65tripleblack

Of course. But why?

Loren Smith

To run with my original block if I wanted to put it back in.

65tripleblack

Overkill for a 302 IMHO. Plenty of good sets of double humps out there. I have a strong feeling that your engine will be more than enough for you without porting done to a good pair of "as cast" double humps.

Anything larger than 350 cu-in is too much for stock double humps, and where an engine builder doesn't have the time, knowledge, patience, or desire to port himself than these TF heads are the smart solution for a mild engine build.

GearheadJoe

My guess is that the combustion chamber of the TF heads could be increased by a few cc if TF provides some guidance on the wall thicknesses and the areas where it's okay to remove some material.

When trying to get combustion chamber volumes to match, it's pretty common to remove some material to add a small amount of chamber volume. This is easily done with some light grinding around the perimeter of the chamber.

I've been surprised at how little grinding is needed to add 0.5 cc. It wouldn't surprise me if several cc could be added if the person doing the work knows where it's safe to do so.

Increasing the chamber volume might make it possible to achieve the desired quench while keeping the compression ratio at the desired value.

Mossy66

I was planning on using them on my 383 build. They recommend a head gasket that measures about 40 thou thick. I want a tight quench, less than 35 thousandths. That means the Pistons will be at least 5 thou out of the hole. Compression will be way high. Looks like custom dished Pistons...unless I look elsewhere.


Gerry

GearheadJoe

There are several parameters that need to be considered for setting this up, but it's easy to play with the various parameters using an online compression calculator such as this one:

http://www.csgnetwork.com/compcalc.html

With aluminum heads and tight quench, you can probably go as high as 11:1 static compression ratio on 93 octane, provided that the cam is big enough to limit the dynamic compression ratio to about 8.25.

If you play around with the above calculator, you will see that a 60 cc chamber and .035" quench require a piston with a -10 cc top. Increasing the chamber to 65 cc leads to a -5 cc piston. The Mahle flat top pistons that I used are -5 cc, so that combination would get you there. There are lots of other combinations that could be considered, and the above calculator makes it easy to compare options.

If you are using the original block and you don't want to lose the pad stampings by decking it, you will likely have to use a very thin head gasket to get the quench down to .035". Most stock blocks have a deck height around 9.025", which places the pistons about .025" down in the hole.

It *IS* possible to carefully deck a block and leave the pad intact, but most machine shops don't want to spend the time. The trick is to deck only the surface on which the head gasket rests, leaving the exposed part of the deck untouched.

The typical approach for achieving a quench of, say, .035" is to zero-deck the block and then use a .035" head gasket. In theory, you could achieve the same quench by having the pistons .025" down the hole and using a .010" head gasket (good luck finding a suitable .010" gasket, though). Or, you could use the stock 9.025" deck height with custom pistons that put the pistons at deck height, combined with a .035" gasket. All of these combinations achieve .035" quench.

One thing to keep in mind is that the actual deck height of any given production block can vary considerably, and it may not be the same front-to-back or side-to-side. So, if you are trying to achieve a specified quench very precisely on every cylinder, you may be forced to deck the block.

Another thing to keep in mind is that if you want to use MLS gaskets, the deck surface has to be very smooth. This usually requires decking.

For my 383 I was using a block where protecting the pad was important to me. While I could have engineered .035" quench with careful decking or custom pistons, I ended up just letting the quench be sub-optimal, at about .060". I have 10.2 compression with iron heads, and there is no sign of detonation on 93 octane.

68hemi

My aluminum head 383 has true 11 to 1 compression and run on 91 pump gas detonation free.

Low Rider

Isn’t it amazing how many people are interested in increased performance as long as I can pretend it’s stock, but are critical of anyone who dares to build a restored....

