Engine rebuild on my '67 Coronet 500 - 383 4 BBL

[dieseldazzle]

Why are you using undersize cam bearings???

 

[TekHousE]

What?

I am not using undersized bearings. Are you talking about the ones I posted in my first few posts?

They were the factory ones...Obviously not reusing them.

 

[TekHousE]

My heads are coming along nicely.

I received a few photos from Bruce Toth, who is doing the porting, and other head work.






My Hughes Whiplash Roller cam is on it's way, with all the other gear, such as their roller rocker set, true roller timing gear etc.

Hopefully we can start bolting things together in a couple of weeks time.

 

[MT_Mopar]

Nice

 

[TekHousE]

Getting ready for the rolling assembly next weekend. Filed the rings today.

A few car **** shots..

 

[TekHousE]

Rolling low end assembly is done! Trans is rebuilt, we added the Transgo reprogram kit. Added more clutches and steels too, plus steel/carbon fiber bands.

 

[TekHousE]

Here are my heads, just before Bruce Toth sends them out. The flow numbers look great. Bruce has been porting heads for Mopars forever. Here is a story on him:

http://performance-mopar.com/index.php/4-bruce-toth



He told me that pure flow numbers do not tell the story. I asked him what he meant by that, and he said how FAST heads flow is really more important than the pure flow volume. Of course this makes sense, once he mentioned it. Of course he is right, if a head flows well 'eventually' that is one thing, but if a head flows Quickly and at high volume that is better. you fill the chamber with more air/fuel faster, which is obviously the objective.

 

[HT413]

Heads look great! Yeah flow is complex that's for sure. I'll throw another wrench into the machine - regardless of lift, an engine can only draw so much cfm per rpm, no matter what the cfm of the heads is, of course because the cylinder is only so big. For instance, your 383 can only pull 47.875 ci of air into each cylinder per rpm, or 287,250 ci per minute at 6000 rpm. This equates to 166cfm that your 383 will draw at 6000 rpm. So how can your motor benefit from this heads?? The answer is that CFM is proportional to RESISTANCE TO FLOW. So your motor has to waste less HP pushing and pulling all that air and can put it into turning the wheels.

I know I'm not an engine builder, but I love talking about this stuff (much to my wife's unending frustration lol).

 

[TekHousE]

Heads look great! Yeah flow is complex that's for sure. I'll throw another wrench into the machine - regardless of lift, an engine can only draw so much cfm per rpm, no matter what the cfm of the heads is, of course because the cylinder is only so big. For instance, your 383 can only pull 47.875 ci of air into each cylinder per rpm, or 287,250 ci per minute at 6000 rpm. This equates to 166cfm that your 383 will draw at 6000 rpm. So how can your motor benefit from this heads?? The answer is that CFM is proportional to RESISTANCE TO FLOW. So your motor has to waste less HP pushing and pulling all that air and can put it into turning the wheels.

I know I'm not an engine builder, but I love talking about this stuff (much to my wife's unending frustration lol).

That is interesting. Do you have a calculation or formula that I can use to determine this for other CI sizes? I am guessing it is based on bore size and stroke correct? How does it change (most likely nominal) for oversized bores?

Is there a calculation for what HP is wasted for example?

 

[HT413]

That is interesting. Do you have a calculation or formula that I can use to determine this for other CI sizes? I am guessing it is based on bore size and stroke correct? How does it change (most likely nominal) for oversized bores?

Is there a calculation for what HP is wasted for example?

The calculation for how much cfm of air an engine pumps is pretty straight forward - 383 ci / 8 gets you 47.875ci per cylinder = 0.02770 cf. then multiply that by the RPM and you get the cfm each cylinder will draw. So at 6000 rpm, your 383 ideally would draw 166 cfm. This assumes 100% volumetric efficiency, but in reality I think most street engines only draw in 80% of their volume with fresh air/fuel, with 20% of the exhaust gases remaining in the cylinder, so really you only draw in around 130 cfm at 6000 rpm.

