Engine Rebuild/ Upgrades - Does yours need it?
08-04-2014, 10:51 AM
#1
Drifting
Thread Starter
Engine Rebuild/ Upgrades - Does yours need it?
Whilst I don't pretend to know a lot about rebuilds I often get PMs and the likes about engine rebuilds. Thanks to this great place and my own experience I've learnt about the approach one should take to rebuilds.
When replying to one email on the subject this morning, I thought I'd post my reply here also.
■ Does my engine need a rebuild?
As we know, these cars were sold in a time of recession and received bad press: About oil leaks due to the lack of a head gasket on early models and failed flywheels.
The result was that a lot of 964s became cheap fast and so ended up in the hands of people who very often couldn’t afford to maintain them properly.
Often it’s heard that a 964 engine will last around 100K miles and whilst there is some truth to this - I would strongly suggest that if these engines had been properly maintained and cared for there would be no reason for them to see 200K miles. Which is not unheard of at all...
It also regularly happens that a 964 engine will be rebuilt unnecessarily… just because your engine leaks oil doesn’t mean it should be rebuilt. In fact quite simply the gaskets may be shot. Therefore just reseal and get going. I’ve even read cases where someone will rebuild purely because they think it’s about time/ 100K miles have past!
If you’re happy with how your engine pulls - then leave it be. The only real way to test the health of your engine is to carry out a leak down and compression test.
However! Don’t go and have a compression test on your engine if you are happy with how she pulls. Most engines will have a few low compression/ leak numbers. So what, if you’re happy with how she drives. Just keep going until something breaks.
If it ain't broke don't fix it. Your butt dyno is the best diagnosis machine.
■ Cost/ reward?
Unless you have a ten figure budget, most will strip their engines down and then decide what to upgrade. For example if your crank shaft needs replacing the cost is eye watering, which will reduce the money you have for upgrades significantly. If for example your pistons and cylinders need replacing, then now may be a good time to go for a 3.8 or if your camshafts are shot, maybe some Cup cams would be nice.
The point being is that by opening up your engine, you are effectively opening a can of worms. Some things may be beyond salvaging and therefore will take up a big chunk of your budget.
So before you plan crazy upgrades: Strip it, find out where you stand, then plan your build.
■ Synergy?
These air-cooled engines are wonderfully upgradable. Some run big naturally aspirated engines, others turbo and others supercharge. Point being is that the possibilities are endless, and so can be the hole in your wallet!
Synergy, most upgrades on their own make little difference but when all the little upgrades which are often negligible on their own come together the results can be awesome.
An example of this would be an increase in capacity. Upgrading to 3.8 P&Cs has limited and not jaw dropping results unless you upgrade other parts to go with it…
Every upgrade you make to an engine has a knock on effect to everything else. Design a specification that creates the synergy between all the parts.
■ Application?
How you will use the car is also very important and may well be the most important element to know when deciding on your upgrades.
As an example a race engine will get stripped down and rebuilt very often and so faster wearing parts (but with bigger performance gains) will not be applicable for those who wish to rebuild their engines in another 100K + miles.
For example, high lift cams and an aggressive flywheel would be a nightmare in traffic but a joy on track. Light weight pistons maybe awesome for a track car, but for a road car will they last another 100K Miles, like Mahle items would.
Build an engine to suit your application.
■ Builder?
There are a huge amount of builders out there and a lot of info online.
In most cases you will be spending a considerable amount of money on your rebuild. You owe your ££,£££ respect, so spend it wisely by doing your homework. Read through forums, speak to builders and crucially speak to several past clients.
The last thing you want is an engine that goes bang or one that goes way over budget without you knowing until the bill comes… Agree on a quote. Of course there may be surprises once the engine is stripped, so may be get two quotes: a best case and a worse case. Go in with your eyes wide open.
Remember that builders will always have different view points. The possibilities are so endless that there isn’t a definitive right or wrong answer. Take your time to make an educated decision on who should build your engine.
I would also debate that a rebuild is only as good as the builder... For example a specialist may have a great reputation, but who is the builder? Is it the same bloke who was there a month ago or has their mechanic changed?
Eventually will come a point where you’ll have decide on a builder. You’ll have felt chemistry in that together you’ll have decided the best engine spec for your personal application and budget. Once you choose your builder and dropped off your car you should be completely relaxed and just impatient for the work to be completed.
■HP?
No such thing. Every dyno is different and the variables are always inconsistent, all quoted figures/ dyno plots should be taken with a pinch of salt. As said before, your butt dyno is the most accurate. The only thing a dyno is really good for is mapping and setting a base line for comparison. The same car tested on different dynos/ days/ room temperatures will always give you different readings.
■Conclusion?
In 99% of cases the biggest factor that slows a 964 down is the mushy bit behind the wheel. These cars are more capable than a lifetime of track driving can give us. The best performance mod you can make to your engine is to take driver training.
I know it may be hard to believe but in most cases you will get used to the increased HP. Chasing performance is an endless game of getting used to it and moving on to the next upgrade...
And finally and obviously, the best performance upgrade which effects all areas of your car's character is weight loss. Oh and it happens to be cheap also.
■Post Script
These are merely my thoughts on rebuilds and I'm sure there are plenty of others.
Last edited by BLACK-BETTY; 11-10-2014 at 08:31 PM.
08-04-2014, 01:46 PM
#7
Rennlist Member
Great write up. I did a reseal on my 91 Tip at 70k miles and engine looks awesome now. My 1990 C4 now needs a reseal as well. It is just pouring oil out of the common leak points. Re-seal means changing out all the o-rings everywhere to new ones (including cam shaft seals). And the "while your in there" for a reseal means rebuild power steering pump, service dual distributor as necessary, clean injectors, new spark plug wires and coils. You can dress up the engine as well. I imagine some shops would advise a customer to rebuild as evidence by the oil coming out everywhere when you don't need to open the motor at all for a reseal.
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08-11-2014, 03:07 PM
#10
Racer
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I believe any car getting close to 100k miles is going to need a top end no matter how it has been taken care of. If I was in the market for a used 964 I'd be leary of any car advertised wih that kind of mileage as not burning any oil and not having had the top end done.
08-11-2014, 03:48 PM
#11
Burning Brakes
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Well said, Frank. It should also be noted that by simply rebuilding an engine, sans modifications, can have a profound affect on the performance of the vehicle. An old worn engine will typically not perform as well as a new one
11-10-2014, 05:17 PM
#15
Frank, this is an excellent piece of advice to finish your list of well written points from a balanced perspective