1973 455 Stage 1: now 8.5:1 compression, how much higher possible for 2018 Premium fuel?

Slow it down, man.. relax the deadlines, take your time and do it right. What's the rush? The last thing you should be doing is making decisions based on insufficient information or lack of understanding. Take your time and learn first, then start spending money when you're not shooting in the dark hoping for the best. I don't know about you, but most folks don't have money to burn on building an engine a second time because it wasn't done right the first time. I've done a fair bit of work for people with strict deadlines, and more often than not they end up disappointed when the final product does not turn out the way they expected or hoped. With personal projects and toys, I have no idea why anyone would put a higher priority on making their deadline rather than making sure the finished product was right.

 

I agree, but I am really excited about driving this car, so I am trying to make decisions quickly. I just cannot help it... too excited.

My current thinking is that I REALLY want to keep my cam. I don't want any kind of lope, and I like the idea of very little overlap, for fuel economy and overall smoooooothness. So the only way that I can see to reduce the dynamic compression is have pistons custom made with exactly the right volume, to provide a perfect compression ratio. A head expert advised me that the fully dished pistons, that I will get off-the-shelf, will not be as good as reverse-dome pistons with a squish zone where the head is flat, and the actual dish only in the valve zone.

So I will use the calculator to reverse calculate my optimum piston volume, for a compression that'll work with the cam I already have. Well, that's my plan for now, until everyone here complains that I am not thinking it through well enough.

 

Ahah! I am on the right track. As the article that Larry provided states (and I partially suggested above to do):

"A good approach when building an engine is to determine the duration and LSA needed for the desired RPM range. Once this is known, manipulate the chamber size and piston valve reliefs (and sometimes the cam advance) to provide a DCR around 8.2:1. Now that the correct piston volume and chamber size is known, enter the actual crankshaft stroke in your CR calculator to see what Static CR to build to. Often the needed Static CR is higher that you would expect. Note: The quench distance (piston/head clearance) should always be set between .035" and .045" with the lower limit giving the best performance and detonation resistance."

But I still have not exercised the equations or calculator yet.

 

What is my nominal Intake Lobe Centerline, assuming stock location of the camshaft?

Basically, I am not doing well with the calculator numbers to input, because this is not the only number I don't know what to enter.

My idea still is that I want to know what piston volume will allow me to use the camshaft that I have, and provide a DCR of about 8.2. But there are other variables in play, such as the location of the piston below the deck (I guess at TDC). I suppose that is something my engine rebuilder will have to measure with a dial guage. And what is the significance of the question "Domed pistons" or "Flat/Dished pistons"?

And I think I will ultimately need to calculate (using this calculator?) what SCR to aim for, in order to achieve the goal of DCR=8.2. Right?

Am I correct in believing that the two unknowns, that I am seeking to specify (to the rebuilder), are the piston dish volume (if I order custom pistons) and the SCR (that the rebuilder should measure to confirm)? And then maybe also a shift in the Intake Lobe Centerline, to fall exactly onto the goal of DCR=8.2.

As you can see, I read everything carefully, took notes, and am starting to understand. But still not there.

 

Yes, I downloaded the calculator, and tried to enter some numbers. That is why I ask if you have an Intake Lobe Centerline nominal value for me to use.

Lobe Separation Angle, I believe is 112 for my cam, right?

And piston to deck clearance, hmmm, I cannot guess. Everything else, I have some nominal numbers in mind: 0.040 gasket, gasket diameter the same or a bit larger than bore, etc. Pistons, start with 22.5 cc dish.

 

Wow, you are good at using it.

What is the significance of Piston-to-Deck Clearance and Quench Distance, which seem to be the significant changing factors here, and most contributed to the difference in DCR from 7.9 (the 1st calculation) to 8.7 (the 2nd calculation)? How is this controlled in the hardware? Height of the piston's top surface from it's connecting rod bearing center? Are these something I can specify if I make custom pistons, and achieve the right DCR this way, using my cam?

The article recommends 7.5 to8.25 DCR target, and suggests close to the higher end of that range, but not above. You recommended 7.5 to 8.0. Why that discrepancy?

