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post #1 of 9 (permalink) Old 02-13-2012, 09:48 PM Thread Starter
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cleveland 4v open vs 4v closed chamber?

hey eveyone I would like alittle input on what heads I should use I have 70 closed chamber 4v heads and 71 open chamber 4v cj heads Im building a clevor or boss. The block is a 74 w 351 that will be bord 30 over.The car will mainly street drivien but I will race it alittle for some fun.I want to run on pump gas. If I have to put bottle of octane boost that will be ok only if I have to.And what kind of work should I have done to make the heads better.
THANKS FOR ANY INPUT ANYONE CAN GIVE ME
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post #2 of 9 (permalink) Old 02-13-2012, 11:33 PM
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Re: cleveland 4v open vs 4v closed chamber?

the closed chamber heads will handle a little more compression b 4 detonatins occurs. you also dont need a dome and thats better and if a dished piston works for the compression you want thats better for flame travel and less plug shrouding. 9.5 compression with iron heads is about if on pump gas b 4 you run into detonation. 10.5 can be run with aluminum heads. race gas is good fur 13+
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post #3 of 9 (permalink) Old 02-17-2012, 03:50 PM
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Re: cleveland 4v open vs 4v closed chamber?

Quote:
Originally Posted by shiftthis View Post
the closed chamber heads will handle a little more compression b 4 detonatins occurs. you also dont need a dome and thats better and if a dished piston works for the compression you want thats better for flame travel and less plug shrouding. 9.5 compression with iron heads is about if on pump gas b 4 you run into detonation. 10.5 can be run with aluminum heads. race gas is good fur 13+
shiftthis , where were you during the talk on the flat vs dish in the allteck section . . your knowledge of spark plug shrouding would have been welcomed
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post #4 of 9 (permalink) Old 02-19-2012, 09:40 PM
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Re: cleveland 4v open vs 4v closed chamber?

You might want to consider something like these...

MPG Heads - 351-302 Port Plates
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post #5 of 9 (permalink) Old 02-20-2012, 02:16 AM
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Re: cleveland 4v open vs 4v closed chamber?

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Originally Posted by pvan View Post
You might want to consider something like these...

MPG Heads - 351-302 Port Plates
those were tested on a dyno and didnt do sheeet ! a wast of money. BUT the exhaust port plates in the fotos do work. the exhaust port is milled off the head and these thick aluminum plates installed. some port work is need. the results are more power. the is known as the "high port head". works on the boss 302 head to.
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Last edited by shiftthis; 02-20-2012 at 02:24 AM.
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post #6 of 9 (permalink) Old 02-28-2012, 11:25 AM
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Re: cleveland 4v open vs 4v closed chamber?

Quote:
Originally Posted by shiftthis View Post
those were tested on a dyno and didnt do sheeet ! a wast of money. BUT the exhaust port plates in the fotos do work. the exhaust port is milled off the head and these thick aluminum plates installed. some port work is need. the results are more power. the is known as the "high port head". works on the boss 302 head to.
Do you have a link to the dyno tests or article where they discussed them? I would be very interested to see more.

Years ago I started to fill the exhaust ports on my Cleveland quench heads and was told the port plates do the same job without modifying the heads.

Sounds good in principal, but seeing dyno pulls with before and afters would be very cool.

Thanks,
Paul

1969 R-Code, 4-Speed, Drag-Pack Cobra Fastback Project
1967 Mercury Commuter Wagon w/mild 429

http://mycarrestorationprojects.blogspot.com/

Last edited by pvan; 02-28-2012 at 11:26 AM. Reason: add sig
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post #7 of 9 (permalink) Old 04-03-2012, 11:29 PM
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Re: cleveland 4v open vs 4v closed chamber?

Quote:
Originally Posted by pvan View Post
Do you have a link to the dyno tests or article where they discussed them? I would be very interested to see more.

Years ago I started to fill the exhaust ports on my Cleveland quench heads and was told the port plates do the same job without modifying the heads.

Sounds good in principal, but seeing dyno pulls with before and afters would be very cool.

