Why so much inital timing???

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Lustle said:
OP said he recalled that IVC was 60. He didn't mention which pistons specifically. But .030 over with 9.6 static compression. I did not see a mention of which carb he used.

Or head gasket
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Notice what? That OP gave the IVC as 60? Or that I guessed that same number? lol Or wait! Did you mean that I said DCR was probably between 7.85 and 7.98? Or that with the IVC at 60, I calculated DCR at 7.90:1? Look at that. There's me. Right again lol.
You act like you're the only person who could put that together, you're full of yourself, plus your numbers are still shy and give the same conclusion of what his dynamic there or about is...and its not stellar
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I'm not torn up over anything. I said DCR would be good for iron heads. And it was. I also said that max DCR on iron head's isn't worth it on an everyday street motor. He's right up where he and his builder wanted it, and it's great for the street.
I said ideally ...BUT YOU straight say "the max for iron heads" , when that is complete bullshit. You have no clue, you just spaz and round off numbers to as to seem right when you're wrong
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You're the one throwing a temper tantrum and disliking everyone's posts just cause they disagree with your "opinion". I call that torn up lol.
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I disliked instead of railroading this thread. So much for that...
 
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moper said:
Too much chaff on this one so maybe I missed it but - OP - What was the intake closing point again? What pistons were used? What carburetor's on it?
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Just looked at the cam card. IVC is 39* @ .050". Since advertised duration is 275* and @ .050" duration is 231*, does that mean seat IVC is 61* (275-231/2 + 39)? I recalculated SCR again based on notes in my file. Looks like it's right at 9.7:1. Heads are 65.2cc, Pistons are speed pro L2316 with a -7.5 cc volume and are .015" out of the hole. Gaskets are 521SD felpros with 4.18" bore and .054" compressed thickness for a quench distance of .039".

The carb on it now is a 85670 Holley 670 street avenger. It's on the small side since the throttle bore and venturi sizes are the same as an 1850, but I've also got a 650 proform double pumper with throttle bore and venturi sizes of 1-3/8 and 1-11/16. I've also got an old 4-corner idle 4779 to try as well.
 
If the motor runs well with no detonation leave it as is and go to the 1320 dyno. Make a pass or two and dial the AFR in. Once fuel delivery is good, best mph is achieved, move on to bumping ignition up or down and see what mph does. Take good notes and make one change at a time. Have fun and learn what your combo likes.
 
RustyRatRod said:
I am not trying to take sides here, but, IMO the camshaft has too late a closing event for that (whatever it is) compression ratio. This is why you can crank in so much initial timing.........essentially why you HAVE to for it to run well.

That's no insult to you or whomever built it, it's just a fact. You could be making more power with either A) more static compression and the same camshaft, or B) a camshaft with an earlier closing event to build more cylinder pressure.

You have 9.6:1 compression and a camshaft with a later IVC, more overlap and more duration @.050" than the factory 340 camshaft in an engine rated at 10.2:1. All those "mores" add up to lower "than could be" cylinder pressure. Those are the facts..

This means that theoretically, your camshaft "should be smaller" (earlier IVC) than the factory 340 camshaft.

That doesn't mean it's a dog. That just explains why you have to have so much initial timing. With a "smaller" (earlier IVC) camshaft, OR more SCR, you would make probably a substantial amount more power, because doing either would raise the DCR.

Just my 2 cents.
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This guy gets it.
Sad for the rest of you who don't.
 
mopowers said:
Just looked at the cam card. IVC is 39* @ .050". Since advertised duration is 275* and @ .050" duration is 231*, does that mean seat IVC is 61* (275-231/2 + 39)? I recalculated SCR again based on notes in my file. Looks like it's right at 9.7:1. Heads are 65.2cc, Pistons are speed pro L2316 with a -7.5 cc volume and are .015" out of the hole. Gaskets are 521SD felpros with 4.18" bore and .054" compressed thickness for a quench distance of .039".

