[JoshW]

I'll try my best to keep my frustration to a minimum...

Took the cobra to a shop for some troubleshooting and an eventual dyno. Fixed the fuel issues and when they put it on the chassis dyno it produced way less numbers than I thought I was going to get based off what the engine builder advertised; oh and a wonderful leak coming out near the bellhousing.

It's a 445 stroker (built by Southern Automotive) with an estimated 500hp at the crank but only made 360hp on the dyno. Engine has 20 miles on it.

Quick specs:

Block: 390 cast iron (prepped and machined)
Crank: Eagle specialty
Rods: Eagle specialty h-beam comp
Pistons: Mahle HP - forged
Bearings: Clevite HP
Cam: Hydraulic flat tappet - comp cams
Timing chain: Comp cams double row
Heads: Edelbrock performer #60069
Intake: Blue Thunder aluminum 1x4
Carb: Quick Fuel 750
Compression 10.2 - 1
MSD distributor and box

If I recall correctly, tech at the shop said it was adjusted to 35 degrees at 3k rpms. Need to double check.

I really don't know what to do at this point, or if I need to do anything. Maybe I had unrealistic expectations?

Thank you in advance!

 

[Gordon Levy]

500 is a little pushing it for a 390. Knowing the cam profile would help a ton. the heads and intake will definitely make the power. using a 22% parasitic drive train loss you are making 440 flywheel. Variables are dyno calibration, corraction factors, altitude, temp, etc... It makes a difference. You may g to a different dyno and make 450rwhp so don't too wrapped up in the numbers. Are you happy with the performance while driving it?

 

[egchewy]

might be a silly question, but flat tappet broken in appropriately?

 

[JoshW]

500 is a little pushing it for a 390. Knowing the cam profile would help a ton. the heads and intake will definitely make the power. using a 22% parasitic drive train loss you are making 440 flywheel. Variables are dyno calibration, corraction factors, altitude, temp, etc... It makes a difference. You may g to a different dyno and make 450rwhp so don't too wrapped up in the numbers. Are you happy with the performance while driving it?

Unfortunately I don't have a cam profile. I'll see if I can get one though. Other info I have on the heads:

Intake: 2.09
Exhaust 1.66
Head cc: 72

To be honest and fair, I haven't driven it that much (only 20 miles or so) but when I did get on it I wasn't too impressed. Don't get me wrong, it pulled but it wasn't what I was expecting. If I put a $100 bill on the dash and floored it, you would definitely be getting it easily; even in first.

 

[JoshW]

might be a silly question, but flat tappet broken in appropriately?

I know the builder ran it on the stand for several hours after the build. Beyond that, I haven't driven very much at all and even when I did the rpms never went about 4k.

 

[Gordon Levy]

Cam profile would help a ton. Maybe shoot some vid and send it to me in messenger and let's see how it performs.

 

[JoshW]

Cam profile would help a ton. Maybe shoot some vid and send it to me in messenger and let's see how it performs.

Alight will do. I think they are going to make another adjustment on the dyno tomorrow so I’ll try to be there when do.

 

[Bob Cowan]

Those are pretty big heads, even for a 455. Should make a lot of top end power, at the expense low end power. If you are also using a low rpm/high torque cam, you could be losing intake charge velocity. I've made that mistake before. If Southern built the engine, I would not expect them to make a mistake like that.

Posting the dyno sheet would be helpful.

Go back and look at the basics:

• How's the fuel curve on the dyno sheet? Are you running out of fuel?
• Inspect the plugs. Maybe someone dropped one, and closed the gap.
• Make sure all the plug wires are clean and solidly attached.
• Look under the distributer cap. Dirt? Carbon tracks? Damage?
• Mash the throttle to the floor. Are the carb blades fully open?
• Do a compression and leak-down test.
• When the engine is hot, check the header tube temps. They should all be about the same.
• Run the dyno test again with no air filter.
• At 5,000 rpm, are you producing at least 14 volts?

Sometimes it's the little things that hurt us the most.

 

[PaulProe]

You're really trying to compare apples to oranges. Dyno's are more for detecting changes made than comparing output from one to another. Comparing an engine dyno to a chassis dyno generally won't be close. Too many other variables come into play.

