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Carb head combustion chamber question.

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GPGoverMPG
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Re: Carb head combustion chamber question.

Post #51 by GPGoverMPG » Wed Nov 28, 2018 8:50 am

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.
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Re: Carb head combustion chamber question.

Post #52 by GPGoverMPG » Wed Nov 28, 2018 8:59 am

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.
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Re: Carb head combustion chamber question.

Post #53 by pmuller9 » Wed Nov 28, 2018 9:13 am

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.

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Re: Carb head combustion chamber question.

Post #54 by Max_Effort » Wed Nov 28, 2018 10:55 am

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.

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Re: Carb head combustion chamber question.

Post #55 by pmuller9 » Wed Nov 28, 2018 11:24 am

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.

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Re: Carb head combustion chamber question.

Post #56 by GPGoverMPG » Thu Nov 29, 2018 7:52 am

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.
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Re: Carb head combustion chamber question.

Post #57 by pmuller9 » Thu Nov 29, 2018 9:09 am

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.

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Re: Carb head combustion chamber question.

Post #58 by THE FRENCHTOWN FLYER » Thu Nov 29, 2018 9:37 am

Stay with the two 1.08s. They will work fine.
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Re: Carb head combustion chamber question.

Post #59 by MechRick » Thu Nov 29, 2018 3:19 pm

pmuller9 wrote: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.
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Re: Carb head combustion chamber question.

Post #60 by THE FRENCHTOWN FLYER » Thu Nov 29, 2018 3:56 pm

MechRick wrote: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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Re: Carb head combustion chamber question.

Post #61 by pmuller9 » Thu Nov 29, 2018 4:27 pm

MechRick wrote:
pmuller9 wrote: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 OP has made an intake manifold with long runners that will help with intake port reversion at low rpm similar to the EFI intake.
It should tame the lope so there is very little at a slightly elevated idle.

I like FTF's idea of "Dial a Lope"

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Re: Carb head combustion chamber question.

Post #62 by THE FRENCHTOWN FLYER » Thu Nov 29, 2018 4:46 pm

TRUE STORY

I was in a meeting where lots of people smarter than me spent a long time discussing ways to get idle quality up to a "10" on our engines. And by "10" they meant a smooth-as-silk-electric-motor-smooth idle. I finally couldn't contain myself any longer and said, "Guys. You have to know and recognize your customer base. Sure, some folks will want a 10 idle. For another whole group of customers a car with a 2 idle will be wonderful. Heck, when I was a teen some guys would pull a plug wire off just so when they pulled into a drive-in other hot rodders would think the engine was "built"."

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Re: Carb head combustion chamber question.

Post #63 by GPGoverMPG » Thu Nov 29, 2018 6:05 pm

I looked at the Crower Cams web site and I'm pretty sure that's gonna work. I know to disregard the RPM rating. I'm going to play with some numbers tonight.
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Re: Carb head combustion chamber question.

Post #64 by guhfluh » Thu Nov 29, 2018 8:11 pm

THE FRENCHTOWN FLYER wrote:
MechRick wrote: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!

They already have it out there in "ghost cam" tunes on vehicles with variable cam timing.

I found about the same with my Comp 268H cam. I can make it lope by leaning it out and retarding the timing at idle. I can make it smooth as stock by richening it up and giving it vacuum advance at idle. I've actually been thinking lately of going to a bigger cam...
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Re: Carb head combustion chamber question.

Post #65 by THE FRENCHTOWN FLYER » Thu Nov 29, 2018 8:59 pm

guhfluh wrote:...They already have it out there...

Dang! Another missed opportunity.
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Re: Carb head combustion chamber question.

Post #66 by pmuller9 » Thu Nov 29, 2018 9:13 pm

GPGoverMPG wrote:I looked at the Crower Cams web site and I'm pretty sure that's gonna work. I know to disregard the RPM rating. I'm going to play with some numbers tonight.


It will give you a nice wide power band with the ported head.
Abandoned Bronco has an identical cam from Erson and it pulls smoothly from 1000 to 5000 rpm.
He is currently battling an issue with the engine running at WOT

Waiting to see what the final combustion chamber volume ends up being.

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Re: Carb head combustion chamber question.

