Why so much inital timing???

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Lustle said:
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.
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Thanks. I'm gonna run the piss out of it as is. It runs very well for what it is. I'll report back with ET's and mph numbers. The .040" head gaskets won't work for me as my pistons are .015" out of the hole which will put my quench distance too close for comfort. I appreciate the input. The combo is what it is. I was just wondering if 28* of initial timing was out of the question. I received the answer on the first page. The last two pages of bickering have been pretty entertaining though. Let's see how long we can keep it going. LOL I wonder if the dude I ignored is still responding. Something tells me he is. :rofl:
 
MOPAROFFICIAL said:
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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Oh is that what he's runnin? I honestly didnt pay attention there........If that's the case, then I double down on agreeing with you. Closed chamber heads with .039 quench is good for 11:1 with the right stuff.

I just assumed this was regular open chamber crap.
 
mopowers said:
Thanks. I'm gonna run the piss out of it as is. It runs very well for what it is. I'll report back with ET's and mph numbers. The .040" head gaskets won't work for me as my pistons are .015" out of the hole which will put my quench distance too close for comfort. I appreciate the input. The combo is what it is. I was just wondering if 28* of initial timing was out of the question. I received the answer on the first page. The last two pages of bickering have been pretty entertaining though. Let's see how long we can keep it going. LOL I wonder if the dude I ignored is still responding. Something tells me he is. :rofl:
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Oh ****, we can drag this out for days. That's not even breaking a sweat. Not all of it was a waste. There is some good math in here, along with other pertinent stuff. I don't think most discussions are useless, especially if you have disagreement. When someone must support and argument they generally eventually get to the point.
 
B3RE said:
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.
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But if you run locked out advance on the street you're....

Nevermind. Made that joke already.

And no. DCR isn't everything. Like I always try to say, pick an engine for how it's components work together. Not because you saw this part in a mag, or that part on another guys car. An engine, and the car it's in, is always a combination of everything you put into it. Parts have to work together. I think I mentioned this in a cam thread. Don't pick a cam based on it's duration or lift. Pick it based on how it will run with your combo. It's like that for all parts of an engine, or car.

RustyRatRod said:
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?
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That was kinda one of my points from the beginning. If this was a race motor? Yeah. I'd be looking for 8.5:1 or more dcr and all that jazz. It's not. It's a street motor. That's gotta put up with good or bad gas, good or bad tunes, good or bad timing, and everything else a motor like this will see. I'd rather see a guy make 400 horse and drive the thing everyday for two years with a smile on his face. Then make 420 horse and worry about where he fills up.

mopowers said:
Thanks. I'm gonna run the piss out of it as is. It runs very well for what it is. I'll report back with ET's and mph numbers. The .040" head gaskets won't work for me as my pistons are .015" out of the hole which will put my quench distance too close for comfort. I appreciate the input. The combo is what it is. I was just wondering if 28* of initial timing was out of the question. I received the answer on the first page. The last two pages of bickering have been pretty entertaining though. Let's see how long we can keep it going. LOL I wonder if the dude I ignored is still responding. Something tells me he is. :rofl:
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I completely forgot about that quench. You do got great quench.

I wouldn't stress it. That cam is fine. Your DCR is fine. Timing is fine. You got a strong street motor that won't give you headaches everyday. That's good in my books.
 
RustyRatRod said:
Oh is that what he's runnin? I honestly didnt pay attention there........If that's the case, then I double down on agreeing with you. Closed chamber heads with .039 quench is good for 11:1 with the right stuff.



I just assumed this was regular open chamber crap.
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RRR, like me, the OP gets his quench by sticking the piston out of the deck. Some people think quench can only be had with a zero deck and closed chamber heads. All bullshit.


Like I've said before, you'd have to have a damn good closed chamber to make me give up the open one. You want quench, run the piston out of the hole.

This also reduces crevice volume. And that's a big deal.
 
Yeah, THAT part, I saw....but I somehow missed the close chamber head deal.

I look at it this way. Different people do things different ways. As long as we all have fun with our own stuff, that's all that counts.

yellow rose said:
RRR, like me, the OP gets his quench by sticking the piston out of the deck. Some people think quench can only be had with a zero deck and closed chamber heads. All bullshit.


Like I've said before, you'd have to have a damn good closed chamber to make me give up the open one. You want quench, run the piston out of the hole.

This also reduces crevice volume. And that's a big deal.
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RustyRatRod said:
Yeah, THAT part, I saw....but I somehoe missed the close chamber head deal.

