2V vs 4V

[hyena429]

I think you missed my point. If BOTH combinations were built to take advantage of their strengths, the 2v would win at under 4500 rpm and the 4v would win at above 4500 rpm.

The valve releif in the pistons have nothing to do with it. Comparing open chamber to open chamber is comparing apples to apples as they have the same sized chambers. Cutting the deck surface of a head to true the surface has minimal effect on compression and is best practice when rebuilding a set of heads.

It would have a big deal to do with it...the open chambered heads would not have the same compression in the test...they milled and boosted the compression....now if they used 4v" closed chambered" heads...then it would be valid...with wrong manifold...wrong everything..the 4v would struggle...and not show correct numbers is what im saying.

i would say...a 2v will win low rpm gunt...but i dont think there numbers are too correct..is all im saying pretty much.lol

 

[droptop73]

Why would giving the 4v head an advantage with a higher compression ratio by using a closed chamber make the test more valid? Both the 2v and 4v open chambered headshave identical combustion chamber volume. The only difference is the 2v heads have smaller valve diameters.

Am I missing something here?

 

[Wolverine]

May I chime in...about another forgotten component in the powertrain....the transmission of power to the rear wheels.

If you have an automatic with a 1500 RPM stall converter, I suspect the 2V would outperform the 4V unitl 4500 RPM for all the reasons stated here. The 4V needs to pull for 4500-1500=3000 RPM before it will begin to blow away the 2V.

If you have an automatic with a 2500 RPM stall converter, the 2V will still outperform the 4V until 4500 RPM...but the difference would not be as large because the 4V only has to make a 2000 RPM jump to get to its sweet spot.

If you have a 4 speed, and you drop the hammer at 4k, the 2V will not pull nearly as hard as the 4V. At 4500 RPM, the 2V is near its peak. The 4V has just started.

And of course, there is also the rear gear ratio as well. A 2.10 gear will be more kind to the 2V because shifting gears will significantly drop the RPM...the 3.25+ will be kinder to the 4V as the gear shifting will be done at higher RPM.

As a result, you should look at the entire powertrain. BALANCE.

 

[hyena429]

Why would giving the 4v head an advantage with a higher compression ratio by using a closed chamber make the test more valid? Both the 2v and 4v open chambered headshave identical combustion chamber volume. The only difference is the 2v heads have smaller valve diameters.

Am I missing something here?

Having the cylinder heads milled to flatten the mating surface and reduce the size of the combustion chambers to boost compression....They do not say anything about the open chambered 4v heads being milled to lower there compression...Am i missing something too? ..Plus they used a single pattern cam..Which a 2v could take much better advantage of.

Treat 2V and 4V engines as completely different when it comes to picking components like cams, heads, and intakes. The primary difference between 2V and 4V heads lie in the ports. as we know from the size.

The 4V exhaust port has a hump then a sharp drop with an exaggerated area change. The port exit area is very large but much of it is wasted and the flow velocity low. The resulting poor intake to exhaust flow ratio requires a cam with additional duration (typically 10 degrees or more) and lift on the exhaust side for best results. 4V heads work best with a dual pattern cam....Im saying..You cant build them the same...the 4v heads need to be set up right...Or the numbers on the dyno will not be the same....specialy if those opened chambered heads are not milled...and just plain jane.....If the 4v had the right cam...It would make more power and have a diffrent read on the dyno....i agree that a 2v has more lower end..it was made too...But there numbers can be way better with the right set up for the 4v....To compare them proper...they should of been built on seperate motors.

 

[69 Rustang]

They did such an awful job with the Cleveland that test should never be considered for any purpose. They used the same intake for both sets of heads-- our assumption is that it was a 2v intake--was it? We'll never know. Along with all the other issues with that test it is not relevant.

 

[t.klapperich]

May I chime in...about another forgotten component in the powertrain....the transmission of power to the rear wheels.

If you have an automatic with a 1500 RPM stall converter, I suspect the 2V would outperform the 4V unitl 4500 RPM for all the reasons stated here. The 4V needs to pull for 4500-1500=3000 RPM before it will begin to blow away the 2V.

If you have an automatic with a 2500 RPM stall converter, the 2V will still outperform the 4V until 4500 RPM...but the difference would not be as large because the 4V only has to make a 2000 RPM jump to get to its sweet spot.

If you have a 4 speed, and you drop the hammer at 4k, the 2V will not pull nearly as hard as the 4V. At 4500 RPM, the 2V is near its peak. The 4V has just started.

And of course, there is also the rear gear ratio as well. A 2.10 gear will be more kind to the 2V because shifting gears will significantly drop the RPM...the 3.25+ will be kinder to the 4V as the gear shifting will be done at higher RPM.

As a result, you should look at the entire powertrain. BALANCE.

As I was reading thru these posts I was wondering when someone would bring up tranny and rearend. I agree 100% with this post. Correct me if I am wrong but the Boss 351 was the fastest production mustang in stock form up until the 93 cobra. This was done with a 4V cleveland, closed chambered heads, 4 speed toploader and 3.91 traction lock rearend.