65tripleblack

TF stated in another thread that there is plenty of meat on these heads. Opening the head further in the shoulders of the intake valve is always a good idea. Playing with the chambers is not always advisable as changes to swirl can make things worse rather than better. If it were mine, I'd use the thinnest possible head gasket in the interest of tight quench. Better still, I like to deck the block so that the head gasket thickness less the negative deck height (usually about .003 - .005 does the trick) combined with a .038" MLS gasket yields .033 - .035" quench. If the 4 cc smaller chamber is a detonation concern, then the cam can be retarded a couple degrees to keep DCR within an acceptable range (8.25 - 8.75). A careful build with tight quench will allow DCR @ 8.75:1 with an aggressive spark program and pump fuel.

Another advantage of a tight chamber is that less spark advance is necessary in order to achieve the desired result of max cylinder pressure occurring at about 14 degrees ATDC for maximum mechanical energy extracted from maximum cylinder pressure. This spells more power.

As an example, the SCR on my 331 is 11.65:1 and the DCR is 8.65:1. I use 93 octane gas with 21 degrees static timing plus another 15 all in @ 2300 RPM with 14 degrees vacuum advance. I have had no success in trying to get this engine to detonate, even if I stand on the gas while lugging the engine.

It's meaningless to say "anything higher than 11:1 on pump gas will cause detonation". Stating a SCR alone, without associated IVC event timing is idiotic, but yet I hear guys say it all the time. They leave a LOT of power on the table by shooting from the hip and "designing" an engine without knowing how it all works as a system.

SWCDuke

Don't worry about quench clearance. It's a way overrated performance parameter for a road engine.

Due to detonation complaints in '62 GM began double gasketing SHP/FI engines and this continued through '63. With nominal .025" deck clearance and the OE .018" steel shim gasket quench clearance was .043, and the additional gasket increased it to .061", but the near half-point drop in CR eliminated the detonation complaints, and as the broach tools worn, deck clearance increased as much as .015", which added one to one to quench clearance.

Taylor states in his textbook that the benefit of increased detonation resistance is lost when quench clearance exceeds .005 times bore diameter, which is .020" for a 4" bore engine, and that's less than GM's recommended .035" minimum.

Aluminum heads on cast iron blocks require multilayer composition gaskets to avoid fretting and subsequent failure due to the different thermal expansion rates of the two materials.

Duke

Vortecpro

Very cool! I like the way you guys think. I have a nice 360 inch flattop project going together, looks like I found my heads.

Drothgeb

I’m using these heads on a 360 as well. With Wiseco PTS505 pistons, 6” rods, .037” quench and a 65 degree ABDC cam, I’ll have a 8.5 DCR. Should work very well.

Cozmacozmy

Do you plan on leaving them stock as they come from TF or do you plan on porting them out at all? I can't wait to see what magic you do to that 360 you are using these on.

Dr L-88

It's been a few months since this thread saw any action so I'll breathe some life into it. I REALLY like the look of these heads. Who among you has actually used them and what are your thoughts?

I'm thinking about building a Dart SHP block with 4.125 bore, 3.75 stroke crank and 6.0 inch rods but the compression ratio would be astronomical with these 60 cc heads...................so much so that I would probably have to use blower pistons to achieve an acceptable compression ratio.

Just looking to build a strong dependable street engine.

Thoughts................comments anyone?

Thanks,
Rex

Tom Austin

Rex,
Mark C is one day away from firing his 327 with these new heads! He'll give a full report at some point!

Pop Chevy

L-88, I am looking to build a 406 also and am looking at Wiseco pistons. They make one with -12 cc dish and if you put it .010 below the deck , you might be o-k. Check em out.

MarkC

I bought a set and the install started last week. We ran into an issue Friday afternoon with the 8 inch damper and a Cloyes timing chain cover. I am also doing a roller cam. I have a tread on Roller Cams in which I posted pictures of the heads. We should have it running shortly.

Drothgeb

Probably will have mine running shortly, but it’ll be a while before I’m driving it.

Kory Kubicki

I am planning on purchasing these heads for my 64 c2 327/300hp. my question for you is what rockers should i use to allow my stock valve covers to still fit?

silver837

To get a answer please start a new thread. This is 5 years old.
I slid through this thread and almost left before I got to you.