My first V8. Iron or alloy Block?

[Chas]

Jono and Randy,
The 9.5's will be here in three weeks I'm told. We'll have the production 8.2's in Sept, as of latest report. This 9.5 deck block weighs 108lbs w/caps and sleeves. Our aluminum SBC(called Motown) weighs 100lbs and has a 9.025 deck. I'm afraid to weigh the 8.2 when it gets here-I may have to stand on the scale with it.
Our build combinations for the 8.2 are 4.0x3.0 (302), 4.00x3.47 (349) and 4.125x3.47 (371).
We build the 9.5 in 427 (4.125x4.00) and 460 (4.155x4.25). All are/will be available in Aluminum.

 

[Jono]

Chas,
Cheers for info/update.
Are the power / torque ratings (and curves) likely to be fairly similar to the corresponding iron block combos you offer? I'd quite like an engine that will rev up to 6.5 - 7k but not at the expense of low end grunt. My daily driver (scruffy old sierra xr4x4 with 24v cosworth V6) redlines at about 6k and I find myself wanting more....., but that engine only really works above 3.5k anyway, but I digress.
I guess what I'm asking is, is it worth spending more on a higher revving engine or am I just going to get annoyed with low end power / torque loss a result? Would the larger longer stroke 8.2 deck engines e.g. 371 suffer more than a smaller displacement at low end?

 

[Chas]

Zebra,
Hopefully dyno sheets will help you decide.The split sheet is a direct A to B test on the aluminum 427. It shows our original Windsor Sr CNC alum head compared to our brand new 18deg as-cast head. The power improvement comes clearly at the top of the band. With each you start at 3500 with 496lb.ft. and are above 500lb.ft. from 4000 to 5800 RPM.
The only sheet for iron vs. aluminum is not a fair comparison as we were previously using 1.6 rockers and our Windsor Sr head. We've switched to the current combination but the iron at the time was down 35 to 40HP and lb.ft. compared to this revised spec. The iron would most likely show very similar graphs, built to the same spec. Remember, all of our aluminum blocks employ ductile iron sleeves so the wifes tale about iron producing superior numbers is not valid at World.
Also shown here is the 371 iron Man O'war 8.2 deck engine built with hydraulic cam, 870 carb and 9.5:1 compression. 474HP and 433lbft peaks. Does that look like "suffering"?
As for RPM, we test our street engines to the mid 6000's and our Drag version to 7000. All are pump gas except the Drag versions.
Hope this helps you decide which way to go. see below:

Edit: Sorry, the split sheet is mislabeled, it's the aluminum engine not the 427 Iron...

 

[Jono]

Dyno sheets are very helpful thanks. Out of interest (please don't think this is meant as a criticism, it's more for my understanding), the new FRPP Boss is supposed to be available as a 331 with circa 500HP. How do they get that power out of a much more smaller displacement than your 371? Does it have stronger internals allowing higher revving to get to peak power?

What I was getting at before (in my last post) was not really about peak power levels, but whether a smaller displacement torquey engine would be more "driveable" than a larger displacment longer stroke engine built with top end power in mind. My car will mainly have fast road use with trackdays as often as I can afford them, and will hopefully be built more with acceleration and handling in mind over top speed.

Seeing those dyno figures however it would seem that bigger is better.

 

[Chas]

Jono,
Frankly, I'd love to see the dyno sheet of the FRPP offering to analyze such data. It would take heads superior to ours, an extremely aggressive cam, much compression and and a large induction system to accomplish that. Also RPM.
The 371 I illustrated produces an average of 411 lbft over a 2800RPM power band which should be very "driveable" under track-use conditions.
The 3.47 stroke should be providing superior torque to a 3.25. (Which I believe is common in 331 builds but correct me if wrong)
I sincerely doubt the Boss has superior strength but neither we nor the Factory have tested to destruction. I can tell you that we have some 9.5 deck Man OWars running at the 1700 HP level in competition and these 8.2 irons and aluminums have the identical bottom end save main size.
Of course if you want 550 lbft from 3500 to 5500 (with a peak in the low 600's) you need our 460, 9.5 decks.
Look for superior torque in the band that your car's geared for.