440 problems/quenching?/advice needed

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AJ/FormS said:
Now here's a little math; Let's start with a stock stroke and bore+.030. That would be 4.35 x 3.75. That calculates out to a 921.7 swept. If in fact the engine was previously 10.75Scr(post 36), that requires a total chamber volume of 94.53 cc.; 909/(10.75-1)=94.53
Since we know(or you say) the block is zero decked and you have flat-tops with no reliefs, it's easy to figure the chamber volume is 94.53 less the gasket.I have to guess at the gasket bore; say 4.40 and the thickness of .038,well that makes about 9.5cc. so that tells us that he the PO was using 94.53 - 9.5=85cc heads. That was his combo, and it makes sense, if he started with 90cc

Now your combo with the same 9.5cc gaskets and 78cc heads comes to
{921.7 + (78 + 9.5)}/87.5 = 11.53Scr
The Wallace calculator puts this at a Dcr of 8.7 and the cranking compression pressure at 177psi, with an ICA of 70* degrees using that 292/509 cam.
Now that is for sure testing the limits of pump 93. But guess what; you have the .038 quench going for you and by your own admission you're not into racing. So if you're not interested in the max power, then there is no reason to run max timing. You can run 34* or 32* of power timing if that is what it takes to kill WOT detonation.
Now let's talk PT(part throttle) detonation. At 8.7Dcr this is again pushing it, But guess what; you have not done any timing loops. There is a ton, a TON of tuning you can do to get it out of detonation at PT. A TON.
Detonation is also load sensitive. Let's take an engine that is on the edge of detonation with full timing, that is stuck in a chassis with 2.76 gears and a 2400 TC. So then you put in 3.55s and a 2800 TC, and move the detonation up several hundred rpm. Then take out 1 or 2 or 3 degrees of power timing and problem solved. But guess what; you may be able to run full PT timing and have a dynomite engine , at anything short of peak torque! See what I mean about tuning.So you can start your tune with carburetion.If the engine cannot ingest a full load of air it will not experience a full load. So a smaller carb than optimum is on the table.Well that is not said right, but the result is the same. Take the 850 off and try a 750 or a 650.Or something with a load-sensitive secondary.

Now lets put those open chamber bad boys on there with a 284/484 cam. Let's say they come in at 90cc. The Scr will be (921.7 + 90 + 9.5)/99.5 = 10.26Scr and the Wallace calc. puts that at a Dcr of 8.06,with a ICA of 66*, and pressure of 161. Phew you dodged a bullet. This is pretty safe. But guess what; you are still stuck with the problematic rocker gear.And you have lost completely, all the Quench benefits, which may have allowed the prior 11.5SCR.And you may have given up some terrific PT benefits.Which you are wanting.

I know which combo I would want under my hood. But I am willing to measure stuff and calculate stuff and tune it til it wails.

Quote from Doosterfy,(post 70)
"There are plenty of guys, engine builders in particular who will steer people away from pushing it. Its been my experience over the years (I've been at this since the 70s) that keeping compression and/or cylinder pressure up makes a car much more fun to drive, much better off idle throttle response, less throttle opening to propel the car, it sounds better and the car will simply have more snap to it. I got talked into staying at 9 to 1 or lower twice and both times I was very disappointed with the results after spending my time and money building the engines".
(My experience as well. AJ)
Sorry for the novel; it was a lot shorter in my head.

OOps, One more thing, If the big 440 gets tirespin, it is no longer loaded.Wrap your head around that for a sec.
Click to expand...
Sounds like you have a more in depth understanding of engine theory than I do. IDK if you read the entire thread. A few things to consider that he has told us. Its not a race car and he never plans to race it, its a cruiser. He had some unknowns with the valvetrain and suspected there was a bunch of mismatched parts in the valvetrain and turns out he was correct about that. He also said he wants to avoid using anything other than pump gas and wants the engine to be easy to deal with. He's also a novice builder, at least with Mopar. I agree with most of what you're saying and can't actually pinpoint any one thing you said that I disagree with. If I understand what you're saying correctly, you are saying that dropping the compression by swapping to open chamber heads will likely net him no gains in avoiding detonation because he will be giving up quench which is good at reducing it (detonation). That is a good point as are the points you made about tuning as far as timing and fuel curve. With what he had going on in the valvetrain I think trying to tune it would have been nearly futile. If it were mine, and its not, I would have left the heads on, corrected all the valvetrain issues, got it up and running and got on the tuning to see how it ran and if it would tolerate pump gas. My guess is that with iron heads and nearly 11.5 to 1 it would not without going to a much longer duration cam, which is something I think he does not want. My guess and its just that a guess or estimate is that with the open chamber heads, a moderately sized hydraulic cam and good tuning he'll be right near the detonation threshold with 93 octane pump gas. I think if he kept the small chamber heads and ran the same moderately sized hyd cam the cylinder pressure would almost certainly put him into detonation. One thing I've learned is to start with the tuning as close as possible to where it needs to be the first time the engine is started. I've found that vacuum advance is more trouble than its worth with any cam that's larger (duration) than dinky. What I've been doing for a long time and getting good results is to run as much initial advance as the engine can handle and on most V-8s, including big block Mopars, it's about 20 degrees and a total advance somewhere between 36 and 40 degrees and to get all the advance in as soon as possible without causing detonation and that's usually about 2000 rpm. That means setting up the distributor before even installing it on the engine, preferably on a distributor machine and as soon as the cam break in is done setting the initial to 20 and leaving it as long as the starter can crank it and it does not ping at throttle tip in under load. once that is done I move onto the carb tuning and after that go back and start experimenting with the timing a little to see if there's any gains to be had, and finally back to the carb again. Before I learned all this, I remember chasing my tail turning the dizzy back and forth trying to get engines to run right only to find out (eventually) that the advance curve in the dizzy was way too wide. At this point I hope we don't overwhelm or confuse the guy with all this info. There is one magic bullet that would pretty much solve any detonation issues with this engine and that is a set of aluminum heads like Edelbrock rpms with 85cc chambers or 440 Source Stealths with 80cc chambers. Its his money and I have no idea what his budget is and/or it permits the investment in those. Your thoughts sir?
 
