924Board.org

[Mkol]

Hi guys, ive recently acquired a ‘79 924na that im planning on taking my time to restore. My experience is mainly in the kit car scene and although ive messed around with cars for years theres still many things ive never done and so have so much to learn.

One thing i wanted to do with this project is an engine rebuild, ive never doen one before and really just wanted to go through the process to understand better.

My question is with limited experience am i taking on a crazy job?, im happy to throw time at it but dont want to find down the line i have to spend thousands, Essentially i was hoping to strip, replace essentials, clean paint and rebuild totally stock just for the joy in learning for as little outlay as possible. The engine does currently run.
So essentially im not exactly fixing anything but just freshening up and hopefully acquiring soem new knowledge on the way!

Any advice and suggestions welcome!

[924RACR]

It's not the worst engine to learn on; it's just a water-cooled VW design, they're pretty simple, and starting with a running one will cut down on the difficulty level.

Aside from cleaning and replacing all seals and gaskets, your main refresh components will be new rod and main bearings (though the latter may not even be needed), new rings (with a freshening-up of the cylinder walls via ball hone), and cleaning and re-lapping the valves into the head. Probably would be wise to also do new valve guides and springs while you're at it.

Many will say you're crazy to dive into that when it runs... but having a clean engine that doesn't leak oil is kinda nice!
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Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

[morghen]

First advice is: if it runs, dont touch it.

I'm rebuilding my engine as it was worn out in every way possible.
If you are replacing pistons, bearings, camshaft, bolts, seals and misc parts, expect thousands in parts cost indeed.

You'll likely run into rusty bolts that need extracting and replacing, all seals, maybe piston rings if you can find them, if not then complete new pistons set.
All crank bearings, clutch, head refurbishment....if you take it all appart...it makes sense to replace the worn parts...just taking them appart, cleaning and painting does not constitute a rebuild in my opinion.


So if you take a running car appart, better replace the parts that need replacing:

-pistons maybe? (NA pistons usually develop ringland wear)
-crank bearings
-all seals
-all exhaust bolts and nuts
-rod bushings (most of them are out of round by now)
-complete clutch
-head valves
-valve guides and seals
-camshaft maybe and oiler elbow
-followers maybe
-torque tube bearings rebuild?
-CIS rebuild
-alternator
-starter motor
-all the small stuff like thermostat, temp switch, belts, filters, fluids, brake pump seals

Then if you take off the engine, you'll need to do suspension and brakes as well.
If you do that, you can also do the transmission mounts and linkage bushings.

All in, its thousands + work...but easy to work on and rather pleasant in my opinion.
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https://www.the924.com

[Mkol]

thanks guys, interesting to see slightly different angles on the question yes i can totally understand the if it aint broke dont fix it approach!

i can also completely see that if you getting stuck in then the temptation is to replace more parts than you were intending and be led on to an increasing list of jobs.

I think if i go into this i would want to only replace parts that are damaged/worn out rather than everything, really dont want to be having to fork out for new cam, valves or pistons, rings seem readily available. so would be hoping to get away with gaskets/seals and bearings.
I dont know how naive this sounds...

but then again maybe i should find an engine that is actually kaput and it would make more sense to work on.

[Beartooth]

In terms of simplicity, I think this would be a great motor to rebuild for your first one; unfortunately, it's not so great in terms of parts availability. It's not that bad, but it takes some legwork (and more money) for things like pistons, rings, bearings and such. If you wanted to rebuild an engine more for the experience, something more common that you could buy a complete engine kit for might make more sense.

By "rebuild," I'm thinking compete tear-down, replacing and machining anything that's out of spec. I'd check the oil pressure and do a leak-down test before considering that. If the compression is off or it's got low oil pressure (and you want to put a good gauge on it - the oil pressure gauge in the car is really more of a general indicator), then you're talking about taking it down completely. You may need to have the crank machined for undersize bearings; that process requires some delicate measuring on the crankshaft. Then, you'd need to check the bores and pistons; if they're worn too much, have the engine machined for oversize pistons (more money, particularly for the pistons, which are no longer produced other than custom order pistons). On more run-of-the-mill rebuilds, it's pretty common to just overbore and replace the pistons, but the cost and availability aren't such a big deal there. Ultimately, I have to agree with those saying "if it aint broke, don't fix it" - but specifically for a full rebuild, especially if you're spending a lot of time and money finding out-of-production components just to replace ones that are still serviceable.

Now, what I'd call a refresh could be just as rewarding, but with much less expense and risk of something going wrong. You'd want to make sure you've got a good candidate - an engine can run decent and be just about worn out - but there are plenty of original engines (or ones that have been properly rebuilt at some point) that are fine internally but could use some in-depth attention. You'd remove the engine, take it down to the long block (leave the crankshaft and pistons in place), maybe leave the head alone too, other than to check for warping and make sure the valves and seats are in good shape. Then, replace all the gaskets and seals, clean up the decades of grime and rust, paint the engine block, and throw it all back together looking like new. It's no small undertaking; I wouldn't just do it on a lark to a car that's running well. That said, it can be rewarding, and no amount of steam cleaning and such can make an engine look as shiny and new as a stripped-down refresh. And, on a new-to-me car, I might pull the engine and decide how deep I go based on what I find. If you decide to tackle it, take your time and don't think you're going to do it in a couple weekends, get some good instructions on the topic (Haynes is ok; you'll probably find some shortfalls), and make sure you get some good advice if you come across something that doesn't look or feel right.
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1980 931 diamond in the rough

[Mclaren924]

[Mkol]

Beartooth i think you might have just given me the advice i was looking for but didnt know it! A 'refresh' sounds like a perfect stepping stone to doing a more in depth rebuild on a motor one day that perhaps has easier to source parts for less ££ (Im in the UK!).

If taking this approach which seals would you replace in addition to head/crankcase/oil pan gaskets?

Im not worried about the car being off the road for some time as Mclaren924 has mentioned, i have a Tiger Super 6, with 170bhp weighing 600kg for the drivers experience.

the 924 is really for my own learning and hopefully driving fun one day!