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

This afternoon I removed the distributor and plug wires, reset the engine to TDC, reinstalled the dist and wires...no improvement. Put my timing gun lead on all plug wires and verified they were all firing.

I then adjusted/closed the carb idle screws on all four corners and it seemed to reduce the vibration...maybe 30%. I noticed #1 plug was fouled again when I was setting TDC, so I'll replace them all and continue to tune the carb. Also, I shot the header tubes with the infrared gun after adjusting the carb and the temps were much closer to each other.

Lastly, I removed the counterweight on the flywheel and weighed it. Mine weighs 161 grams and the PRW tech I spoke to yesterday said it should weigh 156.1 grams. He said more than a couple grams could effect the balance. I know 5 grams isn't much (weight of a quarter), but I'm hoping with it being so far from the crank centerline, it's causing the vibration. Fingers crossed. I'm going to have him send me another...with the correct weight.

Daniel

PRW is sending me a 156.1 gram counterweight that'll be here Friday.

On another note, I did a compression test today-
1- 215
3- 215
5- 210
7- 215
2- 215
4- 215
6- 205
8- 210

I'm ready to get the vibration solved and drive.

Daniel

Good news, the engine vibration seems to be gone/acceptable. I installed the replacement flywheel counterweight and that reduced the vibration about 20%. Then I tuned the carb with a vacuum gauge and that reduced it another 70%. I initially had the corner idle screws out 1.5 turns per Holley. With that, I only had 4hg of vacuum. I adjusted the screws until I had 11hg of vacuum at idle and 20hg at about 2500 rpms. The corner idle screws are at about 1/2 to 2/3 of a turn out from fully seated.

I believe the remaining 10% is just me not being used to a big cammed stroker motor. I visited my painter on Saturday and he has a 68 Camaro with a 383 stroker and has as much vibration in the steering wheel at idle as I do now.

My engine temps are much better as a result. It sits about 190-195* at idle.

I have 3 current issues I’m working on:
-after about minute of idle, the exhaust starts to “pop” every few seconds. I guess the pop would be considered a backfire
-when I let the clutch out and I’m coasting, the car surges/bucks
-when I shut the car off, I have engine run on for a few seconds. I can get around this by cutting it off in gear. But I’d rather fix it properly.

I feel that these issues are tied to the carb and I need to continue to tune it. But, I don’t really know what to do next. I did retorque the header bolts and sprayed carb cleaner around the carb hunting for a vacuum leak, but didn’t get an rpm change.

Daniel

That is great news! The rest of your issues sound timing related to me. What are you using for a distributor and ignition?

Lance- I have about 35* total timing (15 initial, 21 mechanical advance). I have an MSD billet distributor, MSD Street Fire ignition box, MSD Blaster SS coil, Taylor 8mm plug wires, and Autolite 3922 plugs. All of those are new.

Daniel

You should consider getting the car tuned at this point. Might not be easy finding someone that knows how to tune a carb unfortunately. I agree with Lance. Your current issues are carb/timing issues.

Glad you go the vibration figured out.

run on is usually timing, maybe carb if the engine isn't worn out. I'd verify TDC (ie make sure your timing mark is accurate) then throw a light on it. Most SBC like around 18 initial and 18 mechanical. But I'd be surprised if 15 initial caused run on. Is the carb new? If not, did you put a rebuild kit in in recently? Also, not sure if i saw what you said you had the idle set at...

Trey- Funny you say that. Yesterday, a friend gave me the number of a local guy that tunes carbs. I have a few more things to try on the carb, and if those don't pan out, I'll probably take it to him.

I hope I can figure it out on my own, because I'll need that knowledge/skill in the future with this car.

Steve- The carb is new. The idle is about 900rpms. I'm going to pull the carb and check the transfer slot adjustment. My idle mix screws are only about 1/2 a turn out. I think the car maybe idling partly on transfer slot fuel. At least that's my understanding from reading the past few days.