Doosterfy
I agree with everything except;
1)I like to spend some time with the vacuum advance.A lot of time,actually.All my experience is with cams of 292/550 or less.I like to balance the initial timing against the Vcan,using the sparkport only.By using the can, I can bring 40 to maybe 50* degrees in at PT, and up to 55* or so at cruising speed. This really helps with drivability and fuel economy.This combo at 11.5/8.7 will be tricky for sure.The initial might need to start a little lower and the rate might need to be slower. For a 440streeter this is no biggie.It all ready has a preponderance of torque. We're not looking for every last drop.So maybe start at 14*,bring another 14* in by 2800, and then slow it down to finish at [email protected] sounds like a crappy curve, but you mighta forgot; it's a streeter. 3600 is 35mph or so in first. We're done.Stick it in Drive and let's cruise.Plus with the Vac sec. 650 or so, It might not even have opened the secondaries yet. So it's lightly loaded and primaries WOT to 3600, and cruise.I think I could make it work. Then cruising at 35mph/1550rpm(3.55s), the total timing might be as much as 37*. You just can't get that without the Vcan. That 37* will smooth that 292 cam real nice. Without the Vcan, and setting the initial to 20*/36*@2000, the same 35 mph/1550rpm might be 30*, which, since none of it will drop out when the hammer falls, will surely be too much, whereas in the Vcan equipped engine 20 or more will drop out leaving just 17*, which stands a real good chance of not detonating.Certainly I would try to bring more in earlier, but I'm just throwing conservative numbers out there.
---At the 10.25/8.0, it will need/want/take,all the Vcan you can find.
2) If you're not going for track-time, the power timing can be dialed back, making tuning the sub torque-peak timing so much easier, and since the closed chamber heads are already on there, it just makes leaving them on,for me, an easy decision.And the smaller vac.secondary carb should keep it out of detonation, esp. with 3.55s or better and the 2800TC.
Man I would try everything I know to try and make that tyre-fryer work with those heads before I would yank them. And then, if I just couldn't do it, I would stick a bit more gasket under them and try all over again.If it can be made to run this way( remember,we're not going racing, and most of it's life will be spent below 4000rpm/62mph/2nd gear, and very lightly loaded), it will have a dynomite lower end. In a lightweight Dart without traction aides, or tubs, it will light em up anywhere, anytime.I mean 275s is about all you are gonna fit in those stock tubs, and almost any warmed over teener can light those up ,under the same circumstances.So it's like hunting rabbits. Why use a cannon if a 22 will do the job.The rabbit is gonna be just as dead. And the 440 will annihilate those tires even easier.
3) so this is not just engine science; this is whole pkg, street science.By his opening post, he just wants to enjoy the car, and he's on a budget. So fix the rocker issue, tune it, and drive. Badaboom.
Did I mention that I once put a complete teener top end on a 340.Same idea here. Plenty of compression, small carb, sharp tune,go like stink to speedlimit. And on low dollars spent!
 
AJ/FormS said:
72 posts and nowhere did I see a timing curve,compression results, or jetting loops, or even that the fuel was fresh 93 octane.
The single biggest contributor to Detonation is in-chamber heat.I did not read anywhere about what circumstances lead to the detonation.There are so many things and so many ways, and................not one word.
Oh wait,"Not sure on the timing. Haven't had time to get out there and check it. I know the timing is close to where it needs to be. It starts with a bump."
This is about the silliest detonation diagnoses I've ever read.

Now heres the thing; by dropping the compression with open chamber heads, thus loosing that fabulous .039quench, and then introducing an earlier closing intake, you are moving in every wrong direction. Your Dcr could very well go up, and without the favorable quench, you may end up with even more detonation.

