Howdy guys!

Im in progress of building a 305 with trickfow TFS-30310006 175cc intake runner volume 56cc combustion chamber.
I want to order the right parts in advance that the engine builder just need to do the machine work, assemble and adjust everything.

Part of that my question is: What head gasket will I need to use for the heads?
Trickflow recommends Felpro, either 7733PT-2 head gasket, which is 4.125 in. and .039" compressed thickness, or #1003 they said up to 4.060" bore but it is labeled with 4.166" bore diameter at summit and .041" compressed thickness, or #1010 - 4.166" bore and .039" compressed thickness.

The 305 bore size is 3.736" and maybe it gets to the next oversize bore which would be 3.766" bore diameter.
The head gaskets all are more than 4" and I think thats right cause of the combustion chamber of the heads. But what diameter should I exactly choose?
Also what about the quench height? It is the result if you calculate how far the piston is in the cylinder at #1 TDC + the compressed thickness of the gasket, isnt it?

And I read of having a quench height of under .035" will the piston may kiss the valves at high rpm, .035 - .040" should be a good quench height and all above 0.40" the advantage of the quench would be gone. I will read myself more into it after posting this and of course a professional will make the machine work BUT I also want to know what to do and building a good engine. So that info is important for me to maybe tell the engine builder to zero deck the block that the piston and block is on the same level? Than with the 7733-PT2 perma torque gasket the quench would be at 0.39"? Or am I missing an important detail?

Thanks in advance for your technical knowledge and your advice!
Greetings,

Chris

 

You are on the right track. But you can't order the gaskets until AFTER the machine work is done and measurements taken as to how far the pistons are sitting in the hole. The same holds true for ordering push rods. Shoot for .040" on the quench. Do not zero deck the block. You will be losing strength. Think about it - you are going to remove metal and replace it with a gasket. Only have the decks cleaned and trued.
My 334 (stroked 305) is .030" over and IIRC, the head gasket I used had a 4.100" completely round hole. I forgot the thickness at this moment.
There is also a FelPro HG specifically for the 305. But it is also .040" thick.
You are forced to wait until you can get an actual measurement. In the meantime, start compiling a list of possibilities.

Look at this old thread: https://www.thirdgen.org/forums/tech...-305-head.html

This gasket could be a possibility: https://sdparts.com/i-24102221-mr-ga...i-1957-91.html

Here is what Summit has: https://www.summitracing.com/search/...28-in_0-030-in

 

My 383 is built with a 4.060" x 0.028" compressed GM MLS Vortec head gasket. Used the same gasket on the L30 305 I put together with ETec 170 heads that I had in my Tahoe. L30 305 pistons were 0.018" down for a 0.046" quench, as good as I could get. Unless your block has been decked your pistons will be atleast 0.015" down the bore if not closer to 0.025". I would suggest no tighter than 0.038" and no wider than 0.045" with 0.040" being ideal. My 6.0L with ported and 0.020" milled 862 heads has the pistons sticking out of the deck 0.006" from the factory and has a stock GM MLS 0.051" compressed head gasket. Runs well at nearly 11:1 on pump gas.

 

Going by the set of heads a buddy of mine got from them a few months ago, you need to mock up the heads with the guide plates off so you can make sure the pushrods are not connecting with/rubbing on the block - especially if you're running 1.6 rocker arms. Also check to make sure TFS fixed the problem that they were having with their CNC program - all the openings were not finished and some of the push rods were rubbing. The rest of the head looked good though.

As others said pushrods will need to be ordered last after at least a mock up.

I've used and recommended the Mahle 5746 that he ended up using. It's a good gasket for the money - the specs on Summit is wrong it's a 4.100" bore gasket, .026" thick compressed. Prefer .040min-.042max quench but anything under .050 won't end the world.

Also, incase you're planning on running a double roller chain, you'll need to do some clearancing.

 

Thanks alot guys for your input! Great technical help here!

Sooo, to cover all posts:

The head gaskets 7733PT2 are already here, I ordered them also with all the other parts I needed just to maybe save one more shipping cost to Germany later.
So maybe there is hope to use that gaskets, but if its not good for the builder, then of course another gasket needs to be ordered. I was to fast with this step.^^
The point is clear now, order gaskets after measurements.

The quench is also clear now for me and for what it is. Aimed value is .040".
The heads were used with comps great ultra pro magnum roller rocker arms. They are self aligning so I wont use the guideplates. I know I need to shim the screwed in studs a bit to clear, but otherwise it should work pretty well. They dont have a CNC chamber, its rough casting in the chambers. I already went through it with some minitools and kind of "polishing/smoothing" the chambers out. I also smoothed out the pushrod alleys so there is no sharp edges they can scratch on.

Also I want to run a double roller timing chain and have one here already. https://www.summitracing.com/parts/sum-g6601r-9
That one. What was your problem with the block? Could you explain that a little more? Will yours fit under stock timing cover?
You mean the blank metal right over the cam at 12 o´clock?

Greetings,

Chris

 

You're still on track Chris.

Only ONE method at a time can be used to guide the rockers:
1) pushrod slots in head
2) guideplates
3) self-aligning rockers
If you attempt to use more than one method at the same time, there will be interference and/or binding issues.

A double roller timing set is obviously wider than a single chain, so you usually have to do some grinding/clearancing to the block in the area you pointed out.