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308 GT4 Engine Rebuild

Discussion in '308/328' started by marklintott, Jan 6, 2018.

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  1. marklintott

    marklintott Formula Junior
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    Jul 13, 2005
    508
    Taipei / UK
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    Mark Lintott
    Taking my daughter to the airport after my father's funeral back in June my GT4 packed up on the M5 heading to Bristol UK. A loud bang was followed by massive drop in power and a sound like nuts in a tin can......

    Of course I pulled over immediately and it was flat bedded back home. Great start to my sole ownership. I used to share it with my Dad and split everything 50/50. When he passed I got the lot so there's a sense he's smiling down on me but not in a good way!

    We're in the West country UK and qualified repair places are few and far between. It was suggested I check out Ftech and Carrs the "local" main dealer. Both were highly recommended even for this age of car. In the end I opted to leave it with Ashley and Chris at Braunton Engineering, Devon as they have worked on it before and although mainly Porsche people Ashley was keen to do the work.

    I''m overseas most of the time so the first chance I had to meet with them face to face was after they had removed and fully stripped the engine. First pics were emailed to be beforehand and its clear what happened. Few pics below....
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  2. bertspeed

    bertspeed Formula Junior

    Sep 19, 2009
    277
    wow,sorry to hear of your misfortune. At least when its done you can drive it with a peace of mind. What was the history of the cars use,did it sit for long periods or something else that may have caused this.
     
  3. marklintott

    marklintott Formula Junior
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    Jul 13, 2005
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    Mark Lintott
    Met with Ashley just before Christmas. He had fully stripped and examined most parts. It all cleaned up very well and despite the usual trouble of separating the heads from the block it all looks pretty good. Heads have been lightly skimmed, new valves and guides fitted and high comp pistons ready to go in. They still have to renew the big end and small end bearings but basically the bearing surfaces looked okay.

    I had assumed this was all caused by the notorious sodium valves hence the valve head floating around in no. 1 cylinder. In fact on closer inspection it looks like the front timing belt slipped a tooth introduced the exhaust valves to the pistons on that bank. There are slight dents in each piston crown for that bank. The broken one put a hole in its piston and slightly damaged the area of head between the 2 valves. Why the belt slipped I don't know. They were changed a couple of years ago and its done little mileage since then. However the guard on one of the pulleys has broken off. The originals seem to be all plastic of some sort and perhaps a stone or something got thrown up into the pulley causing it to slip and break.

    Anyway other items to be done "while we're in there" are:

    New JE piston set with all new bearings, bolts caps etc
    Higher flow valves from Superformance
    Stone guards to protect the cam pulleys and belts on the engine side
    New pulley set - not sure yet if to use the Forza set from the US or go for the more basic model from Superformance
    Replace the forward manifold with SS to match the rear
    Renew all hoses throughout including the long ones going to radiators
    Renovate the engine bay to bring it back to "as new"
    Some minor rust repairs although generally it seems pretty solid from underneath

    More pics below...

    cheers

    Mark


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  4. marklintott

    marklintott Formula Junior
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    Jul 13, 2005
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    Mark Lintott
    Thanks. It will be nice to be more confident in the mechanicals and perhaps a very slight increase in performance...
    Its only done a certified 36000 miles so yes its spent long periods sitting around throughout its life. Inevitably that's not good.
    It did strike me that I've seen several 308's in the past without the black shields protecting the cam belts etc. This can't be good and rather invites dirt and debris into this area.

    Mark
     
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  5. PDB

    PDB Formula Junior

    Feb 1, 2011
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    Leicestershire, UK
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    Paul
    It looks like he’s doing a good job. Those pistons look nice.
    These cars need to be used and used hard. The engines are really strong if they’re well maintained and used regularly. I took mine to Spain and back in September and it didn’t miss a beat. They’re fantastic classics for touring with great luggage space and a terrific ride.

