No more high compression street builds for me

[Paul_G]

I’m at 195 psi, and on the edge of detonation with 93 octane

I plan to run the same cam that was in the 505, now with lower compression pistons. The problem still leads me to think I got a tank of 87 octane out of the 91 pump. I wish there was a way to test the octane level of the fuel in the tank now.

 

[Dodge Bros]

Trick Flow Power Port 240 aluminum heads. I dont know the quench? I did record compression numbers when it was running good. They were in 210 to 215 range.

210 to 215 is a 93 octane range in a 505. Judging by those compression numbers and the .050” cams specs I am going to guess that is a custom XFI HR cam. If that is correct, those cams are very aggressive off the seat and pump a lot of compression for there size. The 240 heads have very efficient ports, if you keep with that cam (and I am correct on which cam it is) in a 505, the compression needs to be dropped to 9.4 to 9.6 for 91. The TF240s are very efficient ports, with that cam, I doubt you will even miss the compression with your 505.

A different cam would fix it to and leave the compression alone. But it sound like that cam isn’t a bad fit, the compression is just high for the desired fuel.

 

[lewtot184]

Years back i tried to research the causes of detonation. I was looking for the smoking gun. I came to the conclusion that detonation can be multi faceted: not just one problem. I also came to the conclusion that it's impossible to build a detonation proof gasoline engine. It is possible to build detonation resistance and the only true "resistance" is to build a little more conservative. We are working with 1950's designs with 21st century power adders and compromised fuel. What could possibly go wrong,... Do you folks know that big cylinder bores contribute to detonation? Very small amounts of oil or water in the combustion chamber are death on a high compression engine. At 9.5 1 static compression ratio 1cc of carbon will raise the compression ratio 1/10 of a point. Did you know that .010" of carbon build will raise static compression ratio 1/2 a point in a 440. Do you make allowances for carbon build up in your street engines? We've known for a long time that 180psi cranking pressure is about the limit for premium pump gas in these old dinosaurs. The onus is on you the builder/end user. Ditch the false bravado. Use your gray matter and not your testicles when you think this through.

 

[Paul_G]

The pistons I bought to put in the 505, 440 Source 5074, are rated for 9.9 compression. to be sure on that I have to measure the deck clearence when I get the rotating assembly back in. The rotating assembly is at the machine shop right now waiting it's turn to get balanced. Using .020" in the hole an MLS head gasket in the upper .040 range might get me in to the mid 9's on compression. Thats using Summits compression calculator.

A good friend of mine who has restored many cars builds his engines back to stock. He is watching me go through all of this with the 505, and I can see him kind of shaking his head and wondering why I am doing this. He is not a racer high performance guy. Sometimes I wonder too why I am doing all of this. Then I go do a big smoky 50' long, 2nd gear burn out with a 4 speed not doing a brake stand and the reason I do it becomes clear. Running 12's in the quarter with potential for more, auto cross with the ability light up the tires at will when I screw up and cant save the run, in a 50+ year old car with blue tooth radio and AC. Thats why I do it. We all find our fun in different ways I guess.

 

[68 Sport Satellite]

Years back i tried to research the causes of detonation. I was looking for the smoking gun. I came to the conclusion that detonation can be multi faceted: not just one problem. I also came to the conclusion that it's impossible to build a detonation proof gasoline engine. It is possible to build detonation resistance and the only true "resistance" is to build a little more conservative. We are working with 1950's designs with 21st century power adders and compromised fuel. What could possibly go wrong,... Do you folks know that big cylinder bores contribute to detonation? Very small amounts of oil or water in the combustion chamber are death on a high compression engine. At 9.5 1 static compression ratio 1cc of carbon will raise the compression ratio 1/10 of a point. Did you know that .010" of carbon build will raise static compression ratio 1/2 a point in a 440. Do you make allowances for carbon build up in your street engines? We've known for a long time that 180psi cranking pressure is about the limit for premium pump gas in these old dinosaurs. The onus is on you the builder/end user. Ditch the false bravado. Use your gray matter and not your testicles when you think this through.