The carb on it now is a 85670 Holley 670 street avenger. It's on the small side since the throttle bore and venturi sizes are the same as an 1850, but I've also got a 650 proform double pumper with throttle bore and venturi sizes of 1-3/8 and 1-11/16. I've also got an old 4-corner idle 4779 to try as well.
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The Pro Form will out perform the 4779.
 
mopowers said:
Just looked at the cam card. IVC is 39* @ .050". Since advertised duration is 275* and @ .050" duration is 231*, does that mean seat IVC is 61* (275-231/2 + 39)? I recalculated SCR again based on notes in my file. Looks like it's right at 9.7:1. Heads are 65.2cc, Pistons are speed pro L2316 with a -7.5 cc volume and are .015" out of the hole. Gaskets are 521SD felpros with 4.18" bore and .054" compressed thickness for a quench distance of .039".

The carb on it now is a 85670 Holley 670 street avenger. It's on the small side since the throttle bore and venturi sizes are the same as an 1850, but I've also got a 650 proform double pumper with throttle bore and venturi sizes of 1-3/8 and 1-11/16. I've also got an old 4-corner idle 4779 to try as well.
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Get a 750 and you pick up power right there alone.
Btw see how fuzzy it is, now its 9.7 and the head gasket got thicker and quench on the higher side.
 
MOPAROFFICIAL said:
You gotta be kiddin me, why are you still talking?
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Giving you a chance to say something of value?

You're pissed off because the guy runs what YOU think is a bunch of initial.

He ain't going for fuel mileage. Evidently he's not bitching about a rough idle.

There is ZERO wrong with what the OP is doing. You don't like it. You don't agree with it. Who cares what you think?
 
RustyRatRod said:
I am not trying to take sides here, but, IMO the camshaft has too late a closing event for that (whatever it is) compression ratio. This is why you can crank in so much initial timing.........essentially why you HAVE to for it to run well.

That's no insult to you or whomever built it, it's just a fact. You could be making more power with either A) more static compression and the same camshaft, or B) a camshaft with an earlier closing event to build more cylinder pressure.

You have 9.6:1 compression and a camshaft with a later IVC, more overlap and more duration @.050" than the factory 340 camshaft in an engine rated at 10.2:1. All those "mores" add up to lower "than could be" cylinder pressure. Those are the facts..

This means that theoretically, your camshaft "should be smaller" (earlier IVC) than the factory 340 camshaft.

That doesn't mean it's a dog. That just explains why you have to have so much initial timing. With a "smaller" (earlier IVC) camshaft, OR more SCR, you would make probably a substantial amount more power, because doing either would raise the DCR.

Just my 2 cents.
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With his IVC and compression. Gives him a DCR of right around 8:1. Could there be more? Absolutely. Is it worth it? Ehhhh. I don't think so. What's half a point of DCR worth? 5 horse? And with the headaches of good gas, detonation, pinging, etc etc that comes with max DCR on iron heads. Gotta remember, factory 340 cars had a lot better gas around to run on. He's at sea level, with cali 91 octane, not a recipe for high compression unfourtunately. Given that the builder was aiming for 8:1 DCR, and landed right near it. I think it's a good setup.

MOPAROFFICIAL said:
I disliked instead of railroading this thread. So much for that...
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I never said I was the only one that could put things together. I said I figured it out when you couldn't or wouldn't. You just made the broad statement that "His DCR is too low, he should be at 8:1 to 8.5:1. Which he is at. I'm a details man. Rather than say "You did this wrong". How about you try and figure out if he actually did it wrong first. That's my point.

I'm not derailing anything. I'm giving him actual and intelligent advice. Rather than saying "No you did this wrong". I'm saying "Well this is what you got here, and this is what you got here". See the difference? One is just telling someone they did something wrong. The other is teaching someone. You were already asked to leave this thread by OP. If anyone is derailing anything, it's you.

mopowers said:
Just looked at the cam card. IVC is 39* @ .050". Since advertised duration is 275* and @ .050" duration is 231*, does that mean seat IVC is 61* (275-231/2 + 39)? I recalculated SCR again based on notes in my file. Looks like it's right at 9.7:1. Heads are 65.2cc, Pistons are speed pro L2316 with a -7.5 cc volume and are .015" out of the hole. Gaskets are 521SD felpros with 4.18" bore and .054" compressed thickness for a quench distance of .039".

The carb on it now is a 85670 Holley 670 street avenger. It's on the small side since the throttle bore and venturi sizes are the same as an 1850, but I've also got a 650 proform double pumper with throttle bore and venturi sizes of 1-3/8 and 1-11/16. I've also got an old 4-corner idle 4779 to try as well.
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Oh good, exact cam specs. Now we should be able to tell you exactly what you got. Using Wallace Racing - Cam Degree Calculator. Your IVC is 61.5

I'm curious how you came to 9.7:1 compression? Punching everything in you came up with on Compression Ratio Calculator - Wallace Racing gives me 10.67:1.

