Why so much inital timing???

[Lustle]

All assuming it is a true 10.1 motor which I see no evidence of, he has no real idea for he didn't measure it himself. I bet its more like 9.5 or so, but only way to really know is by taking it apart and measuring everything.
You can all build how you like, or claim to at least, but don't for one minute assume you do it better than everyone else.

Actually I bet it's 9.6. Like he mentions in his first post:

Engine is a .030 over 340, 9.6 SCR, RHS heads, 231* @ .050"/.561" lift/108 LSA hydraulic flat tappet.

He also mentions the shop opening the chambers a bit and purposely figuring out DCR at close to 8:1 with the custom spec cam. So it sounds like they know what they were doing to me.

 

[MOPAROFFICIAL]

Actually I bet it's 9.6. Like he mentions in his first post:


He also mentions the shop opening the chambers a bit and purposely figuring out DCR at close to 8:1 with the custom spec cam. So it sounds like they know what they were doing to me.

And again...I won't knock that shop, but they took the balls off that doggy with that compression ratio. It probably cranks 155psi..and again, that's why he can crank up the initial timing.

 

[mopowers]

All assuming it is a true 10.1 motor which I see no evidence of, he has no real idea for he didn't measure it himself. I bet its more like 9.5 or so, but only way to really know is by taking it apart and measuring everything.

What makes you think I didn't measure it myself? I've measured everything I could. And everything I couldn't, I had the machine shop measure it. Pistons are .015" out of the hole, gaskets are .052" (if I recall), heads are 65cc, SCR is at 9.65:1. Nowhere did I mention the motor was 10:1. I didn't want it that high. You can go away now.

 

[Lustle]

And again...I won't knock that shop, but they took the balls off that doggy with that compression ratio. It probably cranks 155psi..and again, that's why he can crank up the initial timing.

So they took the balls off by getting 8:1 DCR like you recommended earlier? Or are you just saying that now cause you're upset?

I said it before and I'll say it again. In a daily like this (I'm assuming it's your daily mopowers, if I lived in cali my scamp would be my daily), I'd rather run 8:1 DCR, give up that WHOPPING 5hp that .5 DCR will give and not have to worry about where I get my gas. Or how hot is it out. Or tune up. ESPECIALLY on that shitty cali gas.

 

[mopowers]

Either way, I got my answer. 28* of initial timing isn't unusual and doesn't indicate a huge problem, if everything is running well. Thanks

 

[MOPAROFFICIAL]

So they took the balls off by getting 8:1 DCR like you recommended earlier? Or are you just saying that now cause you're upset?

I said it before and I'll say it again. In a daily like this (I'm assuming it's your daily mopowers, if I lived in cali my scamp would be my daily), I'd rather run 8:1 DCR, give up that WHOPPING 5hp that .5 DCR will give and not have to worry about where I get my gas. Or how hot is it out. Or tune up. ESPECIALLY on that shitty cali gas.

I actually live here in California, I know what the gas quality is, so please already..
That was a common rule of thumb I repeated when in reality if you're going with after market heads and let say even a roller...you wouldn't give up cylinder pressure if you were bright.
I read your posts and all ill say is...you like to argue for sake of arguing.
His cylinder pressure is low, that's why he can crank up the timing...and you know it.

 

[MOPAROFFICIAL]

Either way, I got my answer. 28* of initial timing isn't unusual and doesn't indicate a huge problem, if everything is running well. Thanks

And if you took me right, that's all I was saying...it could be better but its fine if you like it. But that is the answer to your question, lower than ideal dynamic compression imo.

 

[MOPAROFFICIAL]

If you're so smart...why in the hell are you asking a question you should already know the answer to...lmao

 

[nm9stheham]

I understand that. I'm just wondering what the calculators use. If they don't say, is it safe to assume they are using the "at the seat" IVC event?

Most calculators use the IVC-at-the-seat, but I see 1 or 2 use 15* beyond the .050" angle on the intake closure cycle. The latter will estimate an 'effective' IVC that is 5 to 10 degrees earlier than actual IVC-at-the-seat (which is a smaller ABDC number), and will give you a higher DCR computation.

 

[nm9stheham]

BTW, OP, what measurement or indication are using to judge that the motor is 'happiest' with the 28* initial?

 

[mopowers]

BTW, OP, what measurement or indication are using to judge that the motor is 'happiest' with the 28* initial?

