Porsche Enthusiasts Club Forum

Im rushing as usual and Ive barely even skimmed Pats post, but if youre looking for a multi-valve head - had you looked at a 20vT part? I reputable engine builder and Porsche preparer told me that he had looked at the VAG engine and noticed a number of similarities which lead to him concluding that it was based on the EA425 block (inc blanked off cam carrier from its original DKW/Auto-Union OHV incarnation).


Simon

Actually, I'm in the process of making a cage for it in the spare wheel well Steve Hehe.

I've hit a brick wall with starting the new engine. Experienced advice suggests the engine will need to be turned over for 1-5 minutes to gain oil pressure. Engine builder expected pressure in 3-4 three second bursts, which isn't possible. They are now stumped in trying to plumb in an external pump to run oil around the engine and gain instant oil pressure on start up. The car is now stuck in their workshop whilst a solution is found. They will not crank it any more without oil circulation/pressure. I won't take it from them until they start it to preserve any come back if there's any issues down the road. I am really pissed off today and restraining myself from throwing expensive toys out of my pram.

Pre-pressuring pumps are certainly available. I first saw one on a Starion Turbo in 1988, fitted by my uncle to one of his sponsors cars. It took about about three seconds of high-pitched whining after turning on the key before you could start it and it achieved about five BAR of pressure.

Engine shop have an external pump ready to go but no idea where to plumb it in. Oil cooler was one option but this is closed by the thermostat whilst cold. Back pressuring the oil relief port will only push oil back into the sump. They are now looking at the oil filter housing and oil pressure sender port. Won't be a quick solution and yet more money being haemorrhaged as its more work for them and not entirely their fault to be FOC!

I sympathise Steve. Itll be worth it though and it is an addition that Id recommend to anyone with a performance engine. Between this and a remote take off filter (which filters down to a few microns) you can make an engine last forever.

Where's Jon hen you need him?

Ta-Daaaa!!!

I take it they had the plugs out and the oil filter primed with oil before they tried turning it over didnt they?

Often a 924 engine will never prime itself from a fresh build, I used to pull out the oil drip rail and back pressurise oil down its feed hole until oil came out the sump plug, then put in the sump plug and fill her up with oil normally, then make sure the plugs are out and the battery is fully charged and give her up to 10 seconds on the starter, which was not normally needed because in about 2 seconds it would have full pressure.

One other thing they could try is to seriously over fill the engine with oil, just enough so it is a couple of inches over the crank centre line, leave it over night (allowing oil to creep in and find its own level in the pump, crank etc) then turn it over by hand by about 10 turns the next morning or after a couple of days, drain the oil into a clean container, and then refill back to the right level before spinning it over on the starter with the plugs out.

The main thing is making sure you have oil in the pump.. Even if you park a car for a year, you will never have a completely empty oil pump and oil ways, priming it is often necessary, with 944's we back prime them via the oil filter manifold, on a 924 you do not have that luxury and they can be a bugger to prime up.

Hi Jon, yes the oil filter was primed and I pulled the plugs and killed the fuel supply before I was cranking. Bloody nervous as hell when turning the key. Even more nervous when no pressure was building. Its like two steps forward and one back with this car

Missed a call late afternoon from the shop and only just spotted it on my phone now. Lets hope its some good news.

Thanks for the tips. I was hoping to be on the road this weekend and possibly swinging by your new workshop en route to Poole Quay on Friday. I'm not sure yet this may happen as the car needs to be running well and MoTd before I venture on a long trip.

Having the oil filter primed but the oil pump and oil circuit not primed with oil may have aggravated the situation, as it would have meant you had an oil gallery leading to the filter housing, oil pump and oil pickup tube all full of air, which even if the oil pump could effectively move, it would be trying to build up enough air pressure to move the oil in the oil filter.

Do you have a wideband AFR sensor fitted?

