331 cam

[iismet]

Originally Posted by blykins

For a 6500 peak on a solid roller for your application, I would use the Comp Cams Xtreme Energy lobes. They are aggressive enough for power, but not aggressive enough to cause valvetrain issues.

How efficient the cam is depends on how well the heads flow, so with a decent head, I would go with something like a 230/234 @ .050", 112 LSA, .561/.561" with a 1.7 RR.

Those lobes work really well but aren't spring eaters or valvetrain breakers.

Thank You -

Originally Posted by blykins

I would personally rethink the Eagle bottom end and use the Scat crank and rods. Mahle makes a really light piston for this application that's already coated and has a thinner ring pack. Good stuff.

Can you expand on this- why do you prefer one over the other? I was going to purchase a forged kit. They both make one - Eagle supplies Mahle Pistons but they are probably not the ones you specify. You are right on the money - a lite assembly. I'll need to study this further.

Originally Posted by blykins

An aluminum flywheel works well with the road race applications, but keep in mind that an aluminum flywheel will make a high strung engine a little harder to drive on the street, and the result is having to slip the clutch more to get the car going.

My car is an ERA. ERA runs a heavier frame. I thought I would try to get the thing as lite as I could. It weighed 2440 with the 351. I store the car in the country and that is where it is mostly driven. I've never been a stop light racer - the car is iconic - when stopped at a light that is good enough for me - back roads are a different matter.

It's like the solid vs hydraulic for me - I'm committed. If there is not enough inertia I will swap it out.

Hugely appreciate your input.

[ERA2076]

I just realized I logged in as iismet. This is an old name I have used for ever. I never could get it to work here when I joined so I used era2076. Then out of habit, one day I logged in as iismet and I was in. Unfortunately, I forget who I am from time to time when I log in here and either is accepted.

[Fullchat289]

LOL....I was about ready to ask that "iismet" guy who he was, and why he was hijacking your thread...

-Allen.

[ERA2076]

Originally Posted by bobcowan

AFAIK, the specs you want don't exist in an off the shelf solid roller cam. I'v searched, and haven't been able to find one from any manufacturer.

The wide LSA is important for Webers, or any IR intake system. That keeps overlap to a minimum. Since you don't have a common plenum, the overlap will create the fuel cloud from reversion.

I rtan a cam similar to this one (hydraulic roller) in my 427W. It makes great power, and pulls like a freight train all the way to red line. It makes power pretty much everywhere.

Use caution with your head selection. I'm using some Dart Pro-1 195 heads. They have a 2.02" intake valve. A couple of years ago I tried a set of Brodix heads, with 2.08" valves. I lost all my low end torque. The intake was too big for the throttle body, and the intake charge lost it's velocity. The intake valve should not be larger than your carb/TB bore.

Your carb bores are 48mm. Your intake valves are 50mm. You might have a mis-match there. The blades and other stuff do take up some space, so you might be OK. If you haven't purchased your heads yet, you might reconsider that choice.

BobCowan - can you discuss this a little further. I found info that states the 48's can flow 330 cfm per throat. Your 427w is still using a 51.3 mm intake valve - ideally a 1.89 inlet valve diameter match the 48 bore.

My understanding is the optimal intake valve size would be .5 to .56 of the bore (perhaps old school so it may discount all below).

On a 4.030 bore a 2.015 - 2.25 would be the optimal inlet diameter based on the premise above. Clearly the 48 is not adequate once the inlet valve size crosses a threshold (Graph Above - and thank you for posting).

You stated you thought you could gain a little more by resizing the intake again to 2.05 yet this would be slowing the intake charge at the valve as you stated. Am I to conclude there is a narrow margin where you can run the intake valve a little larger and the fuel separation has a negligible affect? If so, does displacement somehow play a role? Why would it work on a 427 and not a 331 - the throttle bore and inlet valve dia are the same on both.