Thats the point at which I get the highest vacuum reading in gear at idle. It's also around where the RPMs stop increasing when adding timing. Also, it seems to fire up and idle a lot faster at that point, than say the 20* where I had it before when I was messing around with it, with better throttle response too. Am I off base? Thanks for the input btw. Didn't mean to start a **** storm. Just never had an engine that seemed to 'want' this much initial before. I runs great though, with no hiccups. Once I finish tuning a couple different carbs I have for it, I'll be taking it out to the track for some testing.

 

[Lustle]

I actually live here in California, I know what the gas quality is, so please already..
That was a common rule of thumb I repeated when in reality if you're going with after market heads and let say even a roller...you wouldn't give up cylinder pressure if you were bright.
I read your posts and all ill say is...you like to argue for sake of arguing.
His cylinder pressure is low, that's why he can crank up the timing...and you know it.

He's not giving up anything. 8:1 DCR on a street motor with iron heads is good. Even you said you should aim for 8:1 - 8.5:1. Then you find out you're wrong, his DCR isn't in the shiter and he's at 8:1 and you keep arguing? Who likes to argue for the sake of arguing now? Can he run more DCR? Yes. I said that from the start. Is it worth it? No. What will he gain from .5 DCR? Maybe 5 horse. What does he risk? Detonation. Timing issues. Tune issues. Gas issues. Etc etc etc.

His build is obviously a well thought out build. With time and attention to detail. Does it squeeze out every last horse? No. Will it run every day for a long time? Yes.

And if you took me right, that's all I was saying...it could be better but its fine if you like it. But that is the answer to your question, lower than ideal dynamic compression imo.

I thought you said ideal DCR was 8:1-8.5:1. He's at 8:1. So its not lower than ideal in your own opinion.

If you're so smart...why in the hell are you asking a question you should already know the answer to...lmao

If you're so smart why can't you get 3 replies into one post? lmao

Most calculators use the IVC-at-the-seat, but I see 1 or 2 use 15* beyond the .050" angle on the intake closure cycle. The latter will estimate an 'effective' IVC that is 5 to 10 degrees earlier than actual IVC-at-the-seat (which is a smaller ABDC number), and will give you a higher DCR computation.

The 15* addition is an ok way to guess. But generally the smaller cams (under 220duration) will be more 12*-13* where as bigger cams (over 250/260) will probably be in the 18*-20* range. So you can see, for 8 out of 10 street motors, guessing 15* will get you close. That's why I much prefer getting the actual IVC at seat, for best accuracy. The power is in the details on engines.

Thats the point at which I get the highest vacuum reading in gear at idle. It's also around where the RPMs stop increasing when adding timing. Also, it seems to fire up and idle a lot faster at that point, than say the 20* where I had it before when I was messing around with it, with better throttle response too. Am I off base? Thanks for the input btw. Didn't mean to start a **** storm. Just never had an engine that seemed to 'want' this much initial before. I runs great though, with no hiccups. Once I finish tuning a couple different carbs I have for it, I'll be taking it out to the track for some testing.

That's a good way to go about it. Generally add timing to get best vacuum/rpm. Then shut it off for 20, try and start. If it starts no problem. Get it up to operating temp. Then shut it off for 10, try and start. If it starts no problem, get it up to operating temp. Then **** it off for 5. If it starts no problem. That's where it should be.

Ideally, you would be able to take it to a dyno and figure it out. Best vacuum/rpm should also be best horsepower. But you don't know unless you dyno it. I will say this. If you play around with the timing. You will find an initial that it just runs awesome at. I remember with my car when I first got it I was tuning and I played with it, brought it up from 18-22. It was night and day. Throttle response was much more immediate. It barked a lot harder. And just absolutely wanted to run hard. It was the definition of scalded dog. If you looked at the pedal it would squawk the tires. You can and will notice the difference in better initial timing.

 

[JoeSBP]

I was making highest idle vacuum/RPM at around 22*. Once I properly set the primary t-port so the idle circuit was actually doing anything and used only the secondary to adjust idle, highest idle vacuum/RPM was now around 19*. I suspect if I give her even more air via drilling holes in the butterflies, I'll be down to 15*-18*. So could be as simple as overly rich from t-port or leaking pv right?

 

[yellow rose]

Thats the point at which I get the highest vacuum reading in gear at idle. It's also around where the RPMs stop increasing when adding timing. Also, it seems to fire up and idle a lot faster at that point, than say the 20* where I had it before when I was messing around with it, with better throttle response too. Am I off base? Thanks for the input btw. Didn't mean to start a **** storm. Just never had an engine that seemed to 'want' this much initial before. I runs great though, with no hiccups. Once I finish tuning a couple different carbs I have for it, I'll be taking it out to the track for some testing.

