here is the Dyno screenshot in case anyone wants to see it.

1202171134.jpg
 
Too bad you don't know what's inside and what has been done to it. A proper distributor advance curve can make a huge difference. What tuning did you do on the dyno?
 
Tune can and will make a huge difference. Sounds crazy, but you may have upwards of 100 horsepower hiding in there. Proper curve, plugs, jetting and small bolt ons like a carb spacer go a long long way
 
A whiff of nitrous might wake it up. But better money spent on the dist tune.....
 
Did the dyno tester do any adjustments to the timing or change the carb jets for peak performance? Your post says that was your intent. If he did those adjustments then look else where.
 
Car had a new set of Champion RJ12Y plugs and a new Accel cap & rotor. The tech working on the car noticed it went a little rich in the middle of the first pull. He said he thought it might be dirty air tubes and shot some cleaner in four corners of the carb (Air tubes) and did another pull. The A/F mixture evened out and looked pretty good through the full pull so he didn't do anything else on the carb. He adjusted the timing up a couple degrees, then a couple more when he saw a drop off in horsepower so he backed it back down to 15 initial and 45 all in (mechanical and vacuum advance)

He mentioned that 30 degrees seemed to be a lot. I told him when I first got the car, the vacuum advance wasn't hooked up. Well, technically it was, but there was no vacuum to the port he had it hooked to, so essentially, it wasn't hooked up. The Demon carb has two vacuum ports on the passenger side, near the front of the carb. The front port has no vacuum, so I moved the vac advance line to the second port. The tech didn't try it with mechanical advance only.
 
I will say that the shop owner came out during testing and said it "Sounded lazy" and suggested giving it more timing, but was surprised to hear that we were already at 45.

Do you think it may want more initial and less advance? Should I try pulling the vacuum advance and going back to straight mechanical, then give it a little more initial?

Can there be gains in increasing the jets if the A/F ratio is already running in the 12-14 range? Wouldn't it go rich if jets are increased?
 
Last edited:
It seems like your timing and jetting are on the money. Since you don't know specs on cam, maybe pull valve covers and check valve lift and make sure everything is okay up there. I just put a 4 barrel manifold on my 318 and it ran terrible. Thought it might be air leak pulled manifold off and found every pushrod bent. Also distributor was missing a clip to hold down advance. Put new rods in and new distributor and it runs great now. Car didn't run that bad with 2 barrel carb, but terrible with 4 BBl.
 
I was just doing some reading about Demon Carbs and read that of the two ports I was mentioning, the rear port is constant vacuum and the front only has vacuum when the engine is revved. They said that the vacuum advance should go on the front port. I do not recall if there was vacuum on my front port when I rev it. I just know there was no vacuum at idle.

I will put a vacuum gauge on that front port and rev the engine to see if it develops vacuum when on the throttle. Could it be that I am hooked to constant vaccum so advance is coming in too early?

Just a thought
 
tonysrt said:
It seems like your timing and jetting are on the money. Since you don't know specs on cam, maybe pull valve covers and check valve lift and make sure everything is okay up there. I just put a 4 barrel manifold on my 318 and it ran terrible. Thought it might be air leak pulled manifold off and found every pushrod bent. Also distributor was missing a clip to hold down advance. Put new rods in and new distributor and it runs great now. Car didn't run that bad with 2 barrel carb, but terrible with 4 BBl.
Click to expand...

I will check that. I want to pull the plugs and check compression on all the cylinders anyway.

Is there a way to determine lift and maybe duration by putting a dial indicator on the rocker and rolling the motor over?
 
You've done more than most to find extra power, ie.dyno tune. I'd move over to the charger.. If you feel you just can't leave it alone, try a bigger carb, 850ish, for a bigger, easy bolt on boost. Jmo
 
Go back to the original owner and see if he found his info. Find out if the cam was degreed, if he doesn't know what your talking about assume it wasn't and degree it in. At that time the info on the cam should be seen on the snout so you'll know what you have there and where to degree it. 2-1/2" exhaust would help.

FYI, Dyno's are a tuning tool, you could drive over to a shop across the street and see a 25hp difference either way. If you do changes, go back to the same dyno, as long as it maintained and the operator knows what he is doing you should see results, good or bad.
 
Frnknsteen said:
Hi Guys,

I posted on this yesterday in my restoration thread, but thought it might make more sense to post here.

