Blocks - How much is too much????

[Pete]

I did a spot of calculation on Roydon's engine and its performance.

Using the weight (very kindly measured by that lovely Mr Connolley) and the timing slips from the 'Pod, the various on-line calculation tools indicated the motor was making 660 bhp using Nitrous.

The block was a nicely prepared one, but is only a 2 bolt R/B one with no BCR Billet caps or Girdle. Indeed, they are stock nodular Iron caps.

Now, the "guess" is: "How much more can we push the block in terms of more Nitrous or a cam change before we start risking bottom end unreliability and possible catastrophic failure?"

Roydon is reasonably happy with the current performance but would obviously like to Bananarama! a bit more. However, be does not want to end up with a box of expensive scrap.


At present the motor shows no sign of detonation and the ignition is retarded 8 degrees when using the Nitrous from the standard 34 degrees.

What are your views on how much you can SAFELY get out of a 2 Bolt R/B?

Many thanks.

[Cannonball]

Dont ask me why but i think a 440 making 700hp plus on mtr alone is going to kill itself yet using the gas on a milder 440 does not seem to hurt them anywhere as much i would pump 400 shot in to it,,,,,,,,

[Pete]

Thanks Duncan.

I think the secret is probably to keep the RPM down; though I always build screamers!!!!

Roydon is quite conservative with the revs and shifts at 6500 rpm.

The Shift light is just coming on at the top end as he passes under the gantry.........

[Pete]

...and we are currently at 210 bhp Shot of Nitrous....

I have a feeling it is a case of diminishing returns, as you pump more and more Nitrous in and make smaller and smaller gains.

It seems to me that about 150 bhp shot gives the best return on investment...

[Pete]

..I called "Chicken" on an R/B at around 650 bhp and retired it. It just got the Dart into the 9's.

I then went to a 400 Block with Billet Main Caps and that make about 697 bhp with No Nitrous shifting at around 7200 rpm .....and that proved to be a very reliable engine.

[Les Szabo]

...and we are currently at 210 bhp Shot of Nitrous....

I have a feeling it is a case of diminishing returns, as you pump more and more Nitrous in and make smaller and smaller gains.

It seems to me that about 150 bhp shot gives the best return on investment...

.....generally from my experience with a cheater and then a big shot kit.......125hp= around 4>5 10ths - 175hp = just under a second - 250hp = just over a second, when I put 250 on the 340 it went from 12.4 to 11.01. The 440 went from 10.71 n/a to 9.9 with a 175 shot and 10.21 with a 125 shot.

I think your already on around 700hp at 141mph with a weight of 3100>3200?? all in but that really suprises me that you use a 210 shot to gain just 8/10ths, thought it was a 150.....keeping rpm down will keep it alive longer your right and limit cap walk.

Les

[Pete]

Car weighed in at 3019 Lbs with the Hobbit in it........

With the Nitrous it picked up a bit on the 60 foot (which is still not great at 1.41 from a 1.53 with no Nitrous) but lots of mph......

We only did one run with the 210 jets in it for the 9.68.

It ran back to back 9.7's with 150 jets so it may go better in due course.

The purpose of this thread is to ascertain when to draw the line.....so to speak...

[Les Szabo]

Car weighed in at 3019 Lbs with the Hobbit in it........

With the Nitrous it picked up a bit on the 60 foot (which is still not great at 1.41 from a 1.53 with no Nitrous) but lots of mph......

We only did one run with the 210 jets in it for the 9.68.

It ran back to back 9.7's with 150 jets so it may go better in due course.

The purpose of this thread is to ascertain when to draw the line.....so to speak...

I'm sure you don't need any advice on that .....thanks!

[Pete]

[Blue]

It's impossible to say, you are at the point where the generally accepted opinion is you can expect a well prepared well treated engine to be reliable.
How near the point of fatigue is your 40 year old block? are the cylinder walls thicker or thinner than average? and so on just too many variables to say it'll take x amount of torque or x amount of horsepower before it goes bang.
I bet if you built a few identical engines on old blocks and upped the ante till they blew up you'd get wildly differing results that still wouldn't answer the question.
Caps, girdles and even filling it won't make the block any stronger, it just gives it a better chance of survival. Lighter better quality rotating parts help in one way but as the torque level goes up it will eventually rip the block apart.
I'm afraid it's a case of keep upping the horsepower till it blows up and then backing off 50hp...

[Pete]

A great response, Blue.

Not sure whether to twist or stick

The motor is a 512 with a 4.250" stroke so it is pretty torquey already.

I think we have ruled out a re-cam as we are not sure on the V-T-P clearances, so we could increase the nitrous a bit and also increase the rpm on the trans-brake but I sense that we are about done in reality....

Would be good to run a 9.50 as the chassis can clearly take it......

[Cannonball]

It's impossible to say, you are at the point where the generally accepted opinion is you can expect a well prepared well treated engine to be reliable.
How near the point of fatigue is your 40 year old block? are the cylinder walls thicker or thinner than average? and so on just too many variables to say it'll take x amount of torque or x amount of horsepower before it goes bang.
I bet if you built a few identical engines on old blocks and upped the ante till they blew up you'd get wildly differing results that still wouldn't answer the question.
Caps, girdles and even filling it won't make the block any stronger, it just gives it a better chance of survival. Lighter better quality rotating parts help in one way but as the torque level goes up it will eventually rip the block apart.
I'm afraid it's a case of keep upping the horsepower till it blows up and then backing off 50hp...

you are absolutly correct, blue, you could have 20 blocks build them all the same they would blow up at very different power levels you just gotta take a chance if looking for improvement,,,, if like the yanks we got plenty of track/tuning time it would be very prudent to strip the mtr very regular to keep a check on what is going on,
that hemi head 440 stroker i had made an honest 760 hp on mtr on a old skool dyno non off this modern workin out on the screen what power it made, now i abused that thing 7,500 rpms when i pulled it apart the bottom end, crank bearings/rods were like new perfect, however pete had the block in a deal and he found lots up with the block, i never even checked the block as moving up to a mega block, and that block was half filled ,,,,,,

[Blue]

Boils down to 3 choices really,
Leave it as it is.
Keep upping the power and whatever happens happens.
Sell the motor while it's worth more than scrap metal and start afresh with anew block.
There's probably a 4th option but that will likely involve wearing comedy clothing and taking up golf....

[Pete]

I'm up for that as long as it does not involve country dancing.........

Personally, I have gone for a cross bolted Mega block for more horsepower......

[TW71]

The 440 stroker I have (512) 40 over has the girdle fitted which has good reveiws on it, I do not read to much into it but over 800 horse or more has been reported over the pond!

To be honest I take the attitude if it breaks it does, do what you can to keep it together thats all you can do.

Its all down to money as usual, but i think a fresh new siamesed block is the way to go but then there will be something else!

My one with a proper carb on (not the 950 HP Holley first gen one that breathes 833 cfm that it was dynoed with) will make over 700 horse and I will not take it much over 6k for the very reason of making it live.

Will be interesting