RPM ?s

[2 Darts]

Tried to ask these questions over on the /6 Forum, but their server is kinda buggy at present. I have a 73 Dart 225/904. This is going to be the first /6 I have ever done anything with other than drive. The goal is to come up with a good highway cruiser. Want to keep it on regular gas. After reading some books on the /6, there are some questions that remain unanswered.

1. What is the RPM for a completely stock 225?

2. Is the 225 rev limited due to lack of air? (i.e. Would it produce more RPM is cam and carb were opened up?

3. What is a practical redline for a mildly built 225?

4. I have a Comp Cams 260H and an AussiSpeed 4bbl manifold I intend to install. Should I upgrade the valve springs, too?

5. Have read that there are problems with oiling the camshaft at high RPM. True/False/Comments?

6. If you have grenaded a 225, how did it happen? (If this get's too big, maybe I'll enlist a site admin & start a separate thread.)

 

[C130 Chief]

I'm sure there are other opinions out there, but here's my take:

1. About 4500 RPM.

2. Horsepower limited by lack of breathing stock. RPM limited by soft stock valvesprings. Ultimately limited by the long stroke (piston sped) and 4-main crank (harmonics, strength). Exhaust system MUST be upgraded as well.

3. 5500 RPM with stock pistons, maybe 6500 RPM with lightweight forged custom slugs.

4. Yes.

5. Not sure about that. As the cam lubes by oil slung from the crank, if the cam runs dry you've got bigger problems.

6. I would think bolting a 4 barrel onto a high mileage engine would do it if that's your goal.

 

[vynn3]

4. I have a Comp Cams 260H and an AussiSpeed 4bbl manifold I intend to install. Should I upgrade the valve springs, too?

Yes, you should always upgrade your valve springs to match an aftermarket camshaft.

5. Have read that there are problems with oiling the camshaft at high RPM. True/False/Comments?

I'm aware of COMP cams having oiling problems/flaws, but not slant six cams in general. Most experienced slanters seem to have gotten away from Comp cams. There is an Erson group buy you can find out about over on slantsix.org that I'd recommend as an alternative. I'm not running one of the group buy cams (spec'd by Doug Dutra himself), but I'm running one of the last "standard" Erson 270 cams, and I'm very pleased. The only nice thing about Comp Cams with regard to slants is that their website is bigger/better. The Erson takes more effort, but it's worth it.

6. If you have grenaded a 225, how did it happen? (If this get's too big, maybe I'll enlist a site admin & start a separate thread.)

Mine spun a main bearing. Does that count as "grenaded"? Gave me the opportunity to build my long rod engine, which I love.