Daniel

So, in this day and age, there are better ways to control timing than mechanical advance. I have a couple spare MSD 6AL-2 boxes that when used with a locked out distributor you can use to make the timing whatever you want it to be whenever you want it to be. I ran one for about 5 years on my 383 before swapping to EFI couple months ago and it worked great. You can even tie in a MAP sensor to really tie the timing to load as well as RPM.

When I watch the display now of what my Holley EFI ECU is doing to my timing to control my idle and cruise...it blows my mind. I'm not suggesting that you switch to EFI now (but you would love it if you did) but watch this display to see how my ECU makes my stroker idle like a 2016 Camaro.

Are you certain your not 180* out on timing?

Lance- I watched that video in your build thread- jealous. I may end up with EFI in the future, but want to at least build a working knowledge of carbs just for my own weird curiosity.

Mike- I'm 99% certain it's not 180 out. Just to be sure, last week I removed the distributor and plug wires, reset the engine to TDC, reinstalled the dist and wires.

Daniel

You can have TDC on intake stroke and exhaust stroke. Have you tried to run it without the MSD box? I have had more trouble with those than they are worth.

Mike- That's right, and I made that mistake initially when trying to get the engine started for the very first time. But, it wouldn't start at all like that and backfired pretty good through the carb before I fixed it.

I've only used the MSD box. I sent the box and coil back to MSD for them to test to eliminate that as a possible issue and they both tested fine.

Daniel

Something else I discovered after the EFI swap was a low voltage issue. With the carb setup, at times the car would idle very rough...usually when hot out, both cooling fans running and the AC on. I always blamed the carb...

Come to find out, it did the same thing only with worse consequences once EFI was added. I'm convinced now that when the volts would drop below 12.0, the MSD wouldn't fire the plugs hot enough to fire every stroke in every hole.

Just something else to consider if you haven't already.

Wideband works great
 

I got the O2 sensor installed just downstream of the header collector. Connected the gauge, and within a few minutes I had the carb idling best yet, 11hg of vacuum, and 13.75ish AFR. I took the car for the first drive out of the neighborhood and put about 10 miles on it. Woohoo

I also had to raise the primary fuel bowl level a hair and lower the secondary fuel bowl level a good bit. (The car/carb was level when adjusting)

I still have the occasional exhaust pop/backfire and some engine run on when shutting down.

I'll take some AFR readings while driving soon.

The wideband makes a huge difference in tuning ability.

Daniel

If your timing is off that can cause it. So can high idle, running hot, to lean or rich.

Camaroaj- Thanks for the input. I'm going to play with the timing some more. Currently the engine temp is steady at 190* and the AFR seems to be in an acceptable range at idle. I may still have adjustments to make at cruise and WOT.

I haven't worked much on the car recently due to other obligations. I'm dropping the car off at the painter today so he can fix an issue around the trunk water channel, take care of a few pieces of trash that got in the clear and cut/buff it. Next week I plan to have it aligned and get the AC charged.

The exhaust is currently just 2.5" pipe from the header collectors to 13" chinese Flowmaster knockoff mufflers on each side with turndowns in front of the axle. I'm going to install an X-pipe and some 14" Dynomax Super Turbo mufflers to help reduce the noise level. It's currently a bit much for street duty.

Daniel

Still "finishing"
 

I made it out to the local Cars and Coffee a few weeks ago. It was nice to get the car out of my driveway for a while.

This past Saturday was a washout so I decided to tackle the exhaust redo. I got the X pipe and Dynomax Super Turbo mufflers installed. Overall, it went smoother than expected considering I'd never done one before.

I'm still working on the engine/carb tune. My A/F ratio gauge reads 14.5ish at idle, but it still smells very rich, the spark plugs are dark, and I get intermittent exhaust "popping." I may break down and try to find a carb "expert" soon. We'll see.

Daniel

Looks good! Glad you got the car out for some fun.

:captain:

I'm a freakin idiot.....a happy one though
 

I've been fiddling with the carb the last few weeks and felt I was making progress, but still not all the way there. I took the car for a spin on Sunday and the engine still had a significant vibration that would come in at 1500 rpms through 3500 rpms, go away until 4500 rpms, then return. Parked the car...f&ck!!!!!