I don't think there can be a calculation to determine exactly how much HP is lost due to having to push and pull the air out and into the cylinders because it just gets too complex due to competing factors, such as too much flow maybe reducing the charge velocity and turbulence, thus reducing the fuel atomization and mixing. I know a lot of guys talk about intake charge velocity and I can't say what factor that really plays, but I can say that a low flowing head, in order to pull the same cfm, the air would has to travel far higher velocity to enter the chsmber through a smaller orifice than it would I it flowed through a huge race ported head with massive ports and valves. But I think that all that stuff is where the "2HP per CFM" rule comes into play - I bet it's way more complex than that but all anyone can do outside of NASCAR or NHRA testing labs can do is estimate and hope for the best.

- - - Updated - - -

I can say this, this all occurred to me a while back while I was pondering IQ52's port work on one of his low compression motor threads. I reasoned that one doesn't need the flow, but what they do need is the low 'resistance to flow'; so 1 cfm does not equal 2 hp, really the reduced resistance to flow that 1 cfm provides = 2 fewer hp wasted in fighting to empty and fill the cylinders.

I think this is kind of similar to what your machinist was saying. But here's the thing, I went through all of the fluid flow calculations one night and it turns out that all I did was prove to myself flow rate is proportional to the resistance to flow, so measuring cfm flow rate is basically the same thing as measuring resistance to flow. Same damn thing lol.

 

[TekHousE]

I can tell it would be too complicated due to all the variables to see what HP is lost. Thanks for the explanation of how you determined it. I am a visual person so seeing it spelled out like that made it click.

Yep we probably go around in circles trying to work this out. Bruce said this to me:

Because filling of the cylinder is really a timed event, due to the fact that you only have the small amount of time when the piston starts down on the intake stroke and the intake valve begins to open. Once the piston starts up on the compression stroke the valve goes shut your opportunity to fill the cylinder is over at that point. In relation the faster the air speed (feet per second) the more air and fuel mixture can be forced into the cylinder.

A lot of people believe that piston moving down on the intake stroke draws the mixture into the cylinder, That is not the case actually the piston going down causes a void (or opening) in the cylinder which allows the atmospheric pressure to force the air and fuel in. So the faster the air in the port can travel the more air and fuel can be forced into the cylinder while the intake valve is open.

I had a customer in the shop one day and I was explaining the same thing to him, he wasn't understanding the theory. It was in the summer and I had my garage door up and the window in the rear wall open so the breeze could blow through. I told him to go over and stand in my garage door opening and asked if he could feel the air moving through the big opening. He said yes but it wasn't moving very fast. Then I told him to close the garage door and go over to the smaller mad door and open it and stand in it. The he realized what I had been trying to explain to him, he said I can really feel the air rushing past me in the smaller opening. air was being forced in through the same open window. So in respect the larger you make intake port the slower the air speed is, velocity in the port makes more torque. Actually if you can get the velocity in the entire port close to being the same allows the air to move through it more efficiently (no turbulents) allowing it to flow more CFM.

 

[Banzaiii67]

Hi Tek,

I'm just curious and i'm sure your on it, what is your piston to valve clearance with that cam and piston combo?

 

[TekHousE]

I will let you know..Once my heads arrive. Right now from memory, the piston at TDC is .015 from the deck.

 

[Banzaiii67]

I will let you know..Once my heads arrive. Right now from memory, the piston at TDC is .015 from the deck.

Ahh good, sounds like you didn't zero deck your block, just somewhat concerned with flattops and that cam.

 

[TekHousE]

Yes we were concerned about that too. I think we will be OK.

 

[TekHousE]

Transmission is rebuilt and back together. We also rebuilt my 8 3/4. I was worried about the final drive, and we changed from 3.23:1 to 2.76:1 gearing. The new center is an Eaton Tru Trac.

 

[super-bee_ski]

Very nice Tek!
Very nice indeed!
All cool stuff you have there!

I cant wait to see it in the car!

 

[TekHousE]

I think 3 weeks and we are on the road..

Radiator is now rebuilt, just got word of that today. Heads are on their way, cam and rocker gear are here. All we need then is to fit and measure up for the pushrods. Assembly of the rest of the rolling stuff this weekend.

Oh, and the weather just decided to give us a blast of winter again today!

All of our snow was gone..This won't last long temps are now too high for it to stay around.

 

[TekHousE]

Cam is in! New double roller timing gear. New oil pump, fuel pump. Waterpump is cleaned and new thermostat, both installed. Oil pan back on. Ready for heads this week.

 

[TekHousE]

Heads arrived today! They look great. Will test fit them tomorrow, remove the inner valve springs and valve on one cylinder and set tolerances up.

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