306 vs 342 - Page 2

JP · 03-18-04, 09:17 AM

All makes common sense! I'm no engineer. However, I did want an engine that would spin to 7000RPM without any probs.

My 331 made 449HP at 6600RPM.

We ran it up to a max of 6800RPM where power dropped to 420HP. My soft redline is set to 6800RPM.

Max torque was at 4700/4800 RPM.

This engine makes a superb noise and its screams up to 6800RPM with no hesitation! [img]/ubbthreads/images/graemlins/grin.gif[/img]

That's exactly what I was after. Plenty of intoxicating noise, loads of torque and HP high up the rev range.

My engine will be rebuilt every year, I expect the block to last no more than 3 years.

If you go for high revving engines I think you must consider the durability - poor! and money to maintain it. [img]/ubbthreads/images/graemlins/frown.gif[/img] BUT -

WHAT A SOUND - MONEY WORTH SPENT. [img]/ubbthreads/images/graemlins/grin.gif[/img] [img]/ubbthreads/images/graemlins/grin.gif[/img]

Regards,

J.P

John · 03-18-04, 10:05 AM

I don't know exactly how much of a factor it plays, but the weight of the rotating assembly is also an issue effecting power output I would imagine...

So, a big stroker with a heavier crank takes more power to turn as opposed to a lightweight short stroke crank. Same goes for using differently weighted flywheels. A lighter flywheel will generally pick you up some power to the wheels.

John

Kevin M · 03-18-04, 11:27 AM

You know, these cars are all about enjoying them. As Ron got into in another post, there really is no class where these cars are competitive for serious racing.

Since with modern engine technology we can always make enough power to scare ourselves silly in a car this light, it really comes down to what you like. I agree that there is something about the sound of a V8 at high RPMs that sends tingles down your spine. The original 289 and 302 cars had a redline of 7,000 RPM. If you want to match the sound of the originals that would be a reasonable redline to use. A 347 with a 3.400” stroke is at 3,970 FPM at 7,000 RPM so that would work with no problem. With a power peak at say 6,800 RPMs a 347 with good heads, etc. should be capable of about 525 HP (Just about what the original 427 Mk IIs & Mk 4s made, but with a 300 lb lighter car). 7,000 is low enough that you would avoid the more serious valvetrain reliability problems as long as you use a street roller cam and not a race roller, and use the Crower roller lifters with the Pin Oiling option.

A 347 like that would probably be a great engine in one of these cars.

Have Fun,

Kevin

Gary Gibbs · 03-18-04, 08:26 PM

That would be interesting data to look at. What is the rotational intertia differences between a 3" and 4" stroke crank? How does it compare to the rotational intertia of the flywheel, etc. I know the 19 lb flywheel/clutch that I have makes the engine sing up and down fairly quickly. Tilton does post intertia values of the flywheel/clutch would be interesting to see similar data for the crank. Then compare this to the equivalent intertia of the car (in like units).

Kevin M · 03-18-04, 08:42 PM

Remember, the rotational inertia is relative to the diameter. The smaller the diameter the less effect it has. When you look at the total rotational inertia of the whole system, the crank is pretty minor. You have the flywheel & clutch (much larger diameter), 4 large iron brake disks, 4 wheels (at 20 to 25 lbs. each and very large diameter), 4 tires, etc. A change of 25% in the crank might only be 1% to 2% of the total.

Kevin

Gary Gibbs · 03-18-04, 09:49 PM

That was sort of my line of thinking also, but it would be interesting to look at all the data and know where one might make the most impact, etc.

Kevin M · 03-18-04, 10:15 PM

Two places that are essentially “free” (from a compromises standpoint, not necessarily price wise) are the wheels and the brake disks. It is not unusual to see a 10 lb. difference between different brands of wheels. That’s 40 lbs. total weight with a very large diameter. Changing from solid 1 piece rotors to 2 piece floating rotors with aluminum hats will also save you a fair amount. The wheels obviously would give you the biggest benefit.

The third place that has little penalty (for a car where performance is primary) would be the flywheel. Much of the weight of the flywheel is there to give the motor a smooth idle. If you don’t care too much about that, then you can reduce the weight considerably. Look at the flywheel for a Miata if you ever get the chance, that will give you an idea of how little weight is needed to smoothly launch a light car (and that with less than half the torque of a smallblock V8).

With everything else, there are trade-offs involved.

Kevin

John · 03-19-04, 12:36 PM

I agree, in the scheme of things, I'm probably not going to competitively race the car when I finally to buy and build one. I love the sound of a V8 tearing up to 7500rpm... just makes me smile. [img]/ubbthreads/images/graemlins/grin.gif[/img] But in the long run, I'll never notice a little difference in rotating weight... but if I have the option between two wheels that I like and one is much lighter, you can guess which I'll pick.

John

Gary Gibbs · 03-20-04, 08:39 PM

You can check out the pictures of the lightweight Tilton setup I am using in the other thread:
ZF Tilton Setup

John · 03-21-04, 11:51 AM

Sweet looking setup Gary!

John

Paul Thompson 'Hooligan' · 03-21-04, 05:01 PM

Here's a couple of pics of Roy's Fontana 302 - as supplied, which was the basis of his 347.

Paul Thompson 'Hooligan' · 03-21-04, 05:04 PM

and from below - with stroked crank. Again, these pictures were taken before the internals were extensively reworked to 'get it all to fit' -

Gary Gibbs · 03-21-04, 06:12 PM

Paul,
Please have that motor weighed if possible before it goes in the car and note the configuration during weighing (carb or not, water pump or not, etc.) I would love to know the total weight of an all alumimium 347. This would represent the lightest of engine weights based on the Ford V8, and my aluminium head cast iron block (465 lbs) would be more toward the upper end. I would guess 325 lbs. I expect about 100 lbs going from cast iron block to aluminium and ~40 lbs going to the shorter deck height. Thanks.

Ron Earp · 03-21-04, 06:27 PM

I think it is too late for that Gary, that motor has been raced extensively in the car unless it has been out for freshening.

Kevin M · 03-21-04, 07:13 PM

DART lists the weight of their Iron 302 block as 160 lbs. and their Aluminum 302 block as 75 lbs. The Ford Factory Iron blocks are a fair bit lighter than the DART, which has been considerably beefed-up. The late (1985-on) 5.0 block uses thin wall casting and is the lightest at 120 to 126 lbs. depending on the year. (And also not as strong, unfortunately). The earlier (1969-on) 302 blocks are a little heavier and stronger at about 145 lbs.

If you are comparing to an 85 or later Roller cam block, the Aluminum Dart block will save you about 50 lbs.

(Gary, they list your Iron 351 block at 195 lbs. for comparison. Plus I would add another 10 - 15 lbs. for the bigger crank).

Kevin

Gary Gibbs · 03-21-04, 07:41 PM

Using your numbers it would put the alum 302 at ~330 lbs. Very nice. The Aluminium Dart 351 block lists at ~95 lbs. Thus my motor in all aluminium would be ~365 lbs.

Paul Thompson 'Hooligan' · 03-22-04, 05:29 PM

Hi Gary -
As Ron said, engine has been used for several seasons now, although I did speak to Roy and checking records - he seems to think the block was about 90lbs. I remember that I could carry it 'one armed' but that doesnt tell me very much!

Engine has just gone back in after Winter refresh/upgrade and dry-sump installation.