As for carb. If you got a 750 double pumper around. Give that a shot on there. You might be pleasantly surprised.
 
Lustle said:
With his IVC and compression. Gives him a DCR of right around 8:1. Could there be more? Absolutely. Is it worth it? Ehhhh. I don't think so. What's half a point of DCR worth? 5 horse? And with the headaches of good gas, detonation, pinging, etc etc that comes with max DCR on iron heads. Gotta remember, factory 340 cars had a lot better gas around to run on. He's at sea level, with cali 91 octane, not a recipe for high compression unfourtunately. Given that the builder was aiming for 8:1 DCR, and landed right near it. I think it's a good setup.
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I go along with all that. And I didn't say it was a bad combo........just that MOPAROFFICIAL has a very valid point.

Perhaps.......sometimes like me, his delivery could be a bit more polished, but he is right.

What I would do would be to run a compression test. It costs nothing. I bet the cylinder pressure is at or under 150........but again........so what?

I've run engines before with stock compression and HUGE camshafts......with cranking pressures at 100. LOL

But they sounded kick ***.
 
Lustle said:
With his IVC and compression. Gives him a DCR of right around 8:1. Could there be more? Absolutely. Is it worth it? Ehhhh. I don't think so. What's half a point of DCR worth? 5 horse? And with the headaches of good gas, detonation, pinging, etc etc that comes with max DCR on iron heads. Gotta remember, factory 340 cars had a lot better gas around to run on. He's at sea level, with cali 91 octane, not a recipe for high compression unfourtunately. Given that the builder was aiming for 8:1 DCR, and landed right near it. I think it's a good setup.



I never said I was the only one that could put things together. I said I figured it out when you couldn't or wouldn't. You just made the broad statement that "His DCR is too low, he should be at 8:1 to 8.5:1. Which he is at. I'm a details man. Rather than say "You did this wrong". How about you try and figure out if he actually did it wrong first. That's my point.

I'm not derailing anything. I'm giving him actual and intelligent advice. Rather than saying "No you did this wrong". I'm saying "Well this is what you got here, and this is what you got here". See the difference? One is just telling someone they did something wrong. The other is teaching someone. You were already asked to leave this thread by OP. If anyone is derailing anything, it's you.



Oh good, exact cam specs. Now we should be able to tell you exactly what you got. Using Wallace Racing - Cam Degree Calculator. Your IVC is 61.5

I'm curious how you came to 9.7:1 compression? Punching everything in you came up with on Compression Ratio Calculator - Wallace Racing gives me 10.67:1.

As for carb. If you got a 750 double pumper around. Give that a shot on there. You might be pleasantly surprised.
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I'm using chevron 91 at sea level with an 8.8 /185 dynamic...I live at the beach! 8.1 is weak on our 91 octane..You just like to argue, and its not just 5 hp!
 
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RustyRatRod said:
I go along with all that. And I didn't say it was a bad combo........just that MOPAROFFICIAL has a very valid point.

Perhaps.......sometimes like me, his delivery could be a bit more polished, but he is right.

What I would do would be to run a compression test. It costs nothing. I bet the cylinder pressure is at or under 150........but again........so what?

I've run engines before with stock compression and HUGE camshafts......with cranking pressures at 100. LOL

But they sounded kick ***.
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He's right DCR could be higher. Not arguing against that, I said that from the start. He is wrong in saying stuff like "Because the cam is too big for the static compression. People too many times do not calculate the dynamic/cranking psi when deciding a cam" and "I'm saying the int close is killing your dynamic compression.". Turns out the builder specced the cam specifically to this setup. And, that cam isn't too big, it's at 8:1 DCR. And killing it? To me killing it means 7:1 or lower DCR. That's a dog every day of the week. Then he says "Ideally you wanna shoot for an 8.1- or better dynamic". Which obviously OP was doing, because that's where he's at. And MOPAROFFICIAL would have also known that, had he bothered to take the time to figure it out. He didn't.

