Carb head combustion chamber question.

pmuller9

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I remember you starting the port work.
Do you have any pictures of the completed port work to this point?

I realize the bowl work will change once the larger valves are installed.
 

GPGoverMPG

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I spent most of my time cleaning up the bowl areas stayed away from short side radius and cleaned up the ports. Can still do more if you think it will help. Kind of chickened out didn't want to hurt more than help.
 

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pmuller9

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That's good enough and safe as far as hitting water jacket.
The throat will open up with the larger valves and you will just simply do some blending.

In order to keep a 9.5 compression ratio the advertised duration of the intake lobe should be around 288*
It can be less by 4 few degrees if the cam is installed 2 degrees advanced instead of 4 especially if it has a 108 LSA.

We can push it and figure an absolute minimum of 280 degrees with a 108 LSA.

That would be a 224* .050" duration in a Jones cam but the exhaust duration would need to be 232* to have 12 degrees of overlap.
The cam will idle between 800and 900 rpm and will smooth out just above 1000 rpm.

There are a few here running 218 to 220 degree .050 duration cams and they are still mild.
Hot street really doesn't start till you get near 230 degrees intake duration.
Jone's recommendation 212 degrees is way too short for what you want to do.
 

pmuller9

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So try again but this time supply these numbers.
All the engine measurements as last time plus the following.

Cam Type = Hydraulic Flat Tappet
Lifter Diameter = .875"

Max engine rpm as 5500 rpm
Max HP at 5000 rpm
Intake valve diameter 1.94"
Exhaust valve diameter 1.60"

Intake Port Flow:
@400 = 192
@500 = 204
@600 = 212
Max Flow = 213 @ 650

Exhaust port flow:
@400 = 145
@500 = 163
@600 = 178
Max Flow = 185 @ 650

Exhaust header Type = Hedman 1.5"

Intake Manifold = Custom ram tube

Carb Size = 600 cfm.

In the comment section say
Off road mud competition. Need strong midrange and upper rpm power with peak power at 5000 rpm

Then see what you get back for a cam recommendation.
 

GPGoverMPG

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Yes Sir, I'll send it off in the AM. I'll also get some more recent pictures of port and combustion chamber work. Thanks again
 

GPGoverMPG

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Here are couple of more recent photos of where I'm at with my head work. Thanks for the help. Any recommendations for improvement will be considered and attempted if I can. I sent the updated request to Jones Cams we'll see how they respond.
 

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pmuller9

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Don't remove all of the material from behind the valve guide. Leave a small bridge
Work a little more around the sides of the intake guide to make a wider path.

[image]https://www.dropbox.com/s/e6w8emvynulnqx1/Intake%20Port%201.jpg?raw=1[/image]
 

GPGoverMPG

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I can do that for sure. I'm taking my time and trying to make sure they all match as closely as possible. I have seen some pictures here where the exhaust guide is removed to the roof of the exhaust port. Seems extreme, is it worth it?
 

pmuller9

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At the rpm range you will be operating at there is plenty of time for the exhaust to blow through the port with the work you have done.
The larger exhaust valve will complete the job.
 

GPGoverMPG

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Thanks again, that kind of confirms what I was thinking. I'll do the additional work on the vacuum side and get after it with some sanding drums to smooth it out a bit. I think with the intake I built I'll have trouble with laminar air flow pulling the fuel out of the mixture. Run it fat to make up for it I don't think leaving the short intake port rough will help any.
 

GPGoverMPG

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Got a response from Jones cams and they recommended the following:
216/220 @ .050
.305"/.310" lobe lift
.488"/.496" valve lift
110 LSA
cam# F300/I6, H68305-69310-110
In the comments says:
With 9.5:1 compression, this cam will be fine with 89 octane. Going to anything with more duration, will hurt the torque, and gain nothing below 5,000rpm.

I have not had time to play with a calculator for Dynamic compression ratio yet.
 

GPGoverMPG

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Got a response from Jones Cams. Recommended the following:

Cam# F300/I6, H68305-69310-110
216/220 @ .050
.305"/,310" lobe lift
.488:/.496" valve lift
110 LSA

In the comments:
With your 9.5:1 compression, this cam will be fine with 89 octane. Going to anything with more duration will hurt the torque, and gain nothing below 5,000rpm.


I have not had time to play with a dynamic compression calculator yet. I'll plug this stuff in this evening and see what I get.
 

pmuller9

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If you run that cam straight up with a 9.5 compression ratio the DCR will be 7.56
The idle will be smooth.

