Std GTD Flywheel posn?

[Paul Thompson 'Hooligan']

Hi all -

Here's a puzzle for you, I am looking at an oil leak issue on a GTD at the moment and whilst talking to the owner, he mentioned a 'heavy vibration' throughout the rev range, since having the flywheel lightened recently.

The original Essex flywheel was shot, so a replacement was sourced and lightened by someone he describes as very knowledgeable who also balanced it (with clutch) to match the older, already lightened, but defective flywheel.

Now I have driven a car with the flywheel in the 'wrong' position and it did indeed vibrate like hell and he said the motor was silky smooth prior to this work being completed.

SO, does anyone know the correct position for the flywheel to the crank??
I was under the impression that they are indexed by a slightly offset mounting hole, but he also mentioned that the 'person' who had removed the flywheel and refit (NOT the balancer/lightener) said something about 'filing one of the holes'.... (hmmmm - but was it the right one?....)

If I remove the thin inspection cover from in front of the adapter plate below the rear of the sump, I can view the rear of the cast flywheel.

So, I figure if I turn the motor so that the center of the counter-weight cast into the flywheel, is pointing directly down, eg '6:00 o-clock', I could then count how many degrees I have to turn the crank clockwise for TDC no. 1 cylinder... This, compared to another standard GTD should indicate whether the flywheel is one or more lugs (each 60 degrees) out - or am I missing something...?

Motor is standard 302 (2-bolt) with 15426378 firing order, should it make a difference which I cannot see it doing so.

Any ideas to confirm would be appreciated as the owner has lost confidence in the previous 'mechanic'....


I also think that I should be able to tell by looking at the damper position on the front of the crank, but am not sure, hence the question.

[Jac Mac]

Paul,

If you remove either #4 or #7 plug, bring either of those pistons to TDC, then turn the crank clockwise a further 15 deg [approx 1" on Damper] the counterweight should be at the bottom.

To Double check the counterweight on the Damper is 180 deg from that on the Flywheel.

Firing order makes no difference to counterweight position.

Jac Mac

[Paul Thompson 'Hooligan']

Originally Posted by jac mac

Paul,

If you remove either #4 or #7 plug, bring either of those pistons to TDC, then turn the crank clockwise a further 15 deg [approx 1" on Damper] the counterweight should be at the bottom.

To Double check the counterweight on the Damper is 180 deg from that on the Flywheel.

Firing order makes no difference to counterweight position.

Jac Mac

Many thanks - I can now relatively easily check and give the owner the good/bad news accordingly....

also - I now see your logic..... the additional balance weight is 180 deg opposite the nearest rod crank pins, so as the pistons+crank pin go up - the nearest counterweight goes down to assist the balance....

Reading again - I must engage my brain before opening mouth (or typing).... each time I read the answer it seems more obvious.... doh!

Still better to check first though.....

[Paul W]

On my car there are no markings or idents to indicate the position that it bolts to the crank in. Not sure if I have the right end of the stick here but - The holes in the flywheel and crank are not spaced evenly so only allow fitting it in one position. I remember fitting it for the first time and revolving it through the 6 positions to see which one all 6 bolts into the crank line-up. It would be possible to get 5 of them to work and to file the last hole to fit - flywheel being in the wrong position. Is it a standard 302 flywheel thats been lightened ?

[Paul Thompson 'Hooligan']

Hi Paul -

Nope, the flywheel fitted is another (but NEW) Essex flywheel, which is smaller in Dia than std 302 item, to fit in Renault Bellhousing. The item should have only fitted in one position, but the fact someonee has 'filed' it makes me think it may be in wrong position. I'll check tonight and post findings...

[Howard Jones]

Paul, I was under the impression that the V6 flywheel that is "standard" on GTDs will not fit onto a V8 crank as originally drilled to fit onto the V6. I think GTD re-drilled the flywheel to fit onto the V8 crank bolt pattern and shipped it that way with the kit.

As a aside, My original "standard" GTD flywheel was 190 grams out of balance when balanced to use on a 50oz 302 crank. I think that if you only have one set of crank mounting holes then it was never re-drilled to fit on a V8. The "filing" may well have indexed the flywheel but it may still be WAY out of balance.

I have learned that to use one of these V6 flywheel it is BEST to disassemble the engine and rebalance the rotating assemble as a whole with the flywheel.

My "vibration thru-out the RPM range" turned out to be a spun rear main bearing. I believe this was the result of a miss balance of the flywheel among other engine assembly issues related to the "crate engine" that came from SVO.

Thanks again Jac Mac.

[Jac Mac]

Paul,

You might be getting into a can of worms here. If this car has seen some miles [ like more than a hundred as a ballpark ] since the 'new' flywheel was fitted damage to the main brg's is likely to be underway. Did you find any loose bolts around the rear of the pan area while checking the oil leak?
For peace of mind a full balance job is the safest way. Check back thru my posts for info.

cheers
Jac Mac

[Paul Thompson 'Hooligan']

Thanks for the additional input guys... I'm off to fit headers to another car today, so I won't get to have another look at the flywheel issue till tomorrow or day after - I'll post what I find out of interest once I've looked.

I'm not convinced that I (or even the owner) has heard the full story yet of what has been 'filed' and what hasn't....

Time will no doubt tell........

