Maybe I'm spoiled by my blower motor. But I just knew my 572 was going to make more steam than it did. Trying to figure out why this is all it made, so throwing it out there for the experts to diagnose..
I was hoping for 950+.
Specifications
KB block deck height 10.200 (.500 short)
B1 Originals 69 cc, 2.300 int, 1.78 exh
4.5 stroke, 4.5 bore, 7.100 Oliver rods, Ross pistons and calculated compression ratio of 13-1 rounded down.
Bullet cam, image this is a 4-7, 2-3 swap 55 mm roller.
Tunnel Ram with Enderle mech fuel injection
Headers 2 1/8 diameter 29 length primary, with a merge collector 3.5" outlet x6 length with a 9* transition with a 4 " cone, Collector is 10 inch overall.
Attached is the dyno sheet of last pull.
It needs a little more fuel but this was with smallest pill I had at the time. Just a tad lean. 36* advance
It wanted more timing every pull. We went to 38 but it fell off a little.






Dave

It looks like 4700 RPM for peak torque and from 6800 to 7000 for peak HP
I would take it to the races and try shifting it 6000 RPM and then 6500, 7000 and finally at 7500 RPM to see where it is quickest fastest in all the increments, 330, 660 and 1000 as well as the 1/4 mile Unless it is a 1/8 mile track but I would still try testing the shift RPM to find out exactly what your combination likes at the races
My old pump gas 505 C.I. 400 block stroker motor with a low deck six pack set up on it made peak torque at 4500 RPM and peak HP at 5500 RPM but went the quickest and fastest MPH by shifting that stupid motor at or above 7500 RPM
I ended up trying to shift it at or a little bit above 7000 RPM to help the motor live longer

Some of what the numbers are comes down to the particular dyno.

But....... I’ll agree, those numbers seem way down.

You don’t say what the fuel is, but a 572” with good heads and a TR should be up about 100ft/lbs from where those numbers are.

Looks like one of those “start low/end low” situations.

It’s almost like there is a slight dip in the power curve, right where I’d be expecting the TQ peak to occur(5500-ish).

a 10.200 deck with 7.100 rods and a 4.500 stroke only leaves .85 for compression height on the piston. I don't think you can go any less than 1.06 or so, so I think there is something wrong with the info.

Are the pistons domed?

What is the deck clearance?

The set of b1 originals I have only go 375 at .650 and fall off from there.


Just my first thoughts.

Definitely no expert.

If the heads aren’t “ported”........ the power numbers would make more sense.

And of course, then the question about how “correct” the manifold dimensions are comes into play.

I got ya Cab.. That is my theory when I can get to the track. The info messed with FTI when I ordered the converter. It should flash 61-6200. I usually start my shift point at 6800 but plan om starting at 69 on this one.
I'm more disappointed in the numbers.

Dave

I agree, but this one belongs to a friend and I know he keeps it calibrated. In fact he had to take it apart to replace the starter ring gear so I'm pretty sure he checked it.
Sorry about leaving out the fuel. I run alcohol fuel injection.

The numbers to me were disappointing and I agree peak torque not only seemed low but peak at 4700 surprised me. Everything I've built peaked around 5600..

Dave

Piston compression height is 1.105, slight dome is .280, and piston volume is -8.7 cc because of valve reliefs. Pistons are out of the deck .012, because of machining the o ring groove out. That was to make the cometic gaskets happy. Gaskets are .080 compressed.
The guy I got the heads from had them filled 1 inch from the bottom with epoxy to run on the street. But the opened up the port before they epoxied them. To be honest I think they screwed them up because the cut them into the push rod holes and then put a super thin brass tube for the push rod to come through. Part of my theory of why the power is down is either the ports in the heads are screwed up or the headers are to small.

Dave

I don’t have much dyno experience with alky, but it usually shows a gain in TQ over gas.
So, to me that makes the max of slightly over 700ft/lbs look even worse.

It’s one that makes you wonder...... how can it be so low?

Mine were ported and then filled about 1 inch up. They were flowed for a street engine. Looking at them they had ground them to whatever size they wanted then epoxied them, and flowed. I knocked all the epoxy out and scuffed up the ports before installing them. Mine is not a street engine. So I do not consider them to be ported or at best a hack job at porting.
As to the manifold. It only flows air as I am port injected. Fuel is injected 1 inch above the head port. Alcohol. Although I was listening to a few minutes of Daren Morgan's seminar and he commented that mech injection and port injection would benifit with a smaller port and valve in order to keep air velocity up. Goes against everything I thought but keeping velocity up makes sense..lol

Dave

Yeah, I've just about scratched all my hair out thinking about it.
I'm going to run it as is at first. Then if I come up with something simple to change I will change it to see if it improves. But the changes will be made at the track or just prior to going there.
Kinda hoping someone would see this and say "hey dumba** you got this all screwed up..lol

If it does end up being in the ports I wonder if they could be epoxied and then ported or if I will have to get the ports welded before porting..
Epoxy would sure be easier not to mention cheaper..lol

Dave

Joe called after seeing this and said I posted the wrong dyno numbers.. No graph just numbers. You need to look at the 3rd and 4th lines after the rpm column. He said the first set was with a 50 lb flywheel. The STPIP and STPIT columns show the corrected numbers.

Dave

The dyno I use doesn’t have inertia correction as part of the software, so we’re only correcting for atmospheric conditions.

Our 8 bolt flywheel is a billet steel 11” unit...... weighs at least 45lbs, and then you bolt a drive plate to it.

This is an example of how dyno results from different shops can end up not agreeing with each other.

Since we are talking about my dyno, I though i jump in here. Dave posted his J607 corrected numbers, we were making pulls at 600 RPM per second with a 45lb flywheel. Now most of you should see the issue, all that weight takes Hp/TQ to accelerate. My dyno also has inertia correction which gives the same hp as a step test.
attached is Dave's STPIPw and STPiTr

Joe
edit i was selling some honey while dave was posting.

Dave

What were the uncorrected numbers?

Look at the STPP and STPT columns of the above post.

Dave

I still don't get the shortblock math
7.100+ 2.25+ 1.105 = 10.455 deck height.

But it sounds like you have unhappy ports. If the short turn was fugged up now without the epoxy, would that make the torque come in low and down, then not run up top. With the floor lowered it would seem the it would have to turn more

Assuming the dyno numbers are correct and that the engine is working properly then I'd say your port size is too small. If the ports are the correct size for that engine then it should make a lot more power. The headers are big enough and so is the cam and a tunnel ram should support the power so that leaves the ports as the likely problem. But before jumped all the way to that conclusion I'd check everything over while the engine is on the dyno. Do all plugs look good? Are the EGTs fairly even? Did you check intake vacuum at WOT? Double check firing order? Run a compression check, a leak down, etc.? There are so many ways that engines can get messed up on the dyno you could write a book about it.

Were you really running 9 inches of vacuum at WOT? That is probably a bad number but if it is real then that would be an issue.