I have a truth teller session scheduled for Wednesday 10th. Feel free to post your guesses and two cents. I’ll be posting the results that afternoon. Here’s the combo.

Low deck
4.25 source crank
Mahle 1.12ch flat top-metric ring pack
6.7 scat rods
11.6 compression ratio
265/269 .660/.652 108lsa installed at 105
1.6 Mancini rockers. Final lift will be .683/.675
Untouched TF 270 heads
Deep port matched Indy 400-2 and a little plenum work
1050/4150 pro form carb
TTI 2 to 2 1/8 step headers
7 qt source pan 1/2 pickup
No Vacuum pump. No tricks. No gas ported pistons, no dry sump.
Just a basic motor anybody can replicate.
What are your thoughts and guesses?
I’d like 1.4hp ci, but my dyno operator said he hasn’t seen it on a combo that wasn’t race gas and this simple.
I’ll be happy if it makes 675.

Without any calculations, I believe around 700 hp is realistic.
I am thinking the Indy intake with port match to MW gasket will be larger than the TF 270 head opening. That will trip up the flow somewhat.
I look forward to the results, including the max hp RPM.

Jim,
The ports match up great, but it wasn’t without a lot of work. The ports were smaller but the casting sucked. It had to be filled in with quite a bit of spool weld and reshaped. A few ports were way out of alignment to the point the intake gasket hung into the ports.

Depending on how good that carb does with tuning you should be able to make close to 700 HP on Oregon pump swill, what brand engine dyno and has it been calibrated recently ?
Ignition timing, spark plug heat range and valve lash are all items that are tunable that can help you get the most out of your parts
Have fun

Cab,
Plugs are NGK #8 heat range. I do plan to mix for a bit more octane to be safe.

Here’s the plenum work

There’s the “every dyno is different” thing to factor in, but if I had it here I’d be fully expecting it to make 700+.

I'll guess 680-690hp, with that compression ration. Sounds like a nice combo.

Duane the last motor I put on this dyno you guess was almost right on for hp and tq. I made just a little more tq with a spacer. But without your guess was almost exact.

MarkZ’s 505........ a little less cam, a little less compression, a few less cubes......on the BES dyno:

Duane those numbers are very impressive. For some reason I don’t want to get too optimistic. He shared his dyno sheets with me. Very broad and impressive power curve for sure. I’m curious about the correction numbers.

I like your combo, and believe you will be close to your 1.4 per cui.. With the work on your intake and that stroke I think torque will be over 700.

I saw nothing in the weather data for Marks sheets that seemed out of line at all for that region of the country, at that time of year.

Correction factor seemed in line to me.

For your combo...... over 500”, good CR, heads that flow 350+, big intake, correctly sized headers, adequate lift and duration.........700hp...... it’s just not that hard to get there.

Like I said, if I had it here, I’d absolutely be expecting it to break 700.

Thank you for the replies so far. I did build it with 700 in mind and a flat torque curve. 700 is what I want.
My combo is extremely similar to marks528 combo. If I get similar results I will be beyond extatic.
I still have to swap to 1.6s as I started with 1.5 and changed my mind.

I reckon 719hp, we have a bigger motor +78ci but only @10:1cr, -13 heads that prob do not flow as much as your 270's at our 625" and 260/270@.050 s/roller with a 440-2, an old 950HP and 2.18" TTI's and we made 694hp on the dyno which is just 1.18hp/ci.

I wouldn't be concerned with a number. That said, it should make good power as long as the carb and ignition are capable.

Depending on the actual valve events, you have the makings of a great motor with a broad power curve.

Peak numbers are for magazine headlines and Internet racing. If it makes better avg numbers that will make for a much better street driving experience ... unless it was going in a Daytona or other featherweight.

On Edit: Best of success and have fun!

All of your responses make me more optimistic. I am just surprised these heads are that capable without going too crazy. I’m guessing it’s the excellent mid lift numbers that help this head to perform?!

Sounds fun. Why the short 6.7 rod length? Low deck? How would the motor respond to a 7.1 rod. I ask because the differences in rod length/rod ratio are not so clear in my mind. It would be nice to hear some info on the choices.

Good looking combo except I'd put a 1050 Dommy on there and #8's are WAY too cold imo.....

it's all he can fit in a low deck. the CH on the piston is already only 1.12"