2v power?

[cazsper]

I really don't need to wind past 6000. I have two strokers Windsors now and love them. I have a 393w in my '68 coupe and a 415w waiting for a vortech or Paxton and fuel injection. As for my initial reason for this post, I was wondering at what point do the 2v heads end and where do the 4v heads start.

My use, however, is purely street. 5-speed TKO-600, 3.50:1 gears, Edelbrock Air Gap intake, and a set of Sanderson headers. My biggest issue is what displacement and what cam.

 

[hyena429]

I really don't need to wind past 6000. I have two strokers Windsors now and love them. I have a 393w in my '68 coupe and a 415w waiting for a vortech or Paxton and fuel injection. As for my initial reason for this post, I was wondering at what point do the 2v heads end and where do the 4v heads start.

My use, however, is purely street. 5-speed TKO-600, 3.50:1 gears, Edelbrock Air Gap intake, and a set of Sanderson headers. My biggest issue is what displacement and what cam.

2v is good too 5,000 before it starts to drop off...4v had a stock rating of 6150ish.

 

[turtle5353]

I really don't need to wind past 6000. I have two strokers Windsors now and love them. I have a 393w in my '68 coupe and a 415w waiting for a vortech or Paxton and fuel injection. As for my initial reason for this post, I was wondering at what point do the 2v heads end and where do the 4v heads start.

My use, however, is purely street. 5-speed TKO-600, 3.50:1 gears, Edelbrock Air Gap intake, and a set of Sanderson headers. My biggest issue is what displacement and what cam.

2v is good too 5,000 before it starts to drop off...4v had a stock rating of 6150ish.

My 2v pulled good up to 5500-5800. had rev limiter set at 6100. But thats was with a lot of work done to the heads.

 

[mach71351c]

It's very simple. A 2v motor with a good cam and valve train will make a good mild street motor. If you plan on spending money on porting the 2v heads your wasting your time and money. Just step up to 4v heads and don't look back. I had a mild 2v motor and a mild 4v motor in my 71 Grande using the same carb-trans-stall and rear gear. The 2v motor made noise and got beat by my brothers bone stock 85 GT. About 6 months later the 4v motor smoked his GT by 3-4 car lengths. The 2 motors felt about the same till about 2000 rpm, then the 4v motor pulled strong to 6500. The 2v motor was all done at 5000. I was one of those guy that preached the 2v motor was better for the street.:shrug2:

 

[73vertproject]

Here's a video showing the stock tach during a test drive of my 2v right at 500 miles after the rebuild. The tach may be off at higher RPM, but it is within 50 RPM at idle according to my meter. I'm pretty sure it was still pulling good at 5K.

 

[CZ-75]

Here's a video showing the stock tach during a test drive of my 2v right at 500 miles after the rebuild. The tach may be off at higher RPM, but it is within 50 RPM at idle according to my meter. I'm pretty sure it was still pulling good at 5K.

Nice! Was your gas gauge on full before you floored it?

 

[wwhite72]

It's very simple. A 2v motor with a good cam and valve train will make a good mild street motor. If you plan on spending money on porting the 2v heads your wasting your time and money. Just step up to 4v heads and don't look back. I had a mild 2v motor and a mild 4v motor in my 71 Grande using the same carb-trans-stall and rear gear. The 2v motor made noise and got beat by my brothers bone stock 85 GT. About 6 months later the 4v motor smoked his GT by 3-4 car lengths. The 2 motors felt about the same till about 2000 rpm, then the 4v motor pulled strong to 6500. The 2v motor was all done at 5000. I was one of those guy that preached the 2v motor was better for the street.:shrug2:

with all due respect, you didnt really give enough detail to draw a conclusion.

 

[73vertproject]

Here's a video showing the stock tach during a test drive of my 2v right at 500 miles after the rebuild. The tach may be off at higher RPM, but it is within 50 RPM at idle according to my meter. I'm pretty sure it was still pulling good at 5K.

Nice! Was your gas gauge on full before you floored it?

lol CZ-75. I don't remember for sure, but I know that after rebuilding that dog, even with just a "little" 600CFM Holley, I'm thinking 12 - 14 MPG sounds pretty good. :s

 

[sm3570]

It's very simple. A 2v motor with a good cam and valve train will make a good mild street motor. If you plan on spending money on porting the 2v heads your wasting your time and money. Just step up to 4v heads and don't look back. I had a mild 2v motor and a mild 4v motor in my 71 Grande using the same carb-trans-stall and rear gear. The 2v motor made noise and got beat by my brothers bone stock 85 GT. About 6 months later the 4v motor smoked his GT by 3-4 car lengths. The 2 motors felt about the same till about 2000 rpm, then the 4v motor pulled strong to 6500. The 2v motor was all done at 5000. I was one of those guy that preached the 2v motor was better for the street.:shrug2:

with all due respect, you didnt really give enough detail to draw a conclusion.

I believe there is a thread somewhere on here about it.

Here's a video showing the stock tach during a test drive of my 2v right at 500 miles after the rebuild. The tach may be off at higher RPM, but it is within 50 RPM at idle according to my meter. I'm pretty sure it was still pulling good at 5K.

Man, Doc, that sounds nice! ::yourock:: ::beer::

 

[73vertproject]

My intent in posting the video was not to dispute Mike's experience with his 2V and 4V heads, but rather to reinforce the different dynamics that influence the results of having 2V or 4V motors with a variety of builds.