 

Looking carefully again at the 1st go around, with Piston-to-Deck Clearance 0.050, the SCR 9.4 and DCR 7.9 seem to be just about perfect with my cam. I just need the rebuilder to measure real numbers and insert again for more correct answers.

 

To up the static a tiny bit and help with quench, either mill deck .005" or get head gaskets .005" thinner.

Having the quench in the sweet spot will help a lot more to detonation resistance than having less static and being out of the sweet spot.(.035" to .045" piston to head clearance, sweet spot for quench)

 

Can you please write this a bit more long-windedly? I have read it 5 times, and I just don't understand what you are saying.

 

What Derek is saying is that putting the quench distance tighter will help the engine tolerate pump gas better, even if the numbers seem scary. It is a near certain fact and a confusing phenomenon that requires a bit of reading to take in.
You can read all about it from Google or anywhere.
Patronize your skilled people. Ship things to Derek and other contributors to machine, buy parts through the ads here.
People supply links, teach the experiences of the hobby, from their actual working profession, and spend great amounts of time educating the technical aspects without the want for business.
I understand what it's like to be excited about learning and unsure of how to go about things.
I'm noticing a tendency to ask everyone to do everything for you.
People are putting a great amount of effort into helping you get away from the original direction of your post, as well as how your Pontiac ended up (cool engine, BTW. On that one, you might be way ahead having those heads ported and a much bigger cam...giving you better gasoline octane tolerance and a whopping power gain. It's a 2 sided gift.)

 

Larry and Derek, thank your VERY much for sharing your expertise with me. I am so greatly appreciative for your help, because you have armed me with the information I need to make my Buick drive MUCH better than it would have without learning so much from you.

I am not doing any work on this car myself. In fact this is the first time in my life for having a mechanic take the engine out, and do all the final assembly. I am simply too unhealthy now to do it. And I have more money now than I had in my younger years. I am up to over $10,000 already, invested in this engine, including the exhaust, radiator, all the TA parts, and the labor so far. And of course my distributor and carb expertly rebuilt by Everyday Performance. Crazy more $ so far than I expected. I drove the car for 2 days, then the bottom end started to break, so that is why the engine is out, now, and getting a full rebuild.

My engine is now in the hands of an engine rebuilder that came highly recommend to me by a guy who creates exotic hot-rods from old cars, for customers with too much money to spend. I don't know yet if my rebuilder knows all these things you have been teaching me. I think he does. I will slowly discover his expertise, as we work together, and guide him to execute these concepts. Some he will want to do himself or arrange with his local vendors. The custom pistons for example, well, maybe he knows where to have them made, or maybe I will be able to suggest who will make them. If I have the opportunity to choose anyone here do some of the work for me, I will ask here for advice who.

I bought the pair of Stage 1 heads from the member who offered them to me, earlier in this thread. They are the same casting number as mine, HEAVILY ported for the Buick racer Dave Benisek. He used them for a short time, and then went to aluminum heads. The original cost of this head work was at least $1800, and that was 10 years ago. The ports are so much larger that guides were installed for the head bolts. Exhaust ports are so much larger that I will have to match my exhaust manifolds to their shape. But I am not going to use headers, and I still maintain that I do not want a lope. I am told that flowing heads like this WAS for running 12:1 compression and a roller cam... but that does not mean I will not get great benefit at low RPM if I use a much milder cam, and of course lower the compression ratio to about 9.5:1.

So, it seems logical to me that heavily flowing heads like this WAS for more high RPM power, and that it should make little or no difference for low RPM torque and power. Never-the-less, the experienced people I asked so far said, no, flowing heads helps everything. What do you think? Am I backing myself even more now into a situation where it makes TOTALLY no sense to use the cam that I have, and like, and want to use? I want low RPM torque MUCH more than high RPM power, this is my goal. I am going to drive on the freeway, not on any track, ever. And I will occasionally be in Los Angeles traffic, applying a little blip of power from idle to squeeze into one lane from another. And I do want to be stunned and amazed when I get-up-and-go on a freeway on-ramp... or the freeway opens up into a no-mans-land in front of me... at the same time I want a timid sounding car with extremely smooth idle and amazing low-rpm grunt. I know what I want, please do not try to talk me into creating a dragster.