I'm a novice at all of this and learning as I go. The carbon build up is something I often forget. If the motor is tuned well and no detonation or pinging, I suppose with miles over time there will still be carbon build up? I just looked back at my records and my 10.2:1 motor with aluminum heads measured 175psi cranking pressure. On the edge? I was hoping for 100K miles out of the motor, which is why I did a milder build. Maybe wishful thinking...
I know I have the wrong pistons, but I'll probably run it a few more years before I think about swapping pistons with a different cam.

 

[lewtot184]

The pistons I bought to put in the 505, 440 Source 5074, are rated for 9.9 compression. to be sure on that I have to measure the deck clearence when I get the rotating assembly back in. The rotating assembly is at the machine shop right now waiting it's turn to get balanced. Using .020" in the hole an MLS head gasket in the upper .040 range might get me in to the mid 9's on compression. Thats using Summits compression calculator.

A good friend of mine who has restored many cars builds his engines back to stock. He is watching me go through all of this with the 505, and I can see him kind of shaking his head and wondering why I am doing this. He is not a racer high performance guy. Sometimes I wonder too why I am doing all of this. Then I go do a big smoky 50' long, 2nd gear burn out with a 4 speed not doing a brake stand and the reason I do it becomes clear. Running 12's in the quarter with potential for more, auto cross with the ability light up the tires at will when I screw up and cant save the run, in a 50+ year old car with blue tooth radio and AC. Thats why I do it. We all find our fun in different ways I guess.

You can run in the 12's with a near stock engine. You can run in the 11's with a moderately modified 440. I'm not trying to be demeaning and it's your car and money, but sometimes we don't work as smart as we should on a dual purpose car. Anyhow, i wish you the best!

 

[lewtot184]

I'm a novice at all of this and learning as I go. The carbon build up is something I often forget. If the motor is tuned well and no detonation or pinging, I suppose with miles over time there will still be carbon build up? I just looked back at my records and my 10.2:1 motor with aluminum heads measured 175psi cranking pressure. On the edge? I was hoping for 100K miles out of the motor, which is why I did a milder build. Maybe wishful thinking...
I know I have the wrong pistons, but I'll probably run it a few more years before I think about swapping pistons with a different cam.

175psi isn't a killer. Carbon build up with a poor tune up can be be. Poor assembly technique is usually swept under the rug. Poor parts combo is a killer. Doing your homework leads to longevity.

 

[68 Sport Satellite]

175psi isn't a killer. Carbon build up with a poor tune up can be be. Poor assembly technique is usually swept under the rug. Poor parts combo is a killer. Doing your homework leads to longevity.

the good thing with my motor is that it was assembled by one of the most knowledgeable and experienced mopar engine builders I've met and he's a personal friend. It's on me for selecting the pistons ahead of the cam instead of the other way around.

to the OP - hoping your motor rebuild goes well and your car is on the road again soon

 

[lewtot184]

the good thing with my motor is that it was assembled by one of the most knowledgeable and experienced mopar engine builders I've met and he's a personal friend. It's on me for selecting the pistons ahead of the cam instead of the other way around.

to the OP - hoping your motor rebuild goes well and your car is on the road again soon

Pistons need to match the combustion more so than the cam match the pistons. The top of the piston is the floor of the combustion chamber. This must match up for the engines intended use.

 

[Paul_G]

You can run in the 12's with a near stock engine. You can run in the 11's with a moderately modified 440. I'm not trying to be demeaning and it's your car and money, but sometimes we don't work as smart as we should on a dual purpose car. Anyhow, i wish you the best!

I see people doing that, running in the 12's with mild cars. The vast majority of them are running high 13 low 14 on stock 440's. It is much easier to do with an automatic. I could never master the clutch with the 505. Stock clutch was a smoke show. I put in a dual friction clutch which was all off or all on. At the line one of three things would happen. Imediately blow of the tires letting the clutch out 3000 rpm. Slip the clutch more to not blow off the tires and leave slower and while smoke the clutch. Or blow off the tires at the 1 to 2 when I lay in to it. 12.8 was with slicks which did launch better. But dumping the clutch at higher rpm just blew off the slicks or bogged the engine. And they did a nice smoky 2nd gear burnout in the water box.