I just have a problem when some guy comes into a thread, doesn't take the time to actually look at what is going on, and just says "I'm a genius and you did this this and this wrong." Do I tell people what's wrong? Yup. Do I also teach and show them the reason behind it? Yup. Because to me, the devil is in the details. Working with methanol race engines taught me that.

Which, speaking of that and your mention of big cams, I can't tell you how many guys I met that wanted that "race engine idle". Not realizing that this things sit there at 1700+rpm idles, with 700+ lift cams, and and only make power from 7K-9K RPM cause all they do all night is go around and around in a circle at full throttle. And that oddly enough, that doesn't work so well on the street!
 
RustyRatRod said:
I go along with all that. And I didn't say it was a bad combo........just that MOPAROFFICIAL has a very valid point.

Perhaps.......sometimes like me, his delivery could be a bit more polished, but he is right.

What I would do would be to run a compression test. It costs nothing. I bet the cylinder pressure is at or under 150........but again........so what?

I've run engines before with stock compression and HUGE camshafts......with cranking pressures at 100. LOL

But they sounded kick ***.
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What's strange to me is I wasn't rude, blunt...but I went kn to say its fine and he is happy, then all dorks on deck start in..
I said the IVC is hurting the dynamic "killing the dynamic" shouldn't set off red alarms.
 
Well.......most people.......self included pick a camshaft on the large side. I mean seriously, I know I don't want my crap to SOUND like crap........but through the years, I've learned to be more conservative as that usually yields better results......at least on the street.
 
MOPAROFFICIAL said:
What's strange to me is I wasn't rude, blunt...but I went kn to say its fine and he is happy, then all dorks on deck start in..
I said the IVC is hurting the dynamic "killing the dynamic" shouldn't set off red alarms.
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Yeah well.......there've been times I was blunt and not rude and got the **** kicked outta me. LOL
 
Lustle said:
He's right DCR could be higher. Not arguing against that, I said that from the start. He is wrong in saying stuff like "Because the cam is too big for the static compression. People too many times do not calculate the dynamic/cranking psi when deciding a cam" and "I'm saying the int close is killing your dynamic compression.". Turns out the builder specced the cam specifically to this setup. And, that cam isn't too big, it's at 8:1 DCR. And killing it? To me killing it means 7:1 or lower DCR. That's a dog every day of the week. Then he says "Ideally you wanna shoot for an 8.1- or better dynamic". Which obviously OP was doing, because that's where he's at. And MOPAROFFICIAL would have also known that, had he bothered to take the time to figure it out. He didn't.

I just have a problem when some guy comes into a thread, doesn't take the time to actually look at what is going on, and just says "I'm a genius and you did this this and this wrong." Do I tell people what's wrong? Yup. Do I also teach and show them the reason behind it? Yup. Because to me, the devil is in the details. Working with methanol race engines taught me that.

Which, speaking of that and your mention of big cams, I can't tell you how many guys I met that wanted that "race engine idle". Not realizing that this things sit there at 1700+rpm idles, with 700+ lift cams, and and only make power from 7K-9K RPM cause all they do all night is go around and around in a circle at full throttle. And that oddly enough, that doesn't work so well on the street!
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Now you are splitting hairs...
7.1 is when you finally call it a dog, hmm telling. You picked a line or two, took them funny and then ran with it.
Talk about triggered...
 
Lustle said:
I'm curious how you came to 9.7:1 compression? Punching everything in you came up with on Compression Ratio Calculator - Wallace Racing gives me 10.67:1.
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I used this one- RSR Static Compression Ratio Calculator and used positive 7.5 cc's for the piston valve reliefs and -.015" for deck height since the pistons are out of the hole. It seems backwards, but that's the way the calculators work. The calculator I used doesn't take the larger bore diameter of the head gasket into consideration though. The wallace one does and produces 9.64 with my numbers. Either way, the SCR I get is 9.6-9.7:1, depending on the calculator. Obviously, the 0.1 difference is lost in the noise.

Lustle said:
As for carb. If you got a 750 double pumper around. Give that a shot on there. You might be pleasantly surprised.
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You think??? Even though the venturi and throttle bore sizes are the same as the proform? It'll be interesting to test when I go to the track. I've got a wideband to help get them both tuned well enough before the track shootout.
 
