OWEN WB Posted June 26, 2021 Report Share Posted June 26, 2021 TR6 engine runs well enough, plugs all the right colour. Just trying to run through basics and put vacuum pump on brake servo pipe outlet to check pull and timing. Maximum suck i could get was around 12 inches... but i have had a 6 cyl engine pull 15 before. 12 doesnt seem very good. Slight wobble on vacuum gauge needle too - not so massive but noticeable. This TR6 is new to me, so just trying to work out if; - i have a bigger issue (like needing the valve guides on the head done) - i have used the wrong point to check the vacuum - these levels are quite normal. Any thoughts appreciated. Thanks Owen Quote Link to post Share on other sites
Rob Salisbury Posted June 26, 2021 Report Share Posted June 26, 2021 If it's a Pi then that's a good vac figure. Cheers Rob Quote Link to post Share on other sites
stuart Posted June 26, 2021 Report Share Posted June 26, 2021 Depends on the cam too. Stuart. Quote Link to post Share on other sites
Steves_TR6 Posted June 26, 2021 Report Share Posted June 26, 2021 Yes, i’d be pleased with a vacuum reading of 12! Quote Link to post Share on other sites
Mike C Posted June 26, 2021 Report Share Posted June 26, 2021 My idle vacuum is 10" Hg. Always has been. The Pi system has been calibrated for this and the engine runs perfectly. Re the idle wobble- what speed is your idle set at? I set mine at 800-900 rpm to prevent pressure pulses and subsequent flutter of the throttle butterflies. Quote Link to post Share on other sites
OWEN WB Posted June 27, 2021 Author Report Share Posted June 27, 2021 16 hours ago, Mike C said: My idle vacuum is 10" Hg. Always has been. The Pi system has been calibrated for this and the engine runs perfectly. Re the idle wobble- what speed is your idle set at? I set mine at 800-900 rpm to prevent pressure pulses and subsequent flutter of the throttle butterflies. The engine is PI, sorry, should have said. When i do the vacuum gauge stuff its around 750-800 if the rev counter is to be believed. Advancing the timing gets the vac gauge up to 12, then backed it off to around 10. Its cracking to drive! But i had a triumph with a 2500 6 cyl PI and that could pull up to 15... so just thought I might have an issue. Many thanks all for the comments! Quote Link to post Share on other sites
Andy Moltu Posted June 28, 2021 Report Share Posted June 28, 2021 CP or CR cam (or non-standard) - The CP cams and quite a few of the fast road cams have relatively limited manifold depression at tick over. Quote Link to post Share on other sites
Nigel Triumph Posted June 28, 2021 Report Share Posted June 28, 2021 My CP series TR6 pulls 12-13" vacuum, so your reading of 12" seems fine. Also worth mentioning that unless properly calibrated, vacuum gauges are unlikely to be very accurate. 10" on one gauge could easily show as 12" on a different gauge. Quote Link to post Share on other sites
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