Serious debates about the pros and cons of 2V and 4V engines are better left for the many other forums that are more dedicated to those discussions. 7173mustangs.com is dedicated to supporting all enthusiasts of the 1971 - 1973 Mustang, and whatever their owners envision for their 'stangs.

Thanks everyone for your input. This comes around every few months, understandably.

 

[mach71351c]

It's very simple. A 2v motor with a good cam and valve train will make a good mild street motor. If you plan on spending money on porting the 2v heads your wasting your time and money. Just step up to 4v heads and don't look back. I had a mild 2v motor and a mild 4v motor in my 71 Grande using the same carb-trans-stall and rear gear. The 2v motor made noise and got beat by my brothers bone stock 85 GT. About 6 months later the 4v motor smoked his GT by 3-4 car lengths. The 2 motors felt about the same till about 2000 rpm, then the 4v motor pulled strong to 6500. The 2v motor was all done at 5000. I was one of those guy that preached the 2v motor was better for the street.:shrug2:

with all due respect, you didnt really give enough detail to draw a conclusion.

I have already posted specs on other threads. Both motors were built about the same, 30 over 11to1. The cam in the 4v motor was a Ford Motorsports and the 2v had a Comp Cams. The 4v had a Weiand X-larator intake and 2v Edlebrock performer. The 2v heads were all done up. Nothing to special to the 4v heads.The valve train was about the same. Let's see a stock 85 runs high 15s in the 1/4. I ran 12.83@ 108 with the 4v motor on a hot humid day and 1st time I ever been to the track. The stock 4v was in a 70 Rustang Mach 1 when I got it and i would say it ran every bit as good as the built 2v did. All I'm saying don't put a bunch of money into the 2v heads like I did.

 

[Widowmaker00]

I think it should be pointed out that 4v closed chamber heads are much better than the open chambers.

I find it interesting, my 4v seems to be done by 5500 rpm....maybe my cam is just too small.

 

[73vertproject]

Thanks, Mike, for your input. The 2Vs have potential, and the wide variety of applications affect the outcome, obviously. I'm thinking I got lucky with how I set mine up. Yet, I still have a long way to go to get it "perfect", and will be asking a lot of questions in the near future.

 

[cazsper]

I think it should be pointed out that 4v closed chamber heads are much better than the open chambers.

I find it interesting, my 4v seems to be done by 5500 rpm....maybe my cam is just too small.

Is that only due to the compression ratio or is there something else to it?

 

[Widowmaker00]

I think it should be pointed out that 4v closed chamber heads are much better than the open chambers.

I find it interesting, my 4v seems to be done by 5500 rpm....maybe my cam is just too small.

Is that only due to the compression ratio or is there something else to it?

Compression ratio and combustion chamber design.

 

[72HCODE]

i have open chamber V4 heads on my engine i can confirm they should be taken to a dump and recycled, they are garbage and cause all kinds of tuning issues.

the only way to save them is using domed pistons to try and compensate for the compression loss and also low vacuum at lower rpms.

basically the engine runs badly under 1500rpms all the time. above 1500rpm it wakes up and is fine but i'm not doing laps at 100mphs on a track i'm tring to drive on the street.

Closed chamber V4s only, lol.

 

[cazsper]

So for a 351, closed chambers with dished pistons would be better than open chambers with pop up pistons. But if I were to go the stroker route (393 or 408), would the added displacement work with the open chambers?

 

[72HCODE]

the closed chamber is going to up compression just by themselves, they also have a different combustion shape.

now when you build a engine,,, you must start with the cam and build around that. if you know you will use 4v closed chamber heads, then you need to figure out the compression you are looking for, then pick the pistons at that point. If you want to go stroker then the pistons will of course need to be changed on paper.

don't just make a list of things that are good alone, make sure you are picking the best of the combo you need;

Starting from the cam design itself.

now other things might get in the way as you start the build you may find the deck is warped and you need a .20 shave, that is going to throw a monkey wrench into the compression as well, and your parts combo might need to be altered again.

if later you decide i want a super charger or a turbo charger then you may have a serious problem if you decided now you want a 11:1 compression motor.

basically you start with the cam you want, then the block gets checked so you know what you are dealing with. pick the heads, then the pistons, and the piston rods so you get to the compression ratio you need for application.

 

[cazsper]

Nice.. Thanks..

Now, living in California, we have 91 octane. My 393w has 10:1 compression with aluminum AFR heads. How much compression can I run with iron heads and 91 octane?

 

[72HCODE]

i hope i helped i learned even after i tired to dot my i's and cross my T's i had major problems.

There are far too many variables. I have seen engines with 13:1 run on 93 octane with no problems, and I have seen engines with 8.5:1 ping like crazy and run like crap. As a general rule 10:1 with flat top pistons will work fine with 93 octane. 91 might be a crap shoot. with me i have a 8.6:1 and it was a nightmare on 97 gas, even with a 108 octane booster. How fast your timing come on and maxes out has a big effect also. When i built my engine i told my builder i wanted to use 87 or 89 octane gas and on purpose we went for a lower compression ratio. thing is i think we shot too low for the combination with the open chamber heads. I throw up my hands in this case just too many things can add up to a problem or not. I would recommend coping a known combination that is close to what you want at least that way is a margin of safey, and i would join the 351 cleveland forum and ask questions there as well.