The difference that good cylinder heads will make....

[blykins]

I dyno'd two 347's on Friday. I got a lot of good data to pass along...

Engine 1 was a D9 302 block, Scat cast crank, Scat I-beam rods, Mahle pistons, 10:1 compression, 1.5/1.5/3mm ring pack. RHS heads, out of the box with a good valve job, with careful setup and assembly. Used a Weiand intake, pretty short dual plane, with a Quick Fuel Slayer 650. Cam was a custom Comp hydraulic roller, 230/236 @.050", 110 LSA, 104 ICL, .608" lift.

It made 425 hp @ 5750 with 445 lb-ft at 4500. Not too shabby for a mild engine. Going to a customer on the island of Malta...

Engine 2 was an E7 5.0 block, Scat cast crank, Scat I-beam rods, Diamond pistons, 9.5:1, 1/16, 1/16, 3/16 ring pack. CHI Boss 185cc heads, hand-ported, along with a hand-ported CHI Boss intake manifold. Basically a Boss 347. Used a Quick Fuel Slayer 650 again. Cam was a Comp hydraulic roller, lobes hand picked, 223/227 @ .050", 110 LSA, 104 ICL, .635" lift.

It made 517 hp @ 6200 with 463 lb-ft at 5200.

Now, I know it's not a "control" experiment with just a head swap, but I'll tell ya, the cylinder heads make the engine. Not only did we make basically 100 hp more, but the peak hp rpm was 600 rpm higher with a shorter duration cam.

The funny thing is that I built Engine 2 for a car builder in Mississippi. He originally wanted to put it in a '69 Boss 302, so I had Joe port the heads and intake and I wanted to put a real nice cam in it to match the setup. He got rid of the Mustang before I got the engine build started, and bought a '52 Ford F1 pickup to sell and decided to put this engine in it. His very words were, "Make this a very mild engine..." I was upset at first because we spent the time and money to have the heads and intake ported, and I basically thought we were wasting a good engine.

With 9.5:1 and a short cam, I really thought this was going to be turd-puller, but it goes to show you that sometimes you get what you didn't expect.

The lower compression showed its head though, as this combo took about 4-6 degrees more timing than the usual CHI headed builds do. It actually picked up 25 hp going from 30 degrees total to 34 degrees total.

Was also very happy with the cam. I tried some new lobes that I hadn't tried before and they were very quiet, but was not getting any evidence of valve float, even at 6500.

This was the first 347 that made 425hp....



And the Boss 347....

[MAStuart]

What size valves did the CHI heads have? I have a set of Boss Chi 185 setting in my garage for some time now. I listed them here on CC and put them on Craigs list . But after reading your post it has given me renewed interest in using them for a build. Any chance I could get a price on some pistons to use with them. 3.250 stroke, 5.400 rod, .912 pin, 9.5 to 10 cr. Not sure what chamber size my heads are.

Mark

[blykins]

If you want to sell them let me know....

We typically use 2.07/1.65 valves.

Custom forged Racetec pistons are around $600 a set with pins and locks.

[MAStuart]

I forgot to ask in my first post. What size valves and ports did the RHS heads have.


Also could you take a guess at what the ChI heads motor would make it you changed the heads to a set of AFR 185 and victor jr and the same carb you used.

One more question do you do your own balancing work. I have a new assembly that I just had balanced and would like to get it changed to internal bal.

Mark

[blykins]

These rhs heads had 2.02/1.6 valves, but I did a 347 with a victor jr and rhs heads with 2.05/1.6 and it made around 440 hp.

Similar combos with AFR heads are usually 470-480 hp, but with solid cams.

I can balance your stuff but you can prob find someone close so you don't have to pay shipping both ways.

[MAStuart]

So the RHS heads had 2.02 /1.65 . What size runners.

My other question was about the boss style engine. What is your guess as to the power if nothing else was changer but the heads and intake to AFR 185 and victor jr. On paper the Chi 185 and AFR 185 flow about the same numbers.

Mark

[blykins]

On paper, a lot of stuff works. I can attest that many heads don't flow what they are advertised to flow. The larger CHI heads do ok on the bench, but the 185's back up at around .600" lift. These had been ported, as I mentioned in the initial post. Also, flow is not everything....velocity is as important, or more so.

You are looking at around 450 hp with the AFR's and a Victor Jr.

[MAStuart]

Thank You for your reply. And the RHS heads had how many cc runners.

[blykins]

215........

[MAStuart]

Thanks! ahah They sound big and this is where the port velocity show its strength in the CHI 185.


I want to call sometime . When would be a good time?

Mark

[blykins]

Nah, not really big.

The RHS heads do ok but just aren't in the same league as the others. A canted valve head will usually outperform an inline head as well. However, as I stated, I've tried 170cc Twisted Wedge heads, 185cc AFR's, Victor Jr's, etc., and they are all usually right around the same spot.

[olddog]

I have been a believer that heads make the engine a long time now. When you see an engine with excellent heads make power all the way to 8K rpm with duration in the 230 @ 0.050" range, you realize that radical cams are a crutch for poor flowing heads. I'm not saying you could not have made more power with more cam. However with good heads more cam gives up low end for top end, and usually your giving up way more on the bottom than what you are gaining on the top. For the street I would prefer the bottom end. Good heads and mild cam makes for a great street engine.

[olddog]

double post

[Chaplin]

Brent-
Can you post the dyno graph for engine #1?

[madmaxx]

What do you think of AFR heads and is any machining to optimize performance needed. In other words do they come from AFR already at the most efficient point? I know AFR customer service was top notch, it was like lifetime warranty send it back if you think there is an issue and we will handle it.

[blykins]

I'm sorry I've been missing these posts guys. I did not receive any thread update emails....Club Cobra has been sub-par here for the last few months.

Madmaxx, the AFR heads are pretty good out of the box. I buy them bare with valves and custom assemble them with the springs to fit the camshaft. If you're not looking for max power, they can usually be used without any machine work....maybe just a mill to end up with the combustion chamber size that you want. If you're looking for the most hp that you can get, then any head can always be improved. Really good head though from AFR.

Chaplin, here's the dyno sheet for engine #1.

[Chaplin]

Thanks. Interesting. I would have expected a flatter torque than that.

[blykins]

Some of it can be the way the dyno is loaded, especially with a manual valve Stuska.

However, most of it is because it's just a little engine. When you try to make a 347 pull to 5500-6000 with a milder head, the torque curve just isn't there.

[Chaplin]

Do you think AFR 185s would have changed the results?

[blykins]

With the same cam, it would probably have made it worse. With a more efficient head, you need less camshaft to get to the same point. Throw a big head and a big cam on an engine, you get more hp, a higher peak, and less torque.