The one reason for going with a custom cam is there aren't any "Off the shelf" cams with much more than a 220* .050" duration.
Based on Jones recommendation you might as well go with the Crower 19205, 220/222, 284/290, and have a lower DCR that you can work with.

You would have to give up the Rough Idle requirement and have smooth torque right from an idle which is better for playing around on the rocks anyway.
 

Max_Effort

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I use Jones a lot and his stuff works. He's never made a dud for me and I've won some championships with his cams improving my program.
You cannot just look at seat duration and .050" numbers.
.100, .200 etc... are doing much more for air flow.

Also.. I don't get too obsessed with DCR numbers. Intake valve closing is just one event.
I calculate and look at DCR to see if it's crazy, but I don't find .5 in DCR makes or breaks a combo. It's called DCR, but its just a static calculation based on intake valve closing.
There is so much more going on dynamically in a running engine.

Empirical evidence with a particular cam in an engine is important. However, it really has to be Apples to apples, changes in the combo will change how it everything works together.
 

pmuller9

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Here we look at DCR specific to the Ford 300 six and is based on many build combinations.
Yes it is only a reference number but it has been useful for street builds. Racing is an entirely different situation.

I've been in a position where I advised pushing the compression .5 based on the info given to me that didn't turn out well.
Dropped the compression by .3 and all was well
If I'm building the engine and have control on checking accuracy of every part and the assembly that's one thing.
If I'm advising hoping all is correct then I'm going to provide margin for error.

It has been demonstrated that on a 300 six a DCR between 7 and 7.5 works with 87 to 93 octane respectively.
It can be pushed if the piston is zero decked with a .040" quench distance but I like to take the extra as margin.
Those that push the DCR find themselves backing off on ignition timing or at least the timing advance or using the next grade of pump gas.

Now to be fair If proper attention was paid to quench, combustion chamber clean-up, Air Fuel ratio, ignition timing, cold air intake ...ect I'm sure it would be a different story.

Yes I also have used Jones cams and the quality alone is worth it and I prefer his lifters.

The difference is I talk to Mike directly and we discuss the need and come to a mutual agreement.
I will be seeing him at the PRI trade show next week.
 

GPGoverMPG

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Ok so as everyone has probably noted, I'm thick headed. I can give up on the sounding cool at idle. It's way more important that it is fun to play with and making good horsepower and torque with the money and work is the best way. So staying with my rod and piston choice, my ported head, roller rockers, and the zero deck block. What's the very best cam choice? What kind of number could I expect? And what RPMs should I be running? I am going to use my dual 2100 intake that has runners 17.7" from plenum to back of intake valve. When I built the intake I assumed a 3100rpm torque peak. I currently have two 2100 1.08v carbs but, I can get my hands on 1.14 and 1.23v carbs if they would be better. Thanks for helping me get this done. I've wanted one of these motors since I worked at a dealership in Ohio in the mid '70s I'm having a great time with it.
 

pmuller9

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The Crower 284HDP (19205) .509”/.517” 220/222 284/290 110deg is going to give you smooth power from idle and have enough advertised duration to work with a 9.5 compression ratio.

The peak torque will still be close to the 3100 design criteria.
The torque curve for a 300 six with a ported head is very wide and flat so it really doesn't have a peak that stands out.
The intake manifold itself will be part of what defines the peak torque.
 

MechRick

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pmuller9":12aw96s8 said:
The Crower 284HDP (19205) .509”/.517” 220/222 284/290 110deg

Based on my experience with Comp's 268H (219 @ .050", 110 LC) that *might* lope a bit with a carb intake. Depends on idle RPM.

The lope went away with an EFI intake and aftermarket (Megasquirt) fuel management.
 

THE FRENCHTOWN FLYER

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MechRick":2hr1byng said:
The lope went away with an EFI intake and aftermarket (Megasquirt) fuel management.
That is very interesting, and not surprising I guess. So with today's electronically controlled everything (traction control, ride control, engine management control, ABS, creature comfort controls, etc.) how long will it be before somebody comes up with an "idle quality" control.

I can picture it now. Out on a ride with the wife or an important client? Dial in a smooth-as-silk idle. Going to the local drive-in burger joint on cruise night? Dial in a lumpy lope. Just by varying the amount and timing of the "squirt" going to each individual cylinder.
Probably even more effective with today's DI engines.

Hey, that could be my next condo in the Caribbean!
 
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