I got 9.645 using the United Engine calculator. I think we are all pretty close. It should run ok. I'd drive it.
 
mopowers said:
I used this one- RSR Static Compression Ratio Calculator and used positive 7.5 cc's for the piston valve reliefs and -.015" for deck height since the pistons are out of the hole. It seems backwards, but that's the way the calculators work. The calculator I used doesn't take the larger bore diameter of the head gasket into consideration though. The wallace one does and produces 9.64 with my numbers. Either way, the SCR I get is 9.6-9.7:1, depending on the calculator. Obviously, the 0.1 difference is lost in the noise.



You think??? Even though the venturi and throttle bore sizes are the same as the proform? It'll be interesting to test when I go to the track. I've got a wideband to help get them both tuned well enough before the track shootout.
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Some of these guys are pissing in your cereal because you CAN run all that initial. To them, they think you have the cam too big, not enough CR etc. But they didn't spec the cam. If you spent the drachmas on a custom cam, I will absolutely promise you the cam is correct. So is your timing. Run that biotch. Just because they can't/won't/don't do it doesn't mean your wrong.

You did it right. You picked a CR and then bought a cam for the CR. That is how you do it when you do it.
 
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MOPAROFFICIAL said:
Now you are splitting hairs...
7.1 is when you finally call it a dog, hmm telling. You picked a line or two, took them funny and then ran with it.
Talk about triggered...
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Cause below 7:1 is a dog. 7:1 would run on pump regular. Why build a performance engine to run it on regular?

I didn't pick a line or two. In one post you straight up said his cam was too big for good DCR. That he needed 8:1 or more. When he was already at or very close to 8:1. So which is it? lol Don't get bent out of shape cause you got caught skipping the homework. And triggered? No. Triggered is taking the 10 minutes to go through and dislike every post in a thread cause you're having a hissyfit lol.

mopowers said:
I used this one- RSR Static Compression Ratio Calculator and used positive 7.5 cc's for the piston valve reliefs and -.015" for deck height since the pistons are out of the hole. It seems backwards, but that's the way the calculators work. The calculator I used doesn't take the larger bore diameter of the head gasket into consideration though. The wallace one does and produces 9.64 with my numbers. Either way, the SCR I get is 9.6-9.7:1, depending on the calculator. Obviously, the 0.1 difference is lost in the noise.
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Ahhh ok. When you said -7.5 cc volume. I took it the other way. Usually negative volume means you ADD compression. By making the compression chamber smaller. Make sense?

So lets just say 9.6 for sake of argument. With 61.5 IVC, put's your dynamic compression ratio at 7.80:1 .Your dynamic cranking pressure is 154.70 PSI. According to the wallace calculator.

So yeah. There's more in there for DCR. You could go to a .040 cometic head gasket. Pick your static compression up to 9.92 and DCR to 8.05. IF that really matters to you.

mopowers said:
You think??? Even though the venturi and throttle bore sizes are the same as the proform? It'll be interesting to test when I go to the track. I've got a wideband to help get them both tuned well enough before the track shootout.
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Well I whenever I say double pumper I just mean the style itself. Holley, AED, proform, quick fuel. Whatever. 750 doubles seem to work great on 340s.
 
Honestly, if I could get away with running a locked out mechanical advance on the street, have it start every time, and not detonate, I'd do it every time. There's nothing saying you can't run a vacuum can with a locked out mechanical.

I have real issue with all of this DCR talk also. To me, a DCR is nothing but a STATIC measurement that doesn't take into account the many other factors that influence cylinder filling. Its like saying you have a 10:1 compression ratio because you put in 10:1 pistons, and it says so right on the box. There are a lot of other things that affect it. So, exactly how does the intake valve closing point dictate exactly how much intake charge actually gets trapped in the cylinder. Does it play a role? Absolutely, but it is not the end all, be all that it is made out to be.
 
Yeah it;s really splittin hairs to a point, especially on a street motor......but some guys think the same way about all engines. Gotta get as much power as possible......and that's cool. But not everybody cares about that last little bit. I say build what you want to and run it. Every combo leaves something on the table so what the hell?
 
RustyRatRod said:
I got 9.645 using the United Engine calculator. I think we are all pretty close. It should run ok. I'd drive it.
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Yep I agree, and it will run 87 octane too.
I called it early on, I mean...I could maybe accept that dynamic with old open chambers and no quench...but rhs closed chambered heads, hmm.
 
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