Tim30 Posted November 26, 2008 Report Share Posted November 26, 2008 Hello all. My first post on the forum but I have been soaking up all the collective wisdom and experience over the last year. I bought an 'almost' finished TR4A last year. Engine wasn't running and I was advised it needed a new camshaft. I spent the next 12 months reading up on, and finally changing the cam (complete mechanical virgin I'm afraid). I fitted a new TT road cam from Moss. Engine (to my utter amazement) fired up and ran for 20mins. Next time I fired it up it ran poorly and backfired lots... rest history. Turns out the cam gear and distributor drive gear had chewed each other up - devastating stuff. The damage caused in 20 mins is enormous – on one side the teeth are completely stripped off the dizzy gear, the cam gear has numerous chips – brand new cam b*ggered! I had been careful to ensure the dizzy drive gear was properly engaged with the oil pump – it was, I had good oil pressure for the short time it ran. I measured the float on the end of the cam and the distributor housing – as per Haynes manual. After taking various advice I suspected the oil pump might have seized causing the cam gear to strip the teeth off the dizzy gear. As of last night I took the engine out and whipped the sump off, the oil pump looks fine, free of any obvious wear and turns freely. Has anyone come across this before? I thought maybe worn cam bearings, but they look ok, the cam felt pretty secure. Any views on this would very much appreciated, struggling to know what to do next! I should add, the chap I bought the car from experienced the same problem (hence the engine not running) but thought it was wear on the camshaft. So it has happened twice. I'm concerned about chewing up yet another cam.. Thanks very much Quote Link to post Share on other sites
Smokey Posted November 26, 2008 Report Share Posted November 26, 2008 Maybe the original owner was right: the initial damage might have been caused by a worn camshaft. The worn camshaft might have damaged the distributor drive gear, and when you installed the new cam, the worn distributor drive gear did not mesh properly with the cam gear and caused the damage. I had a similar experience with a damaged wire wheel splined hub, and ruined two wire wheels before I realized that if one mating part is worn, it will quickly ruin the other part. I finally solved the problem by installing a new wire wheel and a new splined hub - simultaneously. If all the bushings are ok and all the clearances are correct, it seems the most likely culprit is the gear itself. Just a thought.... Quote Link to post Share on other sites
Rob Salisbury Posted November 27, 2008 Report Share Posted November 27, 2008 A new cam and an old dizzy drive gear always take their chances on how long they last, trouble is the drive gear is NLA new so we are stuck with best match SH, .......check the next one very carefully, try all the usual suppliers(though Revington TR have 106981SH in their cataloge). You may want to check that the dizzy is not siezing when it gets hot, (oil pump and drive shaft for that matter) Good luck Rob Quote Link to post Share on other sites
Smokey Posted November 27, 2008 Report Share Posted November 27, 2008 Is the tach drive ok? Quote Link to post Share on other sites
Tim30 Posted November 27, 2008 Author Report Share Posted November 27, 2008 Is the tach drive ok? HI Smokey, Rob. THanks for the responses. I'll double check the tach drive, though everything turned freely enough before I installed the housing/dizzy. The dizzy gear has no markings/damage on the actual gear which drives the tach, looks pretty clean. When I replaced the cam I used a replacement dizzy gear - it came straight from an old 4a engine - looked in good order, but I didn't have it professionally looked. Appreciate the responses so far. If it is a case of used parts being in danger of not bedding in I suppose it is a risk I will just have to take! Worrying though as I might be getting the a rebuild of the bottom end whislt the engine is out - would be a shame to smother it in shredded gear teeth (again!). Thanks Tim Quote Link to post Share on other sites
Rhodri Posted November 27, 2008 Report Share Posted November 27, 2008 (edited) If the following link works, then you can see that one of our contributors on this forum has had a similar problem. http://kaskastnersforum.yuku.com/topic/393...lth.html?page=1 Edited November 27, 2008 by Rhodri Quote Link to post Share on other sites
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