How do i figure out what Im dealing with

[Shuie]

Im about to unleash a barrage of questions that I couldnt figure out how to do a comprehensive search on. I apologize if any, or all of this has been covered before:

My goal:
To end up with a fun car better suited for the street than pure track. I'll do some DE's, but I wont try to race it competetively.

Me:
Im not a mechanic. I own some tools, but I tend to destroy things with them.

My car:
SC flared 73T with 40mm Webers and S-brakes. 7R case, single plug, w/mag 915. Smoked a little last time I started it (it has been idle for a little while), but was clean when I bought it. I have only driven the car gingerly 3 or 4 times since I bought it so I have no comment on performance or feel.

Im in the early stages of re-building the car from nose to tail and am trying ot make a decision on the engine before I get too far into the front suspension and brakes. I dont want to have to re-work suspension or brake setup because I decide to go with a heavier engine etc. If my current engine is worthy, Id obviously like to clean it up and keep it. If not, I'll sell my current motor and start down a different path.

Im clueless as to what is inside my engine. Since someone has taken the time and spent the money to flare the car and add a set of Webers and S-brakes to it, I wouldnt be surprised if there were a set of S/RS cams, or if it had already been converted to S/RS spec. The PO didnt realize there were Webers on the car, so I cant rely on what he has told me.

My tech library:
101, the engine book, Weber tech manual, BA's performance, book, and the Haynes.

My questions:
What other reference material do I need?
The carbs are obvious, how do I tell if a PO added cams, etc?
Ive got the engine out of the car, what do i need to do now?
How do I tell if it has already been punched out?
Is a short stroke 3.2 with 40mm webers a bad idea (the book mentions 46mm webers or Euro spec Motronic), what else should I budget for with a short stroke 3.2 w/40mm Webers?

Thanks guys, any help is appreciated.

[Wayne 962]

Sounds like you're good for now on the tech library. The only thing I might add would be a Bentley manual.

The only good way to check for the cams is to send them out to a cam shop and have them measured. There are other round-about ways: check the overlap on the cam timing and then compare it to the chart in my book, or actually measure lift on the cam as you rotate the crank with a degree wheel.

"Ive got the engine out of the car, what do i need to do now? "

Read chapters 1-7 of the rebuild book?

"How do I tell if it has already been punched out? "

I'm confused on your nomenclature here? What does "punched out" mean?

I'm building a short stroke 3.2 right now with the following:
3.0 Euro Carrera aluminum case
3.2 RSR upgrade pistons for the 3.0 rods
2.7 crank and rods (can be used with 3.0 case)
Turbo Heads ported, and twin plugged
Weber 40s (good for street, 46s would be ideal for track)
Twin Electromotive HPX ignition systems

Cost: $10K-$12K retail.

You wouldn't be able to build this engine using your engine case...

-Wayne

[ChrisBennet]

Wayne,
"Punched out" means the bore was increased.
"My motor is a 3.2 punched out to 3.4 using 98mm P&C."
-Chris

[Shuie]

Thanks Wayne, I appreciate the help. Im really new at this. Without your books and this site, I never would have attempted to do any work on this car.

By punched out, I meant is there and easy way to tell if the displacement has been changed from 2.4 or if it had been bored over. A PO has spent some money on this car at some point adding the flares, webers, H4s, brakes. It wouldnt surprise me at all if I found out the car already had cams or if had been increased to 2.7, etc.

If the engine turns out to be something like S spec or a 2.7 with cams, Id fix the existing oil leaks, add tensioners, rebuild the carbs, and put it back in the car.

If turns out to be a fairly stock 2.4 T motor, I'm thinking of selling it off. Id keep the webers and go for a 3.0 or a 3.2 short stroke with the carbs and a nice cam setup.

Best case is that I clean up the existing engine and put it back in the car. I'm trying to make sure I know what Ive got before I start changing things like the front suspension components.

Thanks again guys.

[911pcars]

Wayne,
You're not that young are you? "Punched out" is an old hot rod term for overbored (larger P/C).

Shuie,
The most common method to find out is to remove the cylinder head and measure the cylinder bore. A more involved process would be to tip the engine on it's side and measure the volume of the cylinder + combustion chamber (w/piston at BDC) using liquid from a measured burette through the spark plug hole. You may have to do some research on chamber volumes and do some calcs and extrapolating to arrive at a best guess of your engine displacement.

However, before you get too far into dismantling the engine, hook up a battery to the starter and perform a compression test (even a leak down test). From this, you'll have an idea of the integrity of the engine. "Smoking" could indicate worn valve guides or valve guide seals, tired oil rings, or merely an overfilled oil tank or a leaking valve cover gasket.

