Opinions please

[Bitzleftover]

Hi all, Couple of weeks ago I did a day at Snetterton car went well all day. On the drive home I could tell something wasn't right I had a vibration through the car at low revs say 1500- 2500 and on occasion a metallic knocking around the bell housing area so my first thoughts were that something was wrong with the clutch although I could get the gears ok. So I ordered a new one and me and a mate pulled the box off today. When we did there were marks on the inside of the bell housing where ring gear had been hitting it which explained the knocking but nothing obiously wrong with the clutch.Checked the fly wheel all seeemed ok and the adaptor plate was nice and tight so the only way I can see the ring gear hitting the casing is excessive float in the crank. I am having the end float checked on Monday but till then I throw it open for any other suggestions. Edited to add car is a 406ci SBC running dry sump

Thanks

Dan

Edited by Bitzleftover on Saturday 14th March 18:42

[Thevet]

Similar sort of thing happened with my first engine and box; unbalanced 406 caused the ring to touch the bellhousing, which also unfortunately deformed the main shaft in the box....all very expensive and annoying. Make sure you check the shaft is not offline thro' a full 360 before replacing the box.

[GTRCLIVE]

Is it a after market internally balanced Crank ??
Also have you got a later or early clutch and flywheel set up ?? Is the Starter ring close to the flywheel or more nearest the gearbox side of the clutch ??

[Bitzleftover]

[quote=GTRCLIVE]Is it a after market internally balanced Crank ??
Also have you got a later or early clutch and flywheel set up ?? Is the Starter ring close to the flywheel or more nearest the gearbox side of the clutch ??

Engine was bought complete from American Speed car built in 2007/8 with parts from Ultima. Starter ring is closer to the gearbox side.Box is a G50/03 if that helps.

Thanks

Dan

[738 driver]

Along with end-float check I would be very tempted, for peace of mind, to have a DTI run over the crank/flywheel boss, just to make sure the crank is still running true and has not suffered a slight twist/bend.
Also, many engine builders use good quality thread-lock on performance engine flywheel bolts, which is okay so long as the flywheel stays put. However if a flywheel is slightly out of balance/harmony with the engine they can and do loosen with time. When the flywheel bolts are treated with locktight this can easily be misleading, we check the bolts and they appear tight, however they are only locked in position.... not actually clamping properly.
The out of balance comment does not really surprise me. It is normal in quality, performance engine building to dynamically balance the engines rotating assembly along with the final-fit front-end pulleys, flywheel and clutch assembly all at the same time. I dont see how this can possibly have been carried out in many instances.

Edited by 738 driver on Saturday 14th March 21:15

[Bitzleftover]

Thanks yes will check with DTI as well. Flywheel and clutch was fitted by me this side of the pond and the car has now done 3000 miles so there could be a slight deformation in the crank. I am off out for a pint and some deep thought .

Dan

[Steve_D]

Ditto has had this on at least two occasions.
I think it is OK now but I don't think he ever found out why.

Steve

[CanAm Dave]

Hi Dan

I have seen a few issues with the fitment of the flywheel on the crank. I had to modify my flywheel as it was not a good fit on the crank. It was too loose! The flywheel should be a good interference fit.

738 driver said:

It is normal in quality, performance engine building to dynamically balance the engines rotating assembly along with the final-fit front-end pulleys, flywheel and clutch assembly all at the same time. I dont see how this can possibly have been carried out in many instance.

Just to please you Dave! As you can see the crank has my flywheel, damper and supercharger pulley fitted.

http://www.youtube.com/watch?v=jglo8HvFrXk

Regards Dave

[spatz]

The out of balance comment does not really surprise me. It is normal in quality, performance engine building to dynamically balance the engines rotating assembly along with the final-fit front-end pulleys, flywheel and clutch assembly all at the same time. I dont see how this can possibly have been carried out in many instances.

does not really surprise and enforces my opinion on custom or blueprinted engines, better get an industrial built LSX engine and stay away of the "specialist" in engine building.

[60mph]

Sorry to hear of the ring gear problems . I failto see how a distorted crank could cause enough movement at the rim of the flywheel to let the teeth hit the gear box bell. The rear main bearing has only 3 thou running clearance and it is cantilevered by others down the lenght of the crank .Any distortion on this scale would wreck the bearings and would be obvious. Am I missing something ?

Frank

[738 driver]

If you measured a series of production motors Spatz you would find quite large and alarming tolerances/variences so your comment does not really support the reality....GM's warranty merely offers you some peace of mind.

The real problem here is that (hopefully) most engine builders do understand the importance of a 'complete' balance job (including the clutch cover). However in this situation (a kit/stage build) it does not seem to be promoted.
Simply put and irrespective of SBC/LS, factory or tuning shop build, we have a V8 engine more normally fitted with auto-trans, fitted with a unique flywheel and very heavy clutch cover from an opposed 4-6-8 cylinder engine. The balance properties/principles of the two engines are completely different and therefore, stock, individually balanced components will have a degree of incompatability.
The original Porsche (not aftermarket) clutch cover I have is an enormous lump, I would not like to bolt this to anything and turn it at more than snails pace without having first balanced the combined assembly.
Remember balancing this lot is not just about rotational problems, a change in mass on the end of the crank will affect its balance.
The balance job wont really affect power output (within reason) but it goes a long way toward reliabilty in a performance engine.

