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Re: TR6 valve seats

To: "Paul Mitchell" <paul@cynthesys.co.za>, <triumphs@autox.team.net>
Subject: Re: TR6 valve seats
From: "John Macartney" <standardtriumph@btinternet.com>
Date: Mon, 5 Dec 2005 17:53:22 -0000
> My mechanic has been trying and failing to fix a persistent
> mis/back-fire on my TR6. Have changed or fixed everything he can think
> of, he reckons that it may be a cracked valve seat. The car pops and
> spits a few times when it's cold, then idles unevenly, and no. 2
> cylinder is apparently cooler than the others. Other than that it seems
> to be fine. Does his diagnosis sound reasonable?
> > If it does sound fair, then what is involved in fixing it, given that
> while I've got the head off, I might as well prepare for unleaded fuel?
> Thanks
> Paul
> 74 TR6 PI
> Cape Town

Hi, Paul

>From what you say about #2 cylinder being cooler, makes me wonder if its 
firing at all! Cracked valve seat, duff ignition or zero fuel supply are the 
pointers. Have you done a compression test? It should be around 160-180psi 
for the PI engine.
You haven't said anything about injector pipe *pulsing* as fuel goes down 
it. If there's no pulse, it's likely the injector is blocked. A quickie way 
(though dependent on crud content) is to pull the injector with the engine 
running and flick the tip of it with your finger nail. If all you get from 
it is no conical spray or just a dribble, then there's a block. However, the 
key question is 'where is the block'? To exhaust all options, fit a new fuel 
filter at the back end and use an airline to blow down the supply pipe to 
the disconnected pipe on the metering unit. Suggest taking the metering unit 
off and removing the gauze filter to #2 pipe on the MU. However, you're 
probably aware that refitting the MU is pretty critical in ensuring its 
timing isn't disturbed.
You don't say whether you've recently switched (by choice or necessity) to 
unleaded fuel. If you have, its likely the fuel has attacked the seals in 
the MU and they're breaking up. If so, no option but to take the MU and 
injectors to an injection specialist and have the whole lot re-sealed. Hope 
this helps

Cheers, Jonmac

1970 2500PI Saloon 


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