Probably safe to say that Southern did everything they could to get high readings (no air cleaner, timing tweaked, dyno settings, etc) With all that, 500 HP from a 390 hydraulic flat tappet is VERY aggressive. Not saying it can't be done but it would be a challenge.

On the other side, when you go to the chassis dyno, the way it's strapped down, air filter now installed, and parasitic losses (trans, differential, tire slip, etc), it would be almost impossible to get similar numbers.

You probably would get better results if you asked the chassis dyno operator to offer suggestions on anything he sees that would improve numbers. You'd be surprised what a little more timing, proper jetting and different air cleaner could make. Use his dyno and input to evaluate changes to make it optimum.

my 2c

Paul

 

[tom welch]

I'll try my best to keep my frustration to a minimum...

Took the cobra to a shop for some troubleshooting and an eventual dyno. Fixed the fuel issues and when they put it on the chassis dyno it produced way less numbers than I thought I was going to get based off what the engine builder advertised; oh and a wonderful leak coming out near the bellhousing.

It's a 445 stroker (built by Southern Automotive) with an estimated 500hp at the crank but only made 360hp on the dyno. Engine has 20 miles on it.

Quick specs:

Block: 390 cast iron (prepped and machined)
Crank: Eagle specialty
Rods: Eagle specialty h-beam comp
Pistons: Mahle HP - forged
Bearings: Clevite HP
Cam: Hydraulic flat tappet - comp cams
Timing chain: Comp cams double row
Heads: Edelbrock performer #60069
Intake: Blue Thunder aluminum 1x4
Carb: Quick Fuel 750
Compression 10.2 - 1
MSD distributor and box

If I recall correctly, tech at the shop said it was adjusted to 35 degrees at 3k rpms. Need to double check.

I really don't know what to do at this point, or if I need to do anything. Maybe I had unrealistic expectations?

Thank you in advance!

Just a guess, but maybe fuel line/filter restricted? I have a 302 roller from blueprint engines with 320 hp/360 torque a the flywheel and when I smash the petal it really sits me back in my seat. I would expect your build to bearly keep in on the road! Others above have a lot more knowledge than me so I would follow their lead. Keep us informed. We are curious on any resolution you find.

PS... you mentioned unrealistic expectations. Your other car is not a top fuel dragster is it? I could see how comparing the acceleration of a 3 second 300 mph car to f5 mkiv would be disappointing.

 

[JoshW]

Just a guess, but maybe fuel line/filter restricted? I have a 302 roller from blueprint engines with 320 hp/360 torque a the flywheel and when I smash the petal it really sits me back in my seat. I would expect your build to bearly keep in on the road! Others above have a lot more knowledge than me so I would follow their lead. Keep us informed. We are curious on any resolution you find.

PS... you mentioned unrealistic expectations. Your other car is not a top fuel dragster is it? I could see how comparing the acceleration of a 3 second 300 mph car to f5 mkiv would be disappointing.

Haha I was definitely not expecting a sub 4 second 1/4 mile run at all. We'll see what happens today on the dyno after the adjustments. Timing was set at 34 and should be at 38 so hopefully it will make a difference.

 

[JoshW]

Those are pretty big heads, even for a 455. Should make a lot of top end power, at the expense low end power. If you are also using a low rpm/high torque cam, you could be losing intake charge velocity. I've made that mistake before. If Southern built the engine, I would not expect them to make a mistake like that.

Posting the dyno sheet would be helpful.

Go back and look at the basics:

• How's the fuel curve on the dyno sheet? Are you running out of fuel?
• Inspect the plugs. Maybe someone dropped one, and closed the gap.
• Make sure all the plug wires are clean and solidly attached.
• Look under the distributer cap. Dirt? Carbon tracks? Damage?
• Mash the throttle to the floor. Are the carb blades fully open?
• Do a compression and leak-down test.
• When the engine is hot, check the header tube temps. They should all be about the same.
• Run the dyno test again with no air filter.
• At 5,000 rpm, are you producing at least 14 volts?

Sometimes it's the little things that hurt us the most.

 

[JoshW]

Those are pretty big heads, even for a 455. Should make a lot of top end power, at the expense low end power. If you are also using a low rpm/high torque cam, you could be losing intake charge velocity. I've made that mistake before. If Southern built the engine, I would not expect them to make a mistake like that.