Post #67 by xctasy » Thu Nov 29, 2018 11:43 pm

I cant sppon feed it to you, but the secrete is that duty cylce over lap hurts idle and wide open throttle performance. The muddy waters to this are other things entirely.

Port on port carburation isn't being done here, but the same basic principals apply. A port on port discussion is here

viewtopic.php?f=2&t=77685&p=608580#p608817


The principlas are two fold.



1. Only when overtly large, and independent runner, port on prt carb systems, does an engine respond to pulse tuning. Pulse tunning allows more fuel to get in with less air flow.


2. On all other Non port on port Examples, you have to avoid earlier production common USA I6 and V8 2 and 4-bbl thinking. Not that its bad at all, its just that it focuses on cost and undercarburation, and using cam design is a crutch as opposed to to sizing the the average carb venturi areas to the total the engine capacity for a given rev range. Mike Stacey from Chrylser Australia Party found that port on port worked best, but that 4-bbl long branch intakes like the Dutra 4-BBL also worked. So did a Repco Ford Falcon development engineer. Both realised that it was carb venturi to engine size relationship that made up for a lack of port on port intake design. A great deal of that information filtered into the early 4-bbl Big Six experimental intakes, showing a real understading of how to make a n I6 idel, and perform with very big carbs.

"Pulse tuning" for carbs only happens at about 11 to 18 feet per second of air flow, so you have to go really REALLY big to pulse tune. Forget all that CFM flow rate hocus pocus. Well, not exactly forget, but don't get het up on it. My advice is to Only focus on the ventrui area required to match the peak power rpm for the capacity of engine. This process is called Dimensional Analysis, and all great benchmarking engieers use it. They just don't tell you they benchmark.

Oversizing is okay if you work within known limits. Then engine will rev well above the peak power rpm band . 5500 rpm is a good figure to punt for. Twin 1.08's might work, but other bigger Autolites and Motorcrafts can and do work better, without hurting idle.



viewtopic.php?t=41010
Bret wrote:I found the flow rates for MC2100/2150 2 barrels.

This information comes from CJOFFROAD.COM. That website has a ton of information on these carbs.

2V 2100/2150 at 3"Hg. Venturi size listed first.

0.98 = 190 CFM
1.01 = 240 CFM
1.02 = 245 CFM
1.08 = 287 CFM
1.14 = 300 CFM
1.21 = 351 CFM
1.23 = 356 CFM
1.33 = 424 CFM

In order to compare these carbs to 'metric' carbs, here is a conversion list. Remember that venturi size is not the same as bore size. In example, a Weber 32/36 has venturies of 26mm/27mm. The MC2100/2150 carbs have syncronous butterflies, just like the Weber 38/38 DGS carbs.

0.98 = 24.9mm/24.9mm = 190 CFM
1.01 = 25.6mm/25.6mm = 240 CFM
1.02 = 25.9mm/25.9mm = 245 CFM
1.08 = 27.4mm/27.4mm = 287 CFM
1.14 = 29.0mm/29.0mm = 300 CFM
1.21 = 30.7mm/30.7mm = 351 CFM
1.23 = 31.2mm/31.2mm = 356 CFM
1.33 = 33.8mm/33.8mm = 424 CFM


THE FRENCHTOWN FLYER wrote:Thanks for the info. This info is often sought after. It should be on the FAQ post above.

Remember that four barrels are flowed at 1.5 "hg. So these flow numbers do not equate to 4V flow. To convert divide by 1.41.

So, for example, a 190 2V would be equivalent to a 135 4V.
A tri-power using 3 of these 190s equals a 404 cfm four barrel.


For idel and max performance, Peak venturi size (ie, if a 1.08 is gonna work better than, say, a 1.14, 1.21 or 1.23 or 1.33) is goverened by if the runners are isolted from one another. If they are, the duty cycle is improved, and you can always go bigger to an optimum size from the Weber carb chart.


Then you can multi layer from two barrels to met the same target 1bbl cross sectional area.

So if one 40 mm venturi per barrel is what you need to make power to 4600 rpm on a 300 six, you can also use two holes of the same equal area. more tahn one barel per port has been done with huge success.

Any time you get an idealised venturi area in the Weber chart, you can Root 2 it to 1.414, and find two 28.29 mm venturis will do the same thing.

