Don Terrill’s Speed-Talk

How much HP can a Ford 302 block take in a mild road race ap. ?
11 to 1
solid cam
standard stoke 3.00
Windsor 2.02/1.60 heads
RPM limit 7k

We've run a dry sump 306 SBF road racer with an original 1970 Boss 302 block for 4 years; 2 making 500 HP @ 7300 RPM with Crower crank and rods, Wiseco pistons & 11:1 CR and 2 with it freshened via 12.5:1 TFS 185 CNC heads and a solid Jones roller to 625 @ 8,000. We just pulled it down and (almost*) everything looks perfect. *Rocker studs showed some fretting distress, as did the damper bore. The univeral opinion is we've been deep in the Red Zone since day one.

450-500 is about it for a regular 2 boult block with any reliability IMO, Drag guys get away with more for awhile.

This will depend upon a lot of other influences.
Keeping it out of ANY detonation, getting the horsepower through high RPM instead of brute torque and NA horsepower instead of "pressurized" power will raise the amount of horsepower which the block will be tolerate.

One of my customers broke a 289 block with approximately 430 hp.
It separated above the mains and it has not been detonated.
It was run in road racing and lasted for 2 years.
It is a copy of a Daytona Cobra with IDA 48:s and tri-y:s so it has a lot of torque.

Erland

425hp then u need a girdle

fishman wrote:425hp then u need a girdle

I've seen them break when they had a girdle. I don't think it helps much if any. I have some 347's making a little over 500 hp. That makes me nervous. I wouldn't be comfortable going over that.
Bob

avengerengines wrote:

fishman wrote:425hp then u need a girdle

I've seen them break when they had a girdle. I don't think it helps much if any. I have some 347's making a little over 500 hp. That makes me nervous. I wouldn't be comfortable going over that.
Bob

I think it depends on whose girlde you buy as everything in this world can be better or worse then others and i think if u buy one that u can mount your windage tray on will be worse then one without

What's the feeling re stud size? Do the increased clamping loads of 1/2" ones (especially inners) matter more than the loss of web material due to the larger threads?

The girdle will only help to keep the rotating assembly from falling on the ground when the block splits. The '78 and earlier blocks have more web material in them than the later roller cam blocks and can be good for 500 hp or so. The roller cam blocks, cross your fingers at about 450 hp. As mentioned, detonation can break them sooner.

One thing I've often pondered about the split blocks is how much the motor mounts come into play. If you use solid motor mounts, and you have chassis flex, all of a sudden you're trying to transmit chassis forces thru the block.

So then if you look at the attachment points of the motor mount, and where the forces go thru the block (between the cam tunnel and main journal), that sucker's like a big ole wishbone waiting to be split in half.

Again, I don't know if this has any bearing at all in why they break, but I don't think it would take a lot of force at the motor mounts to split it...combine that with detonation...

The blocks that I have seen break, and where they brake, the girdle is useless.

I seen an early non-roller block come un-hooked on the dyno. That engine made around 400hp.

Seen a late model roller block based 347 break. That one made maybe 450 hp.

Neither was detonated.

Seen other 302 based engine make 500hp, with no issues.

It's a guessing (or waiting) game with these bocks.

Keith

Low Rpm and 0 balance of the motor helps to keep these blocks to last!!!

fishman wrote:

avengerengines wrote:

fishman wrote:425hp then u need a girdle

I've seen them break when they had a girdle. I don't think it helps much if any. I have some 347's making a little over 500 hp. That makes me nervous. I wouldn't be comfortable going over that.
Bob

I think it depends on whose girlde you buy as everything in this world can be better or worse then others and i think if u buy one that u can mount your windage tray on will be worse then one without

The cracks start above the crank. How will a girdle stop that?

Some girdles angle out and up and are sandwiched at their edges between the pan and the block, anchored by the pan bolts..