Quench and MY mismatched Setup! I need advise please

[devilish64]

Im in the process of building a 306 from a shortblock wich consists of stock polished crank, stock style forged rods, probe SRS forged pistons(10471-030 for twisted wedge heads), trick flow 170 twisted wedge 58cc track heat heads(bought to go on a stock shortblock) with comp 1.6 roller rockers, Trick Flow stage 2 Camshaft, weiand excellarator intake and a quick fuel 650 carb. 3.55 gears, and a t5 in a 64 ford Ranchero.

So I am building this 306 as my first motor of my own and therefore just want it to be optimized. The machine shop that put the shortblock together decided to put in a dome top piston when I told them I wanted a 10-10.5 compression, in a 91 octane street motor. They said I would be leaving allot of power on the table by using a flat top piston(In my opinion this was definatley the wrong move, but I don't have the time to send it back to get new pistons). Probe list's that piston as 11.4-1 compression with a 58cc head wich seemed to high for 91 to me. My friend who works for a local speed shop recomended me a super thick(.075") MLS head gasket. I bought them as the maching shop said it would bring me back down to a much more street friendly 10.25-1. THEN i learned about QUENCH...:pat:.. what would be the most cost effective, yet best option for me at this point? Or am I just over thinking this in a light, already overpowered car? What compression do you guys run on 91 octane with a CARBURETOR? Any help would be greatly appreciated.

CAMSHAFT: http://treperformance.com/i-653-tfs-stage-2-camshaft-sbf-ford.html (http://treperformance.com/i-653-tfs-stage-2-camshaft-sbf-ford.html)
PISTONS: http://www.summitracing.com/parts/PBP-10471-030/ (http://www.summitracing.com/parts/PBP-10471-030/)
HEADS: http://www.summitracing.com/parts/TFS-51400010-M58/ (http://www.summitracing.com/parts/TFS-51400010-M58/)

[MarkM66]

Is tearing it back down out of the question?

I bought a 454 once with pistons that had a dome that was to large. I removed them, and had a machine shop mill the domes down. It cost a lot less then a set of pistons.

No way would I run that thick head gasket.

[speED]

.075 is a thick gasket, I wouldnt run anything thicker than an .053.

[Chevelle598bb]

How far is the piston down in the hole? We need to know this measurement. With a zero deck compression will be right at 11.73, with .010 in the hole 11.36 and with .015 11.15. These are all calculated with a .039 thick felpro gasket (1011). For piston to head clearance I run .045-.050 on sbc and sbf on the street. Ls motors I like to run around .040.

Easiest thing to do would be to order a set of probe flat tops and rebalance. Shouldn't need a rehone since you would use the same piston make and series (always check and measure) and shouldn't take a machine shop but just a few days unless they are busy. Hopefully they would expedite it since they put in the wrong piston to begin with.

Or order a new set of trick flows in 64 cc chamber and that will bring the compression down to about 10.3 to 1 with a the 1011 gasket assuming you have a .010 deck clearance which would put the piston to head clearance at .049.

Typically you get a better flame travel with a flat top or dish (reverse dome) piston then a dome. This is especially true for motors that use a high efficency small chamber such as your tfs. Do not use a .075 because the quench will go away and detonation will come. With the cam you have chosen you must keep a good quench and keep compression below 10.4-10.5. The cam does not have a lot of overlap and if your tune is not spot on you can run into issues. Of course this is assuming you are at sea level.

[devilish64]

Thanks for Responding..... Chevelle598BB.... your post really got me thinking. That is just not the right pistion for the parts that I have. Now that I have learned a bit more about Quench, I WILL NOT run that gasket($190 for the pair... woops live and learn right). Doesnt seem to be a cheap fix at this point. I talk to the people that built the shortblock and they are saying that they don't think they can take any kind of return because they met their requirements(10-10.5 compression for a street driven motor.... Yeah right they screwed me) I purchased the 170 port 58cc heads because I planned on building a stock shortblock with them. I could really probably benefit from a 185 port head with the 64cc chambers. I'd just rather not spend another $1400 on heads when I just recently did.... but i'm sure someone will buy the 170's. I wonder if I can CNC port the 170 out to 185 or if that is even cost effective(Fox Lake?). How do you think the SRS dome piston will work with the smaller .04-.05 head gasket? This should put me right were I was SUPPosed to be I think. The pistons are made tor the twisted wedge head so I assume PTV will be good. Thanks! I'm learing allot from this

[Chevelle598bb]

The head gasket thickness will depend on what your deck clearance is. We need to know how far the pistons are in the hole before you can choose the correct gasket to put your quench where you want it. After you measure the deck clearance then order a set of head gaskets that will place the piston to head clearance at .045 to .050. Then you have to check piston dome to chamber clearance. You measure this with modeling clay. You want at least .050 clearance everywhere on the dome. As far as piston to valve clearance goes you won't have any issues with that cam. Check the clearance anyways just for grins but you won't have issues.

Short answer is we don't know what gasket thickness you will need until you measure the deck clearance.

[Rod]

I agree with an original assessment that the easiest thing to do would be to order a set of probe flat tops and re-balance, I don't think there's an easier answer, I say keep every thing but the pistons, you'll be happier with few points off that compression, didn't we talk about this at the shop the other day? and welcome to the forum chadster

[devilish64]

:] thanks ROD! need to get to checking the deck height as the next option I guess then. The build sheet that came along with my shortblock has no dimension listed for "deck height" (that would have been way to easy) so I'm going to have to set up a dial indicator or something. Never done this before! Im probably going to just wind up getting some 190 fast as cast trick flow heads with 64 chambers to solve the problem. Thanks

[devilish64]

easiest thing to do would be to order a set of probe flat tops and re-balance, I don't think there's an easier answer

Agree 100%..... build entire motor around chinese piston with questionable forging process. That has to = a WIN right? I will learn from building this motor one way or another! CHEAP..... FAST..... or GOOD...... YOU CAN ONLY HAVE 2 : ]