Stopping the knock: Lower compression and ported heads...

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been following this thread from the start, lots of GOOD advise, some not so good.
many of us have been running high compression on the street for over 30 years.
I stick with oldschool tech, so I don't give too much advise.
listen to the guys who are doing it NOW, because they have taken knowledge from the past into the future. the recipes are easier today!
 
I can't recall who wrote it and where, but someone mentioned that I'd be better off running a lower compression ratio that allowed me to run a cam that suits my driving style.
Smart words.
I'm not interested in drag racing. A drag race car often needs a big cam, a big converter and it spends its time at WOT for several seconds, then put-puts back to the starting line again. This car needs to idle in traffic, roll along at 20 mph in residential streets and run on the freeway at 2600-3000 rpms. Fuel economy isn't the top priority but it is a factor. Idle quality is of little importance to the driver of a drag car but I'm getting tired of the car shaking at stoplights.
Now that I'm running less compression, I'm thinking about moving on with more changes to make the car more fun for the type of driving that I want to do. I like the feeling of a car that has instant off idle throttle response. Currently, this car feels loose at any speed at part throttle. Sure, it scrams once I lean into it and the converter decides to tighten up but I miss the immediate response of an engine built for torque.
Yeah, these changes I'm contemplating DO include another cam swap. A milder cam will choke off power at the top end, but so what? How often does a street car need to rev to 6500? The milder cam will certainly idle better. I could switch to a 3.55 ratio from the 3.91s I have now as well as going back to a tighter, bigger converter.
 
I'm almost betting many of us saw your combination and assumed, despite your described intent, you wanted to make the current sum of parts work best and all the problems that kept developing as time went by just frustrated all of us...

I guess it's kinda difficult to go back on this build unless you feel like taking the engine apart and going with lower compression slugs...but it seems to me if you want a big block car that's as docile as you describe immediately above, a simple lightly cammed 440 would be more up your alley. But, if memory serves, that's what you had before, right?
 
"I" would not waste money (it would be to me) on a stroker for the street. A good ole low comp 440 that would run on most any swill would be what I would aim for and put the money in the heads. Like Jim Laroy's low compression 440 build. You can run 87 in that from get to go and never have a worry. Regardless of what people have run for 30 years, race bred builds are race bred builds and street builds are street bred builds. We've all pushed the envelope with engine builds and in extreme street conditions such as heat soak, they protest. If something is already built on the edge, it doesn't take much to push it over.
 
When I built this engine in 2004, I was in a bit of a hurry. I had just thrown a rod in a rebuilt 440 and needed to put something together because the wife and I had bought a house and we were moving. The rod in the 440 broke between the big and little end. This made me think that I'd be better off buying new rods for the next engine. I figured that since I needed new pistons and rods, why not get a whole rotating assembly?
I'll admit that I was mesmerized by the feel and sounds of a rumpity-rump cam. If all I cared about was looking like a "neighborhood gearhead with the hot rod" I'd stick with the current combo. As I have said before, the majority of the engines that I have built were pretty close to stock. This was my first stroked engine, my second with aluminum heads, my first solid cam....I had no experience with driving and owning a car with a radical cam and a high stall converter. This has shown me that I prefer an engine with better low to midrange power and better street manners.
 
...and now you're married to it. Even if you were able to sell it, you'd get hosed something fierce. And I'm going to assume you can't grab a basic 440 with some modest upgrades and put the 493 in moth balls.
 
I have 3 440s in my garage. One is an 80,000 mile 1971 version from a Chrysler 300.
I see no reason to pull this 493. I'll just pull this Lunati and slip in something oriented towards" idle to 5500" power. It is just a matter again of....which cam to choose. The 493 is 12% larger in displacement compared to a 440 so is it fair to guess that I need a cam approx 12% larger (In lift and duration) than a 440 Magnum cam? I've read good things about the MP 528 solid.
 
Frankenduster said:
I'll just pull this Lunati and slip in something oriented towards" idle to 5500" power.
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That's the funniest thing I have read throughout this entire fiasco. What do you think that will do to cylinder pressure? You will be right back in the same boat as before lowering the compression. If you're serious about that statement, you may as well sell the car now because your ability to learn from your experiences is naught.
 
(Sigh)

...I really have no idea what to suggest now...if you install a smaller cam you'll likely only increase your cylinder pressure due to sooner intake closing, which will only make your detonation issue re-emerge.
 
it shouldnt be shaking at stoplights. i think once you get your distributor timing set how it should be, you will be fine. no need to swap camshafts to fine tune the beast.

try 8* initial 35* total. make sure the vacuum lines are where they should be, pcv in front usually brakes in back any unused should absolutely be plugged. which carb???, we'll try to get you a diagram.

shaking at idle could just be a vacuum leak. i have not followed the whole thread, but if someone wants to suggest a different standard timing let him know. it sounds like it's way retarded or advanced right now. or vacuum leak.
 
moparlover said:
it shouldnt be shaking at stoplights. i think once you get your distributor timing set how it should be, you will be fine. no need to swap camshafts to fine tune the beast. try 8* initial 35* total. make sure the vacuum lines are where they should be, pcv in front usually brakes in back any unused should absolutely be plugged. which carb???, we'll try to get you a diagram. shaking at idle could just be a vacuum leak. i have not followed the whole thread, but if someone wants to suggest a different standard timing let him know. it sounds like it's way retarded or advanced right now. or vacuum leak.
Click to expand...