(oh and the car has only run about 10 miles since assembly)

[Paul Thompson 'Hooligan']

Got down under the GTD this evening and guess what - no cover plate in front of flywheel so that should make it easy.

Wound motor to about 15 degs past TDC Cyl4 - no counter-weight, looked again and no counter-weight at all on flywheel. In lightening the flywheel, ot would seem that all the balance, both the cast lump one side and the 10mm rebate opposite has been machined off.

pic of flywheel. (sorry about image quality but it was a frame from my video camera)

[Paul Thompson 'Hooligan']

Another contributory reason for the vibration might be this:

http://www.smart-tech-services.co.uk...20Flywheel.wmv

click on the link to download and play a short video clip....

Am I imagining things or does that flywheel look 'pi$$ed' to you?
('pi$$ed' being a technical term used to describe something that does not quite look right.... )

So, did the 'balancer' machine the flywheel 'off-centre'? - or did the 'fitter', file more than the offset mounting hole(s)??....

Comments..?????

oh - and sorry about the slightly blurred video, lying on my back under the car with a 500W halogen lamp, video cam in my right hand, whilst 'jumping' the solenoid with my left, was trickier than I expected...

[Jac Mac]

Hi Paul,

Have a nice day/night taking it all out! Is that an adapter or spacer between the crank / flywheel. If so it doesnt have the counterweight on it does it?
The possibility still exists that the flywheel has been balanced with holes drilled from the clutch face, but its not good practice in this case as its further from the area requiring balance.

Jac Mac

[Paul Thompson 'Hooligan']

Originally Posted by jac mac

Hi Paul,

Have a nice day/night taking it all out! Is that an adapter or spacer between the crank / flywheel. If so it doesnt have the counterweight on it does it?
The possibility still exists that the flywheel has been balanced with holes drilled from the clutch face, but its not good practice in this case as its further from the area requiring balance.

Jac Mac

Hi Jac Mac
I won't be taking anything apart yet, the owner wishes to 'have a word' with the 'balancer' and possibly 'the fitter' first and I'm off to Longleat Hill Climb Friday for Sat competition, so nothing happening on my part before Monday.

I see what you mean about 'spacer' but I'm fairly sure that there is not one fitted and that the part you see is in fact the very back of the cast flywheel. To me it looks like possibly the fw has had LOTS machined off it's rear, too much I would guess, but I am no expert on cast flywheels.

Having said that, a badly machined spacer could give a similar effect I guess. Doesnt seem a good idea fitting a spacer behind a flywheel in my opinion, an area of critical stress... Anyone??

[Jac Mac]

Originally Posted by p thompson

Another contributory reason for the vibration might be this:

http://www.smart-tech-services.co.uk...20Flywheel.wmv

click on the link to download and play a short video clip....

Am I imagining things or does that flywheel look 'pi$$ed' to you?
('pi$$ed' being a technical term used to describe something that does not quite look right.... )

So, did the 'balancer' machine the flywheel 'off-centre'? - or did the 'fitter', file more than the offset mounting hole(s)??....

Comments..?????

oh - and sorry about the slightly blurred video, lying on my back under the car with a 500W halogen lamp, video cam in my right hand, whilst 'jumping' the solenoid with my left, was trickier than I expected...

I Dont Know about being (pi$$ed) but I have a feeling you are going feel the effects of the "Hangover".

Like I said, Have fun taking it all to pieces. I would love to be in the room next door while the creator/s of this problem explain themselves! I think I will have a Rum & Coke tonite with me feet up while your working!

Cheers
Jac Mac.

[Paul W]

That flywheel is definately not right - I can see the same thing. My money is on the bolt filing didn't need doing and the fw is in the wrong position. I would guess that the machinist would/should have adjusted the bolt holes if they needed it as this is something that you wouldn't attempt afterwards.

[Paul Thompson 'Hooligan']

Hi again -

Dragged myself away from editing club mag to post an update re the flywheel.

There is no spacer behind the flywheel and it is zero (neutral) balanced with no counterweight present on the reat - see pics.

Before removing it I fitted a dial-test-indicator and rotated the flywheel recording results. It has 0.038" of run out - i.e. runs out of true to outer rim (not ring gear) by 38 thou...

Further checking shows that the item is not a close fit on the register protusion on the crank end. The centre hole of the flywheel allowing up to 0.0060" of movemment in any direction with no bolts fitted.

Talkin of bolts - I spun them out with a hand ratchet on 5/8 socket. The ratchet was no longer than approx 7" and I estimate the bolts to have been fitted to a torque of less than 20-25 ft/lbs eek!

I'll call the 'balancer' tomorrow as I now have his details, but to my mind -

a)the bolt holes are not drilled correctly in the flywheel face (not sure who drilled them) hence the flywheel does not spin about the centre of the crank.

b)even if it were centered, surely the flywheel should have some counterweight (i.e NOT neutral) as the front has a weighted damper so the crank is not internally balanced. (difficult on a 302)

Would be handy if the owner still has the flywheel that was removed as he said the motor was silky smooth with that one. Despite the 'balancer' measuring it as 'only 3g off Neutral and therefore negligible' - hmmmm.

Flywheel front: Rear: and on crank with Dti. Comments welcome....

[Jac Mac]

Paul ,if you can get 'old flywheel & post 'old/new' pics of front & rear side by side would help. With all those extra holes close to each other in centre it is a bit of a grenade looking for somewhere to explode!!

Jac Mac