    Paul
     
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  6. kiwiokie

    kiwiokie Formula Junior

    Aug 19, 2013
    686
    Tulsa, OK
    Those pistons have a high dome and pronounced ridge between the valves that I dont remember my JE Pistons having. From memory they did not have any off-the-shelf 308GT4 pistons. Did you supply drawings for them to use?
     
  7. killer58

    killer58 Formula 3
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    Jun 30, 2010
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    CA & DC
    Perhaps the valve did fail. Then, as the piston compressed the remains, the belt slipped due to the resistance? Just a thought (guess).
     
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  8. yelcab

    yelcab F1 Veteran
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    Nov 29, 2001
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    Mitchell Le
    I don't know if they have replaced the liner orings, but you should ask them to. For a job this big, it would be a shame not to do that. Check the flatness of the deck, as well as liner protrusion.
     
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  9. marklintott

    marklintott Formula Junior
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    I think they came from Superformance here in the UK although I didn't order them myself. I'm assuming they'll fit...! :eek:

    Comparing the old ones to the new - you're right there is quite a difference in their height. They are described as "high compression" which might account for it. Ashley at Braunton said he would be dry assembling the heads/block/pistons etc to check clearances which sounds like a good idea considering the extra space taken up by the piston crowns.

    Mark


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  10. marklintott

    marklintott Formula Junior
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    Yelcab, thanks - good reminder on the O rings. I believe the liners have been out and checked during disassembly so I'm fairly sure the O rings would have been replaced then. Worth double checking though. The deck and heads have been checked for flatness already and all is okay apparently.

    Anybody got any suggestions for other things to check/replace while the engine is out? I thought about replacing the engine mounts but when cleaned up and inspected they seem to have got a clean bill of health.

     
  11. Squirrelmonkey

    Squirrelmonkey Karting

    Dec 27, 2010
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    Manitoba ,Canada
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    Tom Thieme
    Cam drive bearing seals for sure ! They will be hard as a rock by now and will shatter eventually ! Talk about oil leaks !!! lol
    Yeah someone mentioned the liner O-rings ?? very important to change them out. It would suck the have a coolant leak into your oil after you have installed all those nice expensive gaskets etc.
     
  12. marklintott

    marklintott Formula Junior
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    Jul 13, 2005
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    Update on my GT4 rebuild....

    Finally got to pick up my baby from Braunton Eng on my birthday after what's been more than a year since it detonated on me last may.

    Ashley and Chris from Braunton did a great job and more than expected in terms of "while I'm in there" stuff. They repainted most of the accesible chassis members, renewed the firewall insulation, hoses etc etc. Car goes great and very smooth. There is still some fine tuning to be done on the carbs which I think are probably overdue for a full rebuild. Lots of popping and a slightly irregular idle but the change in performance is very noticable. Ashley will take a look at it when he brings back my other Italian.

    We're not entirely sure of cause of the original failure but it seems to have been a sodium valve that broke and made the belt jump a tooth or two. In the process it put a hole in a piston. Or possibly a stone thrown up from the road got into the belts causing one to jump etc. In the process it took the lip off one of the cam sprockets. These seem to be some kind of plastic which seemed odd to me. I've now got stone guards fitted to protect the belts etc - from Superformance.

    Can't recommend Braunton Engineering enough. They have done what they promised close to the budget promised and have always been open to discussion or questions. (the length of time is down to me being so far away most of the year)

    I'm glad its over and the car is home again. Once a few teething issues are ironed out it will be better than ever. Thinking of saving up for electronic ignition to eliminate the weaknesses of the original single distributor set up but that for next year I think.

    Anyway, here's a few progress pics to bring the thread up to date.
     

    Attached Files:

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  13. Portofino

    Portofino Karting

    Sep 17, 2011
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    Yorkshire UK / Switzerland/ Cote d Azur
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    Portofino
    Great to see it back .
    What do the stone guards look like and where do they fit please .
     
  14. marklintott

    marklintott Formula Junior
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