Increasing the power of a Chrysler 65

[Guest vintagent]

I'm currently looking to modify my standard chrysler 65 engine, so as to acheive a similar power to a chrysler 75, I was wondering if there are any improved camshafts, oppurtunities to bore out the cylinders etc? Any advice or guidance would be great.

[Rusty_OToole]

Wouldn't it be simpler to buy a newer car?

I can't imagine why anyone would want to do this. But if you tell me what you want to use it for I can tell you how to hop it up.

[Guest 1929model75]

I would try to find a red head for it. I had one for a 65 sold it a few years back. The head should add around 9 horse.

[Guest vintagent]

we are planning to use the chrysler to do trialling in the UK, Vintage Sports-Car Club - Gallery see photos, this may not be your cup of tea but far from hotrodding. we've looked at red heads but aren't they just skimmed heads?

cheers

[Rusty_OToole]

The red head was a high compression head. Whether it had a different contour or was just the standard head cut down, I do not know.

When working on an engine like that aftermarket parts are out of the equation. You have to go back to the good old days and improvise.

There are certain time honored mods that can be done to practically any engine. Here are some of the most popular.

Skim the head for extra compression

Have the camshaft reground

Add an extra carburetor. This is done by welding 2 short pieces of pipe onto the stock intake, and topping each with a flange. There are exhaust pipe flanges that fit the stock carbs, available at muffler shops. Block off the original stub for a twin carb, or use 3 carbs. This may be overkill for your application.

You can buy a Holley Weber progressive 2 barrel carb and adapter instead of modifying the intake. This is probably the best and easiest carb for your app but does not have the old time look.

Install oversize valves and enlarge the intake and exhaust ports. Go easy here. Probably the best thing to do is gently clean up the ports and do a 3 angle valve job and let it go at that unless you are an expert.

Construct an exhaust header with the 3 front pipes going into 1 exhaust pipe and the back 3 into another. Or, split the manifold for dual exhausts (the classic solution).

Lighten the flywheel. Again, for your app you might want to go easy here as a heavy flywheel might be what you want for trialling.

Use the lightest pistons you can find and have the engine balanced.Deck clearance .040 to .060

Convert the distributor to electronic ignition and recurve as necessary.

Shim the spring on the oil pump relief valve to give 10 PSI per 1000 RPM

Do this properly and you should have the fastest Chrysler 65 on the track until the rod comes through the block.

Actually the Chrysler might be one of the best 1920s "cooking" engines to hop up. It was the first high compression engine and had a high specific output for the day, and it also has 7 main bearings and pressure oiling. They had considerable vogue in England and Europe, and won races in their day. They even finished in the money at LeMans, behind Bentley and Stutz.

Edited November 22, 2010 by Rusty_OToole (see edit history)

[28 Chrysler]

Do not cut the standard head down. The red head was made because the standard head could not be modified to hold up to the higher heat and pressures

[Rusty_OToole]

There was another mod used in the twenties to increase compression that is now long forgotten. That is to "dead end" the combustion chamber. The idea was to partly fill the combustion chamber with clay, and use the clay as a mold to cast a brass or bronze "chip". This chip could then be fastened to the head with screws.

[Guest vintagent]

Great cheers for the info guys, one final thing do you think there is any room to bore out the cylinders at all to increase the capacity?

[Rusty_OToole]

In those days all engines had very thick cylinder walls. They expected they might be rebored 2 or 3 times during their working life. It should be possible to bore the cylinders at least 1/8 oversize, on some engines it is possible to go up to 1/4".

Today you can have the block sonic tested and find out exactly how thick the cylinders are, whether there is any core shift or corrosion damage in the water jackets. This is especially advisable on an old engine like yours.

Would suggest you do not go too far with the boring bar, leave enough material for at least one more rebore. Partly to keep as much strength as possible in the block and also in case of some accidental damage that requires a rebuild.

[Guest 1929model75]

The combustion chambers look different then that of the standard silver dome.

[Steve29]

The picture below is from the "Features Brochure" and shows the difference between the two heads. The redhead and silverdome heads were designed with different combustion chambers. I couldn't find the reference but I read that the redhead design was licensed by Chrysler and was supposed to reduce pre-ignition, allowing the increase of the compression ratio to 6:1 which was very high for that time.

Edited January 18, 2011 by Steve29 (see edit history)

[Steve29]

Here's a quick follow up to Chrysler combustion chamber design that I couldn't remember when I posted my previous message. The engine was designed with Ricardo combustion chambers. The Ricardo heads created turbulence in the combustion chambers and made the engine quieter and more powerful. Attached is a copy of a page from a Dykes manual describing the Ricardo combustion chamber.