DWC's 1968 Camaro project - Lateral-g Forums

**WSSix** · #1 08-18-2019, 07:37 PM

Did you have the new flywheel balanced matched to the old one? You can't just replaced an external balanced flywheel with another external balanced unit. They aren't necessarily counter weighted the same.

If you didn't do this, you need to take the old flywheel and clutch pressure plate along with the new flywheel and clutch pressure plate to a machine shop and tell them what you're trying to do. Don't ever assume a clutch pressure plate is zero balanced out of the box. Always include it when doing any balancing work.

DWC · #2 08-19-2019, 05:55 AM

Trey- Unfortunately, I did not do that because I was unaware it needed to be done. The engine had an SFI external balance flexplate on it when I bought it (he ran an auto trans). I called PRW, told them my setup, verified their flywheel would work with the McCleod clutch I was getting and ordered the flywheel. They did not mention any balancing was required.

Here is the flywheel I ordered.

https://www.jegs.com/i/PRW/228/1640081/10002/-1

Since the specs matched what I needed, I thought it was good to go out of the box. I sold the flexplate the engine came with. I guess I can try to get in touch with the buyer and see if I can get it back.

Thanks for the input,

Daniel

SSLance · #3 08-19-2019, 08:42 AM

Are you convinced it is a balance issue and not a misfire? Maybe get it running where it is shaking at it's worse and put a infared heat gun on each header tube to verify they are all firing.

I have found that a long stroke SBC feels differently than just about any other engine, at times I've felt like mine was out of balance as well. I can tell you though now that I have EFI controlling both the timing and fuel delivery...it is buttery smooth everywhere and I didn't change any hard parts pertaining to balance.

Just a thought...

DWC · #4 08-19-2019, 09:04 AM

Lance- it's funny you mention that. When I was trying to tune the 830cfm carb and adjust timing, I used an infrared gun to check the header tubes. But, I did it quickly and didn't pay much attention because our attention was drawn to another issue that day.

I will check the tubes today now that the new carb is installed. Honestly, I was hoping it was a carb tune/timing issue that was causing the vibration, but the new carb didn't seem to have any effect on the vibration.

Thanks for the input,

Daniel

nicks67ca · #5 08-19-2019, 09:42 AM

I the engine is truly out of balance this may sound low tech but if you don't want to re-balance the whole engine you could remove the trans and clutch. Then run the car with just the flywheel. this would take the clutch out of the equation. Then using the bolt holes for the clutch you can add weight to different areas to see if it helps you balance. If you find a combo that works you can take your flywheel and have weights added or removed.

DWC · #6 08-19-2019, 11:02 AM

I spoke with a PRW tech this morning and he had me verify my flywheel counterweight was bolted on in the correct position and had the correct part number stamping. Apparently, there are 2 positions. I verified my weight IS in the correct position and I have the correct part stamp. He advised me to remove the weight and verify it weighs 156.1 grams, which I'll do this evening. He says if it's a few grams or more off, it could cause vibration.

nicks67ca- Thanks for the tip. I really hope I don't have to pull the engine and tear it down.

Daniel

DWC · #7 08-19-2019, 04:36 PM

Interesting thing I discovered this evening. I brought home a cheap infrared temp gun from work to shoot the header tubes. Cylinders 1, 2, and 6 seem to heat up much quicker than the rest of the cylinders. Those cylinders are reaching 300* really quick, and the other cylinders are still in the mid 100's. I'm only letting it idle for less than a minute. I don't want to run it anymore than I have to until I figure out what's going on. I'm ASSuming if I were to let it get up to full temp, the cylinder temps would still be inconsistent.

Thoughts?

Daniel

Panteracer · #8 08-19-2019, 07:30 PM

Last time I saw that much heat difference
was when my dizzy was 180 out in my Pantera
I would double check. Yes it ran but not good

Bob

DWC · #9 08-20-2019, 06:09 AM

Bob- I would love for that to be the root of the issue. I'll double check tonight. When I originally installed my old distributor, it was 180 out and the engine would backfire, sputter, barely run at all. Currently, it starts right up and idles decent, but a little rough. Then when revved above 1k rpms, vibrates and sounds like ass.

I need to post a video and maybe someone can pick up on something I've not mentioned.

Daniel