807 engine balance.

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brettr

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Can 807 gurus please comment.

I have a few periods of vibration in my engine.

Mild at 2000, harsher at 3100.

Yes I made my engine brackets and everything else is modded to the max etc etc. I admit there is more parts on it than in the space shuttle.

My pistons, wrist pins and rods were all within a gram.

I didn't balance the crank balanced because 2 I got checked in the past were good from the factory.

I'm using a different flywheel than the one that came with this crank.

Did the factory balance as a set?

I didn't balance the flywheel or press plate either.

It's costing me $10 a day in super glue to keep gluing my fillings back in.

Any 807 guru comments?


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Buffeting as the car just starts hitting the sound barrier?

Otherwise the crank and fly (along with the clutch) were balanced as a set from the factory.
 
Considering the revs you have reached on that motor I would definitely balance the clutch and flywheel as an assembly and not assume the factory spent the time and effort necessary for an engine with your mods. Same goes for the crank. I have seen the result of a wobbly flywheel coming out of a bellhousing on a Porsche then through the rear parcel shelf at 8k rpm (not mine). It may be worth checking to see if the flywheel bolts are all tight, from what I have seen with other people’s engines, if there is a balance problem. the flywheel bolts usually loosen up before letting the flywheel escape.
 
I concur. The harmonic balancer, crank, flywheel and pressure plate need to be balanced as a set and marked for assembly.
 
Had issues with rough 807 engine. Maybe not as bad as you have
After rebuild never put back the two large weights on each side of engine at the front.
Forget what they were called, DePhasers?
Refitted with new rubbers and all good.
Never used a front pulley either, aka R16,
I recall flywheel only fits one way by bolt hole pattern. Need locktite so they don't come loose. May be loose bolt here
French would have never balanced the assembly as a whole. They were into saving money!
Just bolt up the individual balanced components at assembly.
Pressure plates are balanced by manufacturer. Look closely.
Always use new bolts on pressure plate. Old ones stretch and break on old Renaults
Ensure they are all the same with the same washer type

You can change these bolts one at a time
 
The 807 cranks I have had balanced have been very close from the factory. If getting balancing done yourself, the flywheel would then be fitted to the balanced crank, and then the pressure plate and balanced in turn. I don't know what the factory did, but I doubt they would have done this. Given I expect you lightened the flywheel it would have been prudent to have balanced it on your crank.

Renault went to a lot of trouble on the R15/17 with the 807 motor to fit a large crossmember with "Dephasers" as Driven has mentioned to try and deal with harmonics. I do remember my 15 having a harmonic vibration at 2700 -2900 Rpm. I changed a lot of parts including the engine, fitting a flex section to the exhaust, engine mounts, and so forth and never did get rid of it.
 
Very interesting reading.
Geko Engineering had picked up on a drive, that my 17 maybe has this similar issue. At around 3000rpm it has a vibration. Ray mentioned harmonic balance.
On the new engine we will be talking balancing.
Good luck with finding the issue Brett.
 
Shoji said:
Very interesting reading. Geko Engineering had picked up on a drive, that my 17 maybe has this similar issue. At around 3000rpm it has a vibration. Ray mentioned harmonic balance. On the new engine we will be talking balancing.
Good luck with finding the issue Brett.
Click to expand...

I'd more than talk. When I last did the R8 I had it fully balanced, clutch included. But then you will be doing it, I'm sure.
 
JohnW said:
I'd more than talk. When I last did the R8 I had it fully balanced, clutch included. But then you will be doing it, I'm sure.
Click to expand...

Absolutley JohnW. Fully balanced, got it!
That includes weighing certain items, yes? Pistons, rods, etc.
I'm sure Geko Engineering will sort it out for me.
 
You don't need to weigh pistons rods, etc, other than making sure they are the same weight, which you can do at home with a kitchen scale (you don't need more precision than .1g). I rebuilt my engine with Bretille pistons from Mecaparts and they were all the exact same weight. Conrods and pins were reused and they were all within the .1 gram accuracy of the scales I used.

The shop where you take your bits will require a piston, a pin and a conrod to factor them in the balancing exercise (based on the assumption they are all the same weight), together with anything that is bolted to the c'shaft for dynamic balancing.
 
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