This is an entire different subject. But mastering the clutch was just about impossible. I had 3 clutches in the car, $$$, they dont last long behind this engine, I have been driving sticks all my life. The current clutch is a dual disk, still in the car. Have not had it to the strip with this clutch and slicks.

 

[lewtot184]

I see people doing that, running in the 12's with mild cars. The vast majority of them are running high 13 low 14 on stock 440's. It is much easier to do with an automatic. I could never master the clutch with the 505. Stock clutch was a smoke show. I put in a dual friction clutch which was all off or all on. At the line one of three things would happen. Imediately blow of the tires letting the clutch out 3000 rpm. Slip the clutch more to not blow off the tires and leave slower and while smoke the clutch. Or blow off the tires at the 1 to 2 when I lay in to it. 12.8 was with slicks which did launch better. But dumping the clutch at higher rpm just blew off the slicks or bogged the engine. And they did a nice smoky 2nd gear burnout in the water box.

This is an entire different subject. But mastering the clutch was just about impossible. I had 3 clutches in the car, $$$, they dont last long behind this engine, I have been driving sticks all my life. The current clutch is a dual disk, still in the car. Have not had it to the strip with this clutch and slicks.

When i was younger i was a die hard 4spd guy. One of the secrets to feathering the clutch is the disc. The thinner the wafer spring between the front and back of the disc the gentler the engagement. Performance or race discs usually don't have the kind of flat spring that is condusive to gentle starts. But, it does boil down to what are you going to do with 600+lbsft of torgue and will you manage it. Control the torque and then the body starts tearing. Almost like a dog chasing it's tail.

 

[autoxcuda]

You can run in the 12's with a near stock engine. You can run in the 11's with a moderately modified 440. I'm not trying to be demeaning and it's your car and money, but sometimes we don't work as smart as we should on a dual purpose car. Anyhow, i wish you the best!

What’s near stock to some, Maybe different to others.

I don’t see many 440 B-bodies running 12’s with exhaust manifolds, 3.23 or 3.55’s, one step over stock hyd cam, 9.5:1 compression, stock heads, aluminum dual plane, edlebrock or vac sec Holley and stock suspension and BFG/Cooper type tires.

 

[lewtot184]

What’s near stock to some, Maybe different to others.

I don’t see many 440 B-bodies running 12’s with exhaust manifolds, 3.23 or 3.55’s, one step over stock hyd cam, 9.5:1 compression, stock heads, aluminum dual plane, edlebrock or vac sec Holley and stock suspension and BFG/Cooper type tires.

BSB67 did. I could have but lost patience. It's very doable with no lumpy cams, loose converters, big tires, headers/open exhaust.

 

[RemCharger]

You can run in the 12's with a near stock engine.

What’s near stock to some, Maybe different to others.

I don’t see many 440 B-bodies running 12’s with exhaust manifolds, 3.23 or 3.55’s, one step over stock hyd cam, 9.5:1 compression, stock heads, aluminum dual plane, edlebrock or vac sec Holley and stock suspension and BFG/Cooper type tires.

Definitely an area of personal opinion. If i was given a bone stock 78 new yorker mill( meaning longblock w/o cam) I'll show you a 12. Yes that would include a 280-290 cam, intake and headers. Good gears, decent converter and tires that stick obviously. We already know these cars run 14s if everything is as produced.

 

[451Mopar]

One issue I have is that my old muscle cars are not driven daily so the fuel gets stale in the fuel tank.
One nice thing with an electric fuel pump is being able to use the electric pump to drain the fuel tank if the cars been sitting a long time.
I try to have 0.040" quench distance on my engines, so even the -27cc dished pistons still have the flat quench pad.
I try not to specify a specific static compression ratio unless I already have an idea of the cam size I plan to use, and look more at the dynamic compression ratio and cranking cylinder pressure.
I would like to say that because of the altitude here in Denver, that I can run higher compression. Technically, it might be true, but practically, they have lowered the fuel octane for the same "grade" of fuel. We are usually 2 octane points lower for the same "grade" gasoline. An engine that might have 160 PSI cranking pressure at sea level might only have 130 PSI here. Idle vacuum really takes a hit too. If you have 20" vacuum at sea level, might only have 14-15" vacuum at 6,000 ft altitude.

 

[Road Grabber]

I’m wondering if your fuel pump was providing enough fuel causing a lean situation.