Your cylinder pressure is so easy to measure.and
Your compression ratio is so easy to figure out.and
Your timing is so easy to measure. and
Your fuel grade and freshness is so easy to change.and
Your lifter preload is so easy to measure.

I hate to sound like a jerk, but hey,you look like your drowning.
Click to expand...

All of the above is pointless to check when you know you have a disastrous combination of parts. Hydraulic lifters on a solid cam, a cam that is much too large for non-adjustable rockers with pushrods that are way too big in length for the circumstances, closed chambers heads on top of a zero deck motor with no valve reliefs. Now, there is no quench in this motor. If you do the math, on closed chambered heads, technically .040 is about right in the middle of the ballpark where you want to be, well with this motor that number is MUCH smaller......

I know how to check all of the above but it is more or less pointless to do so with what I have going on.

Trust me, I have taken in a ton of information for numerous people and forums.. Not to mention I also called some of my local machine shop guys to get their two cents.

Thanks for the info though.
 
AJ/FormS said:
Now here's a little math; Let's start with a stock stroke and bore+.030. That would be 4.35 x 3.75. That calculates out to a 921.7 swept. If in fact the engine was previously 10.75Scr(post 36), that requires a total chamber volume of 94.53 cc.; 909/(10.75-1)=94.53
Since we know(or you say) the block is zero decked and you have flat-tops with no reliefs, it's easy to figure the chamber volume is 94.53 less the gasket.I have to guess at the gasket bore; say 4.40 and the thickness of .038,well that makes about 9.5cc. so that tells us that he the PO was using 94.53 - 9.5=85cc heads. That was his combo, and it makes sense, if he started with 90cc

Now your combo with the same 9.5cc gaskets and 78cc heads comes to
{921.7 + (78 + 9.5)}/87.5 = 11.53Scr
The Wallace calculator puts this at a Dcr of 8.7 and the cranking compression pressure at 177psi, with an ICA of 70* degrees using that 292/509 cam.
Now that is for sure testing the limits of pump 93. But guess what; you have the .038 quench going for you and by your own admission you're not into racing. So if you're not interested in the max power, then there is no reason to run max timing. You can run 34* or 32* of power timing if that is what it takes to kill WOT detonation.
Now let's talk PT(part throttle) detonation. At 8.7Dcr this is again pushing it, But guess what; you have not done any timing loops. There is a ton, a TON of tuning you can do to get it out of detonation at PT. A TON.
Detonation is also load sensitive. Let's take an engine that is on the edge of detonation with full timing, that is stuck in a chassis with 2.76 gears and a 2400 TC. So then you put in 3.55s and a 2800 TC, and move the detonation up several hundred rpm. Then take out 1 or 2 or 3 degrees of power timing and problem solved. But guess what; you may be able to run full PT timing and have a dynomite engine , at anything short of peak torque! See what I mean about tuning.So you can start your tune with carburetion.If the engine cannot ingest a full load of air it will not experience a full load. So a smaller carb than optimum is on the table.Well that is not said right, but the result is the same. Take the 850 off and try a 750 or a 650.Or something with a load-sensitive secondary.

Now lets put those open chamber bad boys on there with a 284/484 cam. Let's say they come in at 90cc. The Scr will be (921.7 + 90 + 9.5)/99.5 = 10.26Scr and the Wallace calc. puts that at a Dcr of 8.06,with a ICA of 66*, and pressure of 161. Phew you dodged a bullet. This is pretty safe. But guess what; you are still stuck with the problematic rocker gear.And you have lost completely, all the Quench benefits, which may have allowed the prior 11.5SCR.And you may have given up some terrific PT benefits.Which you are wanting.

I know which combo I would want under my hood. But I am willing to measure stuff and calculate stuff and tune it til it wails.

Quote from Doosterfy,(post 70)
"There are plenty of guys, engine builders in particular who will steer people away from pushing it. Its been my experience over the years (I've been at this since the 70s) that keeping compression and/or cylinder pressure up makes a car much more fun to drive, much better off idle throttle response, less throttle opening to propel the car, it sounds better and the car will simply have more snap to it. I got talked into staying at 9 to 1 or lower twice and both times I was very disappointed with the results after spending my time and money building the engines".
(My experience as well. AJ)
Sorry for the novel; it was a lot shorter in my head.

OOps, One more thing, If the big 440 gets tirespin, it is no longer loaded.Wrap your head around that for a sec.
Click to expand...

I never said I have .038 quench distance. The motor has a 750 carb on it currently.

("But guess what; you are still stuck with the problematic rocker gear." ) Not sure what you are going off of right here.. With a smaller cam, I eliminate the problematic rocker situation.

Good info.
 
the victor reinz head gasket is approximately .044" and with a 0 deck and flat tops and closed chamber heads the quench is a decent .044" . the exhaust sounded very loud, and backed down timing was tried, maybe it was not detonating. a thinner gasket equals more quench
 
Ok guys, I am going to start a new thread. I have more information on what I have, and want to further discuss this.
 
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