This is exactly what the 8bbl aftermarket non Max Wedge intake below does. It puls tunes 6 cylinders by using 12 venturis. Its overkill, but it worked right to 10000 rpm and over 600 hp, and with valve lifts of 900 "thou".


https://www.hotrod.com/articles/mopp-10 ... ing_insert

Image

And the Jim Headrick Cotton Perry from Georgia was a Sportsman-class, 310 cube 67 M/Elim Chevy II driver who did it all with its three huge 780 cfm 4-bbl DZ option CrossRam carbs.


Image

The way it works is that if you isolate, you can then increase carburation without hurting idle. Ford did this with the bigger spread bore carbs on V8's to countact the cost of running multiple carbs. They then had a heap of other matters to contend with to control idle. Cam design was seen as the great soltuion.

IMHO, Shared intake pulses always hurt idle. To improve shared plenumb or siamesed port engines, you have to look at ideal sizes from historical non USA engines, becasue the USA I-6's and V8's are frequently undercarbed, and don't idle well because of intake restrictions or card size restrictions.

Generally, first in the minds of North Americans is to increase port velocity, which is what actually Causes idle quality degradation, and peak power loss. The smaller the ports, even if really nicley gasflowed, the more the idle suffers. Its big ports with big cams and insufficent carb area that causes a lot of idle and wide open throttle issues, which Detriot covered over with secondary barrel operation.


Going to a bigger carbs on non isolated runner systems can also work darn fine. Although absolulety none, nada, nil, nein in line six or V8 US production performance engine ever ran port on port induction (exception...some British build, US order 289 GT40's did)

Non port on port Examples:

1) The work the late ex Ferrari engine designer Aurelio Lampredi did on the six cylinder Fiat 2300 in the 60's (two 0.9375 " venturi 2-bbls) , and


2) David Vizard did on the big 44mm 1-3/4 inch 2bbl venturi carbed 145 hp Mini 1275 four cylinder car his daughterSamantha piloted in the 80's , and

3) the 245 hp Holden XU1 Torana with three 48 mm venturis three 1-7/8"did in 1973 showed this.

All these cars cars idled a lot better than many realise despite realatively small capacity, and made exceptional power with really big cam duration.


For example 1, 2 and 3 above, you have 138, 78 and 202 cubic inche engines. On a carb venturi area per cubic inches of engine basis, they all have twice to three times as much carb venturi area than a set of 1.08's on a 300.

Be prepared to experiement with bigger venturis, and trst that the long runners will help the idle and wide open power situation a little by attenuating the pulses to the venturis and carbs. I'd say look around for the bigger A 2100's and MC 2150's.
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Re: Carb head combustion chamber question.

Post #68 by THE FRENCHTOWN FLYER » Thu Nov 29, 2018 11:53 pm

THE FRENCHTOWN FLYER wrote:Stay with the two 1.08s. They will work fine.

GP, After you've used the 1.08s for a while try a pair of the 1.23s. Let us know how it drives.
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Re: Carb head combustion chamber question.

Post #69 by GPGoverMPG » Fri Nov 30, 2018 8:00 am

Helping daughter with tires on her car and didn't get to play with a DCR calculator.

I did find the following Snider Cams:
hyd
284-88H
284/288
224/232 @.050
.512/.512 1.6 roller rockers
108 LSA

Solid
292-96F
292/296
258/262
.584/.584
108 LSA
.020 Lash

I'm still in control of my compression I'm at 81cc and the head has not even had a clean up cut done. I'm for sure going to run the 1.08s to start and break the motor in. I've already run them on my truck one at a time to make sure they work well. The split plenum on my intake will mean setting them up like the carbs on the bikes I once raced and getting them sync'ed right. I'll also be running twin wide band gages to help. Can always go bigger if I get feeling frogie. The 284-88H is a lot like a cam profile talked about earlier. I would say a 10:1 compression is still available if needed. I kind of like the solid idea just cause no good reason.
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Re: Carb head combustion chamber question.

Post #70 by pmuller9 » Fri Nov 30, 2018 9:35 am

The Schneider 284-88H will work.
It has 12 degrees of overlap and will have some lope at idle.

It will also work with a 9.5 compression ratio, not 10.

The Schneider 292-96F solid cam has way too much duration for your engine.

