my '68 has a numbers matching 327/300hp that appears to be original and stock, 82K miles. The car is still fun to drive, but the motor seems tired. I know she could benefit from a set of headers and a tune up from somebody that knows what they are doing with a QJet, but what other options do I have to get more HP? I want to keep the same block, and I'm not cutting or changing the hood, but I'd be open to most anything else.

What kind of gains could be had with heads/intake/cam? What about a stroker kit? I thought I read somewhere that a 327 block can't be bored...?

Anyway, all suggestions are welcome, and if anyone can recommend a shop in the Chicago area that can do the work--even better.

Thanks,

Chris

 

If I remember correctly, the '68 327 is the large journal version and has the same main journal size as the 350. The 302 (Z/28 motor), 327 and 350 all share the same 4 inch bore. Most of these will go up to 0.060" over. What does this mean? A 383 stroker kit should go right in your 327 block.

 

As said above the 68 327 is a large crank and will the 383 kit for sure, but it sounds like you want the car untouched cool, but then I would say leave the 327 stock and buy another block and build that to what ever power level you and just set the 327 aside until?

 

I would bet that your engine...as is...has more capability than it is giving as presently set up. The most gains for little effort/cost can be achieved by: 1) performing a good tune-up, including points, condenser, rotor, cap, wires and plugs; 2) rebuilding the carburetor or having it rebuilt; and 3) rebuilding the distributor and establishing a new timing 'curve' for it.

Some things you should know:
Your Q-jet...if rebuilt and set up properly...has capacity for a much larger engine than yours, only supplies what fuel/air mixture is needed for your engine, and is more economical that most any other carb made due to the small primary venturi design. Don't go buying a new Holley carb because your 'buddy' told you that will be better for performance. NOT!
Doing a tune-up on your engine is a PITA because of all the sheet metal heat deflectors and radio interference shielding that resides on it. Running plug wires...and even getting to the plugs...requires getting under the car (as well as going in from the top) and using a variety of wrenches/sockets/adapters to get that job done. If you can do it yourself, do so. If you have to have it done...and require them to put all of the hardware back where it belongs when done...it will cost you a bundle--mostly because of the labor involved. Learn how to do it yourself, save a ton of money, and get satisfaction from the DIY fairy. Also, consider doing a cylinder compression test when you have the spark plugs OUT. It is very easy to do at that point; all you need is a compression test gauge and a helper to crank the car. A compression test will tell you if the valves or piston rings are leaky or damaged. Knowing that might ease your mind about the condition of the engine, as well.
There are detailed papers on carburetor and distributor configuration for Corvettes in the Corvette Forum Archives and through other websites. With help from this Forum and a couple of instructional books, you can do the carb and distributor rebuilds, yourself. Again, you will learn a lot about those items as well as save a bunch of buck$.

Fix those things first; then check out the performance gains. If you need still more 'juice', then work on the exhaust system, heads, and cam.

 

all the above is correct. I would suggest keep it and build a new one.

 

Thanks to all for the replies. Cap, rotor, plugs & wires all new last year -- not sure about the distributor internals. The carb was sent out for rebuilding last year as well, but I don't think its properly tuned. Off-idle hesitation, missing in hard corners, general sluggishness. I didn't do that tune-up; once I got the bill, though, I resolved to start doing the work myself. I haven't tested the compression yet or looked at the dwell/timing but have the tools. I would like to tune the QJet, but it seems like a complicated procedure, so I've been putting it off. I will try a tune up and see how she feels...

But 383 cubes sound GOOOOD...

 

I have a 327 out of my '67 Camaro
Bored .40 over , crank is cut .120 on mains & .90 on rods ....IE ....it CAN be Bored

 

Numbers matching? Yank the 327 out, preserve it and bag it up on one of those 4 wheel carts. FInd a crate 383 (or build one) drop that in and drive it like a rental car. That way you don't need to worry about killing your NM engine. Yes, it'll sting if it lets go, but nowhere near as much as if the NM 327 does.

 

Setting up the Q-jet is fairly easy, except for fine tuning the rod & jet sizes. The best thing to do is get a book by Cliff Ruggles (Border's, Barnes & Noble) and follow the set-up instructions. One of the most limiting performace issues is the condition and set-up of the distributor. It is not a difficult device to disassemble/reassemble; and, with timing being so critical to good performance, that is where many folks leave so much power untapped. Again, get a good instructional book on the dizzy; take it apart, clean it up, replace the vacuum can (with a correct unit), test the feed wire for shorts/continuity; then rebuild it per instructions. There's really little expense (other than the books) to working on either device, and the benefits are surprising. GM set up the dizzy for 'minimum warranty' damage; in other words, its set up to keep engine power down. Simple adjustments can bring your car to life.

Whether you keep the same engine in the car or bag the original and put in a 'slave' engine is really up to you. I have my original engine still in my [almost totally original] '71 coupe. I step on it occasionally...but don't really wind it up tight. The major components have held together for 40 years; they're probably not going to throw craps from how easy I drive it.

 

 

FYI the sb Chevy bottom end is good for well over 300K mi. You would have to prove you have a bad block with a compression test and a leak down test. 82k mi ain't even midlife yet.

Yes, learn how to tune it before any major engine upgrades like cam or heads. Get into your distributor and set a timing curve. Set the mixture on your carb - try a holley to learn on like a 4175 spreadbore replacement. Holley carbs are simple and a good place to start to learn what jets and secondary mixture plates do. This will get you ready to tune when u change a cam or heads.

BTW i'm looking for a large journal 327 shaft like yours for a project. If a 383 shaft is going in your '68 block i'll take that 327 shaft off your hands for u.

cardo0

 

Thanks again for the replies. I will take a shot at a thorough tune-up this weekend and see where I get.

 

I gotta learn to lift when the valves start to float

she's been rebuilt so many times theres no telling what I have in that short block ???

CardioO > if you need a large journal 327 crank my builder had a few .
Name is Randy Curtis in Corpus Christi,Tx. Randy's Performance and Machine Shop , also might try RPM Machine > Bill Rogers also in CC Tx.

 

Chris,
Take the advice from TimAt and pull the engine. Find a good 350 block and use some of the components from your 327, pumps, alt, carb, to save a few bucks. I have a 68 / 327 and rebuilt the engine with a few more HP than stock but now wish I would have done the above. The care runs well but I could of had a lot more power with a little more cash if I had taken more time to think it through. I am in Palatine, feel free to call if you would like to discuss. 847 963 8134