Underwhelming coronet

[dubber91]

Hi all,

I’m the recent proud owner of a 1965 two door coronet. It looks to have been well looked after and has loads of upgrades in its time.

It’s a 440 car, but it’s fitted with a small block bored 318 (326ci) with balanced bottom end, edelbrock performer heads, Keith black pistons, Holley 670cfm street avenger carb, comp cam and lifters, cLevite bearings, cloyes timing gear, Mallory ignition, and ceramic headers. It’s bolted up to a 727 torqueflite, machined to take bolt in bearing, updated torque converter with B&M shift kick and kick-down kit.

It’s been fitted with some muffler bypass valves and sounds great. The issue is I just find the thing quite underwhelming in terms of straight line performance. I’m wondering if it’s down to the trans or rear differential? It’s only really comfortable sub-70mph on the motorway, so was considering a gear venders overdrive unit as well.

What are your thoughts? Should this sort of combo not disappoint or am I asking a lot? I’ve not driven a lot of American motors so don’t really have a benchmark. Also never drove this with a stock 318.

Assuming everything is ok, what might I want to consider upgrading for a better drive?

Many thanks all- pics for interest

 

[Dako]

In '65 the '440' on a Coronet was a trim level. Engine options were: 273, 318, 361, 383, and 426 Hemi. The original 318 would have been a 'Poly' 318. Looks like you may have the later ('67 and later) LA 318. Very nice car though! Drive it and enjoy it!

 

[496 polara]

Verify basics. Compression,Timing,full throttle on the carb opening.

Rear gear ratio?

With no known cam specs what rpm are you shifting at? What rpm does it stop pulling hard? Can you get any timed runs for 0-60, 1/8 mile, or quarter mile?

Depending on the camshaft that motor should be capable of anywhere from 325-375hp.

Very nice car!

 

[Pecos Bill]

With the car running, put one foot on the brake, held to floor, put shifter in Drive, and put your other foot on gas, and ease into the throttle a little bit. How well does the car pull?

 

[WileE]

What is the C.R. ? What are the cam specs ? Install straight up/advanced/retarded ? Ign timing ? Rear gear ratio ? I've built quite potent 318's back in the day, you should be satisfied with the performance of that engine in that car.

 

[GTX MATT]

Realistically you’re probably asking for a lot, it can be made to make more power but you’ve probably got a 300-320 net horsepower engine there without knowing more specifics.

Do you know which comp cam it has, or what pistons? Looks like it has stock manifolds on it? Gear ratio? Which converter?

There could be power on the table if the ignition timing isn’t optimal and by tuning the secondary opening rate by swapping the spring, but it isn’t likely to set the world on fire. Ignition timing should be around 15-20 degrees at idle and 35 degrees total (without vacuum advance plugged in) at around 2500 rpm for best performance. You can probably also use the lightest secondary spring available.

I guess the important question is what kind of performance are you looking for?

 

[Geoff 2]

It is a reasonably heavy car......& only has 318 cubes to push it along. There is a limit to what 318 cubes can do....

 

[Runcharger]

Great looking car. All above factors could be an issue. Cam specs, torque convertor matched to camshaft, rear end gears, carb tuneup, ignition tuneup. I think the car could run nicely but if things aren't matched you would be disappointed. If you could possibly find out camshaft specs, convertor specs and rear end gears we could help you from there. Otherwise we'd be guessing.

 

[dubber91]

Hi All, whilst i have stacks and stacks of receipts, the detail of the assembly is not clear. Could i infer CR from a Compression test?

The Cam appears to be a High Energy Comp cam, hydraulic lifters. https://www.compcams.com/high-energy-218-218-hydraulic-flat-cam-for-chrysler-273-360.html

Heads should support 330bhp. Is there any way of confirming torque converter specs? Will a torqueflight always change at the same RPM regardless of load? Mine has a kickdown cable fitted.

Regards

 

[lewtot184]

Is that a single plane intake manifold?

 

[toolmanmike]

I would check your rear gear ratio first. It could have a 2.76 or a 2.93 in it. I would suggest a 3.23 or a 3.55 for performance depending on the type of driving you do. Not that you would want to change cams but, it is easy to over cam a 318 and you can easily loose your bottom end performance (which is where you spend most of your time anyway) Often, even mild cams benefit form a higher stall torque converter and a higher numerical rear gear to make them work. I would do a lot of research with the overdrive. A 318 is a pretty low powered powerplant to pull an overdrive at low RPM. A friend on FABO has a 408 stroker with plenty of power and torque and a O/D and it works well. But, he has a lot of power and torque at low RPM.

 

[Runcharger]

That camshaft should be okay for that combination I think. What is your total ignition advance? At what RPM does your ignition advance not increase anymore? Then it might help to get a wideband O2 setup to dial in the carb, they make it quick and easy to get it dialed in.

 

[oldkimmer]

If you’re looking to upgrade the power and torque u should look at the BluePrint 408 strokers. They come in all different flavours. U can even just get the short block and use your top end on it. U can offset the cost by selling your 318. Kim. @johnnymac

 

[dubber91]

Is that a single plane intake manifold?

It’s an Edelbrock performer. Not sure otherwise?

I would check your rear gear ratio first. It could have a 2.76 or a 2.93 in it. I would suggest a 3.23 or a 3.55 for performance depending on the type of driving you do. Not that you would want to change cams but, it is easy to over cam a 318 and you can easily loose your bottom end performance (which is where you spend most of your time anyway) Often, even mild cams benefit form a higher stall torque converter and a higher numerical rear gear to make them work. I would do a lot of research with the overdrive. A 318 is a pretty low powered powerplant to pull an overdrive at low RPM. A friend on FABO has a 408 stroker with plenty of power and torque and a O/D and it works well. But, he has a lot of power and torque at low RPM.

Is there a stamp on the case I could check? Or am I removing the diff cover?

 

[lewtot184]

It’s an Edelbrock performer. Not sure otherwise?

Is there a stamp on the case I could check? Or am I removing the diff cover?

Take a picture of the intake/carb with air cleaner off.

 

[440 4 speed]

Welcome to the site.
If you post a picture of the fender tag, someone could tell how the car was built originally. Especially the rear differential ratio. Most likely that wasn't changed. If it is slow from start, I would believe it might have a 2:94:1 gear ratio. Fairly common back in the day here.

 

[toolmanmike]

Is there a stamp on the case I could check? Or am I removing the diff cover?

Probably nothing on the case. Jack it up and spin the driveshaft and watch the wheels turn. Sure Grip carriers will spin both wheels in the same direction. Open carriers will spin the wheels in opposite directions. If so, block 1 wheel and count the revolutions. A mildly modified LA 318 with the right rear gear should make the car run pretty good unless you are expecting more performance then you should think about may be a stroker or a big block.

 

[lewtot184]

Factory 318 or 273 would have had a 741 case 2.93 axle ratio.