1970 440 Real World CR

[Mc MOPAR]

Does anyone know the real world compression ratio for a 1970 440 engine? From the research I've done on the topic, it looks like Chrysler rated them at 10.2:1. But I've been told enough times by multiple people that this number was not accurate, and that those CR's could be in fact off by 1 putting my engine at 9.2:1. Any truth to this?

 

[RUNCHARGER]

Yes; They come in about 1 point less so 9.2-1 or so. Which isn't a bad place to be.

Sheldon

 

[TC_Cuda]

The machining spec's from Mother Mopar back in the day were big enough to cause most engines to be off from the stated compression ratio
and yes it could be as much as a full point off.

The only way to be sure is to pull a head and measure or, have access to a compression ratio checker, My local race track has one for checking car in class racing.

 

[Mc MOPAR]

That's great news, because I really want to run the Whiplash cam in my 70 440 but there is a warning on there website to only install them in low comp engines 8.9:1 or less...

Whiplash cams are designed for the very low compression Mopar O.E.M. engines such as all the 318's, 360, 400 and all 383 & 440's built after 1971.

The factory built these engines with a combination of low compression and cams that produced very low cylinder pressure and low power (see this tech article CLICK HERE). Normally, to increase the cylinder pressure in these engines you would have to disassemble the engine, buy new pistons & rings (at a minimum), re-bore & hone, rebalance and reassemble. And then you would still need cam & lifters. The cost of this build-up could easily be $2,000.00 or more and take 2-3 weeks.

The unique design of the Whiplash cam will accomplish all of the same results for as little as $340.00 (cam, springs & lifters) and take about one Saturday afternoon to complete. The Whiplash cams are designed, like all of our "real" Mopar cams to take advantage of the .904" lifter diameter which increases the area-under-the-curve, for more breathing time. However, with low lifts (yes we consider .520" low lift) so that you do not need to remove the heads and machine the valve guides.

These Whiplash cams have become one of our top selling items and we have customer that want to put them in engines that are not low compression. The problem is that the cam will still raise the cylinder pressure and your engine may then require race gasoline or a mix of pump and race gas. As a general rule of thumb engine with a true measured compression ratio more than 8.9:1 with iron heads or 10:1 with aluminum heads should not expect to be able to run on just premium gas. And, whatever you do, DO NOT retard the timing to "make it work". That will "work" and also reduce your power & torque considerably. You'll be sorry!

So I should be ok, and if not I could change the head gaskets to composition which would bring my CR down to 8.2:1 as per the CR calculator.

 

[RUNCHARGER]

Hmm: Yes if your engine is untouched it will have big head chambers and thin gaskets. Honestly As you are willing to change the headgaskets I would take a head off and measure deck height and head chamber cc's to be sure of what you have. Do you have 94 octane at your Chevron's over there?
My son honed an original 69 440, put on some ported 452's and a Lunati camshaft and that engine rocks. A freind of mine put a whiplash in a 75 440 (about 7.8-1 true compression) and that one rocks pretty good too. Not so sure I would try the whiplash in my son's engine though.

Sheldon

 

[Mc MOPAR]

If I found some 452 heads, and had some work done to them. Would they not flow better and have less compression then the current mild ported 906s?

 

[RUNCHARGER]

Depends on the work done. I would stick with what you have I think.

Sheldon

 

[TC_Cuda]

I used a set of 452 heads on a 69 383 to lower the compression a little but, mostly because, it had harden seats and, they were ready to go, with a fresh valve job. I also installed a new mild cam at the same time and, the engine ran better than before but, of course I credit the cam with the improvement but, I know the heads didn't hurt the performance any IMHO

 

[Avalanche]

I put a whiplash cam in a 1977, 440. also had 906 heads.
It made a huge difference in sound and performance .
I'm not sure a whiplash cam would be the best for 69 440 with the higher cr.
There might be better options out there.

 

[mmissile]

Aluminum heads.