Hi Frank, 3 thou runout at the hub radius face = how much at the flywheel perimeter? If you have ever tried truing a two-stroke crank you will recall what Im referring to.

We might understand more if we knew how much of the bellhousing was affected....one tiny area alone might indicate runout (unless its a single highspot)..whereas a longer section of damage may point towards wear/loose tolerances.

Edited by 738 driver on Sunday 15th March 10:22

Edited by 738 driver on Sunday 15th March 10:28

Edited by 738 driver on Sunday 15th March 10:32

[CanAm Dave]

spatz said:

does not really surprise and enforces my opinion on custom or blueprinted engines, better get an industrial built LSX engine and stay away of the "specialist" in engine building.

Thankfully we don't all have your opinion Spatz. If you want a crate motor that's fine but you still need to dial in your adapter plate and ensure the flywheel and clutch are zero balanced. There are plenty of good engine builders out there who know what they are doing. For me my Ultima is all about the engineering and trying something different.

Regards Dave

[spatz]

Dave, no question that there are builders that know their job and can deliver a better product than a stock engine !
I have enjoyed your engine build pics and surely you know your stuff, but I have read a lot more reports about premature failing of built engines than of stock ones and some private communication even revealed troubling reports about deliveries of highly respected builders here on the forum. If buying from a builder it should be close to you and cover at least a 1 warranty after installing the engine and using it. I am not an expert in this field, so my choice was an industrial built motor with QCs down the manufacturing process.
I am building this car to drive it so the building process is more like a process that I want to leave as quickly behind me as possible.

[Bitzleftover]

We might understand more if we knew how much of the bellhousing was affected....one tiny area alone might indicate runout (unless its a single highspot)..whereas a longer section of damage may point towards wear/loose tolerances.

Yes the whole top half of the bell housing has been scored.Will do the checks tomorrrow which while the car is apart seems a good place to start. Spoke to AS and he gave a figure of .005 for the crank movement but said as the engine is now run in could be more than this by .002.

[

[Gulf -LS7]

spatz said:

The out of balance comment does not really surprise me. It is normal in quality, performance engine building to dynamically balance the engines rotating assembly along with the final-fit front-end pulleys, flywheel and clutch assembly all at the same time. I dont see how this can possibly have been carried out in many instances.

does not really surprise and enforces my opinion on custom or blueprinted engines, better get an industrial built LSX engine and stay away of the "specialist" in engine building.

oops....

[60mph]

Hi Dave ...I meant mainbearing clearance . If AM are saying .005 " running clearance on the main bearing then presumably if this is what it is on the subject engine , then the flywheel can only move up and down by this amount . With regard to the runout on the crankshaft face for the flywheel, I can't see how this could be out by more than .001 " There are thrust bearings in my AM engine which are adequate for any clutch . Has anyone considered checking the cocentricity of the adaptor plate rebate for the bellhousing with the crank ? It should be easy to measure this all the way round . Any off centre of the gearbox would stress the input shaft and first bearing , and also show up any further slight movement from another cause . My flywheel WOULD NOT go onto the crankshaft .I had to turn the centre out by .002 " diameter and now it's a tight sliding fit .I confess I lost confidence in the torquewrench and did the 6 bolts up with loctite and as hard as I could with a 24 inch bar .My assistant was holding the engine with a purpose made 6 foot bar bolted to the flywheel . I hope more comes to light . I am allmost tempted to take my gearbox out to check the concentric ! To score the bellhousing I think the backplate must be out of concentric . There are tight fit dowels to the block on mine . Has everyone else got these ?Dan , has your gearbox dropped down due to loose backplate ? This might explain wear on the TOP half of the bellhousing.

Frank

Edited by 60mph on Sunday 15th March 17:06

[Al Weyman]

Maybe you have shot the rear main bearing thrusts. I did exactly the same thing on my race Camaro and have had to have the crank reground including the thrust faces and longer rear main bearing shells (not cheap!). I think this mayhave been caused by over clutching but I am still not 100% sure as i pulled the engine out my 2nd gen car and fitted it into the 3rd gen IROC to do the Brands show last year. The oil pressure was still ok and it was not making any noises and the only reason I pulled the engine is it developed a huge oil leak at the rear seal. The other thing I did which may or may not have been a reason for the failure was i changed the clutch flyweeel assemble to fit to the later car from the the one I had the crank originally balanced with. I cannot see this causing the failure but thought I better mention it. Anyhow just going to pop it back into the 2nd gen car now with the correct Tilton clutch it was balanced with.

Edited by Al Weyman on Sunday 22 March 09:02

Edited by Al Weyman on Sunday 22 March 09:03