Posting the dyno sheet would be helpful.

Go back and look at the basics:

• How's the fuel curve on the dyno sheet? Are you running out of fuel?
• Inspect the plugs. Maybe someone dropped one, and closed the gap.
• Make sure all the plug wires are clean and solidly attached.
• Look under the distributer cap. Dirt? Carbon tracks? Damage?
• Mash the throttle to the floor. Are the carb blades fully open?
• Do a compression and leak-down test.
• When the engine is hot, check the header tube temps. They should all be about the same.
• Run the dyno test again with no air filter.
• At 5,000 rpm, are you producing at least 14 volts?

Sometimes it's the little things that hurt us the most.

Really appreciate all the advice and things to check. I'll ask for the fuel curve on the dyno sheet; only had power and torque sent to me via text. Another issue they brought up was that when the car got hot (210-220 F) the car did not want to start after a pull. They didn't give me specifics but just said after it got hot they couldn't start it. After watching a couple pulls from start to shut down I noticed that it seemed like the battery was pretty low. Maybe that's it? Who knows without seeing it firsthand.

I'll check the basics as you mentioned above.

Thank you!!

 

[JoshW]

You're really trying to compare apples to oranges. Dyno's are more for detecting changes made than comparing output from one to another. Comparing an engine dyno to a chassis dyno generally won't be close. Too many other variables come into play.

Probably safe to say that Southern did everything they could to get high readings (no air cleaner, timing tweaked, dyno settings, etc) With all that, 500 HP from a 390 hydraulic flat tappet is VERY aggressive. Not saying it can't be done but it would be a challenge.

On the other side, when you go to the chassis dyno, the way it's strapped down, air filter now installed, and parasitic losses (trans, differential, tire slip, etc), it would be almost impossible to get similar numbers.

You probably would get better results if you asked the chassis dyno operator to offer suggestions on anything he sees that would improve numbers. You'd be surprised what a little more timing, proper jetting and different air cleaner could make. Use his dyno and input to evaluate changes to make it optimum.

my 2c

Paul

Thanks for the 2 cents Paul, I appreciate it! I'll always be the first to admit when I'm wrong or disillusioned and I figured I was part of the culprit. I'll ask the dyno operator for suggestions today and see what happens.

Thank you!!!

 

[railroad]

I think your concerns are warrantied. It might be mismatched parts as suggested, but the rotating mass alone should generate higher tq numbers IMO.
Not familiar with the company that built it, but friend had a corrupt person build his now broken down engine.
He bought a stroker kit, bee hive springs, special rocker arms, etc. Short story, when the engine broke down and was opened up, it did not have the purchased parts.
Your company may be reputable. If so, maybe some cam timing and tuning can wake up your monster.
Good luck,
After looking at your dyno sheet again, it is surprising the engine is all done about 4800 rpm. I am no guru on reading dyno sheets, but something has played out too early. My first guess would be valve springs.
Surely the carb was optimized for the engine. Although small the carb, should pull better and farther up the rpm range. Total timing may be a little high, but dyno operator surely worked his way to the best setting.
Really interested in the rest of the story. Please post where you go with this.

 

[railroad]

Those are pretty big heads, even for a 455. Should make a lot of top end power, at the expense low end power. If you are also using a low rpm/high torque cam, you could be losing intake charge velocity. I've made that mistake before. If Southern built the engine, I would not expect them to make a mistake like that.

Posting the dyno sheet would be helpful.

Go back and look at the basics:

• How's the fuel curve on the dyno sheet? Are you running out of fuel?
• Inspect the plugs. Maybe someone dropped one, and closed the gap.
• Make sure all the plug wires are clean and solidly attached.
• Look under the distributer cap. Dirt? Carbon tracks? Damage?
• Mash the throttle to the floor. Are the carb blades fully open?
• Do a compression and leak-down test.
• When the engine is hot, check the header tube temps. They should all be about the same.
• Run the dyno test again with no air filter.
• At 5,000 rpm, are you producing at least 14 volts?

Sometimes it's the little things that hurt us the most.

My investigation into head specs show 170 cc intake runners and normal size valves.
I do not see heads being too large. Am I over looking some specs here?
Not trying to stir the stuff, just not seeing what I should?