The Boss 351 was the basis of my build. I ended up with 420h.p. Im running a performer intake, 750 holley, headers, 4 speed toploder and 370 gears in the rearend and I have no issues with lowend torque.

And the answer to the question is torque over H.P. I couldn't see having 500 usable h.p. in our cars. I dont know how you would keep the traction to the road. I am running old school lakewoods and have a hard time not cooking the tires!! Maybe I need something better than the lakewoods.

 

[Tnfastbk]

They did prove one thing. Look again at the power and torque curves. The 2v builds power on the bottom end up to 4500 rpm. No matter what you do to the 4v combination it will not improve the low rpm power. The 4v combination will make more power but it will be higher in the rpm range where that head works best. Both combinations are compromizes, the 2v head set-up needed a performer air gap to make it's best low rpm power. If they had maximized both combinations to take advantage of the strengths the 4v would not touch the 2v under 4500 and the 2v would not touch the 4v above 4500 rpm.

Now one final question... what makes a car move horsepower or torque?

Mine seems to do well off the line:huh:

 

[gpierce]

All this talk of Clevelands, heads, etc reminds me there is a lot of dicussion info here (need to register to view posts):

http://www.fordforums.com.au/forumdisplay.php?f=10

I'm sure most of you know about these forums, but there is lot of very knowlegable people there on Clevelands since Australia ran them for much longer in passenger cars.

Greg

 

[Jim and Jutta]

I think this is a pretty good discussion of cleveland heads

http://www.fordmuscle.com/archives/2007/10/351CHeads/

Introduction

Are 4V Cleveland heads OK for my application, or should I run the 2V Cleveland head? The question can spur disputes as fierce as rival religious sects jockeying for land rights. In fact, the debate has been hashed out so many times within the FordMuscle forums that we thought we'd add some fuel to the fire in an pursuit for clarity on the subject. In this article we'll gather flow and swirl test data, and take a three-dimensional look at the design of Cleveland intake and exhaust runners for Ford's factory 2V iron head, the factory 4V iron head, and Edelbrock's Performer RPM 351C head. Once compared with basic cylinder head theory and the often misunderstood topic of "swirl", the results will provide you with a better understanding of which head is best for your next Cleveland buildup whether it's a 351C, Clevor, or the suddenly hip 351M/400.

-Factory Cleveland heads were produced from 1970-1974

-Factory Cleveland heads can be found in both 2V and 4V castings

- 2V and 4V castings are available with and without a quench chambers

- All Cleveland heads can be used on 351C, 351M, and 400 blocks

- Edelbrock, CHI, and AFD all produce aluminum alloy Cleveland heads

- Factory quench chambered 351C 4V Cleveland heads are identical to Boss 302 Heads other than water jacket locations

For complete historical data on the Cleveland see The Ford 335-Series Engine at Wikipedia.

Basic Cylinder Head Theory

While combustion chamber design and volume, valve position, and many other design aspects of a cylinder head have an effect on useable power gains, the design characteristics of any cylinder head's intake and exhaust port have the greatest influence on airflow. This is why so much time and effort is spent by DIY head porters and aftermarket engineering departments on optimizing these areas of a cylinder head for the specific applications in which the head will be used.

Again, while this article is not intended to be an absolute reference on the Cleveland head or cylinder head theory, the following excerpts from the SpeedPro Series book "How To Build , Modify, and Tune Cylinder Heads" by Peter Burgess and David Gollan", will provide you with a basic foundation for which to evaluate the information presented on the following pages.

"A small intake port feeding a large cylinder will have a high gas speed at low RPM, it will be unable to supply sufficient air at higher rpm. Conversely, a very intake large port feeding the same cylinder (think 351C 4V) will only achieve high gas speeds at high RPM and will have very low gas speed at low rpm. Standard port dimensions are the result of designers aiming to achieve the best compromise in terms of filling across a wide range of engine operating speeds."

"Airflow is more sensitive to shape than size, so big ports are not necessarily better than small ports at flowing air. Airflow also hates experiencing sudden changes in direction, volume, and shape. These concepts are supported by the fact that the areas of the port that are easy to get at (when porting) normally have small to moderate effect on airflow; it is more often those bits that are really difficult to get at that usually have the greatest influence on the head's airflow capability"

Both excerpts are applicable to the obvious differences seen between a 351C 2V head and a 351C 4V head, where the 4V's large intake port design is known for better high RPM operation and the 2V's relatively smaller intake port design is known for better low RPM or street performance. Keep in mind however, that port volume alone is just one aspect of an intake runner that contributes to performance and drivability. Port shape and contour are also critical factors, the following pages will take you inside three different Cleveland cylinder heads to demonstrate the variations in runner shape that affect flow performance

 

[BenD]

May I chime in...about another forgotten component in the powertrain....the transmission of power to the rear wheels.

