Feel like my 440 should be faster

[standup303]

You ordered a converter without knowing compression ratio or cranking compression at your altitude?

I explained to Shawn I had calculated my compression ratio at 9.38:1 and typically drove around 5,400’. Altitude was talked about quite a bit during the conversation. He was familiar with specifying converters for altitude.

 

[1MeanA]

I hope it works out for you but I would be concerned about having a 235 duration with 8:1 compression. I once had a low compression 440 with one of the MP mild cams. It was unimpressive.

 

[TT5.9mag]

I explained to Shawn I had calculated my compression ratio at 9.38:1 and typically drove around 5,400’. Altitude was talked about quite a bit during the conversation. He was familiar with specifying converters for altitude.

Was the 9.38 calculated at 5400 feet or sea level?

 

[standup303]

Was the 9.38 calculated at 5400 feet or sea level?

That’s at sea level with no adjustment for altitude.

 

[standup303]

I hope it works out for you but I would be concerned about having a 235 duration with 8:1 compression. I once had a low compression 440 with one of the MP mild cams. It was unimpressive.

That is a concern and a hard lesson learned for me. However for this year I have zero desire to get into the motor. I am already doing exhaust and rear end work to the car so changing the converter and gears are no biggie right now. One thing that really sold me on the Dynamic converter is if my combo changes I can send the converter back for adjustment.

Long term plan (next winter maybe) is pull the motor and go higher compression, different cam and aluminum heads…once I have a solid plan and admittedly a better understanding of what I’m doing.

 

[1MeanA]

Definitely see what you got with the new converter.

 

[roccodart440]

I talked to a few manufacturers. Going to call Dynamic tomorrow. FTI recommended their street racer series 9.5” 3600 stall that I like. Boss Hog recommended their 3600-4000. Waiting on a few more replies to the build sheets I submitted too.

I run a 9.5 as well, from Coan. Dynamic is a great company. Never heard of Boss Hog.

 

[forphorty]

I run a 9.5 as well, from Coan. Dynamic is a great company. Never heard of Boss Hog.

Boss hog, terrible reputation.

 

[1968rt]

The thing about the CR is………at that high of an elevation, the CR is “effectively” less.

After you do a cranking pressure test and have a real number to look at.
Use the Wallace cranking pressure calculator to see how close it is.
Then change the baro pressure to something that represents being closer to sea level.
The cranking pressure number will go up.
Now, start lowering the CR until the cranking pressure number is pretty close to what you’re seeing from the test.
Whatever CR you used to come up with that result is basically what the effective CR is at your altitude.

Edit-
So I ran the numbers on Wallace…..
Current baro reading(station pressure) at Denver airport is 24.79”.
For a 446, 9.38cr, int closing point of 67abdc, and 24.79” shows 121psi gauge pressure.
At 29.50” it would be 144.
For the gauge to read 121 at 29.50” the CR has to drop down to about 8.25:1

Sounds like the Speedpro pistons could actually be the motorhome replacements. L2388
........... CH.........WT.....PIN..... CCS.............DK HT
L2266F 1.991.....876.....225.....0 flat top...... .090
L2355F 2.061.....872.....225..... -7cc..............020
L2388F 1.926.....819.....225.....0 flat top...... .155
L2295 2.029.......817.....250..... 13.1cc........ .051 .140 dome

 

[Illahe]

Sounds like the Speedpro pistons could actually be the motorhome replacements. L2388
CH WT PIN CCS DK HT
L2266F 1.991 876 225 0 flat top .090
L2355F 2.061 872 225 -7cc .020
L2388F 1.926 819 225 0 flat top .155
L2295 2.029 817 250 13.1cc .051 .140 dome

Why would the L2295 2.029" compression high be less than the L2355 2.061" seems illogical considering its a dome vs flat top.

 

[BSB67]

Why would the L2295 2.029" compression high be less than the L2355 2.061" seems illogical considering its a dome vs flat top.

Why?, I don’t know.

I will say that 2.029” was the factory piston compression height for the 69-70 hp engines.

What I find odd is that the 2295 pistons is like 25 grams lighter than the others, including the factory piston, but the pin is 25 grams heavier.

 

[1968rt]

Its measured from the flat part of the 2295. If it had the same compression height as the 2355, with the dome you would be looking at over 12:1 compression with an open chamber head. The 2295 is about .050 in the hole. With an open chamber, somewhere around 10.5-11:1 comp. We used to mill the dome off of a 2295 and run a closed chamber head. ran great!

 

[PRH]

Sounds like the Speedpro pistons could actually be the motorhome replacements. L2388
........... CH.........WT.....PIN..... CCS.............DK HT
L2266F 1.991.....876.....225.....0 flat top...... .090
L2355F 2.061.....872.....225..... -7cc..............020
L2388F 1.926.....819.....225.....0 flat top...... .155
L2295 2.029.......817.....250..... 13.1cc........ .051 .140 dome

Thankfully there are plenty of better options available now.

 

[Illahe]

Thankfully there are plenty of better options available now.

Ross and Icon have economical options.

 

[BSB67]

And, there is the 2286P. The 68-70 hp replacement with the 2.03” compression height. Not available since 1990.

 

[PRH]

Those 2286’s are what was in my first 440, which I built in 1981.

Later on I needed to replace one, but they were long since unavailable by then.
My main concern was getting something where the ring placement was similar.
As it turned out, the 2355 had the rings lined right up with the 2286 when placed next to each other sitting with a wrist pin between them.
Weight was within a couple of grams, and the taller CH of the 2355 basically equals out the CR for the added valve pockets.

After that, I understood why the 2286 went away.
The 2355 was a functional equivalent, but with valve pockets.

 

[Michael Harrington]

In your list, "stock ignition box". If it is an original old chrysler box it will start rpm limiting
around 5000 to 5200 rpm. If it is a stock replacement in the last 25years they start limiting
as low as 4200 rpm. They don't hit a wall like a chip they get lazy. With a box from auto zone
you would have a hard time passing a car on a single lane highway. Get a orange box from
mopar perf or branden at 440 source ect. 6000 rpm. Easy first thing to try. I have 2 of the newer
chrome boxes 1 from auto zone and 1 from advance that came out of pickups. The worst
would not break 3800 rpm on a mountain pass. Stock ignition is very good, bad rep is from
the last 25+ years of garbage service parts. Give it a try. Has fixed a lot of LAZY engines.

Take care,
Rick

This is fact and easy/inexpensive to remedy. As of me typing this I didn't see what brand ignition control box is being used. I remember back around 2013? A company released an Ign Box -the name of the box was the "Revinator." The gent promoting his ign box claimed like 95 hp over the "Stock" ign box. Turns out what was used for the Stock ign box for the before testing was one of those terrible aftermarket versions and it was so bad- like the NITROTRIP mentions above. So of course the engines Before performance was absolutely abysmal compared to the new Revinator performance. I must mention that the Revinator from its launch was and maybe still is a great performing product- it was the presented/skewered deceptive dyno comparo that made the owner initially take some heat.