Camshaft endfloat.

[Deleted]

First time on here so hope this works... Got a late 72 p5b coupe been restoring since march, just sent her off to garage with rolling road for final ajustment and the technician has found that there is very slight movement on the camshaft maybe only .20 thou..   the old cogs off the end of cam and dizzy were sharp to the touch...they seem to be pinching around the 2-2500 rpm range and this is making it sluggish around this band...the two cogs are pinching so much that its even affecting the bobweights in the dizzy... is there a bearing bush or shim plate that can be added/replaced to take up the slack.? The cam cogs and chain etc are all brand new.... Has anyone had the same problem? Sensible answers only please as thousands of hours and pounds is getting into serious arseache problems now... I'm sure you've all been there!!!! Thanks in advance, Adam.

[johnwp5bcoupe]

Adam welcome to the forum

I would suggest you have a word with V8tuner a very helpful guy CAMSHAFT END FLOAT

[Deleted]

Thankyou... Errr how do I do that? Is that by the 'message' bit?

[johnwp5bcoupe]

No just phone him his name is Paul

[Deleted]

Much appreciated, where can i get his number?  Speaking to him tomorrow would be really good as got a meeting with the garage tomorrow afternoon...

[enigmas]

Very odd and strange behaviour. If the old timing gear set had hooked sprockets it would also have had a very worn timing chain. The chain lengthens through age related wear due to pin wear...not stretch.

If the timing gear set is also well worn I'd also say the camshaft is well past its best use by date. Replacing the camshaft sprocket set is your first move...now replace the camshaft. Note that cam lobes are ground at a slight angle and new lifters have a slightly convex base this keeps everything correctly aligned. You really don't require a camshaft thrust plate or anything to limit end float if you rebuild the valve train correctly and replace the worn parts. Use Penrite Classic Light with ZDDP or similar when these parts have been replaced.

PS. Try not to get caught up in too much hype from the dyno guy especially on an old unrestored and tired engine.

[Deleted]

That's the thing....it a newly rebuilt engine with brand new chain, camshaft, timing cogs etc.... The guy is extremely experienced and has seen it before...but it's definitely fouling at certain rpm range and spoils the cars performance...I'm looking at it tomorrow but is there a thrust plate for the cam as sure enough the old dog were sharp to the touch so there must have been some movement on the cam cant be the only person this has happened to...i mean what actually hold the camshaft in place so it doesn't move a millimeter in the first place?

[Deleted]

P.s... I'm not sure in which direction it's moving...  I'll know more tomorrow as he has said he will show me the movement but until it's been stripped down we can't tell how much....all very disheartening as everything else is spot on and it's not really a good time of year to completely strip down the engine....I don't mean if it is a problem than can be fixed as it's going to be a hell of a car when it's done...all best quality upgrades all round....it's about time the bloody thing gave me something back!!!

[enigmas]

I bet you've got a roller chain fitted to it (on expert advice!) Use the standard OEM 'morse silent' chain on a steel (camshaft) sprocket if you must and it won't walk. The original design engineers weren't idiots. The OEM silent type chain limits side walk based on the end play of your crankshaft. The roller chain has more built in side flex/play...hence your issue and the need for a thrust button (in the timing case). Stick with the OEM components unless you want to hot rod the engine...then expect what's occuring without further mechanical mods.

Have you also fitted a non standard camshaft or reground camshaft. If the lobe angles are wrong or poorly ground you'll get this issue.



Why does a newly rebuilt engine have hooked worn sprockets?

[Deleted]

I pulled out the worn sprocket out of the engine and put new ones in... It looks like this is a problem that is cured by taking up the slack with a thrust plate that can be purchased from V8 tuner... It 20 odd quid, guess it makes sense something cannot rotate million of times without slightly wearing on the bit that holds it in... And hence to .20 thou movement was even to pinch the timing sprockets... I will strip down and put this thrust plate (I gather there may be some machining of the part to get it bang on) and it will, I'm sure cure the problem... So if your V8 is getting sluggish at around 2000+ rpm and no amount of new gizmos don't cure it may be worth removing dizzy and shining a torch into the hole to see how the teeth are looking on the sprocket... I will take photos at every stage incase it helps someone else out...I know these aren't fast cars but there still a 3.5 V8.. you should be able to stick the throttle down and the engine should pull without hesitation constantly up until you take your foot off...I must admit I really thought running it in and using it would work through the problem...clear out the cobwebs! But so glad I took it to an experienced guy whos basically diagnosed that using it would just course more damage.... Phew!!