I thought this test was interesting since it is basically the same size as the engine in my Coronet. The compression ratio and the cam timing are also both very similar, but the Ford makes a little more power. I assume the Ford makes more power because these AFR heads are better than the Trick Flow 240 heads on my 496 RB. My 496 made 613 hp and 630 torque, the Ford made 639 hp and 650 torque. Numbers are close but it looks like the Ford has the edge. I'll post a dyno sheet tomorrow. Thing about the Ford is it just lays over before it gets to 6000 rpm. Not sure if it is due to the hyd roller lifters giving up, or if the Sniper is running out of fuel. We're going to play with it a bit more tomorrow.

Andy

If that is a 4150 sniper, it's running out of air. They are rated @830, but anytime I get near 780-790 SCFM I start to pull a good size vacuum. Plus, the AFR heads really flow, I have seen VE as high as 110 on a race engine and 104 105 on a street engine.


Joe

Never mind the big block, (JK!) what's the story on that Cleveland next to it?

Yes, it could be running out of air or fuel. The data log shows the Sniper is over 90% duty cycle so the injectors are basically running full time. We're going to increase the fuel pressure today to see if that helps. I looked at the manifold vacuum on the data logs and it was still around 99 kpa at the end of the pull so it wasn't losing much power there.

The AFR heads are pretty good. We've built other BBF engines with these same heads that make a lot more power. But those engines had more compression and much larger cams. This cam is only 240/248 since it is going into a truck.

We do have some Clevelands in the shop at the moment but that isn't one of them. That is another BBF with Kaase SR71 heads. It is a 521 inch drag race engine. Flat top pistons make 13.5 compression with the SR71 heads. The SR71 heads have raised ports, relocated valves and big SCJ ports. That engine should make 900 hp once we get it sorted out.

OK sorry, I guess it's the camera angle it looked a lot smaller than the one in the foreground.

Would need to be lean/over 100% duty cycle for that to be the reason. 99kpa isn't showing the throttle body being a restriction.

My first suspicion with a big block, HR, and high RR is always lifter issues.

Similar cube combo, 505 BBM, mid-10’s CR, ez-295’s, Indy 2-D, HS 1.6 rockers, HR………. 640/640.o

Are the Bore and stroke the same or did you do the logical thing and go with a larger bore on the Ford???

BBF is a little more bore size but not much. Might be 4.390 for the Ford and my 496 is a 0.060 over 426 so it is 4.310. But bigger bore and canted valves both help make power.

Yeah I agree. I suspect the lifters are just starting to complain at 5800 rpm. It hits earlier in a BBF due to the 1.73 rocker ratio. We made a few pulls today for the customer and it ran better today than yesterday. Probably due to rings seating after a few heat cycles. Peaks were up to 660 torque and 650 hp so it will be a stout truck motor. Going in a F250 4 wheel drive dually pickup.

The Sniper duty cycle peaks at 88% so it isn't running out of fuel. It is pulling about 800 cfm according to the turbine so it is close to running out of air. The manifold vacuum at WOT bounces around between 0 and 1.5 inches so there is some restriction but not a ton.

Not saying you guys aren't right, but I don't understand the how and why.

Yes more rocker ratio puts more load on the lifter but to me it's not load on the lifter but a loss of control. I can't eyball the OD of the spring/retainers but looks huge (heavy)/steel to me.

I have a 460 with a set of SR-71 heads. Its a relatively mild build for durability because its going in my jet boat. Those head castings are really nice and "Fast as cast" . With my setup, based on the RPM I'm pulling the jet pump to I figure I'm a little north of 650 HP @ 5500 RPM. With those heads and the large 2.375 intake and small 1.71 exhaust, the cam is split about 16 degrees more duration on the exhaust.
AG.

650 hp is really nice for 460 inches. Especially if it is pump gas friendly for boat use.

Here is a picture of the dyno screen for the best run. Getting really close to 650 hp and torque is a tad more at 666. The engine just stops pulling after 5100 rpm. It continues to make power but it accelerates very slowly. The airflow continues to go up, the AFR stays where it should be but it just can't accelerate against the brake. It could just be running out of air since the cam is small. I know the heads are good for more power. The Sniper is just about maxed out at 650 hp but I don't think it is the cork.

Just a thought from a novice in the peanut gallery. What would happen if you drop a 1050 dominater on it and solid roller lifters? If it still flattens out, could it be a valve spring issue? Sad to say, it COULD possibly be a combination of issues, not just one?

Been down that road with a Sniper on a Pontiac. Might consider throwing a good carb on and see what happens.

Engine is gone already. Customer watched it run, liked it, paid the bill and took it home.

Glad he was happy. But those of us on hear would want to ring out that extra hp, its just how we are built, right?

Naw, not us