Just lucked into a 1969 convertible, 1 owner previous to yesterday belonged to one of my best friends so I know the history of the car. Has the L46 350. I’ve been out of performance cars since mid 70s and I haven’t kept up with technology. The L46 on this car has been well maintained and has 61k miles on it. Would anyone interested in giving some advice as to whether it would be advisable to try to get some additional horsepower and if so, what should I be looking at doing? Don’t want to get too radical and do anything to reduce drivability.

 

If it is an original car leave it alone don't butcher it up like so many do Post some pictures

 

Picking it up Saturday, will take some pictures and post them. It’s definitely all original except for normal maintenance. My friend was a fighter pilot and later an airline pilot,fastidious about maintenance. Was a daily driven car for about 4 years, occasional Sunday drive since then.

 

Dear Lucky. Leave it alone. The L-46 is a pretty stout engine with 350 HP and 385 Ft lbs of torque. It already has the big valves. It is a four bolt main.

I obviously own a very similar car and my only recommendations are put a Pertronix Ignitor ignition system in it. When I dynoed my engine in 2002 it was making 383 HP.

Bigger headers would help too.

This is the absolute 'sweet spot' for SBC's. Though LT-1's are slightly more powerful, they are also more problematic.

Unkahal

 

Timing chain at 60K is maybe stretched a bit. I seem to remember having my valve seats replaced for unleaded.

A 383 doesn't look any different although it might be a bit stifled by the stock exhaust. It pulls a lot harder. That's a bigger mod, lots of torque and your engine builder needs to know not to deck the VIN. And you need to pull the motor. Then you're into crazy stuff, roller cams, etc. so definitely not worth it for a low mileage car.

However a lightweight clutch and flywheel with a new timing chain gets you a nice little "rip" out of the motor. Wait till you need a clutch for that one of course. Some kind of electronic ignition as L46 suggests is a nice upgrade and easy.

All in all the L46 is a really nice motor, you will be quite happy with it in stock form.

 

Without getting into the bottom end - intake, and exhaust - if you want to go a little more heads and cam. This is all easily reversible if you would want to go back to stock in the future, I agree with the others, leave the block itself alone at this point.

 

I agree, leave it alone. worth far more stock standard and plenty fun to drive just as it is.

 

did the L46 come with a plastic timing chain? if so, it needs to go NOW! it was designed to fail in 5 years. and the only ones still in cars are in collector's items that spent their lives pampered and only driven occasionally. 65 GTO vert i bought in 76 for 200 bucks. (man i wish i kept that car.) had a 326 somebody threw in it. i missed second gear. every tooth sheared off. and this was a 10 year old chain. not 50.

 

A completely stock L-46? Leave it be. Very nice, strong engine but still a good street machine. Why mess with 'perfect'??

But, if you just want to beat the bejeebers out of it, pull the engine and store it "as is". Then stick a crate engine in it and have your fun.

 

Timing chain advice is solid.....change it now or later....pick one.
The L-46 is a great engine....and the leave it alone advice is somewhat solid too.....but they respond well to a couple of changes. The first is a real exhaust with long tube headers.....which, to me, does nothing to devalue the car....the stock manifolds have a 2" outlet and is a real cork........the other is a 2101 Performer intake with the Fel-Pro 1204 intake gasket to block the heat riser. Contrary to the BS you hear about intakes needing heat to function properly, blocking the heat riser cools the intake carb pad a TON.....and helps cure vapor lock issues.....the last thing is a real timing curve and proper timing settings, this is pretty huge, and works with the other two mods to optimize power and efficiency......
A bone stock L-46 compared to one with the three mods I mentioned will pick up over 50hp at the tire and about 40ft/lbs. torque off the bottom into the midrange.......this is noticable, and makes for a sweet sounding engine to boot. It will run faster than an LT-1 with the same mods on the street.
If these mods were done...it would be in your best interest to contact Lars to have him go through your carb and fatten it up slightly....

Jebby

 

Exactly the kind of input I hoped for. I think I’m going to wait until I actually get the car Saturday and drive it some to decide. Leaning to doing the ignition and timing chain replacement mentioned. Exhaust and manifold changes will take some thought. I have a 2013 Cadillac CTS-V and my son has a 2012 GT 500 Mustang both rated over 500 hp ratings. Not sure I want what I regard as the best car in the garage to be last in the horsepower department, on the other hand I’m not buying the vette to race but because it’s a classic and the idea of keeping it original has a lot of good sense. Absolutely not sure the hp ratings will matter once I drive it some. I live about an hour south of Bowling Green and got the chance to do a Chin track day last fall with the Cadillac on the track behind the Corvette museum. They had about 80 ZR1 2021 vettes sitting in the parking lot waiting for pickup… awesome sight!

 

Picked up my ‘69 convertible today. Pictures at this link

2 surprises, first it’s an L48 not L46. Second, the brakes are scary bad. Barely work. Good pedal, just don’t slow down much. What kinds of things should I look for to find the problem? Manual, not power

 

Not to open a can of worms, but since you say you have been away from performance cars for quite some time, be aware of the changes in engine oils and the need for ZDDP in flat tappet camshaft engines. Do a search here as there are numerous threads on it and the result of flat cam lobes. Be aware for your first oil change and enjoy the car.

 

Read up on it, definitely appreciate the heads up

 

After thinking about the brake situation, seems to me that pistons frozen or sticky in the calipers would exhibit that symptom and sorta makes sense since the car has been used so seldom. Thoughts?

 

Lot of difference between an L-46 and an L-48. The latter is fine, but nothing 'special' so you can modify it as you please. I hope you didn't pay a premium price for it thinking it was an L-46.

Good luck with it....

 

Nah, I know the guy I bought it from and while fastidious about maintenance he didn’t really have a clue what engine was in the car so that didn’t affect the price. He cut me a really great price just so the car would go to someone that appreciates it. He and I have been like brothers for 40 years. For such a low mileage car, kept up so well which engine it had really makes no difference to the value to me. If I decide to go with more performance the 383 crate option looks good to me

 

Sounds like you are getting a terrific C3 which you can enjoy and make into what you want. Have fun with it....

 

so you didn't get screwed. and sounds like neither of you did. definition of a good deal all around. replace all 4 calipers, flex hoses and the master cyl. don't screw around rebuilding any of them. eat the core charge and keep the old ones though. rebuilding brake parts is for cheap poor bastids like me who have a high opinion of their own mechanical abilities...

 

Beautiful Lemans Blue with blue interior. And a 4 spd and low miles! Great find.
So it is a nice cruiser not a rocket ship. It will probably never keep up with a "V" without destroying all the originality of the car.

Put very good pads on the manual brakes and you may learn to like them, like Carbotechs or Hawks. Manual brakes in these cars can be very good, but always have long pedal travel.
A distributor & carb tune will help that L48 a lot, as mentioned.
Beyond that, a set of nice aluminum heads and a roller cam will make it fly like it were another engine. (Paint them stealth orange?) But then you need exhaust too. That's as far as I would go with it.
A 383, well, that could be your rocketship motor, but then it needs exhaust, and gears, or a 5 spd, and it is such an original low mileage car, it would pain me to do that to it, if it were mine.