If you have an automatic with a 1500 RPM stall converter, I suspect the 2V would outperform the 4V unitl 4500 RPM for all the reasons stated here. The 4V needs to pull for 4500-1500=3000 RPM before it will begin to blow away the 2V.

If you have an automatic with a 2500 RPM stall converter, the 2V will still outperform the 4V until 4500 RPM...but the difference would not be as large because the 4V only has to make a 2000 RPM jump to get to its sweet spot.

If you have a 4 speed, and you drop the hammer at 4k, the 2V will not pull nearly as hard as the 4V. At 4500 RPM, the 2V is near its peak. The 4V has just started.

And of course, there is also the rear gear ratio as well. A 2.10 gear will be more kind to the 2V because shifting gears will significantly drop the RPM...the 3.25+ will be kinder to the 4V as the gear shifting will be done at higher RPM.

As a result, you should look at the entire powertrain. BALANCE.

this sums it all up, well for me,

the engine is just a part of the whole package, it has to work together with the rest of the drivetrain.

if you build a big cammed 4v 351c with a stock convertor/tranny and a 2.75 rear gearing with 275/60/15 tire combo, yes it will be a pig, the 4v will fall flat on its face regarding low end torque, but stick a high stall convertor in it ,with a 3.50/3.89 gearing and 275-50-15 tire, it will rip the road right off the surface of the earth. it must be a right combination, everything has to work together.

my 4v has more than enough low end grunt to make me smile

 

[mach71351c]

Ok, when guys ask how can I get more power out of my car. After we all recommend normal engine and exhaust mods we say drop the gears. Once you drop the gears to 3.50 or lower the 2v 4v debate is over. It doesn't mater stock or modified 2v will run out power and leave you wanting more. With lower gears the rpms will be in the zone for the 4v to come alive and the 2v to shut down. I have had both stock and modified 2v 4v Clevelands and hands down the 4v is the best performance motor street or strip. ( my opinion ) Not to say you can't make a 2v motor run well.

This is what I know about 2v and 4v Clevelands. I was a believer of the myth that the 2v was better street motor. Till the day I took my brother for a ride in my 71 Grande and he told me that his 85 GT felt quicker.:dodgy: I said B.S. So I ran his bone stock 85 GT and he beat me by 2 car lengths.

The 2v motor in my Grande was 30 over comp cam performer intake 750 holley headman headrs Mallory dis you know a typical build. The trans was a Fairbanks C6 with a 3000 stall and 4.11 gears. I thought it ran well.:-/ After beating the crap out the 2v motor It gave up. Now it came time for the 1970 4v. Pretty much did the same build to the 4v as the 2v using the same carb trans and gears. The car came ALIVE and pulled to 7000 RPM. Ok back to my brothers 85 GT we ran again and this time I smoked him by 6 car lengths. The car ran 12.83 @ 106mph on 245/60/15 T/As.You guys make it sound like the 4v has less torque than a 2.3 pinto. I say if your going to build a Cleveland,build a 4v. With the cam profiles and O.D trans of today their is no reason NOT to use the 4v heads. So that's all I know about 2v and 4v.

 

[Wolverine]

So, from now on, when someone asks which head is better, 2v or 4v, we should respond the redhead.

 

[Totalled]

James, be fair. The 4Vs come on at 3,000.

 

[t.klapperich]

:

Ok, when guys ask how can I get more power out of my car. After we all recommend normal engine and exhaust mods we say drop the gears. Once you drop the gears to 3.50 or lower the 2v 4v debate is over. It doesn't mater stock or modified 2v will run out power and leave you wanting more. With lower gears the rpms will be in the zone for the 4v to come alive and the 2v to shut down. I have had both stock and modified 2v 4v Clevelands and hands down the 4v is the best performance motor street or strip. ( my opinion ) Not to say you can't make a 2v motor run well.

This is what I know about 2v and 4v Clevelands. I was a believer of the myth that the 2v was better street motor. Till the day I took my brother for a ride in my 71 Grande and he told me that his 85 GT felt quicker.:dodgy: I said B.S. So I ran his bone stock 85 GT and he beat me by 2 car lengths.

The 2v motor in my Grande was 30 over comp cam performer intake 750 holley headman headrs Mallory dis you know a typical build. The trans was a Fairbanks C6 with a 3000 stall and 4.11 gears. I thought it ran well.:-/ After beating the crap out the 2v motor It gave up. Now it came time for the 1970 4v. Pretty much did the same build to the 4v as the 2v using the same carb trans and gears. The car came ALIVE and pulled to 7000 RPM. Ok back to my brothers 85 GT we ran again and this time I smoked him by 6 car lengths. The car ran 12.83 @ 106mph on 245/60/15 T/As.You guys make it sound like the 4v has less torque than a 2.3 pinto. I say if your going to build a Cleveland,build a 4v. With the cam profiles and O.D trans of today their is no reason NOT to use the 4v heads. So that's all I know about 2v and 4v.

Right on ! Well said,:sleepy: and I like your use of all the Smilies too !!

 

[cazsper]

Impressed.