Once you get it running, you could do with hitting the road as soon as possible, pulling over occasionally to tweak the fuel adjustment in the fuel metering head to get a nice cruising AFR which does not wash the bores and get at least 200 miles on the engine... that is once you have given the car some time at a very fast idle (3k) for enough time for the camshaft to bed in (presuming it is new) and setting the fueling for this stage.

AFR detection is going to be critical for you at this stage as well as during tuning.

The car will be started on engine shops rollers so we can run 2-3000rpm off the bat with a low load for 30 mins. Then run another 2 hours on the rollers at differing revs and coasting but never idling.

Yes an AFR is fitted as boost gauge and knock sensor. Being on the rollers we can get initial tuning done better than on the road. As soon as this phase is complete we will drop the break in oil, I can get the MoT done and then put more road miles on it.

And there was me thinking that once I fitted the engine that it would be plain sailing!!

The engine has run for at least 30 minutes under load on the rollers and circa 30+ minutes whilst we observe the coolant. However the engine shop is not happy with the coolant flow. Rad sits at circa 70deg but the block is 110 to 120deg. Fan kicks in when temp gauge hits half way which I think is circa 80deg. They have now blocked off the cold engine bypass and removed the thermostat so there is full coolant flow around the block and radiator at all times. Again I'm not sure they are being over cautious with with how these engines work versus their perfect world race engines.

The 944 expansion tank coolant remains very cool despite the rest of the system being 70-80degs. However to me the expansion tank is only a feed and return of excess coolant so I can't see how it would get hot, am I missing something?

Solution offered is new ally expansion tank, new ally radiator, smaller pulley on the water pump to spin faster, bleed pipe off top bleed screw above thermostat to expansion tank, move bleed pipe from LHS of rad to RH side of rad and return pipe to expansion tank, fit new inline water pump to run on after engine shut down to reduce heat soak.

So I have the car back lighter by another £200 for 2.5 days labour!! Engine still timed safe at 10deg (which gets the manifold and down pipe off turbo glowing red hot at 2000rpm and still running its break in oil. I hoped it would be returned ready to go!!

I have an MoT booked tomorrow morning which my workshop guys will be taking for me. Only thing tonight I couldn't get to work was the windscreen washers. Pump runs but doesn't pick up water!! Will see what these guys think of the above issues and go from there. I can still run it on their rollers for a couple of hours, get the timing and fuelling right and check the cooling.

Either way I think I'll trailer it on Sunday to be safe than sorry as I won't get enough mileage under its belt to be sure. Poole Quay has been scrubbed from the diary again.

**** me it feels quick with only a centimetre or so of throttle already!! Turbo spools at 2000rpm and boost gauge builds from 2250rpm. By 2500rpm I have full 0.7bar on the gauge. Just short shifting up to 3000rpm speed builds quickly.

Did a few laps around the local dual carriageway and all was fine. Temp gauge was steady at 1/4, oil pressure at 5 bar at 2000rpm. So I decided to venture up the motorway to Clevedon and back. Did about 30 miles tonight and all is well

See and hear it....

With over a 1000 road miles now done its due a new air filter set up, an oil change and a run on the rollers in the morning.

Anyone want to guess up front the bhp outcome? Jon, Wes, anyone?

I'll start. 200bhp at a stock 0.7 bar and a Carrera GT matching 210 bhp at 0.75 bar.

If I'm feeling lucky I may go for a run at 1.0 bar!

Any advances?

Actual numbers at 0.7 bar are

180whp (est 210.4 hp at the flywheel) at 4829 rpm which is when we came off the gas
198.09 torques (est 229.47 at the flywheel) at 4278 rpm. Of which this figure was fairly flat from 3500-4829rpm when we shut down

This is still with the restrictive K&N air filter and not the larger ITG which will be fitted in due course. This is hitting an AFR of circa 10.x at WOT which is too rich, but safe. Timing was set at 8.7deg at idle

I am happy as I thought it would be circa 200 bhp at 0.7 bar. Sense prevailed today in not pushing it too hard to soon on the rollers. Now its running its best to take baby steps to getting the bigger numbers and getting the set up right first.