It’s a catch 22. The ability to rip the tires now is overwhelming. How much power is really needed on the street. My 440 provided more than enough to get me in trouble.

I have switched to aluminum heads though because the gas is not the same anymore. I never could get a good additive to make up the difference so I decided to switch to aluminum heads. However that created more issues with head gaskets between dissimilar metals.

Chrysler designed great HP motors that tore up the street but because this new stuff is out there the temptation is high to modify and keep up with the Joan’s. If you change one thing it affects something else. Reliable high HP is always going to be a chased goal.

But really. How much is too much for the street? My 440 six pack stayed together reliably for over 25 years until fuel became an issue. Ripped the gears straight through 3rd gear. With a 410 rear it was crazy for the street. Experience snd close calls kept my alive today.

Will these kit 700 hp stroker engines last 25 years? Time will tell until then break out another thousand.

 

[BSB67]

BSB67 did. I could have but lost patience. It's very doable with no lumpy cams, loose converters, big tires, headers/open exhaust.

Yes. 12.80s - 12.90s. 108 - 109 mph.

3.23s
Factory 12” converter
BFG - P235 70s (2.05-2.10 sec. sixty ft times)
MP 0.455” cam
Exhaust manifolds and 2 1/4” exhaust.
Locally ported 915 heads. (245 cfm)
Six Pack
10.3:1 CR
4200 lbs

Considering part of the discussion is the value, or no value in compression, l’m not sure mine is a great example.

But conversely, put that drive train in a 3,800 lb car, sticky street tires and a 9.5:1 CR, it would be well into the mid 12s.

I’ve thought about re-doing this. With what I’ve learned since then, I think I could get to 12.50s at 112 mph with a better cam, 2 1/2” exhaust, better ported factory head, and 9.5:1 CR. I’ve actually assembled most of the parts.

 

[451Mopar]

Yes. 12.80s - 12.90s. 108 - 109 mph.

3.23s
Factory 12” converter
BFG - P235 70s (2.05-2.10 sec. sixty ft times)
MP 0.455” cam
Exhaust manifolds and 2 1/4” exhaust.
Locally ported 915 heads. (245 cfm)
Six Pack
10.3:1 CR
4200 lbs

Considering part of the discussion is the value, or no value in compression, l’m not sure mine is a great example.

But conversely, put that drive train in a 3,800 lb car, sticky street tires and a 9.5:1 CR, it would be well into the mid 12s.

I’ve thought about re-doing this. With what I’ve learned since then, I think I could get to 12.50s at 112 mph with a better cam, 2 1/2” exhaust, better ported factory head, and 9.5:1 CR. I’ve actually assembled most of the parts.

looks like you could knock off 0.3 seconds on the 60' with sticky tires and a higher stall converter?

 

[lewtot184]

Yes. 12.80s - 12.90s. 108 - 109 mph.

3.23s
Factory 12” converter
BFG - P235 70s (2.05-2.10 sec. sixty ft times)
MP 0.455” cam
Exhaust manifolds and 2 1/4” exhaust.
Locally ported 915 heads. (245 cfm)
Six Pack
10.3:1 CR
4200 lbs

Considering part of the discussion is the value, or no value in compression, l’m not sure mine is a great example.

But conversely, put that drive train in a 3,800 lb car, sticky street tires and a 9.5:1 CR, it would be well into the mid 12s.

I’ve thought about re-doing this. With what I’ve learned since then, I think I could get to 12.50s at 112 mph with a better cam, 2 1/2” exhaust, better ported factory head, and 9.5:1 CR. I’ve actually assembled most of the parts.

I've thought about a re-do many times and have an engine and heads built. I'm pretty sure i can pick-up 20 or more hp at the crank now that i have a better understanding of past mistakes. Unfortunately my vision has taken a serious dump in the past year and going to the grocery store may be the limit to my driving from now on.

 

[BSB67]

I've thought about a re-do many times and have an engine and heads built. I'm pretty sure i can pick-up 20 or more hp at the crank now that i have a better understanding of past mistakes. Unfortunately my vision has taken a serious dump in the past year and going to the grocery store may be the limit to my driving from now on.

Sorry to hear that.