I was messing around shooting the headers with an infrared thermo this evening and noticed the #8 cylinder was about 100 degrees cooler than the others. Inspected the #8 plug wire, looked brand new as it should. Then I decided to check the firing order for ****s and giggles...since I've done so over 2 dozen times.

That's when I found the GREATEST STUPID MISTAKE I've made with this build.....I had the #6 and #8 spark plug wires flipped!!!! :eek::p

Flipped them back the way they should be, fired it up and it's so smooth through the rpms now. HUGE difference.

Time to put some miles on it. :D

Daniel

Driveline vibration fun
 

Once I got the engine vibration sorted from my bonehead mistake, I put some miles on the car and noticed a significant driveline vibration. Up to this point, the driveline angles were just eye-balled as everything was installed. So, after a lot of reading about angles and adjustments, I started taking measurements and making adjustments.

I found a great driveline angle app from Tremec. Here is what I started with:

https://lateral-g.net/forums/attachm...1&d=1575640133

My engine/trans angle was pretty much set due to interference with my headers and the firewall/floorpan and interference with the clutch arm and trans tunnel. I did raise the rear ride height slightly to help with angles and to prevent tire rub on the passenger inner wheel well. So, the Ridetech 4-link was where I focused my adjustment. After about a dozen adjustments and measurements, I ended up with:

https://lateral-g.net/forums/attachm...1&d=1575640133

It's obviously not perfect, but after a quick test drive last night it is MUCH better.

Daniel

Hey DWC..,
I love your honesty.
I think the way you diagnose and post on this forum helps us all.
If I don’t screw up twice a day, I ain’t living.
This is my way of saying thanks for this useful post.

PS.
Back in 1976, I took my girlfriend to my high school prom in a 68 camaro with a 230ci straight six.
To make a lumpy idle to simulate a cam, I drove to the prom with two plug wires crossed DELIBERATELY.
Ran like crap but sounded like a funny car!
Lol

I appreciate the comment. I figure nobody knows everything and we all have to start somewhere. It seems I'm always scouring the internet and forums trying to find the answer to some obscure question or issue I'm having. Without forums such as this I would REALLY struggle to make ground and the learning curve would be tremendously steeper.

This build thread not only allows me to document my build, for my own sake, but may hopefully provide a bit of insight for someone else down the road.

Daniel

One of the best things about this forum is the lack of criticism for honest mistakes. You can post your victories and everyone supports you, if you step on your hoo-hoo and everyone still supports you!

That's because we try to make it more of a community instead of a hive mind one up fest like so many other forums turn into. We all have our visions and we'll all need help getting there. It's why I came here from other places. Those other places certainly have valuable information available, too, but this place feels better.

Good work on the car, DWC. I feel your pain with the vibrations. I still have not figured mine out. I swear I have the angles dialed in, but I need to check again with a drive on lift preferably. Keep at it with a methodical approach and you'll get it. Don't forget to keep the working angle of each joint below 3*, as well. I completely missed that in my efforts to make my angles equal and opposite.

I've been putting some miles on the car. Not as many as I'd like though.

My son and I went to the local Cars and Coffee the other week, which is always fun. (I robbed some photos off the C&C Facebook page)

I still have a driveline vibration that's bugging me. The front and rear driveline operating angles are both exactly 2.9* and the overall operating angle is .02*. Even after I was able to get these angles, I still have a vibration at around 2000 rpms, then it goes away until about 4500 rpms. Above 4500 rpms, it's a fairly significant vibration. The engine revs smooth though, in neutral, to the limiter so I'm confident it's not the source.

I took my driveshaft and had the balance checked yesterday- all good. It has new Spicer U-joints. I have sufficient yoke engagement on the trans output shaft. I spoke with Ridetech this morning to see if they had any suggestions and he said with my pinion angles and a good driveshaft, he wasn't sure of where to go next.