I have a '67 Barracuda I am working on. My restoration thread will show what all I have done to it, so I won't repeat here. Basically, the motor was in it and running good when I bought it. I put the transmission back in and got the suspension and steering back in line. I took it to a local shop and had them put it on the chassis dyno and look for best carb and timing settings.

Outcome was that I am getting 254hp and 340+ft/lbs to the wheels. It drives pretty good, but it just seems a little lazy and needs woken up a bit. I hate to say it, but I have no idea what is in the motor. Like I said. It was in the car, ran good, and I got it for what I believe to be a good price after looking at others. Previous owner couldn't find his folder of receipts, and could just tell me they "Did some work to the motor and put a Competition Cam in it".

Specs I know:
1977 400, 906 heads, Speed Demon 750, Tri-Y headers, Magnaflow 2 1/4" exhaust
A833 4spd, 8 3/4 Suregrip 3:23 - 245/60R14 Radial T/A's in back (25.6" Diameter from what I've seen on tire charts)

I really have nothing to compare to determine if I should be happy with the output for this cruiser, or if there are some little things I could do to wake it up a bit. This is a "For Fun" car that I'm driving and enjoying while most of my money goes into the rebuilding of my Charger. That means I've got SOME budget, but somewhat limited.

I'm planning to do a compression check of all the cylinders. I know that won't tell me the compression ratio, but it will tell me how even the motor is from cylinder to cylinder, and tell me how much air I'm moving and if I'm low, like 110psi or doing ok, like 150 - 160psi. It wouldn't hurt to pull the heads off and see where the top of the piston is from the top of the block so we can look at CR, but that's hard to justify when it is running good. Maybe a good winter project though!.

Wondering where you guys would go with this car? Leave it where it is and just enjoy it while redoing my Charger (Then build it up more)? Or is there things I could do that would immediately help perk it up. I do have a set of 915 heads I could swap in to get a bit of a CR boost.

Mark
Click to expand...


Considering where a 77 400 started HP/TQ wise, i think you're doing ok. factory, they were rated at 190hp and 300 ft lbs, gross FLYWHEEL for the 2 barrel and 240 hp and 325 ft lbs for the 4 barrel version. again, at the crank. so considering powerloss thru the drive train is usually around 20-35%, that puts your flywheel HP around 300-330 hp and 400-440 ft lbs. Respectable from what we can assume is a sub 9.5 Compression ratio at best. factory CR was 8.2
 
dano said:
Go back to the original owner and see if he found his info. Find out if the cam was degreed, if he doesn't know what your talking about assume it wasn't and degree it in. At that time the info on the cam should be seen on the snout so you'll know what you have there and where to degree it. 2-1/2" exhaust would help.).
Click to expand...

Thanks Dano. I have tried to contact the original owner twice to see if he found it. First response was "Nope", second response was,.... well, he didn't respond. I don't think he wanted to sell the car so now he just doesn't want to deal with it. You make a good point on degreeing the cam. It wouldn't take me long to get down to that point and then I would at least know what the cam is. I was wondering if there would be markings on the end of the cam listing part# so I could tell what it is.

dukeboy_318 said:
Considering where a 77 400 started HP/TQ wise, i think you're doing ok. factory, they were rated at 190hp and 300 ft lbs, gross FLYWHEEL for the 2 barrel and 240 hp and 325 ft lbs for the 4 barrel version. again, at the crank. so considering powerloss thru the drive train is usually around 20-35%, that puts your flywheel HP around 300-330 hp and 400-440 ft lbs. Respectable from what we can assume is a sub 9.5 Compression ratio at best. factory CR was 8.2
Click to expand...

Thanks Duke! You make a good point that at least I know I am doing better than a stock 400 and it is at least respectable numbers considering what a 400 started with.

I may try to correct the vacuum line question.

Question,.... Should our distributors be connected to direct vacuum or ported vacuum? I'm looking at the Demon Carb manual and it says the front port (where it was connected when I bought it) is ported vacuum from above the butterflies. It says the second port (where I have it hooked now) is direct manifold vacuum from below the butterflies. Wondering which I should have it hooked to on Mopar distributors.

