Nice....Did you end up going with a Low Deck or did you keep the 75 440 block ? Care to share a full rundown of your engine/parts ?

Thanks

That looks pretty lean

The Harland rockers lose a little bit of lift with the stiffer K-950 springs. I think they were .750 with the Trick Flow springs but now are down to 0.738 lift.

Is this a hyd. lifter cam ?

Are you serious...A .750 lift Hydraulic cam

Solid roller cam

What compression ratio, and what fuel did you run?

The BSFC looks good I would look at the spark plugs and try richer first and then leaner second to find out what the motor really likes as far what that O2 systems reads
OP, Did you try higher RPM before stopping the dyno tests? If not I would have

I have another set of TF heads in the shop now.
This set has the 1.550 flat tappet springs and steel retainers.

The spring pressures don't really coincide with the spec sheet that comes with the heads.
The spec sheet shows these heads to come with TFS -16094 springs, and that they have 138lbs at 1.950/430lbs at 1.250, with a 420lb/in rate.
The TF dual spring spec chart on line shows different specs than that, and are closer to what I observed.
TF claims these are PAC springs, and the specs are the same as a PAC 1294, so that's likely what they are.
The specs for that spring are 175lbs at 1.900/442 at 1.275, 428lbs/in.

I have 2 calibration springs for my tester, and according to both I am within 2lbs of those springs.

The springs that come on these heads start to have some coil to coil contact at about 1.300, so at heights shorter than that the rate starts to climb pretty quickly.
The coil bind height is listed at 1.190, and while some would get that low, several wouldn't and were solid at about 1.220-1.230.

My observed pressures at various heights for all 16 pieces are;

145-150 @ 1.980
160-165 @ 1.950
185-190 @ 1.900

390-395 @ 1.400
420-425 @ 1.350
455-465 @ 1.300
465-480 @ 1.275
480-500 @ 1.250

My suggestion for someone using this version head/spring...... Especially if you're planning on running a flat tappet cam and using most of the available lift from the spring is to verify the installed heights and pressures.

This set of heads had the installed heights between 1.945 and 1.960.

Those seem a little on the high side for a flat tappet. Good thing you checked them over.

I checked the guide clearances as well.
6 of the exhaust valve stems were .3413-.3415, the other two were .3411.
The intake stems were all .3410-.3411.
The guides were basically all the same, and had about .0006-.0008 clearance on the intakes, but those larger diameter exhaust stems were pretty snug(for my liking anyway) at .0004-.0005.
The valve stems on these heads are polished to a very smooth finish, and the reamed finish of the guides are also very smooth, and my guess is with those ultra-smooth finishes you can get away with tighter clearances.
However, I went with what I've had success with for over 20 years and set the intakes up at .0011-.0012, and the exhaust at .0014-.0015.

I'll reassemble the heads with the springs at 1.980 for a nominal 150lbs on the seat, and with the cam that will be used with these heads will be around 390lbs open.
These are going on a 493 street cruiser, and that will be more than enough pressure.
I'll assemble the heads with the inners removed for cam break in.

Andy ,
if you are concerned with the pressure how do you feel about Hughes requiring 155/415 spring pressures ?
I am running 130 seat with my Iskys (8305?) at the moment . And am looking at 135-140 for my new motor.
Solid FT cams

Tex

Dwayne@Andy,After getting my TF heads I realized I had ordered the wrong springs for a roller cam, came with flat tappet springs, so I needed to change the springs, so I elected to go with the PAC 1225 dual spring which is 250# on the seat @ 2.00 but will be installed at 1.950 which will increase the seat pressure to 282# and open pressure will be 726# with the .690 cam plugged into Pac's calculator,,do you see any issues going this route? also thanks for the guide info as I will have Doug check and/or correct the guide clearance since they seem a little tight to me also, any suggestions are welcomed.

My advice is to check the actual pressures for the new springs and set the installed height accordingly.

Buttoned back up and ready for the dyno

Are the rockers deflecting to cause the loss of lift with the stiffer spring?

Probably. Either the rocker arm is deflecting or the pushrod or something else. My money is on the rocker arm as the most likely item to be deflecting. If they are deflecting 0.030 each cycle then that tells you why they eventually break.

Sure it's not the shafts............

Aluminium rockers pretty much all deflect under high spring loads. It's the nature of the beast...