Porvair

For the past 2 years I’ve had the pleasure of being the 4th owner of a 1988 Turbo S (137k miles), which has served as a street/DE car since the early 90’s. Car is very in very good condition overall and had been well maintained, but from what I can tell it was also driven vigorously as it was designed for. Car is mostly stock with a Lindsey chip and a manual boost control that I limit to 16lb on 93 octane.

One thing that I’ve had to keep an eye on is oil consumption on the track. Running Brad Penn 20w-50 and consuming a quart per event (say 100 miles or so). Plugs look OK and no excessive smoking, so I’ve been just being uber diligent after each session in checking the oil level. From reading lots of old threads I know that this is not uncommon on tracked 951s.

After burning an exhaust valve last year at a track event, I refreshed the head with a good set of original Porsche turbo valves (thanks Lart) and new guides and seals. My hope was that this would also help the oil consumption but unfortunately that still exists at boost-heavy track events, so I just did a leakdown using a high pressure OTC leakdown tester (which uses 100lb of air unlike some of the Harbor Freight ones that rely on 15lb). Minimal leakdown on 2 and 3 but +20% on 1 and 4, and the air leakage past the rings was audible from the oil filler. Unfortunately I only inspected #2 and #3 when the head was off a I did not want to disturb #1 from TDC. Those looked good, which is not surprising given healthy leakdown numbers.

I see indicators all pointing to worn rings. From the research that I’ve done (mostly old postings here and on Pelican) it seems like I can re-ring the engine without having to mess with the alusil bores, as long as the bores are in good shape and not excessively worn or out of shape. I’d prefer not to do a full teardown/rebuild (replacing pistons, replating cylinder walls, etc.) as that could easily exceed my comfort zone in terms of time, $ and skills. I’d plan on replacing the rod bearings in any event as those were last done at 78k.

So question to the community here is whether others have dealt with similar situations and whether the folks here have any advice. I was also considering whether to try to re-ring with the engine in, but considering all of steps involved in dropping the oil pan it seems to make sense to just drop the engine so I would not have to cobble together a way to hold the engine in place with the top end out.

There are a few reputable independent mechanic by me (Huntington NY – Lynmor and TKX Performance are a couple miles away) so I may also get a professional opinion and price, but I enjoy wrenching and this could be a good winter project.

Thanks for any thoughts and advice.

Sean

V2Rocket

How is the oil consumption while just driving around town (when not being tracked)?
As long as the car runs well and doesn't smoke, and the "normal driving" consumption is ~1L/1000km (1QT/620 miles) or better, I'd leave it alone.

A few quarts of oil is a lot cheaper than a set of rings..

marc abrams

In chassis engine rebuilds are done all the time on trucks and saves a lot of labor. Other than getting some oil in your face I don't see any down side to doing a in chassis rebuild on a car if it's just a reringing. Class 8 diesels the sleeve and piston are replaced together and the sleeves just slide out from the block.

Porvair

V2 -Oil consumption on the street seems reasonable. I don't put a lot of miles on and have not noticed any oil usage in the last 400 street miles. I was planning on taking the conservative route and just adding $10 of oil at every track event, but the high leakdown got my thinking. Maybe overthinking...

Marc - thanks. I dropped a valve seat on my '65 Corvair 15 years ago and replaced the jugs, pistons and heads with the crankase in place. In that case I did not want to risk stripping 40 year old studs from the case and 15 years later it was the right call.

marc abrams

I now see where you get the vair in Porvair

Porvair, do you ever go to the Kings Park Plaza car show on Thursday nights?

Tom M'Guinn

I'm with V2. If the car runs well and isn't fouling plugs, I'm not sure I'd try to re-ring it. The risk is the new rings don't seat right in the used bores and you end up worse off. If you do opt to do it, I'd just pull the motor. On this car anyway, you'll end up spending more time in the long run trying to do it in place, and get less done in the process.

Tiger03447

I wish our cars were wet sleeve like the diesels and the Alfas of yore..

944crazy

I re-ringed my engine on 210,000km used bores without any lapping. I've done about 1300km now and the rings seemed to have seated fine. If you have the time and money, an engine out rebuild is probably a good idea anyway. Especially for a track car, a complete refresh will give you good piece of mind. Just be aware that you will probably find a lot of 'while you're in there' things that need doing, and it might end up taking longer and costing more than you originally planned. That's my 2c anyway...

Noahs944

Agree 100%

Porvair

Thanks everyone for your replies and advice. I'm likely going to take the conservative (and way easier) route and just invest in another case of oil.


I imagine that eventually there may be a need to drop the motor but hopefully I have a few more miles before it becomes a mandatory.

Marc - unfortunately I commute to NYC so don't get home in time for any weekday events. I go out to OBI a few times over the summer and also get together with a few fellow Porsche guys on Sunday mornings for some speedy runs in the Calverton area. I think there is a group from LI heading up to Caffeine and Carburetors in New Caannan CT early tomorrow if interested.

marc abrams

I just figured you might have gone there being so close. I've been to Captree in the winter a few times (the OBI crowd goes there in the winter). I have to have a real good reason to go off of long Island-you know that parking lot between the GW bridge and the Whitestone bridge. So no Connecticut trip for me. Thank God I'll be moving off of long Island in six months. I won't be around for the 5 cent per bag fee.

Porvair

Congrats on that Marc. LI is not so bad aside from the taxes, traffic and too many people and trying to leave.

For what is worth there was no traffic this morning and 100+ Porsches in New Canaan. Mostly 911s which is fitting for 9/11. And one Carerra GT, two 918s, 5 944s, a pair of 914s and a few 550 spyders.