Someone mentioned driveline compound angles, which is one thing I haven't checked. The Tremec app measures the angles on a horizontal plane, but I haven't checked them on a vertical plane. At a glance, it "looks" pretty straight. Anyone have any tips on checking compound driveline angles?

Also, I've grabbed the driveshaft right in front of the rear pinion and tried to shake it and there's very little/if any play. I was told when I bought it that the pinion and axle bearings had been replaced. But, I have noticed a very slight pinion seal leak because the bottom of the length of the rear end pumpkin is slightly damp with fluid.

Any ideas would be greatly appreciated.

Daniel

The driveline angle thing gets compounded when the cars get lowered. Standard driveline angles are calc'd & figured w/everything 'sloping' front to rear (motor higher than trans output; trans output higher the rear pinion). The closer these get or in the extreme cases where the pinion is higher than the trans output, a diff approach is required.

I know this from the custom truck scene. Extreme lowered trucks are faced w/this scenario constantly. Many (most?) ignore it or don't drive them enough to be concerned. My plan on my trucks was to use a single driveshaft vs the more common 2pc shafts; dial in angles as good as possible, & then if that didn't work swap in a double cardan style u-joint/CV joint that cancels vibrations within itself. By using the Dbl cardan style joint, you need to dial in the angles close to zero & let the joint do the work.

Check out Andrewb70's stuff. I don't recall where I saw/read the info but I believe when he did the 'rebuild' of his GTO (the L92 swap period) he really focused on solving the vibration issue. He wound up sourcing a driveshaft/joint combo that while expensive.... got the job done. Since I had already been researching options, his info was REALLY good to read as he was using the same approach I have as far as the whole process of elimination.

Hope this info helps.

Yep, Andrew put a CV joint on the front of the driveshaft. I believe he got it from Driveshaft Shop. I was thinking I needed to go that way as well since my diff is inline if not above my transmission. I'm in the middle of checking something else right now before I go down the path to using one of those driveshafts.

I can't help with your issues. I know it's frustrating as hell. I wish you the best in figuring it out. The car looks great.

Daniel the car looks wicked!! Stoked to see you out driving it and having some fun. The shake down process just just part of the journey.

:captain:

Thanks guys.

This weekend I'm going to take some measurements. I plan to measure runout on the driveshaft, rear axles, and pinion. I'll also try and check the rear end position/alignment if I can figure out a proper way to do it.

Daniel

Runout measurements
 

I took a few runout measurements yesterday evening.

Driveshaft yoke- .002
Front of driveshaft (about 4" behind weld)- .015
Rear of driveshaft (about 4" forward of weld)- .017
Rear end pinion- .001
Driver side rotor (face/lateral)- .003
Driver side rotor (edge/radial)- .005
Driver side wheel lip (lateral)- .030
Passenger side rotor (face/lateral)- .005
Passenger side rotor (edge/radial)- .005
Passenger side wheel lip (lateral)- .025

Anything stand out as alarming?

Daniel

Update
 

So, through some help from multiple sources, I've narrowed down my vibration to a worn out tailshaft bushing in my Muncie.

I'm trying to replace that bushing with the transmission in the car by using an old Snap On bushing removal tool. Snap On made a few different sizes and I thought I scored the correct one today from a local trans shop. But, I tried it tonight and it's *just* to big to work for my 1.5" bushing.

I've read they show up on Ebay occasionally, so I hope one pops up soon so I don't have to pull the trans to replace a $4 bushing.

Here's the tool I'm looking for in case anyone has any leads. It's Snap On part # S8672D.

Daniel

Update
 

I "rented" the correct Snap On tool from a guy on a Corvette forum. It took all of 3 minutes to pull the bushing with the correct tool.

I installed the new tail shaft bushing, seal, and new yoke on the driveshaft. Finally, got some dry weather the other day and went for a drive. The vibration is still there... It may be very slightly reduced around the 2000 rpm range, but the 4000+ rpm vibration felt the same.