Another fact to know is that I have already installed the exhaust system that I thought I wanted, before we got into all these higher performance considerations. What I have is full-length dual exhaust, with 2-1/4 pipe and Flowmaster 50 series mufflers. Again, exhaust manifolds, not headers.

Given all this information, that I have passed on to TA, they tell me my cam is a good choice for what I have and what I want. But, please, express your opinions to me. If I am going to change the cam again, now is the time for me to buy it.

 

I hope I haven't seriously misled you or contributed to hasty decisions, and I hope my bluntness is somehow helpful...

I should caution you to stop right now and give your engine builder almost complete control of your project, or continue researching if you want to make all the decisions.
If you are not doing any of the work it would be wise to let people shine.
They 'should' have the BASIC understanding we are discussing here or be a resourceful enough shop to farm it out.
Now that we get to this point and you state that you want smooth, lope free idle and the insistence of manifolds, it would be prudent to suggest that there isn't enough information to be selecting cams or heads.
If I steered you away from your better interests, keep in mind that all of your goals and needs haven't been discussed, nor am I under your employ.
These posts are merely tidbits of very relevant information, albeit somewhat nebulous and disconnected.

Heads flowing 'heavy' or aluminum ones flowing 'good' and how they relate to the the engines behavior begs for better understanding.
The amount the heads flow in terms of quantity is near meaningless compared to the airspeed and size of the ports.
Engines behave based on the airspeed in the induction and how it relates to the cylinder.
The flow has to start and stop, and takes time to get moving.

2 different examples could flow nearly the same quantity but because of much smaller runner size in one...peak torque and hp rpms would be drastically different even installed onto the same engine.
I've done builds in which 12 cfm of flow and a little bit of port size change either made it idle with a rumble at 900rpm or no less than 1500 while shaking the fenders.

Remember what a turd the 4 bbl Cleveland was from stock? Those hogged out, slow ports don't work well on a tiny engine until you spin it up. They wake up over 5000 rpm though. Fantastic potential on a stroker with a 700hp + goal.
But alas...they are considered good flowing heads.

Another fine example is the LS chevy engines having 'good heads', even 'heavy flowing' ones.
Those still use fast flowing ports sized appropriately to the cylinder size/rpm range, and have long intake runners intended to help the engine maintain response at low rpm.
The entire package should be considered, as well as all of the attributes you are looking for.

Another yet is one I'm 'fixing' that had a poor output end result, despite their catalog selected and hp 'matched' top end package. It's intended for 50-75 more cubic inches. The port area is poorly matched to the short block.
I'm giving it a near 100 cube increase.
It will be impressively responsive while maintaining it's new 150 hp higher goal, at a lower rpm, and now without race gas.

Just to clarify for understanding...those heads don't 'flow' to run 12-1 and a roller cam.
The engine's power goals being at specific rpm's require 12-1 and a roller cam, with those heads' port size, airspeed, and flow volumes. That's how that package adds up.
They may be perfectly usable for your project with more openness to parts selection, or they may not.
You will have to get all of your needs and information together to end up with a happy result.

 

Well, this was a useless and disappointing post, in the guise of advice. It basically is saying, "I don't take any responsibility for what I have advised you, and I am sorry if your engine runs badly if you actually use any of what I have written."

What I asked was this: Is it possible that the high-flow capability of these new heads demands that I use them only with a high flowing motor, designed for high RPM power, or is it equally possible that these free-flowing heads will work well with the restrictions built into my engine, including the cam, and exhaust system, I have chosen? And now your answer is: Well, I am sorry if my advice doesn't apply to you and your engine. Maybe you better just stop thinking for yourself and let your engine rebuilder make all the decisions on his own.

Please don't get me wrong. I appreciate VERY MUCH getting information that helps me think. So thank you for letting me know that you are really not sure about the comments you had made earlier.