Relatively new to the engine building world, have a question on heads.

What makes a cylinder head a performance head or not?

 

Most performance heads, as compared to stock iron heads, are aluminium, bigger intake valves, 'heart' shaped combustion chamber, larger intake runners, higher valve spring rates, dual valve springs, push rod guide plates, screw in rocker studs, roller rockers.

 

Flow.

Jebby

 

flow and the ability to support more lift for a bigger cam.

 

Flow numbers through the intake and exhaust ports. Next would be the volume of the port specific to the motors cylinder olume. There are calculators to find the partcular volume for the engine size
The 175 185 195 are popular for small block motors in the 350 ci area
270 to 300 are recommendd for 396/427 motors All those numbers go up with cam, induction and CI increase. In the Big Block world the performance engines used rectangle ports when it was an OEM cast iron cylinder head versus the oval ports. With the advent of mass produced aluminum high flowing heads , you can get oval ports for the 427 that are more than adequate. Not too many of us want a 427 though, the big motor now is the 502 up to 632 so most of the heads are the very large intake port varienty

 

That brings me to my next question.
I have a 383, 305H comp cam and I’m looking for an upgrade for my heads since my old ones may no longer be in running order. Will Dart 11720040P 64cc 230cc work or do I need more flow?

 

Depends on intentions. That's a big number for a Cruiser. IMO I would not want them with a automatic.

 

Main intentions are a weekend racer for the most part, but I would still like to cruise a bit. Where should I be looking?

 

230 CFMs is a lot of flow to harness on the street. Those CFMs number are intended for a screaming engine that seldom sees under 4,000 RPMs (overkill)

You would be better suited for around 180+ flow. The higher the flow the more the vacuum signal under the carb drops off. And that means unresponsive throttle off idle.
A comparison would be an open plenum Single Plane Intake Manifold with all those big runners = lots of CFM flow, but lousy throttle response off idle.

Take note on listings of Intake Manifold specs. Some do not even start going to work until 3500 RPMs. Same deal with too high a flow of heads.
Keep things in perspective for your intended driving.

 

Currently the car was set up with the comp 305h which is a very mean cam which doesn’t go in until 3k-7k I may be changing this down to a 295h. A weiand high rise dp 1.5-6.7k, world 67cc 170cc. Topped with a 650 Holley Brawler mech secondaries. It felt a bit sluggish the last couple drives before I tore her down. And I believe the heads were my main draw back on it.

 

I never heard of cyl heads making things sluggish, but maybe. I suspect other issues in the carb and / or IGN timing.

That is quite a bit of duration at 305. Barely streetable. You must have the rear gears to match that.

 

3.73 rear with a 3500 stall, she’s very bipolar. Could very well be the carb as I’ve had no one to teach me anything about carbs, or seldom knowledge on timing. I know enough to set it but that’s about it. 10-12 ign when she did run and about 34-35 adv.

 

Those Darts are really race only. I would be looking at AFR 195 to 210s. but I get thrifty. Finding a set good heads from someone moving up or quitting at a discount always works for me.. Machine shops that do a good racing business many times can "hook you up"with sellers.

 

Maybe a bit more initial timing. That cam should like a bit more, starting at 14 on up, in 2-degree increments.
Even at 18* initial, I have no cranking issues because my cam bleeds off cylinder pressure.

Those heads (170s) are fine for your needs Strip / Street / Rally.

Not familiar with your Holley Brawler series. I have the old school 4150 series D.P. as shown in the avatar to the left.
After you get your timing perfect you can tweak the carb. I suspect your sluggish habit is in the secondary throttle system.
Just of the top of my head, the accelerator pump arm and linkage contact "gap" is a known critical issue with Holley. There are videos on how to set that contact correctly on YouTube. Holley themselves has several wonderful tech vids.
Try Google: How to set Holley accelerator pump clearance.

 

It’s not just flow let’s be clear here. There are a lot of factors in play. Flow is a lot of it but particularly in carb’d engines port velocity is needed to keep the fuel atomized. Combustion chamber shape plays a lot into it too.

Don’t fall into the trap that bigger is better. That isn’t entirely true.

 

I would say you have a mis-matched combo which is killing the bottom end. What you refer to as "sluggish"
Cam: way too big comes on at 3000 up to 7000
Carb: too small for 383
Heads: World = good heads
Intake: hi-rise = dual plane? = done at 6500
Gear: 373 good
Conv: 3500 stall = great

I have buddy who has a 69 Camaro with a similar setup as yours but a few important differences. His runs 11.90s. Quick enough?
He has a stock ZZ383 = cam is much milder
His is only 222/230 @ .050 vs yours at 253 @ .050. Yours is way too big for the rest of the combo.
I would really tame the cam down, say 230/240 I/E or so. Bigger is not better, unless you want to rev it to the moon and have no bottom end.
230 ish dur is about all you want on a stong bottom end street engine. It should still rev well to 6500, where your intake becomes a limit.
Turn it into a Hydr roller, they runner better/stronger at the same duration.
Then upgrade to a 780-800 carb. Vac sec or DP your choice. If you are not really good with carbs then go vac sec.
Up timing to 15 degree initial with 36 degrees at 3500.
Keep the heads.
With those gear and convertor It'll practically rip your head off!

If you want more, say 240 ish, then you need an even bigger carb, (850), single plane intake, 240/250 HR/SR cam, bigger heads, and even more gear. But it'll be a rocket if you have traction, which you probably won't unless you have slicks on it.

Most people tend to put too much cam into a build, you are not alone.

That 253 dur H cam is not really streetable, it belongs in a race car. That's almost the exact equivalent dur in a solid as an L88 cam.

Save the head money. Spend it on a HR. I like the XR288HR for your setup. Big enough.

 

and the 170 heads are a bit small for a 383. they belong on a 350. and combined with a too-large cam, it is even worse. 195 to 210 is a good chamber size for a 383. somebody will be happy with your 170 heads. somebody who is not going to put a bigger crank in his 350 just because...

 

I will definitely try that with the timing. I could always get the gapping right I can never get my AFR correct though. It’s always running too rich or not at all.

Some great info here thanks. Deep down I probably knew the cam was too much but when it ran it sounded amazing. I’ve always had issues with trying to buy a carb, I know relatively nothing about them and I always get two different answers when I ask people what I need. But sadly, I reckon I will end up bringing down the cam.

 

So I found Some AFR heads 1002, 64 and 195, should I pull the trigger on them or choose middle ground of 200-205?

 

I've ran into an issue with my head search. The Weiand 8150 has a center intake port on the manifold whereas a lot of the heads I'm seeing do not have this port.
Is this something that needs to be put in by a machine shop or what?