To determine what camshafts you have, use a dial indicator and magnetic stand (can be purchased inexpensively). Remove a valve cover and measure the valve lift at the rocker tip and compare with published cam specs (do a search here). A degree wheel attached to the flywheel or crank pulley will give you a more accurate picture of valve opening/closing specs.

My apologies if you have no idea what I'm talking about. If so, find someone with the tech background to assist. You may have to pay a shop to perform this exploration.

Sherwood Lee
http://members.rennlist.org/911pcars

[Bobboloo]

What is the engine type? It should be written on the case to the right of the fan support next to the oil pressure sender. It should look something like 911/91

What's the VIN on your car. I'm guessing that maybe it's a 73.5'T since you say it has a 7R case.

Are the cylinders iron or alloy? If they're iron they should have an rust orange color since they would be rusted on the surface.

[Shuie]

chassis number is 9113101911, engine is 6133699, case is stamped 901.101.101.7R. Engine and chassis are for a CIS 73T. I dont remember seeing any rust on the cylinders.

[Bobboloo]

I know that the 73' T (MFI) cars had iron cylinders but I don't know if the 73.5' T (CIS) cars had the iron cylinders also. If they did then it would be safe to assume that your car has had the cylinders replaced if there is no rust evident on them.

That particular case (2.4 7R) is the best to build on for a mag case in my opinion.
1. It's a 7R the most reinforced and
2. It's a 2.4T the least stressed of the 7R case motors.

[Wayne 962]

Got it - I thought that's what you meant, but people have different meanings for different words these days (especially with the recent Ricer craze).

There's no easy way to determine if you have a big bore kit on there. Compression test would not tell you anything useful, as compression is somewhat unrelated to displacement. Measuring your valve lift may tell you what you have, but it's somewhat difficult to get an accurate reading if you don't have the proper tools...

-Wayne

[blau911]

Guys,
How about putting it on a dyno? If the 2.4T engine was rebuilt with different components, you would see a significant difference in hp. Your 73T was suppossed to put out only 140 hp @ 5,600rpm's. If the engine was rebuilt to S spec's, the dyno would show that you are putting out something in the neighborhood of 190hp @ 6,5000rpm's. For an RS, you would be putting out 210hp at 6,200rpm. Granted, this would not let you know exactly what is inside creating the extra hp, but it will give you an decent idea. If the dyno testing shows good output, do a leakdown and compression to see what kind of condition the engine is in. If the dyno test and leakdown/compression are satisfactory to you, put it back in and plan to re-build it when it breaks instead of worrying about it now!

[Wayne 962]

Not a bad idea for fun, but a poorly running 'S' engine will put out as much HP as a finely-tuned 'T' engine, so it won't really tell you what's inside...

-Wayne

[jluetjen]

My goal:To end up with a fun car better suited for the street than pure track. I'll do some DE's, but I wont try to race it competetively. ... If my current engine is worthy, Id obviously like to clean it up and keep it.

OK - what about the current motor don't you like?

I have only driven the car gingerly 3 or 4 times since I bought it so I have no comment on performance or feel.

In order to really assess what you have and what you'd like to do, you're going to need to take it out and run it up to the redline a few times and see how it feels. Maybe try a DE or two before you pull the whole thing apart. Otherwise you're going to be spending a lot of money ($5000+) and time doing stuff that may not mean anything to you. Just because someone else says "Short Stroke 3.2's are the way to go" or "2.7RS's are the "sweetest engine"" doesn't mean a thing since those people won't be living with your car and the associated bills resulting from the rebuild.

Anyhow, some possible scenarios...

1) "Holy $hit! This car's performance scares me, I could hardly hold on!" -- Ok, Don't rebuild the motor for more HP, but rather go with something that is easier to live with or else skip the rebuild for now and spend the money on more DE's until your skills have grown to match the engine's capabilities.

2) "Man as soon as I got to 4000 RPM it started missing and was killing mesquetos for miles around with the smoke" -- Ok, it looks like a rebuild will be needed sooner rather then later. I'd recommend totaly up the expected bills for the required items as well as the "do it while your in there" items and compare it with your budget. If there is money left over, do some upgrades. Alternatively buy a larger engine, but keep in mind that there are few if any guarantees, so the 3.0 or 3.2 that you buy to drop in may be just as bad as what you pulled out. Remember that the seller is always selling for a reason.

3) "Yeah yeah", It pulls right to the rev limiter at 6500 RPM cleanly, but it really doesn't have the punch that I wanted from X,000 RPM on up." or... "It runs fine but it keeps running out of steam just before my next turn-in which forces me to put an extra shift in which is killing my times at my last DE", or whatever.

Now have have some specific issues that you can try to come up with a plan to address.

Remember, someone wiser then me once pointed out that...

"$peed is a function of money. How fa$t do you want to go?"