 

[JoshW]

I think your concerns are warrantied. It might be mismatched parts as suggested, but the rotating mass alone should generate higher tq numbers IMO.
Not familiar with the company that built it, but friend had a corrupt person build his now broken down engine.
He bought a stroker kit, bee hive springs, special rocker arms, etc. Short story, when the engine broke down and was opened up, it did not have the purchased parts.
Your company may be reputable. If so, maybe some cam timing and tuning can wake up your monster.
Good luck,
After looking at your dyno sheet again, it is surprising the engine is all done about 4800 rpm. I am no guru on reading dyno sheets, but something has played out too early. My first guess would be valve springs.
Surely the carb was optimized for the engine. Although small the carb, should pull better and farther up the rpm range. Total timing may be a little high, but dyno operator surely worked his way to the best setting.
Really interested in the rest of the story. Please post where you go with this.

Thanks for your input. I too thought the numbers were low, but I am definitely not an expert by any means.

So the 4800 rpm limit was partially due to the tach suddenly not working though it was working fine earlier. Another point of frustration... Could it be valve springs? I have no idea lol.

I'm learning that the assumptions (carb optimized, parts, timing, etc) are just that, an assumption. I think it's safe to go back to the basics like another person recommended earlier. My favorite quote I picked up in the Army is "trust but verify". I think that's where I am now.

I'll keep you posted!

I think your concerns are warrantied. It might be mismatched parts as suggested, but the rotating mass alone should generate higher tq numbers IMO.
Not familiar with the company that built it, but friend had a corrupt person build his now broken down engine.
He bought a stroker kit, bee hive springs, special rocker arms, etc. Short story, when the engine broke down and was opened up, it did not have the purchased parts.
Your company may be reputable. If so, maybe some cam timing and tuning can wake up your monster.
Good luck,
After looking at your dyno sheet again, it is surprising the engine is all done about 4800 rpm. I am no guru on reading dyno sheets, but something has played out too early. My first guess would be valve springs.
Surely the carb was optimized for the engine. Although small the carb, should pull better and farther up the rpm range. Total timing may be a little high, but dyno operator surely worked his way to the best setting.
Really interested in the rest of the story. Please post where you go with this.

 

[MJN]

Did they actually run it on an engine dyno before they delivered it? Was the engine run on the dyno with no air cleaner and open dyno headers? What air cleaner are you running? The short air cleaners needed to fit under the hood of a Cobra are known to kill HP. What headers / side pipes are you running? Again the typical FFR set up has been known to kill HP compared to a good set of engine dyno headers. 360 RWHP should feel pretty fast, if it doesn't then there's something going on more than just the apparent loss of HP.

 

[JoshW]

Did they actually run it on an engine dyno before they delivered it? Was the engine run on the dyno with no air cleaner and open dyno headers? What air cleaner are you running? The short air cleaners needed to fit under the hood of a Cobra are known to kill HP. What headers / side pipes are you running? Again the typical FFR set up has been known to kill HP compared to a good set of engine dyno headers. 360 RWHP should feel pretty fast, if it doesn't then there's something going on more than just the apparent loss of HP.

Hey Mike,

No they didn't run it on a dyno before delivered. Car was ran on the dyno with no air cleaner and ran using the side pipes already installed on the car. Ha, definitely using the short air cleaner (8in if I recall correctly) and not sure on the side pipes but they were built by Unique and are ceramic coated.

Thanks!

 

[phils88gt]

A 170cc head is pretty small for a 440" motor. However port size doenst tell all..The FE if I recall has a pretty short port length since the intake is partially in the head.

I looked around for some flow data and could not find it, but 450 at the flywheel doesn't seem out of place, but cam data would help. I assume the engine builder offered the 500hp figure before the sale.

Typical engine dynos run low temps 150-170f water for sure that will pick up output for a hero pass on the dyno. I'm not an FE guy buy I would not expect it to want more than 36-38deg and even if it wanted 38 I would expect 10 numbers not 50.

If you are thinking it's hurt check the basics, plugs, leakdown and cam lift. Pop the valve covers and make sure all the rockers sure opening a realistic amount. A flat lobe would be easy to tell. ( since the pushrod will be practically falling out )

Phil