So...……..I pulled the trans out this morning. It went smoothly.

Here's a short video of the play in the input shaft.

https://youtu.be/cbggep6tDu0

Axial play is .007"
Radial play is .065" (measured about 1/2" from pilot end of shaft)
I'm pretty sure that's not within spec. Any input?

The pilot bushing, throw-out bearing, etc, look normal too me.

**Not sure why the top two photos are 90* off**

Daniel

Update
 

I measured the bellhousing runout and pilot bushing ID to input shaft pilot "tab" OD and all was within spec. So, nothing abnormal was found with the clutch, pressure plate, throwout bearing, pilot bushing, bellhousing, or clutch fork.

My existing Muncie M21 has had weld repair performed on the mounting ears of the case. So, instead of rebuilding this unit, I'm leaning towards starting completely fresh.

I spoke with the folks at Auto Gear (https://www.autogear.net/motorsports/) and should be ordering a Muncie M20 from them in the next few days.

Here's the specs on their Muncie:

BRAND NEW Auto Gear "Syracuse" four-speed manual shift transmission/gearbox with Auto Gear/Antonio Masiero 'Muncie' M20 gearset (2.52 / 1.88 / 1.46 / 1.00 ratios), ONLY with 10-spline input, 27-spline output, and passenger side speedometer.
Choice of 7 or 8 tooth speedometer drive (typically 7-tooth for 3.55-4.10, 8-tooth for 3.08-3.42s).
It uses the following:
Auto Gear American-made "Supercase"
Auto Gear American-made C355 aluminum midplate
Auto Gear American-made heavy duty tailhousing
Auto Gear American-made, Oilite(tm) Bronze-bushed sidecover
Auto Gear American-made cast STEEL shift forks
Antonio Masiero (Italy) M20 gears (2.52 / 1.88 / 1.46 / 1.00) w/ 1-inch cluster gear
Antonio Masiero (Italy) Auto Gear-designed synchronizer hub & lightweight 27-spline mainshaft (tighter fitting hub-to-mainshaft fit [40-spline press fit and zero lash])
Antonio Masiero (Italy) forged synchronizer sliding clutches
Forged high-silicon bronze synchronizer "blocker" rings
Auto Gear-designed, Antonio Masiero (Italy) produced T10-syle reverse gears (no more chipped up reverse gears!)

Hopefully, this will do the trick...

Daniel

Nice!

The guys at Autogear are knowledge and helpful when I rebuilt my M20 Muncie for the parts I needed.
Not trying to sway your decision in trans selection but maybe you'd be better off with a TKO600 albeit a few bucks more. Higher 1st gear than the M20 plus with the cam it might be better for you, cruising as well. Plus the 600 bolts up to the stock bellhousing and utilizes the stock Z bar.
Shop builds are nice but kudo's to you on your home build, car's looking really good!

Thanks Wayne.

Simon- Yes, they seemed very knowledgeable.

Trust me, I've spent a lot of time debating Muncie vs TKO600 vs T56, in my head, over the couple of weeks.

T56- didn't want to mod the trans tunnel at this point among the other small changes needed. I've had an BMW E46 330i with a 6 speed and wasn't a huge fan. To be fair, I've never driven a T56 though.

TKO600- thought real hard on this one, but decided against it because of cost, weight, clutch change, etc.

Muncie- ultimately a 4 speed will meet my needs (street and occasional autocross). It will bolt right back in with no changes, same weight, less than half the cost of the TKO or T56 (a trans swap was not in the build budget). The wider M20 gear ratios will be an improvement over the close ratio M21 I had with my 3.42 rear end gear. I will never take this car on a road course, so an overdrive wasn't a "have to have."

Who knows, maybe down the road I'll swap it out for a 5/6 speed. They're never *really* finished right? :confused18:

Thanks for the compliment.

Daniel

Or just add a Gear Vendors OD unit .. That's my plan anyway

I actually did take a look at that. But with the cost of the Gear Vendors unit, I would've rather added a few hundred dollars more to get a TKO600.

Daniel