The Demon manual says this:

The large fitting on the back of the baseplate, and the rear most fitting of the two small fittings on the side of the baseplate, are direct (below the butterfly) manifold vacuum sources. The front small fitting on the side of the baseplate, opposite the throttle linkage, provides a ported (above the butterfly) vacuum source (use this port for the vacuum on a vacuum advance distributor).

Demon Vacuum.jpg
 
Why were you dyno tuning for power with the vacuum advance connected?
 
Revhendo said:
Why were you dyno tuning for power with the vacuum advance connected?
Click to expand...

I saw him disconnect the vacuum when adjusting the timing, but it was hooked up when the dyno runs were performed. Is there a reason it wouldn't be connected? I understand vacuum advance doesn't do much at WOT (because of vacuum drop at WOT), but I guess I didn't question if it should be hooked up at all when doing the dyno run. I had never read that before, and I'm by no means an expert at dyno testing.
 
Were the dyno runs "full pull" or cruise speed runs? There are specific reasons for vacuum advances. Am I reading that your afvance can is pulling in 30° of advance?
 
Frnknsteen said:
Yes. I used my vacuum gauge to set my idle mixture.
Click to expand...

What was the highest vacuum reading and was it steady? This can tell you if you have some issues and roughly about how largish of a cam you have.

Did the previous owner mention the engine was rebuilt?
 
dano said:
What was the highest vacuum reading and was it steady? This can tell you if you have some issues and roughly about how largish of a cam you have.

Did the previous owner mention the engine was rebuilt?
Click to expand...

I don't recall off the top of my head what the actual vacuum was reading, but yes, it was pretty steady. I remember thinking it was a little low, but I don't remember if it was around 11 or 13. I want to say it was running around 11 inches because I don't think I would have thought 13 was low. Borderline maybe, but not low. At the time, I wasn't really thinking about specific numbers. I was just tweaking the four mixture screws a little at a time until max vacuum was reached, to make sure they were all set evenly (as per my handy dandy "Tuning Demon Carburetors" book!).

I will run back to the shop and check vacuum tonight. It's about 25 degrees colder today, but I'll let her warm up good and check it quick.

I did find it interesting that the book said to start at 1.5 turns out, but carb was set to 3/4 turns out. I adjusted them out approximately 1/4 turn more (1/8 turn at a time each) before vacuum started to drop off. Reset them back to max vacuum where it started to drop.

Yes,... he clearly said they rebuilt the motor, but it sounded like he had a shop do the rebuild because when he was talking about the engine he specifically said "They did some machine work and put in a bigger cam" not "I" or "We"
 
Revhendo said:
Were the dyno runs "full pull" or cruise speed runs? There are specific reasons for vacuum advances. Am I reading that your afvance can is pulling in 30° of advance?
Click to expand...

Dyno runs were from about 2000 rpm up to just under 5000 rpm. We didn't push it above 5000 rpm because we didn't know much about the motor yet and didn't want to push it too hard. Out of curiosity,... what is safe redline for these big blocks? I've always heard don't push it over 5500 for very long.

No, I wouldn't say advance can is pulling in 30 degrees of advance. All-in advance is 45, but the majority of that should be coming from mechanical advance. If I remember correctly from while originally setting it myself with vacuum disconnected, I set it to about 33 at 2500, then checked initial and it was about 12, so I should be getting around 20 degrees of mechanical. Initial is now set at 15 and full advance with rpms held about 2500 and vacuum connected is 45 (according to his timing light).

That would mean I'm getting about 10 degrees of advance from the vacuum can,.... Correct?
 
Ok,... Went and checked some things when I got home to answer some of the questions.

Engine vaccum at idle hovers between 12 and 13 (connected to manifold vacuum port). I connected to the ported vacuum and no vacuum at idle. Vacuum jumps when I blip the throttle.

Timing according to my light is 13 initial (vacuum disconnected), 33 with mechanical advance only (vacuum disconnected) at 2600rpm, 50 at 2600 with vacuum attached to manifold vacuum port.

Interestingly, timing at idle with manifold vacuum connected is 17, meaning it is not giving full vacuum advance at idle like I thought it would.

Timing with vacuum connected to ported vacuum, at idle is 13, which makes sense considering no vacuum at idle from ported connection. Timing at a steady 2600 with vacuum connected to ported vacuum is 37.
 
What are your ported and manifold vacuum readings @ 2600 and 3000 rpm?
 
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