Tii timing set, strange rattle.

[Mike Nance]

Just got the timing set on the '74 Tii. Full advance at 33 degrees BTDC at 3200rpm. Starts on one key turn. Cold idle around 1300rpm. Once the WUR turns off idle drops to 950rpm. My test drive produces a rattle sound around 2400rpm to 3000rpm and stops after that. When I was setting the timing the rattle sound cannot be heard. Is this a resonance issue or valves. Ive attached videos. Any help would be greatly appreciated. I am attaching a startup video and a driving video. The sound can be heard on the driving video around the three second mark.

Just finished the painting and trim de-chroming. 

 

[Dudeland]

To my ears, it sounds a bit like exhaust.  I don't think it is pinging. 

 

Is it a 123?  if so we can have a look at the curve.   What is the vac advance like? 

[Mike Nance]

@Dudeland it’s an 002 distributor with an 056 cap. .013 gap on the points. I’ll put the car back on the lift and check that all the exhaust bolts are tight. I read on a post from 2009 that the exhaust resonates around 2400rpm to 3000rpm. I’m hoping it’s resonance. 
 

I ordered a 123 distributor from IE last week. 
 

My biggest challenge was removing and refurbishing the injectors this weekend. That was one of the best things I’ve done so far to get the 1 turn of the key start and great idle and timing setup. 

[Mike G]

Your car is beautiful. I love that color with the black trim. 
 

I also think it’s exhaust hitting something. Does it make the sound decelerating through that rpm or only accelerating? 

[Mike Nance]

@Mike GI can only hear the rattle during acceleration. The trim is actually a dark grey with a matte finish. It’s hard to see the color in the pictures. That was a hard paint job to pull off. Matte finish is a difficult process. The vent windows were a pain to disassemble and put back together. 

[Mike G]

Seems likely it’s exhaust moving slightly from engine torque and touching something. Check around rear subframe, tip to tail panel, etc

[resra]

yup....sounds like a lose heatshield bolt on the exhaust manifold heatshield. Check for tightness there. 

[dlacey]

+1 exhaust heatshield

[cda951]

3 hours ago, Dudeland said:

To my ears, it sounds a bit like exhaust.  I don't think it is pinging. 

 

Is it a 123?  if so we can have a look at the curve.   What is the vac advance like? 

 

I cannot hear anything abnormal in either video, but it is 100% NOT pinging because detonation would only ever occur during periods of full load, whether due to flooring it at very low RPM ("lugging" the engine), or during the torque peak of a knock-limited engine (forced induction or high-RPM naturally aspirated and/or very advanced ignition timing).

 

One video is revving in neutral, the other is gentle acceleration, so whatever the perceived noise is, it is not pinging or detonation/spark knock.

[torquewrench80]

Easy diagnosis and cheaper than blowing the top off a piston. Retard the timing several degrees and see if it goes away. That will tell you if it's pinging or just an exhaust rattle. 😝

[Mike Nance]

I thightened all of the exhaust bolts and took a quick drive before the rain set in. The rattle/pinging is still there. I will try @torquewrench80's suggestion and retard the timing a few degrees tomorrow. I made a couple of idle videos. I definately cannot hear the rattle until the car is moving and under a load.

 

Does the engine sound normal at idel to you guys? This is my first Tii.

 

[Son of Marty]

Yes check where the exhaust goes over the rear subframe, do you have the trans exhaust bracket installed and the rubber bits in good shape?

[Mike Nance]

@Son of Marty glad to know the engine sounds correct at idle. I have the trans exhaust bracket installed the rubber mounts are not in good shape. I’ll order some replacements. I have a 2” gap over the rear subframe. But it moves around some. I’ll recheck that item tomorrow when the car is in the lift. 

[Mike Nance]

@Son of Martyquick question, the exhaust is all buttoned up to torque specs. Rattle is still there. I looked at the rocker arms and they are loose(depending on where the can is at. I made a video of the rocker arms moving. Is the movement normal? This Tii engine was rebuilt a few years ago. 
 

@DudelandI also put a 123 distributor in this afternoon with vacuum from the manifold, do you have good advance curve numbers for me to start with?

current setup:

 

 

[Son of Marty]

It looks like it's about normal, but using a feeler gauge is the only way to tell for sure.