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Re: Carb head combustion chamber question.

Post #71 by GPGoverMPG » Fri Nov 30, 2018 6:37 pm

Right, that 292 was looking crazy. The 284 seamed right in the wheel house. I still want to play with some calculators for the knowledge. I have my 455SD '72 Ventura that runs race gas. I bet with the right cam I could afford to street it a bit. I think this truck is gonna be nasty. I was doing two wheel burnout's to day. Keep them lit up into third as is. 33-12.50X15s I wish the cash was coming in faster so I could accelerate this project. Rookie driver in my own parking lot. With the built motor I won't play anywhere it could hook up.
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Re: Carb head combustion chamber question.

Post #72 by GPGoverMPG » Sun Dec 16, 2018 7:14 am

Just a quick up date with a picture showing stock valves and the new 194/160 from SI valves. They have not been set by the machine shop yet but you can see the difference.
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Re: Carb head combustion chamber question.

Post #73 by THE FRENCHTOWN FLYER » Sun Dec 16, 2018 12:08 pm

OK so far. I'd take the chamber surface to a sheenyier shine. I also like to slap an old head gasket on the head to prevent putting grinding marks across the head face if the grinder gets loose and does its dance.
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Re: Carb head combustion chamber question.

Post #74 by pmuller9 » Sun Dec 16, 2018 3:05 pm

Looks good
Have you decided on a camshaft?
The Schneider 284-88H you suggested would be a good choice.

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Re: Carb head combustion chamber question.

Post #75 by GPGoverMPG » Mon Dec 17, 2018 7:31 am

Yea that's the cam I'm going to run. I posted the picture so everyone can see the difference in the intake valves. I ordered some more sanding disks so I can finish the chambers and they must have gotten on the slow boat. I'm goin to need springs and retainers then it's off to the machine shop.
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Re: Carb head combustion chamber question.

Post #76 by pmuller9 » Mon Dec 17, 2018 9:34 am

Use the Crane 96803-12 valve spring with the Comp 768-12 retainer.

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Re: Carb head combustion chamber question.

Post #77 by GPGoverMPG » Tue Dec 18, 2018 7:08 am

Alright I will. Thank you. I'm going to set up my cc'ing rig this morning and double check my volumes. I'll have the machine shop set the valves and install the screw in studs then I'll pick it up check the volumes and I should know how much the have it milled. Then it's measuring twice and shimming to get the springs right. It's going to be some time before the bottom end is ready so I'll store the head with the keepers off.
71 F350 4x4 Super Duty 7.3 IDI
72 F250 4x4 4speed 300 I6
72 F100 2x 428 Tri Power
2014 SHO

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GPGoverMPG
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Re: Carb head combustion chamber question.

Post #78 by GPGoverMPG » Sat Dec 22, 2018 7:36 am

I was trying to play with a dynamic compression calculator and it asks for the intake lobe center line. I did a search of this site and didn't see anything about how this number is reached. The 284-88H cam is split duration and they also have a solid cam that is very close and I wanted to see the changes to compression. So how do you get the intake center line without a cam card? Thanks again
71 F350 4x4 Super Duty 7.3 IDI
72 F250 4x4 4speed 300 I6
72 F100 2x 428 Tri Power
2014 SHO

pmuller9
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Re: Carb head combustion chamber question.

Post #79 by pmuller9 » Sat Dec 22, 2018 9:48 am

The 284-88H cam has a 108* lobe separation angle which means if the cam is installed in a neutral position the Intake Lobe Center will be at 108* ATDC and the Exhuast Lobe Center will be 108* BTDC

The cam card is going to ask you to set the Intake Lobe center at 104* ATDC which is 4 degrees advanced.

The intake valve will close at 66* ABDC based on the 284* advertised duration.

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GPGoverMPG
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Re: Carb head combustion chamber question.

Post #80 by GPGoverMPG » Sat Dec 22, 2018 4:49 pm

yea I thought that was the deal must have fat fingered the keyboard several times. I'll try it again. With my new setup the heads cc at 79cc's I stopped waiting until the valves are installed.
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71 F350 4x4 Super Duty 7.3 IDI
72 F250 4x4 4speed 300 I6
72 F100 2x 428 Tri Power
2014 SHO

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