Heads
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Elder User
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From: Okla.
Heads
I have a few qustions maybe someone help me with. 1 What is the diffents beween OPEN & CLOSED CHAMBER heads? 2 Why can't you get more qunch with open chabered heads? 3 If I shave the deck of the head & the block will I Get more compretion or psi? Thanks Shawn 
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Joined: Jun 2003
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From: Houston/Hope BC
http://www.speedomotive.com/Building%20Tips.htm
should answer Q1 and Q2, Q3 yes... but like everything else in life it is possible to have too much of a good thing.
should answer Q1 and Q2, Q3 yes... but like everything else in life it is possible to have too much of a good thing.
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Joined: Sep 2004
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From: NW Arkansas
Hi! I could use a little advise, please.
I'm considering buying a set of 335 series heads for Cleveland/Modified Fords with pedestle rocker arms (351C 351M 400). Their casting numbers are D5AE-A2. The heads contain NEW one piece forged EV-8 stainless steel 2.19" intake and 1.71" exhaust Race Series valves and competition valve seats (intake 30-45-60-75, exhaust 40-45-12mm radius). This package also includes positive stem seals, NEW 4130 moly steel retainers, and NEW 1.460" diameter valve springs rated at 110 lbs @ 1.800" and 275 lbs @ 1.250". The springs will handle cam lifts to .550". This set of heads feature 78cc chambers prior to resurfacing(approx.74cc now). The heads have been magnetically inspected and are crack free. They're 2V heads with 4V valves (as I understand). I'm planning to put them on my 1979 400 in my F250 4X4. Edelbrock perf.400 with a Holley 600cfm, dynomax headers, and a comp 255DEH cam. Probably will replace the pistons for more comprression.
Question...do these sound like good heads for this application? Thanks! H
I'm considering buying a set of 335 series heads for Cleveland/Modified Fords with pedestle rocker arms (351C 351M 400). Their casting numbers are D5AE-A2. The heads contain NEW one piece forged EV-8 stainless steel 2.19" intake and 1.71" exhaust Race Series valves and competition valve seats (intake 30-45-60-75, exhaust 40-45-12mm radius). This package also includes positive stem seals, NEW 4130 moly steel retainers, and NEW 1.460" diameter valve springs rated at 110 lbs @ 1.800" and 275 lbs @ 1.250". The springs will handle cam lifts to .550". This set of heads feature 78cc chambers prior to resurfacing(approx.74cc now). The heads have been magnetically inspected and are crack free. They're 2V heads with 4V valves (as I understand). I'm planning to put them on my 1979 400 in my F250 4X4. Edelbrock perf.400 with a Holley 600cfm, dynomax headers, and a comp 255DEH cam. Probably will replace the pistons for more comprression.
Question...do these sound like good heads for this application? Thanks! H
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Joined: Sep 2004
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From: NW Arkansas
Thanks for your reply! Would you think a comp cam #255DEH or something a little more aggressive like a comp X-Treme Energy# 268? I noticed a NEW Clevite77 cam with .510/.536 valve lift - with 214/224 duration @.050 duration - 112 lobe seperation
on ebay went for $46! Although,I understood the power at midrange 1800 -5200 rpms
which didn't seem like it would be good for a 4X4 low-end torque. Please advise...Again, Thanks!
Howard
on ebay went for $46! Although,I understood the power at midrange 1800 -5200 rpms
which didn't seem like it would be good for a 4X4 low-end torque. Please advise...Again, Thanks!
Howard
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From: Okla.
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Open vx closed heads
Originally Posted by 74 F100 351m
I have a few qustions maybe someone help me with. 1 What is the diffents beween OPEN & CLOSED CHAMBER heads? 2 Why can't you get more qunch with open chabered heads? 3 If I shave the deck of the head & the block will I Get more compretion or psi? Thanks Shawn
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From: Eastern Pa
Dipstix, while the heads sound like they may be a real nice deal, you mention later that you want good 4x4 bottom end. Those larger valves are going to sacrifice some of that bottom end and give you more upstairs. Be careful to match what you buy with what you want to do with the truck.
Postmaster
Joined: Aug 2001
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From: Delaware
Dipstix,
The 4V valves are a bit of an overkill for your motor, but they will help your top end and won't hurt the low end torque much.
The Clevite cam brings the torque at 2000 RPM down to 411 ft-lbs from 443 ft-lbs with the 255DEH.
The 265DEH brings the torque @2000 RPM down to 422 ft-lbs.
Instead of going to a more agressive cam, you can gain power at high RPMs by improving the head flow. This like the larger valves will have little impact on the low RPM torque.
A hydraulic roller cam with about 0.550 lift and the same timing as the 255DEH will improve torque across the range, but is more expensive.
Be careful increasing the Compression Ratio. I would suggest no more than 1/2 point over what you now have or you will have detonation problems with a 255DEH cam. You could use Badger flattops with that cam and those heads.
The 4V valves are a bit of an overkill for your motor, but they will help your top end and won't hurt the low end torque much.
The Clevite cam brings the torque at 2000 RPM down to 411 ft-lbs from 443 ft-lbs with the 255DEH.
The 265DEH brings the torque @2000 RPM down to 422 ft-lbs.
Instead of going to a more agressive cam, you can gain power at high RPMs by improving the head flow. This like the larger valves will have little impact on the low RPM torque.
A hydraulic roller cam with about 0.550 lift and the same timing as the 255DEH will improve torque across the range, but is more expensive.
Be careful increasing the Compression Ratio. I would suggest no more than 1/2 point over what you now have or you will have detonation problems with a 255DEH cam. You could use Badger flattops with that cam and those heads.
Posting Guru
Joined: Aug 2000
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From: PacNW
The low end torque issue with the 4V heads has more to do with the port size than the valve size. The large volume of the intake ports on 4V heads doesn't allow the A/F mixture to obtain the same velocity under normal atmospheric pressure at low RPMs that the smaller 2V ports do which is the biggest reason for loss of low end torque. Assuming the ports in those heads haven't been "hogged out" too much the larger valves shouldn't result in a noticeable loss of bottom end power but they will increase the amount of A/F mixture that can enter the comb. chamber even at lower RPMs.
Elder User
Joined: Jan 2004
Posts: 867
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From: Eastern Pa
Thanks fo rthat clarification Bill. I thought about that because the flow should be as good as the most limiting factor. If the ports are still the small part of the equation then the valves alone should not hurt velocithy that much.
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