[nobody]

I took the car out this evening and noticed a slight miss. It's noticable at around 6500 RPM or so but not above 7000. Does it sound like ignition or fuel starvation is what I'm wondering. Valve float and too small of mains crossed my mind but above 7 it's fine. It did it in all gears so was wondering what it was. Harmonics maybe?

Since I built it I've never gotten on it that hard so I'd like to figure it out.

Both the speedo and tach gave up so maybe that was part of it.

 

[bear]

Tach quitting I can see that it may be an ignition problem, speedo is mechanically driven by the tranny so that should rule itself out, no interplay between it and the tach. Now the question remains, fix the tach and the problem goes away or remains. Fix the speedo, just to know how fast you're truckin' on. Don't you just love them gremlins.

 

[jeff denton]

Harmonics. Those exhaust pulses are banging around in the exhaust system and at a certain RPM they are combining with a vibration or intake noise and sound funny. It can probably only be heard inside the car, probably sounds great outside. Take it around the block a few laps at 6500 RPM and get some opinions from your neighbors!
That's my guess.

 

[nobody]

the speedo quit at 135 or so and the tach got peged too many times I think. The 0 to 60 was slow. It took a good city block to hook up this time above 8k. I wasn't playing and let it out. When I went past the Royal Gorge exit was over the 6500 Rpm where it was missing but in 5th...... not that I was speeding or had the radar detector going.

Or that the local police would have attempted on an uphill grade to catch me.

No don't do this if you aren't prepared for what might happen.

 

[nobody]

ok recalculated it with tire size and final gear ratios VS overdrive. I only got up around 170. it had me concerned till I got the math right for gear ratios. Not bad for normally aspirated at altitude going uphill.

 

[cristian68rekor]

Ihad the same problem at 4k ,I took out the intermediate muffler and now everything is OK.

Cristian

 

[jordan]

mine would gargle and start to buck at 4500 in 4th and it would stop at 5k but it is tough to get it past 4500 when it's bucking. I figured it was an asperation problem, but hopefully it will stop with the free flowing exhaust system and the ported intake manifold.

 

[nobody]

I think it's harmonics, it pulled well in the 7's but just had that miss at mid 6's. I never figured it, but the stock Speedo and tach won't handle it. The trials you get into on a high speed run I guess.

 

[GTJIM (R.I.P.)]

Stock Limits

I never figured it, but the stock Speedo and tach won't handle it.

The "stock" redline is 6,100 rpm - guess the speedo and tach are not made to handle it above that!

 

[baz]

ok recalculated it with tire size and final gear ratios VS overdrive. I only got up around 170. it had me concerned till I got the math right for gear ratios. Not bad for normally aspirated at altitude going uphill.

think we have a new leader in the how fast is your gt thread
dave give the exhaust an extention of a couple of inches on each outlet(those chrome thingy whatsits {ture technical term honest } that clamp on ricers to make them look bad) to change the harmonics and see where it puts the miss fire

 

[GTJIM (R.I.P.)]

Verification!

think we have a new leader in the how fast is your gt thread

Baz, We need SPEED CAMERA PICS to verify that!

 

[bear]

Well, I volunteered to hold the camera for a high speed run in Nobody's 2.0, but we couldn't hook up to get it done. So, until there is verification, we'll just have to take his word for it. And we know how truthful and forthright "nobody" is. I figure 7K with a 5-speed that isn't outside of the realm of probably did that.

 

[opelgtmaster3]

hey dave.
your car sounds like is really fast. i wish i could drive my car. man i miss my opel.