3.0 Engine Build Advice
 

I picked up a nice 3.0 liter longblock the other day. It's a 78' with the big ports. It had a few broken lower head studs (typical Dilvar), I tore down the engine, everything looks really good. The engine had never been rebuilt but had approximately 100k miles on it. The cylinders look perfect (cross hatching all over with no wear marks) as do the pistons and cams. I'm not sure I want to dump the pistons and replace them and the cam. I plan to run a set of Webers on this engine, the car will be mainly for street except for the occasional weekend autocross. The pistons are the lower 8.5/1 compression ratio. I was thinking about having the cylinders cut down a bit to raise the compression ratio to somewhere around 9.5/1.

My questions are these:

1. Can I safely bump up the compression ratio to 9.5/1 using the stock CIS cams and stock CIS pistons?

2. Can I get the distributor re-curved, can I use it as it is? If it needs to be re-curved does anyone know a good place to send it off to?

3. Has anyone used the GT3 rod bearings on a set of 3 liter rods? I was told that they would fit, they are a coated style bearing.

4. What sort of jetting (air correction, mains, idles, emulsions) will I need to run in my Webers?

5. Assuming I will be running headers and a relatively open exhaust, what sort of power should I expect to be able to pull from this motor using the stock CIS cams and pistons?

6. While I'm rebuilding the engine is there anything I can/should do outside of stock? I plan on having the crank knife edged and the rods balanced.

Here's what I have read, and/or experianced.

I would not try to shave off the heads. Instead replace the pistons for 9,8:1 Mahle, but make sure your cylinders are made of Nikasil (Mahle), NOT Alusil, (Kolbensmitt). (I replaced the entire P/C set)
Also, if you want to use carbs, then replace the cams for a more agressive profile.

I beg to differ...

1- Yes. The euro cars typically ran the higher compression pistons and cylinders. Make sure your timing is right as pinging on SoCal gas may be hard on the engine.

2- Jerry Woods Enterprises does these rebuilds.

3- No knowledge of this. There's nothing wrong with the standard 3.0 bearings, and they often last hundreds of thousands of miles if the oiling on the engine is fine. So, I would think this would be an overkill, even if it did work.

4- It depends upon the cam. I would run as hot a cam as possible, assuming you don't have to pass smog. You're in SoCal, so I'm not sure what your plans are. If you run a hotter cam, then you need to modify your pistons, or get a more appropriate set.

5- Probably about 10-15 HP over stock, maybe a little more. Tuning the carbs is key to this.

6- Knife edging is not really necessary. Spend your money on some S-cams and new pistons and ditch the CIS stuff, particularly if you're planning on running carbs.

Hope this helps,

-Wayne

Oh, and check out the Engine Rebuild Book, of course, it's all in there...

-Wayne

Wayne,

Just saying man ... I recently completed a rebuild and got much much (much) more response on the other forum.

If you compare traffic stats it is clear that the tech forum is significantly more active.

I have only been signed up here for a couple of years so I am not sure when the Rebuild Fourm started. Maybe it is still in its infancy?

Anyhow, we can agree to disagree on whether or not 914obsession will see much traffic here.

Cheers,
Craig

Perhaps another direction.

Bump the compression 9.2-9.5 :1, add DC 22 or WEB 2021 cams and keep the CIS. The CIS injection can be simplified and made to perform quite well.
We have built many of these engines and every customer felt satisfied. The key to the CIS is simplicity. It just plain work.
They start, they offer very smooth operation and even great fuel mileage. The real issues with CIS performance would seem to be exhaust related. Install SSIs or a nice header system with an M&K sport muffler and the throttle response seems to come alive. Expect a number around 220 very drivable /reliable HP.
IMHO carbs should only be used when there is no other choice.

Don't cut the heads or barrels. This only causes dimension problems with things like chains and chain housings.

With the above combination, the the 004 -007 distributor will work fine, but if you decide that you need it, Supertec offers all kinds of distributor services.

We only use GT3 rsr bearing on 53mm journals. They cost a little more but they are worth the cost in peace of mind alone. We are also using the GT3 mains in place of standard Glyco replacements.

Skip the knife edging and have the crank cross drilled instead. Although knife edging offers some weight reduction and really looks cool, in general the gains are minimal.

Stoney (flintstone) on the forum can attest to this engine build.

This car is track driven (PCA, POC) exclusively and the customer couldn't be happier. I offered to swap this 3.0 engine into his 73 1/2 T and building him a race engine for his 74 RS replica. His response was why screw up a great car by changing the engine. The 73 1/2 T got a nice 2.7.

http://forums.pelicanparts.com/uploa...1219718348.jpg

http://forums.pelicanparts.com/uploa...1219719464.jpg

Thanks for all the advice! To save some money, I plan on using the original CIS P/C, they checked out fine. I mooned the cylinders and boat tailed the case ( I know some people think that this is a worthless mod, but it only cost me my time), I'll have to have the cylinders all shaved down at least 5 thousandths due to a little bit of a blemish on one cylinder where the head gasket was blown due to two cracked head studs...

So, it seems like it's not a good idea to have the machinist shave off any more than he has to on the cylinders, bumping up the compression seems like it won't help on my stock setup (minus CIS and with 40IDA Webers). I'll also forgo the knife edging of the crank, but will have the rods checked and balanced along with the flywheel. I will also have the heads gone through. It also appears that I can use my stock 78' CIS distributor with my carbs?

Can anyone tell me whether slightly advancing or retarding the CAM timing will be of any use?

Thanks!

Interested in knowing what's involved with "simplifying" the CIS? I keep struggling with what to do with my 3.0 when the time comes, but 220 or so seems pretty respectable.

Todd

CAREFULL! The top of the cylinders has a bevel as well as the niky coating coming over the top... I can't remember who, but he lathed off .003 and still had resonable results, but if you take off too much or mill it off you risk destroying the coating completely... see:

http://forums.pelicanparts.com/911-engine-rebuilding-forum/339225-3-0l-sc-mahle-head-gasket-groove-machining-can-i-do.html?highlight=ring

Enjoy!

-Michael

Henry is right when it comes to CIS systems. I have a '83 3.0L engine running with a fine tuned CIS and get 23-26 miles per gallon. On a 628 mile round trip last year, I averaged 26.6 miles per gallon. I had to recheck my math to be sure I wasn't making it up since I didn't believe it when I first saw the numbers. However, around town, the numbers do drop a bit, but that is to be expected with these cars.

Very good points made!!

Everyone I talk to thinls they need the 300hp hot motor.. many formulas to achieve and not many of the reach the goal.

Henry:, Very nice set-up in the blue car... any gain from a similar set-up w/twin plug & crank fire?

Would you say that DC 22 or WEB 2021 cams are about as aggresive as you can get with the CIS

Also, I remember talking with someone who had a p/c set for the 3.0 that was 98mm, 10:1 (short stroke 3.2) for CIS.. This was also based on a 78 engine. Any thoughts on this set-up?

Thanks.. great thread!

Paul

Maybe OT but I am also very interested in the 3.2ss ,I have a C3 that I am thinking of refreshing the top end on and would like to know if I can rebore the cylinders and go 98mm.I suppose the heads & valves would also need some work or upgrading ?