440 compression boost

[roccodart440]

What are your plans for the engine? Will it be an everyday street driver? If so, no need for close to 10:1. YOU HAVE 440 cubes at your disposal. It's gonna have pavement peeling torque regardless, as long as you build for the compression ratio you use. You'll be sorry sitting in traffic in the summer with heat soak when all it can do is spark knock and rattle. There are other ways to make one haul *** besides compression. Keep in mind the general rule of thumb is for every 1 compression point raised, your return is only about 3% all else equal. If it's a street only car, my recommendation is to work with the stock compression ratio and build the rest of the engine to match.

Just as you are saying you can build an engine around low compression, you can build it around more compression. Look at other engines that make good N/A power, they all have higher compression ratios, some into the high 11._:1 range.

They don't have to rattle. Choose the right cam and set the timing correctly and they function fine. YEs, this is easier to do with programmable timing and FI, but it can be done with a carb and mech timing.

Cooling one of these engines is not an issue so long as the cooling system is sized and set up properly.

Raising the compression alone may only yield 3%, which for some is a decent amount of HP, but an engine is a package deal.

What was the stock compression ratio on a 375HP 440? It's listed as 10:1, but reaching into the bowels of the search bar, a resident engine expert says it's 9.48:1 in reality. That was also with an antiquated iron head. Most everything now has aluminum heads and many have reverse cooling as well. (which you can run on a BBM)

 

[RustyRatRod]

Just as you are saying you can build an engine around low compression, you can build it around more compression. Look at other engines that make good N/A power, they all have higher compression ratios, some into the high 11._:1 range.

They don't have to rattle. Choose the right cam and set the timing correctly and they function fine. YEs, this is easier to do with programmable timing and FI, but it can be done with a carb and mech timing.

Cooling one of these engines is not an issue so long as the cooling system is sized and set up properly.

Raising the compression alone may only yield 3%, which for some is a decent amount of HP, but an engine is a package deal.

What was the stock compression ratio on a 375HP 440? It's listed as 10:1, but reaching into the bowels of the search bar, a resident engine expert says it's 9.48:1 in reality. That was also with an antiquated iron head. Most everything now has aluminum heads and many have reverse cooling as well. (which you can run on a BBM)

I'm a perfect example. The slant 6 I am currently running is a measured 10.2:1. It has the crappiest early cylinder head on it with the crappiest chambers. Although they are now 34cc lol. I had a pretty bad spark knock problem when I first got it running, but was able to get it tuned out. It'll run on 87 with no spark knock now, but it runs so much better on super that's what I use......well I've settled on 90 non ethanol and it seems to like that fine. So sure it can be done, but I'm not going to be the one recommending it, when "I DON'T KNOW" someone's ability to tune. So my advice errs on the conservative side. Besides, like I said, with all things equal, for a street car, there's no need to try to push the envelope. There's not enough gain to justify ending up with something that's finnicky in traffic on a hot afternoon.....the last place you want it to be. So yeah, you can do it any way you choose, but this is my opinion and I'm stickin to it.

 

[RustyRatRod]

J
What was the stock compression ratio on a 375HP 440? It's listed as 10:1, but reaching into the bowels of the search bar, a resident engine expert says it's 9.48:1 in reality. That was also with an antiquated iron head. Most everything now has aluminum heads and many have reverse cooling as well. (which you can run on a BBM)

It was probably lower than that. Much like the 340s. The early ones were rated 10.2 or 10.5 depending on what you read, but in reality they were "around" 9:1. The later ones rated at 8.5 and were "somewhere" around 8 or possible lower. Again, Mopar used crappy open chambers. Had they used something different like Chevy (I hate to make that comparison) We could be building our old Mopar cores on a quench platform. You look at any small block Chevy head from the same time period. All of them, open or closed chamber are quench heads. And the funny part is, Chevy never really took advantage of it from the factory.

 

[roccodart440]

The numbers I found were from IQ52. 9.48:1 on a stock 69 440. The way I see it, move to a closed chamber aluminum head, a proper cam, proper timing and a true 10:1 or 10.5:1 is not issue.

I run a blueprinted 10.5:1 with CC aluminum heads. 260@ .050 cam with 112LSA and I run 38 degrees of total timing on premium pump of course.

I agree with you, they were all lower than advertised and lets be honest, the factory tolerances weren't the greatest back then on anything.

These engines made a pathetic 375HP in stock trim, in the best years they were made. Impressive then, but by todays standards, not so much.

 

[RustyRatRod]

The numbers I found were from IQ52. 9.48:1 on a stock 69 440. The way I see it, move to a closed chamber aluminum head, a proper cam, proper timing and a true 10:1 or 10.5:1 is not issue.

I run a blueprinted 10.5:1 with CC aluminum heads. 260@ .050 cam with 112LSA and I run 38 degrees of total timing on premium pump of course.

I agree with you, they were all lower than advertised and lets be honest, the factory tolerances weren't the greatest back then on anything.

These engines made a pathetic 375HP in stock trim, in the best years they were made. Impressive then, but by todays standards, not so much.

Yeah, if it came from Jim, then he's probably the go to for the 440, for sure. I wonder if he's measure an original 340. I'd be curious.

I don't know. you can do a lot with that "pathetic" 375HP in a "good car". As you well know, then engine is but one small part.

 

[Bewy]

Agree with RRR on CR. Engines with pistons down the bore like 440s are more critical with CR than quench engines. I would not go higher than 9:1 for pump fuel. The power loss from 10:1 to 9:1 is only about 1.5%. Far more HP will be lost by having to retard the ign due to detonation than reducing CR.