He said in this and related threads past, 8* initial the car barely runs, and 35* total makes detonation unless 100+ octane in the tank...unless that's been remedied with the new thicker head gaskets.

My best advice to you is to read through the entire thread to see where all he's been with this thing in the past year...
 
8* initial? WTF? You can pull a stock motor up past farther than that. His engine needs at least around 20* initial.
 
RustyRatRod said:
That's the funniest thing I have read throughout this entire fiasco. What do you think that will do to cylinder pressure? You will be right back in the same boat as before lowering the compression. If you're serious about that statement, you may as well sell the car now because your ability to learn from your experiences is naught.
Click to expand...

With the engine now at 10.07, I have some room to work with. At the previous Cr of around 11.0, I was against a wall in terms of what cam I could run. I've plugged numbers into the Dynamic calculators to see what effect the intake closing has on the Dynamic ratio. The static compression has a far greater effect on the Dynamic reading than the intake closing. I'm not saying that Intake closing isn't important, just that the static CR is more so.

Check this out:

Previous setup with the 11.0 CR and 509 cam, Dynamic was 8.17.
With the same CR and the Lunati cam, Dynamic was 8.29. With the current lower 10.07 CR, the Dynamic is now down to 7.61. If I had this 10.7 ratio with the 509 cam, I'd be at 7.51.
Got me so far? So.... in order for me to get back into the "Red-Zone" of detonation, I'd have to go with a cam mild enough to have an intake closing of 64 degrees or lower. This is calculated by using the following calculator:

https://www.uempistons.com/index.ph...=comp2&zenid=5886b5a1e26a6addce30f95974e64ff7

I'm going to check Comp cams site to see what a cam looks like that has a 64 degree intake closing.
 
ANY of those dynamic compression ratios listed should be pump gas friendly. I stand by my very first original statement that compression was never your problem.
 
You're still looking at a 280-290* cam depending on mfr choice...and how you degree it...the only way I can think of that your cylinder pressure would be lower is if it has poor cylinder filling, which tells me you want a lazier lobe profile. Have you looked at maybe a custom cam grind yet, as opposed to something off the shelf?
 
This thread has my head hurting. After read ring and rereading this monster, I've gotta agree with Rusty. Compression wasn't the problem at all. Seems you've shotgunned the issue instead of trouble shooting. Sounds like you just need a good tune and check for vaccum leaks. I'm no professional engine builder but I did build my 472 stroker in my old charger. I was running higher dynamic compression than you and I was around 11.5 to 1 with my kit. I ran 93 octane without issue. I also was also running a slightly more aggressive Voodoo can than the one you're running. Listen to these guys, they helped me and weren't wrong.
 
RustyRatRod said:
you may as well sell the car now because your ability to learn from your experiences is naught.
Click to expand...


You say this because I didn't follow your advice to the nth degree?
Many (Not all) thought the thicker head gaskets wouldn't help my situation, yet it has done just that.
Regarding the ignition mods you suggested, I tried slowing the curve. Funny, the word curve doesn't really factor in since a 14 degree amount of advance in a dead straight line hardly appears like a curve...
RRR tried and tried to get me to delay the full advance until 3500 or so. I explained that when I eased up the rpms, THEN floored the car at 3500 or higher the car still detonated. I wrote MULTIPLE times that I felt that if his suggestions made sense to me, at 3500 (When in theory, the full advance would be in under RRRs advice) the car should have not knocked. This may be one of those things where two people are saying things that the other doesn't fully understand.
Again, whether I delayed the advance by way of distr. mods OR waiting until 3500 to floor it, I personally cannot see where the difference lies. There is no reason to insult anyone here either. If anyone cares to help me understand how or why I am wrong here, I'm willing to read. I'm not claiming to be the master of anything. I'm willing to admit where i am wrong.
These internet forums are voluntary. If someone reads my advice on something and decides to go another route, I don't continue to respond to the thread with..."Well, if you would have just done it MY way..." I figure that these threads are a guide to be used, not a recipe carved in stone.
Finally, I am not totally sold on a cam swap just yet. The Lunati was tried as a means to stop a detonation problem and it didn't work out. No biggie, that is life. Its not as if I raided the orphanage fund to buy these parts.
I am considering opening up the valve lash a bit to make the engine see "Less" cam. I might also advance the cam 4 degrees. These 2 moves may shift the power band a bit lower and soften up some of the bite. In reality, I shouldn't have wrote that the cam makes the car shake a bunch. It was an exaggeration. It shakes in comparison to what I'd prefer. No, I'm not looking for a totally smooth idle either. I just want something a bit more street friendly.
 
dukeboy_318 said:
I was running 11.5 to 1 with my kit. I ran 93 octane without issue. I also was also running a slightly more aggressive Voodoo can than the one you're running.
Click to expand...

Read this again.

93 octane? I have 91 here. 2 points does make a difference.
11.5 with a more aggresive cam? Sorta sounds like a wash to me compared to mine.
I was at 11.0 using 91 octane.
 
txstang84 said:
Have you looked at maybe a custom cam grind yet, as opposed to something off the shelf?
Click to expand...

No I have not, but it is a good idea. If the wider lash and 4* advance isn't enough, that may be my next move.
 
Frankenduster said:
Read this again.

93 octane? I have 91 here. 2 points does make a difference.
11.5 with a more aggresive cam? Sorta sounds like a wash to me compared to mine.
I was at 11.0 using 91 octane.
Click to expand...

So if its a wash...never mind. Good luck. I hope you get this thing dialed in to your liking.
 
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