I look at it this way. Different people do things different ways. As long as we all have fun with our own stuff, that's all that counts.
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Yup I agree.


But I was thinking maybe you should start a thread about which is better, a timing curve that has a lot of initial or is locked out, verses less initial vis a vi static CR verse intake closing.


I'd do it but some boner out of nowhere would jump in and screw it up.
 
I don't think one is necessarily better. I think it all depends on what you want, what you have to work with and what you can afford to do. Just make the best of what you have and can do.
 
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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Thanks.
I don't think you have the static compression you think you do based on the piston choice. Best bet would have been using the 1" downfill method and measuring the volume to calculate static ratio. That piston has a lower top ring, and tapered "flat" top so there's more wasted volume than typical math might account for. The intake valve closing can be anything really. I wouldn't assume the ramp is designed such that your math works for it. I've always used the KB site calculator. If I use tht and add a couple ccs for the dead space I'm coming up with 9.3 static, 8:1 dynamic. Given you have the big bore, the huge gasket (not sure what that was needed there), and the dead volume around the piston, the timing lead is probably warranted. I would have done things differently myself but that's neither here nor there. If you want to know why, in my opinion that's why: excessive volume in the chamber. I will never, ever use a vacuum gage to set timing either so we're already taking different approaches to performance. But someone posted this sentiment early on: if it likes it, run it.
 
moper said:
Thanks.
I don't think you have the static compression you think you do based on the piston choice. Best bet would have been using the 1" downfill method and measuring the volume to calculate static ratio. That piston has a lower top ring, and tapered "flat" top so there's more wasted volume than typical math might account for. The intake valve closing can be anything really. I wouldn't assume the ramp is designed such that your math works for it. I've always used the KB site calculator. If I use tht and add a couple ccs for the dead space I'm coming up with 9.3 static, 8:1 dynamic. Given you have the big bore, the huge gasket (not sure what that was needed there), and the dead volume around the piston, the timing lead is probably warranted. I would have done things differently myself but that's neither here nor there. If you want to know why, in my opinion that's why: excessive volume in the chamber. I will never, ever use a vacuum gage to set timing either so we're already taking different approaches to performance. But someone posted this sentiment early on: if it likes it, run it.
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You are correct about crevice volume, but he does have the piston out of the bore .015 so that, in itself reduces crevice volume.

I know my crevice volume but I don't figure it in when calculation CR.
 
Again, doesn't matter what you run as long as a) you're happy and b) it's not pinging.


yellow rose said:
I know my crevice volume but I don't figure it in when calculation CR.
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I'm sure you do. But the OP didn't from the sound of it. Given the taper on the circumference of this particular piston design, there isn't any real loss of crevice volume until the piston is brought out about .025". So it's not any better aside from reducing the chamber volume figure. Not worth arguing about, just my opinion.
 
yellow rose said:
You are correct about crevice volume, but he does have the piston out of the bore .015 so that, in itself reduces crevice volume.

I know my crevice volume but I don't figure it in when calculation CR.
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I knew a girl with lots of crevice volume. Once.
 
Just did a dry compression test with the engine warm. All cylinders were within 5psi with an average of 165. I'll take it.
 
mopowers said:
Just did a dry compression test with the engine warm. All cylinders were within 5psi with an average of 165. I'll take it.
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I would too. All the cylinders very close is good. High PSI for your compression, means good ring seal to me. Good cranking PSI for a street motor. And no need to worry about gas or tune all the time. Sounds like a fun street motor.
 
MOPAROFFICIAL said:
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 end up with less than optimal throttle response at low speeds and timing so high they may as well lock it out at full advance.
Ideally you wanna shoot for an 8.1- or better dynamic but depending on the chamber and head material try and keep at or below 8.5- 170'ish psi dynamic...however if you are experienced in tuning and building, you can run it higher like I do at 8.8 dynamic-185psi
In the future....don't stop thinking after the 10.1 compression pistons go in that its good , think about that cams intake closing, run it on a calculator , cause if you don't...you are building a dog and leaving yourself short on torque.
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This is an older thread, but I thought that moparofficial made a couple of good points. This seems to be just what I'm after, low end torque.
I was just thinking about getting a different cam, because of what an engine builder suggested to me. Now I think see what he was referring to, but I'll have to look into what I actually have and what options to consider. This is all new to me, but it's interesting and Im glad he put me on to this. I'm thankful for the question.
MOPAROFFICIAL, your box is full.
 
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