Thanks,
Paul

1969 R-Code, 4-Speed, Drag-Pack Cobra Fastback Project
1967 Mercury Commuter Wagon w/mild 429

My Car Restoration Projects
Back in the late 70's there was a big push to use the plates to block the bottom of the port on a 4v cleveland . Most of the guys that tryed them seem no gain and soom were trying to sell them. A friend bought a set for his Super stock Boss 302 engine and seen no improvement We tryed the same set on our NHRA J/S stock 1971 351 4V mustang and seen go gain in MPH or ET.
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post #8 of 9 (permalink) Old 04-04-2012, 02:23 PM
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Re: cleveland 4v open vs 4v closed chamber?

We piggybacked some exhaust stuffer testing after testing intake manifolds
on a 351C with closed chamber heads, TRW L2379F flat top pistons and a street
hydraulic roller cam. The dyno used is known to be 4 to 5% conservative
compared to the calibrated Engine Masters dyno running the same engines
(verified with both 351C and BBF - based entries). Also, the testing was
through a full exhaust, unless otherwise noted. With the intake testing
finished for the day, we moved on to some exhaust testing. First we tested
the MPG Head Service "Stinger" exhaust port stuffers. These are not the
earlier flat stamped steel type. Instead, these are the individually flanged
brass inserts with the a rounded tongue that sticks into the 4V exhaust port
floor:

MPG Heads - 351-302 Port Plates

They bolt between the header and the head. Feedback from some of the Mustang
drag racers suggested they might not do anything positive. However, one of the
Pantera guys had drag tested them on an engine similar to ours and found they
made some additional power. Pantera headers differ from most 351C headers in
that they have several inches of straight pipe at the exhaust port exit, before
turning down. Many Mustang 351C headers turn sharply down at the port exit
which might not work with the inserts, so my expectations were the inserts
would make a minor improvement with the Pantera headers but not the Hooker
Mustang headers. Surprisingly, the exhaust port stuffers worked on both the
Pantera headers and the Hooker long tubes to the tune of approximately 5 HP
and 10 ft-lbs.

Pull 10 - Without Exhaust Port Plates (MPG Stingers)
Holley Strip Dominator with HVH 1" spacer 950 HP dyno carb, unported iron 4V
closed chamber heads, Pantera GTS headers and Magnaflow mufflers.

RPM Hp Torque
(HP) (ft-lb)
4000 265.4 345.6
4100 278.0 352.7
4200 280.8 351.7
4300 286.8 350.6
4400 294.2 351.4
4500 304.0 354.9
4600 315.9 360.5
4700 328.9 367.1
4800 339.9 371.5
4900 346.2 371.3
5000 355.0 371.8
5100 360.2 371.0
5200 364.2 368.1
5300 371.3 368.0
5400 377.8 367.5
5500 383.9 366.6
5600 388.2 364.1
5700 388.6 357.8
5800 386.6 349.9
5900 379.5 338.3
6000 376.6 329.7
6100 380.0 327.0
6200 385.1 327.2


Pull 11 - With Exhaust Port Plates (MPG Stingers)
Same setup as pull number 10 with the Strip Dominator HVH intake setup and
Pantera header. The Pantera header comes straight out from the cylinder head
whereas the Mustang Hooker header turns downward more quickly. In this case,
the port plate/tongue seems to help in the next test we'll try it with the
Mustang headers and see if there's a difference for better or worse.

RPM Hp Torque
(HP) (ft-lb)
4000 265.4 348.9
4100 272.6 349.5
4200 283.2 354.3
4300 295.6 360.8
4400 307.0 366.4
4500 317.9 371.0
4600 327.0 373.5
4700 336.8 376.2
4800 348.1 380.6
4900 354.9 380.7
5000 358.1 376.3
5100 367.0 377.5
5200 370.4 374.5
5300 376.2 372.7
5400 385.2 374.3
5500 391.4 373.7
5600 390.9 366.8
5700 385.6 355.5
5800 386.8 350.1
5900 388.2 345.2
6000 383.3 335.9
6100 381.8 329.3

Hooker Competition Mustang long tube headers
These were also slightly better with the port plates. Seems to be about
5 HP and about 10lbs/ft better than without with both of our test headers.
These headers or the Pantera design seem to not be terribly bad about a sharp
quick turn down when leaving the cylinder head as some headers can be on the
Big Block Ford engine.

