Bigdog's SP Engine Rebuild (not 56K friendly)

bigdog · Postby **bigdog** » Sun Jul 26, 2009 5:55 pm

The story so far....

As some of you know my SP's clutch started slipping badly a while back. As I had a leaking exhaust manifold that required removing all the turbo stuff and the manifold to fix it, I thought I would pull the engine and give it a freshen up with some forged rods and pistons which I had ordered on spec from Les in WA. Note that the car was running perfectly, so there was no great need to do all this, just the convenience of having the engine out to do the other jobs. It was also due for a timing belt change in another 20K.

Unfortunately there were some delays getting the rods and pistons, and after suffering withdrawal symptoms from lack of booooost, I said stuff it and dropped it to the local clutch shop for a new button clutch, with the engine pull postponed for 20K.

Next day I got the call to say that having removed the gearbox and clutch they found that the sump had been leaking into the bell housing around the rear of the crank and oil had got to the clutch. Not only that but the sump was leaking around the front of the crank as well. Sooo, out comes the engine, and project rebuild is on again. :roll:

Today I stripped it down and was very pleased with my findings. Basically everything inside is spotless. No bent rods (I told you guys!!), clean bearing shells and perfect bores. The only negative was the heavy carbon build up on the pistons, which points to the very rich setup on the SP, and would possibly have resulted in stuck rings in the future, so my timing is good. The engine has done 170K, and would probably have done another 170K trouble free. Now all I need is my rods and pistons to arrive so I can get the machining done and screw it all back together. Here are some pics of the beast:

you can see the exhaust leak around the top stud

Straight rods!

Carbon build up

Clean bores

Clean crank

AJ · Postby AJ » Sun Jul 26, 2009 6:07 pm

wow, that's in fantastic conditio for 170k with your size 10 hoofing it BD :mrgreen:

how good does that crank look?? :shock:

must be stupidly rich to build up that sort of carbon in an unleaded motor

.......no wonder those things blow so much black smoke

blackster · Postby **blackster** » Sun Jul 26, 2009 6:09 pm

That's great to hear john that the OEM rods & pistons are still good @ 170 k, a tesitmate that the BP bottom end isnt as foulable as some claim.

Are you doing the rebuild yourself?

Sounds like you got some plans with the new donk.

bigdog · Postby **bigdog** » Sun Jul 26, 2009 6:41 pm

I wasn't going to DIY originally, but it has worked out that way by default. I don't plan to up the performance, just wanted to build in some reliability and lower the compression a little to get rid of the pinging that SPs are plagued by. I would have change ECUs and add boost control to go any further, and I am very happy with the way it goes now. My aim is to still be using the car in 20 years time, this should help that.

Garry · Postby **Garry** » Sun Jul 26, 2009 7:48 pm

You're a brave man BD.

I wonder if all that carbon was contributing to your pinging problem? When Mazda replaced the head on my car at 50k km the tops of the pistons were pretty clean. I was surprised considering how rich it runs.

greenMachine · Postby **greenMachine** » Mon Jul 27, 2009 12:07 pm

With the SP off the road, what are you driving?

On Saturday afternoon I followed a white Mercedes van, NSW rego 'BIGDOG' :shock:

, into Murrumbateman heading for Canberra...

:mrgreen:

bigdog · Postby **bigdog** » Mon Jul 27, 2009 2:33 pm

I wish it was me - then i could say I drove a 4 door Merc :mrgreen:

No, I'm getting about in #3 son's Suzuki Cino... with no boooost! :oops:

AJ · Postby AJ » Mon Jul 27, 2009 3:23 pm

bigdog wrote:I wish it was me - then i could say I drove a 4 door Merc

No, I'm getting about in #3 son's Suzuki Cino... with no boooost!

*imagines BigDog doing a "Hightower" by pulling out the front seat of the Cino & driving from the back seat* :lol:

bigdog · Postby **bigdog** » Mon Jul 27, 2009 3:50 pm

Maybe I need a bigger car...

Benny · Postby **Benny** » Mon Jul 27, 2009 6:08 pm

I'm surprised that none of your rods were bent BD.
I guess your car doesn't quite get to 8lbs of boost, and that you treat her fairly gently.

Is this your first clutch change?
Mine was changed at a bit over 50,000k's, and still had some meat left on it, but I was glad to get rid of that shuddering POS.
How do you find the button clutch?

Hammer · Postby **Hammer** » Mon Jul 27, 2009 9:01 pm

Hey BD

Apart from forge rods and pistons, any other update? You going to port it? I kinda wish I had my done now when it was rebuilt.

bigdog · Postby **bigdog** » Mon Jul 27, 2009 11:06 pm

Car has been running 8.5psi for around 80K now, and has had its share of punishment

Don't know how the clutch will be - haven't put it together yet, but it is the same as Dave's setup, so it should be fine. No need to mess with the head Hammer, if I want more grunt I will add more boost. Porting is only necessary when you are chasing the last few horses or have a poorly designed head - ours are great as they are, if anything you would increase the inlet valve size slightly, but with 200rwkw available with ecu and boost adjustment, why bother?

bigdog · Postby **bigdog** » Mon Aug 31, 2009 6:09 pm

- Update - Bigdog's Log 31st August 2009.

All the bits are here. Original gasket set purchased from US had dodgy sump seals (undersize) so rather than take risks I ordered a full genuine mazda set from UK. Turns out almost all the gaskets in the first set were genuine... Oh well, spares in stock for Dave's eventual rebuild on his SP.

Block, new rods, pistons, crank, flywheel and clutch have gone to machine shop in Seven Hills to be bored & honed, bathed and cleaned, balanced and assembled to short motor stage. Will get this back in 2 weeks time.

Only nasty found so far is a score on the front and rear of the crank where the seals sit - not nice, but I will space the seals back a bit in their housings to give them a clean surface to run on. Bit strange on a factory motor to see that happen though...

All I need to source now is new hoses for turbo coolant and take a look at the radiator - might need to do the top tank and give it a clean out.

Sooo, over the weekend I tackled the head - stripped, cleaned and reseated the valves, reassembled and checked valve clearances. Only 1 shim needed machining so all good there, and seats came up a treat with minimal grinding.

Some crappy phone pics of the valve removal/install process. We made a tool to fit in the drill press and an angle bracket to keep the head in the right place, then a wedge to fit under the head to keep the valves in place - worked great and much simpler than using g clamp style tools. (Note that the drill is not used, just the press action 8-) )

Bigdog out -