1970 340 dart

-
What do you mean?

Like back 40 years ago on a new motor back then?

Today its worn out and has been rebuilt most likely in the past. Then it depends on what pistons, bearings, new rod bolts, etc was used in the rebuilt.
 
I'm not sure, exactly, but it has the new performance cam (purple) and was bored .30 over. As far as we know all that you mentioned were replaced, but we don't know with what. So, if a person wanted to take it down the 1/4 mile strip, what would be a good limit to set for the shift? We usually shift between 5200 and 5500 RPM and are not sure how high we could actually take it. Any ideas?
 
Wind it til it blows up and back off 100 RPM

About 5300-5500 is all the stock set up was good for. Anything more was just twisting it for no reason.

The old ad was "6000rpm for under 3K" or something like that.
 
Cracked was just havin' a little fun with ya! In all honesty, if you aren't sure what parts went into the the rebuild, 5500 should be safe,6000, maybe. Which purpleshaft cam are you running?

BTW,I noticed you're in London, I've got a bunch of in-laws that live there, and we visit fairly regularly. With any kind of luck, I'll see your sweet looking Dart out and about!
 
Ok, you need to start guessing. Any idea how long the rebuilt was done? When the motor is cold, best parked outside during the night, do you hear a little piston knock the first few mins when first started / if so it might indeed have forged pistons. If its nice and quite, they are cast or hypers;

Now true, some hot rods are so loud all you hear is the exhaust noise.

Do a compression check also and check the vacuum at idle. You get an idea how the size of the cam and the compression ratio.

And yes, 5,500 should be safe for all rebuilds. Done right, 7,500 is safe. Chances are your motor is somewhere in between.
 
1.jpg
 
Thanks Rick! That's the ad.

JD was correct I was just messing around.

You don't mention which cam you have. Purpleshaft is a generic term for MP cams. A 208/218 @ .050 .429/.444 hyd is going to run much different than the .590 solid cam with 265 @ .050. Need to be more specific.

I'll go back to my cave.
 
Ya...you want to shift it where the engine reaches max power.
Over revving it just looses time and power....and possibly parts!
as stated 5500 should be safe.
If you have a rev limiter like MSD ignition has then you can adjust Redline to fit your engine...
 
Your shift point is the exact rpm of peak horsepower. Anything more than that and you are just wasting E.T. Like others have stated a safe shift point for an engine with your setup(and I don't know them all) would be 5400 to 5500 RPM.
 
One of the limiting factors will be valve springs. With stock springs the 5200-5500 rpm will be about right. Theoretically, with a bigger cam and stock springs, the valves might starting floating earlier.
 
crackedback said:
Wind it til it blows up and back off 100 RPM

About 5300-5500 is all the stock set up was good for. Anything more was just twisting it for no reason.

The old ad was "6000rpm for under 3K" or something like that.
Click to expand...

"Damn, not much of a sense of hummor!"

I was going to say put a brick on the petal and see how high the needle goes.

Seriously, Like what has been already said, You need to know the specifics of your engine. Which camshaft, what pistons and compression ratio, how fresh is the rebuild, etc. All the info you can gather will help us all to help you.
 
Thank you all very much! We are taking it to the track for the first and possibly only time tomorrow night. We just don't want to break it. We appreciate all the information everyone has given and aside from knowing what was put into the rebuild, I think probably the best thing to do is try different shift points and see where the real power is. I think he mostly wants to beat his boss, who has a '70 Cuda 440 six pack and an animal behind the wheel! I didn't know all those things could affect the redline so thanks for that. BTW, the tach is not factory and the MSD doesn't have a rev limiter in it. Didn't think we'd need it! Might have to switch it. So, thanks again and I'll let you know how it went.
 
I think it depends on what type of cam you are running, a higher duration will make your power band higher in the rev range and make your redline higher than stock. Of course your bottom end will have to handle it.
 
You must log in or register to reply here.
-

Back
Top