Two seater, targa topped bus restoration (914)

Discussion in 'Restorations' started by mcswiggs, Feb 18, 2018.

  1. While that lot was away being coated I’ve been sorting out some of the other small parts and got the chance to use the home electroplating kit again... hours of fun. Sometimes it really does feel like a giant Airfix kit.

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    And now it’s time to get back to the assembly work. First up is deck height measurement. The dial gauge makes finding tdc accurately easy.
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    Next up is head volume measurement - an old CD has been cut to size but the syringe I’ve got isn’t really up to measuring accurately so fleabay delivery is awaited.

    Meanwhile, some gratuitous photos of the old and new pistons and barrels; F3D95B91-91AD-4C0D-A7E6-4352DD1BD0E5.jpeg
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    Last edited: Sep 19, 2018
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  2. Now then - I've finished messing about with pipettes and getting everything covered in vegetable oil, so it's time to sort out the CR. The head volume is 63cc (which is more than I was expecting but consistent across four, but the head is different to the more accustomed CJ/CU ones).

    This being a 'GA' engine should have a CR of 7.6:1 (despite what Haynes says (7.4:1)). The measurements I've made of the original engine are;
    Bore 74mm, stroke 71mm, deck height (with case seal) 0.4, head seal 0.75mm this giving total deck height of 1.15 (a bit on the low side?). Piston dish 5.6cc.

    Putting them into the calculator gives a CR of 7.4:1.
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    Hmmm - perhaps Haynes was right after all? But the total deck height is only 1.15mm which seems low at least when compared to Wilson's target of 1.40 to 1.65mm, but still within the overall range of 1 - 2mm.

    Out with the old and in with the new and the new barrels are a tad longer.
    Bore is now 76mm, stroke is the same, deck height (with case seal) is 1.12mm, head seal the same, flat piston. Hmmm - this gives me 7.73:1 - heading in the right direction but not the 8:1 I was expecting and aiming for.


    OPTIONS:

    A) If i don't put the case seal on it will save .25mm of deck height and pop the CR up to 7.9:1 - more like it, with a comfortable deck height of 1.62mm.
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    B) The alternative (other sending the barrels off to a machine shop) is to follow the technical bulletin and bin the head seal and keep the case seal which gives 8.2:1 with a similarly low but usable deck height of 1.12mm.
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    I'm preferring A. I spoke to James at Stateside who recommended keeping the head seal, he does so in all his rebuilds and questions the wisdom of the bulletin. The version of the bulletin I've seen is dated 1990 so about 10 years after production stopped. Surely they would have deleted the head seal at earlier point during the long production run if the seal was really a problem? Also the deck height is a bit on the low side and given it's a new cam I'd prefer a little more deck height clearance to be on the safe side. And James says there needs to be 1.5mm clearance between the start of the fins on the barrel and the head, and I’ve measures it at only 0.8mm when there’s no seal - not good.

    Any thoughts chaps?
     
  3. We’re the original pistons dombed ?
    I used copper head sealing rings mainly as it’s forced induction . For deck height could you not just add shims to base of barrel .
     
  4. The original pistons were dished - I assumed to lower the CR and overall emissions for the US market.

    Yes I could add shims at the case end (if I didn’t put the head seals in to balance the CR at about 8.0:1, but without the head seals I think the top of the barrel fin casting would need machining to obtain the 1.5mm clearance to the head. That’s why option A is more appealing at the moment.
     
  5. Well… I’m surprised Jim retains the head gasket, I would delete it. There is an aluminium (the head) to iron (the gasket) joint without the gasket, with it there is an aluminium to aluminium (the gasket) to iron joint – two leak paths instead of one and once there is small leak the gasket quickly burns up and a small leak becomes a big leak.

    I agree with the VW bulletin and adjust the CR with cylinder base shims. I’m happy with 1mm (0.040”) deck height – unless there is a catastrophic failure the piston is not going to hit the head and the valves are a long way off.

    I have a couple of cylinder types in the workshop I could measure. One Biral set (as used by Porsche) but the other is standard iron – what dimension do you have between the top of the bore and the top of the fin? I’ll measure mine tomorrow to compare but I have never heard of this 1.5mm minimum clearance between the head and the fin before.
     
  6. I was quite surprised too, but he was quite vehement! As ever, thanks for your thoughts. The new barrels come in at 7.0mm and the old ones I've measured at 6.75mm.
     
  7. I got curious and went out to measure them. The used 94mm Mahle is 6.99mm to the step, and a new 96mm Biral is 7.0mm, unfortunately I don’t have an original VW cylinder. The fins are about 0.9mm below the step on both but angled so further out the dimension increases.

    If you ask anyone who seals components together for high pressure they’ll tell you that the more sealing faces there are the more likely they are to leak, but of course the two faces have to be perfect to seal. I’m fairly sure Jim would be in the minority of type 4 engine builders to use head gaskets.

    Your choice but VW decided the gasket was unnecessary due to frequent failures.
     
  8. Thanks for taking the trouble to measure them. Although Jim said it was the gap to the fins that was important I’m sure he meant the gap to where the step for the fin casting starts. My old VW barrels were 6.75mm to the step and the new ones 7mm.