RPM Hp Torque
(HP) (ft-lb)
4000 281.6 365.6
4100 281.0 361.0
4200 286.1 358.0
4300 294.7 360.1
4400 304.7 363.7
4500 316.5 369.2
4600 329.7 376.1
4700 343.1 383.1
4800 349.8 384.1
4900 355.1 381.3
5000 357.9 376.2
5100 363.2 373.9
5200 371.3 374.7
5300 382.1 378.9
5400 387.5 376.9
5500 392.3 374.3
5600 392.1 367.9
5700 387.7 357.5
5800 384.7 348.4
5900 384.8 342.4
6000 378.7 331.7
6100 384.3 330.7

We still had a little time left, so we decided to see if the Pantera 180
headers would fit the dyno. To my surprise, they fit just fine after moving
the coil from off the top of the bellhousing. They worked about as well as
the Pantera GTS headers without the port plates.

180 degree headers without mufflers, no port plates and no real difference in
power. Running Strip Dominator intake with HVH spacer and 950HP.

RPM Hp Torque
(HP) (ft-lb)
4100 264.1 339.3
4200 273.7 341.7
4300 285.2 348.2
4400 300.1 357.9
4500 315.2 367.5
4600 321.1 367.0
4700 328.5 367.7
4800 342.0 373.6
4900 348.6 374.2
5000 353.0 371.0
5100 361.9 372.3
5200 369.6 374.2
5300 371.2 367.8
5400 378.5 368.3
5500 381.6 364.6
5600 384.4 360.2
5700 386.7 356.2
5800 380.2 344.5
5900 376.4 334.9
6000 374.1 327.2
6100 382.2 328.9


Running the 180's with Super Trap mufflers. Down a little torque but
about the same HP. Certainly not better than the more standard Pantera
header on this engine.

RPM Hp Torque
(HP) (ft-lb)
4100 249.9 320.7
4200 258.8 324.2
4300 272.4 332.8
4400 286.7 342.2
4500 302.4 352.7
4600 319.5 364.6
4700 333.9 375.0
4800 340.7 373.2
4900 345.9 370.9
5000 349.1 366.5
5100 355.4 365.3
5200 361.9 366.5
5300 365.2 362.0
5400 371.3 361.0
5500 381.7 363.6
5600 382.6 359.3
5700 379.8 350.0
5800 375.8 340.5
5900 373.1 332.0
6000 373.7 326.8
6100 378.3 326.6

Note the 180's used for this test have a very small collector that
is angled and would not permit testing the Magnaflow mufflers.
A better collector design might improve these headers. We did not
test the 180's with the port stuffers as we were unsure they would
fit with them.

Air-fuel ratios were a bit on the rich side (11.9 to 12.3:1) range but
were fairly consistent so we didn't try any carb fine tuning.

Dan Jones


Dan Jones


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post #9 of 9 (permalink) Old 04-07-2012, 12:32 PM
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Re: cleveland 4v open vs 4v closed chamber?

Sleeper, do you have a piston picked out yet? your choice of chamber may be influenced by the top of the piston... if all you can find is a dish you'll want the closed chamber to keep the CR up, if you find a swingin deal on a small dome you might want the open chamber to keep the CR down and if you use FT's you can go with either chamber depending upon cam, gear & what kind of fuel you want to feed it on a daily basis. building to the ragged edge of needing octane boost or mixing race fuel with pump is a major PITA, more times than not you won't have the can of stuff or can't get the high octane to mix. just build it to run a certain octane that's available anywhere you go, a wise man once told me that 'farmers don't buy Premium'. what that means is that out in corn country the Premium is stale in the underground tanks, and that's what happened, i filled up with Premium in the middle of corn country and the gas was bad for 350 miles to the next fill-up

so anyway, the difference in the chambers is usually about 1.3~1.4 points of compression. a 9:1 engine with OC's will bump to about 10.3/4 with CC heads

i'd base my decision with more info, the piston type and the cam's intake closing point to figure your DCR
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