I have run 20 plus degrees initial on everything I do for years.

My car, a street car, has the distributor locked out at 36 degrees, so at idle, that's what it has. May like 38, but I'm not there yet.

Generally, if you can't run all that initial, you gave up power somewhere else. Even on the beloved Chevy.


You are plenty good. Give your combo what IT wants. Not what the keyboard tuners do. They learned it from someone else who learned it on the net, who learned it from someone who learned it on the net, who learned it from someone who learned it from a dude who leaned on the fence at the track. But the dude could tell a great story.

 

[MOPAROFFICIAL]

Overly sensitive bunch.
Ive done the things I say, that's how I know you can run a lot more dynamic than this.
To some of you...what is under your hood you have built that will back up your talk?
I just got done reading 7+ pages of you goons arguing about cams....hyjack heaven.
Do you even have anything running?

 

[MOPAROFFICIAL]

Give your combo what IT wants. Not what the keyboard tuners do. They learned it from someone else who learned it on the net, who learned it from someone who learned it on the net, who learned it from someone who learned it from a dude who leaned on the fence at the track. But the dude could tell a great story.

For lustle this is true.

 

[Lustle]

I have run 20 plus degrees initial on everything I do for years.

My car, a street car, has the distributor locked out at 36 degrees, so at idle, that's what it has. May like 38, but I'm not there yet.

BLASPHEMY! What do you mean you run a locked distributor on the street! That'll never work. You're getting 1 less MPG than you could if you did it right! Locked out timing is for race cars not street cars! You're missing out on bottom end with that distributor locked! What about vacuum advance! You don't know how to tune a street motor!

End sarcasm.

Overly sensitive bunch.
Ive done the things I say, that's how I know you can run a lot more dynamic than this.
To some of you...what is under your hood you have built that will back up your talk?
I just got done reading 7+ pages of you goons arguing about cams....hyjack heaven.
Do you even have anything running?

Overly sensitive? Say's the guy who can't just admit he was wrong, even after he's been asked to go away lol.

For lustle this is true.

The only thing true for me is that I figured his IVC and DCR with minimal cam specs. And was right on the bat. You know. Those details you didn't, I mean couldn't, figure out? lol

 

[nm9stheham]

Thats the point at which I get the highest vacuum reading in gear at idle. It's also around where the RPMs stop increasing when adding timing. Also, it seems to fire up and idle a lot faster at that point, than say the 20* where I had it before when I was messing around with it, with better throttle response too. Am I off base? Thanks for the input btw. Didn't mean to start a **** storm. Just never had an engine that seemed to 'want' this much initial before. I runs great though, with no hiccups. Once I finish tuning a couple different carbs I have for it, I'll be taking it out to the track for some testing.

I was just curious to know how you set this, and asked for the sake of others who may not know.

SSH (**** storms happen LOL). It's in the internet after all LOL x2

 

[yellow rose]

Overly sensitive bunch.
Ive done the things I say, that's how I know you can run a lot more dynamic than this.
To some of you...what is under your hood you have built that will back up your talk?
I just got done reading 7+ pages of you goons arguing about cams....hyjack heaven.
Do you even have anything running?

Nope. I have nothing. Don't own nothing. Never did anything. Never have. Probably never will.


My goal for 2017 is to go from my parents basement to a bedroom on the main floor.

 

[moper]

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?

 

[MOPAROFFICIAL]

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?

I was wondering someone else was gonna notice this. Even at the number the one clown is giving , its under 8.1 dynamic... and the ve is probably as weak. That doesn't mean it won't run good, but these guys are torn up over opinion.

 

[yellow rose]

Nope. I have nothing. Don't own nothing. Never did anything. Never have. Probably never will.


My goal for 2017 is to go from my parents basement to a bedroom on the main floor.

What the hell dude? You can't disagree with where I live! Holy crap, eat a snickers and get back to me.

 

[Lustle]

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?

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.

I was wondering someone else was gonna notice this. Even at the number the one clown is giving , its under 8.1 dynamic... and the ve is probably as weak. That doesn't mean it won't run good, but these guys are torn up over opinion.

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.

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.

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.

 

[RustyRatRod]

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.

 

[yellow rose]

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.

I agree with this.

But, we are assuming "X" amount of initial timing is good or bad.