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Cylinder heads

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Cylinder heads

Post by David V. on Sat Jun 09, 2018 2:02 pm

Hey guys,

Since many of you are far more knowledgeable than I am. I was hoping to get some input.

Currently debating between AFR 1034 Street Eliminators, TrickFlow Super 23 (TFS-30410003-M64), and TrickFlow (DHC-175) TFS-30210007 cylinder heads.

Currently leaning towards the AFRs because they are full CNC for not much more money, and flow more, especially on the exhaust side, which is what I need to reduce cylinder pressure during the exhaust cycle so I don't get reversion in the webers when the intake valve opens during overlap.

For reasons I cannot understand the DHC-175 (aluminum camel-hump replicas) flow the same, if not more, than the Super 23s, even though they only have 175cc intake runners versus the Super's 195cc.

There are a million other things that I've already researched and considered in looking at these heads, but I guess I'll see where this conversation goes.

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Re: Cylinder heads

Post by Jimboquick on Sat Jun 09, 2018 5:54 pm

Just make sure that your headers will 100% match-up to your choice of heads so that you won't have to fabricate new exhaust pipes ... also consider a "balance pipe", if possible to help torque production.
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Re: Cylinder heads

Post by David V. on Sat Jun 09, 2018 6:45 pm

Thanks for the input Jim! The AFRs are square port, similar to the old camel humps I had on my old motor. The headers will definitely intrude on the port cross-section because the tube diameter is pretty small. I've been planning to fabricate new headers eventually anyways. If they don't leak for now I'll be happy. That was one thing I was debating. Trick-flows are D-port, but the AFRs seem so much better value for money that I might just wait it out on the headers.
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Re: Cylinder heads

Post by Hotrod on Sat Jun 09, 2018 10:31 pm

There are a few things that you need to check.

If you are running camel humps, they are most likely 64cc chambers.  The heads you listed are around that also.  Aluminum heads run cooler and can tolerate at least a point more of compression than similar iron heads.  You may even lose a little power or at least not get as much as you could. I would look into heads with a 55-58cc chamber to bump the compression a little.  With aluminum heads, you should be able to run around 10.5 to 1 compression ratio on pump gas.

Also, if your current pistons have any kind of dome, you need to see if they are compatible with the heart shaped chambers of modern aluminum heads.  Most likely they are, but it is something to look at.

You should measure the deck height of your pistons.  If the block has never been decked, then the piston are most likely around .025 down in the cylinder.  Quench (or squish) is the distance from the top of the piston (not dome) to the flat section of the head.  This distance is ideally .035 to .045.  It can be as great as .055, but you start to lose the detonation reducing benefits of quench when it gets that big.  FWI - Chevy used .020 shim gaskets way back when and with the typical .025 piston depth, you got .045 quench.  A thinner gasket can also bump the compression depending on what gasket you're running now.

The point of all this rambling is that you need to choose a head gasket that gets you as close to the ideal quench range as possible.  However, it also has to be compatible with aluminum heads.

I would most likely pick the AFR heads.  I don't personally have any experience with any of them, but AFR heads in general get lots of good reviews.

Keep in mind too, that the high swirl "fast burn" chambers generally don't need as much timing as the old open chamber heads.  That's another power building benefit of modern heads.

With guide plates on the heads, you will need hardened push rods.  Stock type PR's will eat themselves on the guide plates and send metal through the engine.

There is an aluminum honeycomb header gasket that I have used in the past with good results.  It compresses easily.  I usually retighten the header bolts a couple of times and after that, they rarely ever loosened again.  Never had a leak with them either.  I'll try to locate a link if you're interested.

You may have already knew some of this, but I thought I would throw it out.
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Re: Cylinder heads

Post by David V. on Sun Jun 10, 2018 8:28 am

Wow thanks Hotrod! That confirms many things I was looking at. I usually run 94 octane, and was at 11:1 on my old motor, but I decided to drop it down so I can run 91 since 94 is getting hard to find. For that I was aiming for 10.5:1. Unfortunately I could not find anything less than a 62cc head that fit my standards.

bore is 4.040
Piston to deck height is 0.024
Stroke is 3.5"
Pistons are flat-top (-5cc)
I was looking at 0.018 thick gaskets with a 0.100 bore (though I wouldn't mind the part number on those 0.020 chevy ones if you have it)

So if my calculations are correct I would end up at 10.43:1 if I were to run the AFRs with 64cc chambers. I already have a quote from a local machine shop for angle-milling the heads down a few cc and correcting the intake, just not sure if it's worth it, or if I should go beyond 10.5:1 (aluminum heads + modern heart-shaped chamber).

I do have guideplates on my current ZZ4s, just not sure if they'll be compatible with the AFRs yet. Will choose pushrods once I can measure for them.

Also trying to fit my comp 1.460" dual springs I already have, since they have more seat pressure required to run my solid roller cam. AFR spring pockets are 1.460, but i'm not sure if the spring base will have room to expand under compression. Installed height may also be a problem: might need to shim, but hopefully don't have to mill.
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Re: Cylinder heads

Post by Hotrod on Sun Jun 10, 2018 10:34 am

The .020 gaskets were steel shims and not compatible with aluminum heads.  Sorry to mislead you.  

I'm not sure if the newer multi layer steel (MLS) gaskets are available for the SBC, but if they are, then I would look into them.  They are used on the LS engines a lot and are available in many different thicknesses.  The downside to the MLS parts is expense.  It might be worth giving someone like Fel-Pro a call to see what they recommend.  

A quick search at Summit Racing turned up a potential choice:

[You must be registered and logged in to see this link.]

Just make sure that whatever you use can be used on aluminum heads.  Some gaskets are intended only for iron heads and will damage the sealing surface on the aluminum head.

I personally wouldn't go over 10.5 to 1 on a SBC street motor without some kind of active knock sensing.  You never know if your going to get caught out somewhere that good gas isn't available and I don't like relying on octane booster for a street car.  I would rather leave a little power on the table than have a motor that requires special fuel on a daily basis.  JMO.

Be careful if you have to modify the valve spring pockets.  It's easy to hit water on some heads.  Check with the manufacturer to see before your machinist starts cutting.  The same goes for angle milling and be sure your machinist is on his A-game when angle milling.  It's easy to create uncorrectable sealing problems.

If your current pushrods are holding up, then you should be able to reuse them.  Just check them where they ride in the guide plates to see if you spot any wear.

Another thing about the Trick Flow heads that I just thought of.  TF has been known to rotate the valve locations.  They used to call these Twisted Wedge heads.  The valve pockets in your pistons might not line up if this is the case.  Check it out before you go that route.
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Re: Cylinder heads

Post by David V. on Mon Jun 11, 2018 3:35 pm

Thanks! If I'm not mistaken though, the head gasket bore needs to be at least 0.040 more than your cylinder bore, or at least that's what I've heard??
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Re: Cylinder heads

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