    As you say, I’ve had to make a choice and I’ve gone with keeping a fresh set of head seals and no case seals or shims, giving a CR just over 7.9:1. The car isn’t going to get raced or even used much, so even it it survives with head seals for another 30k then that is decades into the future. And the worst that can happen is I need to drop the engine and redo the barrels. And 1mm shims aren’t well stocked anywhere and there is a 6-12 week back order... and ..and... enough- I’ve convinced myself and sorry for not taking your advice!

    So that’s allowed me to crack on. New set of valves lapped in and assembled with new springs:
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    Bolted back together with the first bits of tinware;
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    Tubes, pushrods, rocker gear rocker covers all assembled and valves adjusted;
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  9. It’s looking good – what deck height have you ended up with?

    I did a bit more research after measuring the cylinders. The standard spigot depth in the heads seems to be 6.0mm to 6.5mm and cylinder top to step is 7.0mm, add a 1mm gasket and that’s possibly where Jim gets the minimum 1.5mm clearance from but of course the fins have more clearance as there is about a 1mm gap between the cylinder step and the top of the fins.

    My conclusion is you can’t have less than 1.5mm head to fin clearance unless either the heads or the cylinders have been machined - that’s without a gasket.
     
  10. So I’m running with Option A in the table further up this page, deckheight with no case shims of 0.87 plus the head seal of .75 giving... erm.. yes, 1.62mm. Seems about right.

    Thanks for taking the trouble to measure your private collection - there is much more variation than I’d imagined - I think your interpretation of Jim’s comment must be right.

    Meanwhile - any of you FI boys know where I can get some of these on the UK? Can’t find them with the usual suspects.

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  11. Isn’t that just bogo pipework?
     
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  12. It might be but I couldn’t find boggo pipe either and have succumbed to an easy but pricey purchase from Autoatlanta.

    Meanwhile those months of scrubbing, cleaning, spraying and painting seem to have ended now and the fun bit strarted - final assembly!
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    Now it’s time to get to grips with the D Jetronic...
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    Last edited: Oct 16, 2018
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  13. looks great - it'll be a shame to hide it in your car - i'd be tempted to have it on display in the living room :D
     
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  14. Don’t know why I’m being so obsessional- even with the engine lid open all you can see is humongous air filter and a load of pipes.

    I’m waiting for a few engine bits to turn up so I’ve turned my attention to the engine bay. The left hand side is pretty good, just needs wire brushing, treating and painting where the rain water has collected in a perfect water trap against the bulkhead. The other side has the same but mixed with a bit of battery acid and has rotted through in a couple of places. The only way to find out how bad it is is to start stripping the interior - not something I wanted to right now but really need to tackle the rot while the engine is out. Took me ages to work out how the seats slide of their runners! That’s evostick on the bulkhead, not rust.

    From the other side the bulkhead is as good as it could be really. Will have to fab a patch or two. 6D52C670-BFDA-4243-B757-576D88C87B05.jpeg

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  15. Look after the engine surround rubber as new ones cost .... looks ok rust wise ..if it gets into the longs it can be pretty terminal .. what’s your plans to paint it with ?
     
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  16. Yep, the rubbers are pretty good and are cleaning up. The longitudinal members I think are fine, but haven’t got the proof of that yet, I can’t get at anything beyond the engine in the lock up.

    For painting the rusty bits I’ve already given most of it a good wire brushing and I’ve cut out the old battery tray. I’m thinking either;
    a) Bilt Hamber rust converter treatment, primer, bit of stopper or filler on the pitting to smooth out and then celly paint if it’s not too cold or 2pk rattle can if it is, or;
    b) Bonda Primer, primer, and colour coats as above.
    Thinking of using the air brush over the scratches to tidy up the rougher bits.

    I’ve learnt the hard way that Bonda Primer doesn’t stick to the Bilt Hamber rust treatment.

    Thinking of using the air brush over the scratches to tidy up the rougher bits.

    Very much open to suggestions!
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  17. I was going to Rustoleum mine but can`t get the colour mixed ....its funny how your hinge pivot has been re-welded .....just like mine
     
  18. 3697C903-DCDD-4133-8FBC-ED3D56C90137.jpeg
     
  19. 3D7A85F5-91F4-44ED-96AA-D14AC8D2379F.jpeg 7A7127BB-F2EC-4E38-BD33-4954BB5318AF.jpeg 3CCD04B3-ACF2-4CA7-90AD-031749CE4E07.jpeg Well that’s filled a hole. Trying to get the welding done before it gets too chilly...
     
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  20. The fuel pump I rebuilt (see page 2) seized up again having been left to dry out for a few months. Although I opened it up and got it spinning again it’s not pushing out the right pressure; diminishing returns and time to give up on it.

    A new aftermarket pump is pretty cheap particularly if you buy one from an online factor rather than the usual suspects.
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    My little rig has allowed me to test and set the old pressure regulator (all good) and check over the operation of the injectors. The auxiliary valve works fine (once I’d remembered it runs on a full 12v unlike the injectors at 3v). The injectors themselves have all got a good spray pattern but one of them leaks - ughh- so now trying to source a replacement.
     
    Last edited: Nov 26, 2018
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