A 1.90 inlet is the closest match for the 48. Why would you want to go up (2.05) instead of down (1.89 optimum) if your were to spend the cash?

I want to order my heads, but want to make the best decision. I found some specs for the 289 Hipo and it seems they started with 1.678 inlet and ended at - 1.788" so the 48 was a no-brainer. I do not know what the FIA's and USRRC cars ran. Would be interesting to know.

I want to order my heads, but want to make the best decision. If I can get away with the 195's that is the way I want to go as the flow rate really hooks up the the 48's 330cfm capability. However, if for some reason 48's and 2.02 inlets are a mis-application on a 331 (based on diameters they are) then I will limit to 1.9. Why does it work on your 427? Would it make more with 1.9? Why not?

Allen - have you had your beauty on a dyno? If so can you share some numbers?

I appreciate any input.

cliff

[ERA Chas]

Aren't Weber chokes sized around 38mm for small displacements?
I thought 48's were used primarily on larger displacements.

[Rick Parker]

The valve sizes in the modified Shelby heads as I recall were 1.6/ 1.875. Any larger and the intake seat was compromised by the 18mm sparkplug. I modified a set of Hipo 289 heads and fit these valves and they worked well. Later when development of aftermarket Ford heads was in its infancy there weren't a lot of choices. World Products was one of the first and their Winsor Jr head had 1.94 / 1.6. it is an ideal fit for a smallblock as the velocity through the ports is maintained regarless of what carburetor is being used.

ERA Chas: The throttle plate on the 48 IDA is 48 MM but the venturi size is standardized at 37 mm but is upsized based on cubic inch displacement or usage.
Go to large and throttle response gets real soft.

There are a couple of specialists that increase the throttle bore to 51-52 mm and install new throttle plates.

[ERA Chas]

Originally Posted by Rick Parker

ERA Chas: The throttle plate on the 48 IDA is 48 MM but the venturi size is standardized at 37 mm but is upsized based on cubic inch displacement or usage.
Go to large and throttle response gets real soft.

Thanks Rick. I remembered pretty close!

[bobcowan]

Because you don't have a common plenum to draw from, air is really only moving through the tract when the intake valve is open. So the air speeds up and slows down all the time. You're almost building 8 single cylinder engines - as far as the intake goes. That's why overlap is so important. If the intake and exhaust valves are open at the same time for too long, you'll get reversion of the intake charge. That famous "Fuel Cloud" you've heard about.

My throttle bodies are right at 2.019". Just about the same size as the intake valve. As you can see from the torque curve, that works pretty well. If I had the time and funds, I would like to try a 2.05 intake valve, and maybe a 200 or 205cc intake port. From some of the reading I have done, a slightly larger valve will work, but too large will not.

Intake charge velocity is not independent of displacement. Imagine if you were trying to inhale a lung full of air through a garden hose vs. a soda straw. For a big engine you need bigger ports and valves. For a smaller engine, you need smaller ports and valves. I don't have the experience to tell you what will work best for a 289 or 302. But if you want to maintain flow velocity though out the tract, don't put in valves that are significantly larger than your carbs.

Carbs of any kind are very sensitive to flow velocity. If the carbs and ports are too big, you'll get a poor vacuum signal and poor metering off idle and into the mid range. Also, if the velocity is too low, the fuel will fall out of suspension before it hits the chamber. That's why big engines with big carbs built for high rpm's often idle at 1200-1500 rpm's. They are not capable of running at 800rpm's.

For my engine, I suspect my throttle bodies are limiting my power production. If I had a 55 or 58mm TB, then I could use a 2.08 valve and 225cc intake port. I suspect that would increase the air flow in the mid and upper range = more power. If I had carbs, intake tracts that big would cost me a lot of bottom end power and drivability. But that's not as big of a problem with EFI.

[ERA2076]

Perfect - Am going to order 1.94 Pro1.

thanks for the replies

cliff

[blykins]

Those dart heads are not big performers.....you sure you want those?

