I'm been having difficulty for quite awhile getting a smooth clutch take up in first gear when taking off at eg. traffic light or in stop and go traffic. Unless I bring the RPM up to about 900- 1000 before engaging the clutch the car tends to have a slight buck. The engine is not hesitating but it just doesn't seem to make a smooth transition to go. Sometimes If I feather the clutch I can limit this but its a challenge each time I stop and go. All other gears it shifts into fine. any thoughts on this?

thanks

 

Have you checked-out the engine mounts?

 

I'll give that a look. Thanks

 

from what I can see the mounts look intact.

 

I had some trouble when I first got my car. Either stalling it or burning the clutch. Took a while to get the hang of it and a few things helped....going down to 225 60 15 tires from 245's, adjusting the clutch engagement point and getting the engine idle and carb. mixture screws set right. Now everything is fine.

Edit Update: Car has a 3.08 diff. gear and std. M20 transmission.

 

It could be the gearing. If you have a 3.55 or higher gear set like 3.08 and you have an M21, first gear is going to be really high. If thats the case you really need to bring up the rpm and slip the clutch alot. I had 3.55 rear gears and an M21 and had the same issue. I then swapped to an 3.70 rear and pulled my input shaft and cluster gear and swapped them for M20 gears. THose are the only difference and it will drop your gearing quite a bit to make off the line starts better. I would stall my car all the time trying to drive slow in parades and parking lots until the switch. The other option is a 5 speed swap that has a really deep first gear and that would change it alot.

stock tire height being 27.1 inches
first gear X rear differential gear = final gear.
m21 2.20 first gear
m20 2.52 first gear.
using this calculator http://www.americantorque.com/graph-rpm-vs-speed/
m21 with 3.55 is 7.81 gearing off the line and at 1000 rpm your car wants to be going 10 mph already
with lower gearing
m20 with 3.55 its 8.95 and wants to be going 9 mph 1.2 revolutions per foot of travel
m20 with 3.70 its 9.34 and wants to be going 9 mph but the revolutions per foot is 1.3 vs 1.2 so you can start with a lower rpm

so at an idle of 750 you can put around at 6 mph with an m20 and 3.70 rear depending on the torque your motor produces at 750 rpm

my point being the lowerr your gearing , the lower the rpm needed to get the car rolling since its not seeing such a high mph need at a given rpm.

as an example throw in a 3.08 with an M21 and your car wants to be going 12 mph at 1000 rpm, but you can ride first gear up to 65 mph at only 5500 rpm.

 

Could also be a bad clutch.

 

mine has a 3.70 M21 transmission. also will do that bucking in traffic if I'm go really slow eg stop and go.

 

how would you go about determining if clutch is bad vs if the clutch is just not adjusted to engage properly?

 

Get it adjusted correctly. Another possibility. Sitting. Flywheel and pressure plate will surface rust. If so, it will slowly get better with use as the surfaces get cleaned up.

 

You'll just have to get used to slipping the clutch to start from the lights, know what rpm it bucks and just keep the rpm above that and use nuetral and coast. That's what I do if it's slow traffic. I try not to hold the clutch in too long and ride the throw out bearing

 

Do you by chance have a high performance cam installed? My car does and it has a rough idle.

 

All good ideas stated here,,, but my first thought, (if it is in proper adjustment) , your flywheel is warped or the machine shop did a bad job re-faceing it ,, if it was ever done,,IMHO,,

 

Running a fairly stock cam for 327/350 as far as I know. had engine rebuilt years ago with what was supposed to be a stock rebuild but they put in an high volume oil pump which was not a stock item so the cam could be a bit more then stock as well.

 

Curiously....how low are the RPM's supposed to be to take off?

Jebby

 

If the clutch pressure plate surface and flywheel are unevenly worn that could create judder - with my L36 (M21 and 3.08) it was an issue but I got used to it. Didn't realise that drivers side engine mount had failed too which made things worse.

 

Also have you tried raising the warm idle a bit? That helped with my cam. I increased it just enough to hear the engine smooth out.

 

It's not a diesel engine.

I've yet to drive a gas powered vehicle that didn't require some throttle application to start moving.

900-1000 rpm and slipping the clutch to get moving is reasonable.

That being said, if you really think something's wrong, here are a few things to check.
WARNING, LEGAL DISCLAIMER, USE AT YOUR OWN RISK ETC..
1. Motor mounts. Yes, you said you looked at them. Unless they are completely fubar, looking doesn't tell you much.
Block the wheels and pull the P-brake up tight.
Open the hood, and in first gear, start easing out with the clutch pedal (you'll need to give it a little gas) and watch for the engine to try to roll to the right.
If the mount is broken, the engine will lift quite a bit.
You might need an assistant to watch the engine movement, if you can't see the air cleaner.
2. Did you check the trans mount also ?
3. Check for loose bellhousing to engine bolts.
4. Check for loose transmission to bellhousing bolts.

When torque is applied, things want to move around, and if anything is loose or broken, it will disrupt smooth, even clutch engagement.

Hope this helps you.

Good luck,
Jeff

 

Clutch judder was apparent from when I first bough the vehicle - much later when checking out clutch adjustment under the car I wondered why there was a grey residue around the Muncie/bellhousing bolts - seems that bolts had not been torqued-up and gearbox/bellhousing was moving around. This partly explained clutch judder. When I subsequently replaced the L36 with a 'built' 489 the 'loose' gearbox/bellhousing fixings showed as the possible reason for some uneven wear on the clutch and flywheel and even some burn marks. Clutch/flywheel were replaced with CentreForce components. The broken driver side engine mount was only noticed once the 427 was 'pulled'. New engine mounts were installed. The new drivers side mount lasted for exactly 200 yards. 600 ft/lbs or torque sorted that out! Best investment was a pair of 'Poly' engine mounts. All judder ceased and the quality of gear shifts also improved significantly with the 'firmed-up' mounts.