[Clois Harlan]

If you have the time contact Dean Lampe of this site. He and his engine builder "Lumpy" built the strongest 302 based engine I have ever seen for his GT40. The car and engine was built over six years ago and has been ran hard at several tracks and still performs like it was new. Strong power at all the right places.

Clois Harlan

[bobcowan]

Originally Posted by blykins

Those dart heads are not big performers.....you sure you want those?

Oh, I don't know about that. Mine seem to work OK.

[blykins]

I like Dart blocks, but that's about it.....have used Dart heads for a few motors in the past and wasn't really impressed with them. Just my experiences/opinion.

[Fullchat289]

Cliff: Here is an interesting article on the swap-out of different sized Dart heads on a 363 bottom end..I'm just offering this for the entertainment value and perhaps you may glean something from reading the comparison.

Cylinder Head Comparison Test - Muscle Mustangs & Fast Fords Magazine

...and to Brent's point...there are other options out there, I'm just working with what was on my engine....another comparison:

Cylinder Head Guide For Your Street Stang - Heads Of The Class - 5.0 Mustang & Super Fords Magazine

When my 347 was on the dyno, it produced 430hp/420tq at the flywheel with 44IDF's. It also ran 12.4 and 105mph trap in the quarter. With the same Dart Pro1 heads, same cam save for the lobe separation, and 48IDA's, the car ran 11.9s and 115mph trap. Simple on-line calculators will tell you that's 50hp, but the car hasn't seen a dyno since I've moved to the IDA's.

- Allen.

[blykins]

What's your cam specs F/C?

[Fullchat289]

Brent:

It's nothing radical, but it works well for me..

CompCams 35-518-8

35-518-8 - Xtreme Energy

- Allen.

[ERA2076]

Dart Head HP Test 302

RPM 195 210 225
2,800 159 171 168
3,000 186 189 187
3,300 217 222 221
3,500 237 241 239
3,800 267 266 266
4,000 283 281 281
4,300 305 301 301
4,500 318 311 311
4,800 336 325 328
5,000 346 341 340
5,300 366 361 361
5,500 374 372 371
5,800 383 387 385
6,000 389 395 395
6,200 386 399 399

Looks great to me - a set of 48's and that 195, on my 331 and I could be smiling. I'm not looking to make 500hp - 420 would be entertaining - a bit over what Shelby ran on a little heavier car.

I stopped and talked to my dyno tuner this morning about the inlet valve size compared to to the Weber throttle bore. He was not concerned at all about a 2.02 inlet dia. He just tuned a SBC 350 Lola with 48's . He stated the 2.02 valve and 48's have been used for many years. He had detuned the Lola while the owner learned how to drive it and had just restored the optimized Weber configuration for 500+.

[jhirasak]

One option on selecting a cam for your 331 engine might be to use the software tool provided by Comp Cam (Camquest free download). It allows you to enter all of the parameters of your particular engine and then compare different cams showing the hp and torque output for each particular cam over the rpm range you plan to operate. When I compared my chassis dyno hp output with the predicted flywheel hp output predicted by the software, the results were fairly comparable.

Just for your information, my engine is a 331 block with the Comp Cam XE282HR (hydraulic roller) using AFR 165 heads, 10 to 1 CR forged flat top pistons, and Shelby tri-y headers with an X-pipe.

John

[Rick Parker]

Ive been runing 48 IDA's on a 289 for a few years. The cam I am using is a solid lifter Flat Tappet. Duration at .050 is 238/248, .536 lift and a lobe center of 107 degrees for intake and 117 degrees for exhaust. I am going to be building another engine soon and will use a cam very similar to this. It seems a little more agressive than many have but it works quite well. Idles at about 900, pulls like crazy 6600-6800, then nozes over. 37 mm chokes currently larger ones may help RPM carry a little further, but the engine is very flexible without and bad spots.