Anybody running the TA 1611 JE 11.0:1 piston? The catalog says they're 11.0:1 but they're flat tops with valve reliefs. Every flat top I've seen is 12.0:1. My Bill Miller's are flat tops with 12.0:1. Are the JE's really 11.0:1?
I`m running those pistons in my engine,Mike @ TA told me that they are 11.1 as did Scotty @ Pee Gee perf. who built my engine. Thanks
George The stock compression height is 1.98. Do you know if your piston is shorter than that? How heavy are they?
Hi Guys, Pistons are only one part of the compression ratio "puzzle". A "12:1" piston will have a compression heighth set to put the piston at about .000" to .005" below deck (unmilled block deck surface). An "11:1" piston is set up with a different compression heighth that will have it lower below deck...around .020" or so give or take. Overall, it's the total combination of the piston (dish is a negative volume as is valve reliefs even for a flat-top and dome is a positive volume; although you will treat them as the opposite when computing your figures) the gasket volume (bore X bore X thickness X .7854 X 16.387 for cc's), and the head chamber volume. Many do not realize this but even after you do these equations you still will be slightly over in your figures of what your actual compression is due to there being additional volume around the sides of the pistons above the top ring-land. That is not figured in unless you measure after the short block is assembled with the piston @TDC. Without measuring EVERYTHING those numbers in the catalogs are JUST "in-the-ballpark-range" numbers and little more!:Smarty: Hope this helps...
I'm sure that's the way they are designed but that will ONLY be with a certain deck heighth, combustion chamber volume and gasket volume! ONLY with the EXACT volume that Mike designed it with. If you end up with it higher (less block deck clearance) then you will need to adjust by adding volume to either the gasket (thicker gasket) or adding more chamber volume. If it ends up lower than Mike intended then you will have to find a way to reduce volume by either a thinner head gasket or milling the heads to reduce chamber volume.:Smarty: Hope this explains more...
What I'm trying to figure out is if the 1611 is designed with a compression height that would require ANY decking to get true 11.0:1. I've got a set of Eagle 6.635 rods and if the 1611 is .020(approx) in the hole with a stock rod, then it'll be out of the hole with a 6.635 rod. I guess I may have to go 10.0:1 and zero deck with the 6.635 rod. I also have a set of Ross 11.0:1's on recon'd rods that I was intending to swap with the Eagle rod, but I just found out that the Ross piston is built with a .040 LOWER pin to make it 11.0:1 without decking. So I can't use the Ross piston with the Eagle 6.635. I liked the Ross piston because it's only 650 grams. Everything else I've looked at is 700+. I considered getting 6.535 rods, but I'll lose .065 on the rod length, gain .040 back with the pin location, putting me about -.025 in the hole but end up with a worse rod ratio.
Reynold....I guess another thing I neglected to mention is that you must remember that our 455's WERE NOT blueprinted from the factory. Meaning that the block deck heighth's are not all the same, there was/is a factory tolerence that needs to be taken into consideration. From that point you have to think of the "build-up" of stacked tolerances and where that can lead...."snowballing", in MANY instances if you will. You MUST measure your deck heighth to know for sure what it is for your calculations to even start to be in the vicinity of accuracy. Our cars from the showroom floor would ALL slightly run different due to these and MANY, MANY other tolerances alone!:Smarty: Keep that in mind that UNTIL mocked-up and accurately measured and computed...all those numbers are just approximations at very best.:grin:
i`m not sure about this stuff with calculations and so on but i know my block(`70 SF block)was not milled and i`m using stock rods,orange crush head gasket i think its like .040 thick and an alumium stage 1 head from TA which is like 65cc if i`m not mistaken. Thanks
Hi George, Your '70 SF block will still have it's own block deck heighth...until it's measured from the crankshaft main parting line to the top of the deck you will not know EXACTLY what it is. 10.570" is what I think Mike has set them up for but not truely sure. A stock, unmilled block from the factory can vary by several thousandth either way above or below this nominal measurement. I've seen many (untouched) 455 blocks vary this way that is why I'm telling you that to be sure it ABSOLUTELY has to be measured and verified!:TU: Stock rods can vary in center-to-center length also so measuring them is needed for accuracy too. For your Orange Crush gaskets...they are 4.380" bore and @ .040" that will give you (4.380" X 4.380" X .040" X .7854 X 16.387=) 9.876 cc's of gasket volume. Without measuring the heads to be sure it's JUST a guess-timation at best. If you were to measure you will find that chamber-to-chamber volume can vary and USUALLY does although it's USUALLY by VERY little but enough in a "stack-tolerance" to make a difference if you are trying to "blueprint" an engine in any way. Overall...a few thousandths here and a few thousandths there can add up!:Smarty: Hope this helps more...
No i completely understand Kerry,i was told i`d have about 11.1 also take into consideration the aluminum heads which you lose a point from what i understand. Thanks
Hi George, The aluminum heads will NOT reduce compression ratio UNLESS your iron heads had smaller chambers with less cc volume. I personally do not see that being the case. If anything you will probably have a little more than your iron head configuration was... I think you have probably misunderstood....aluminum heads will pretty comfortably allow an increase of an additional point of compression ratio on the same octane vs over what the iron head would!:Smarty: In saying that...it's due to aluminum's heat disappation rate vs the iron's disappation rate. Aluminum gives heat off more readily and more rapidly. Heat = HP, so you need to UP the compression ratio to contain the same amount of HP "heat" in the combustion chamber to obtain the same cylinder pressures. I guess another way to put it is...that to achieve the same cylinder pressures you would need to increase the compression to 12:1 to have the same as an 11:1 iron head engine. This is ONLY IF the flow capabilities were the SAME in both the aluminum vs the iron heads....which by the way we know they are not!:grin: So you are still going to increase those pressures from just have MORE intake charge enter the cylinder alone!:TU: Hope this helps...
If you can provide the following numbers, I have a calculator in DeskTop Dyno that will give you a pretty good guesstimate. Bore (stock,+.030, etc.) Gasket bore and thickness Piston volume (of reliefs in your case if true flat top) Head chamber volume How far piston is in the hole at TDC PM me for fastest results.
Checking back on my list,it stated 10.6.1 compression with the cast stage 1 heads that were on there and with the aluminum heads he had told me it`ll be about 11.1. Thanks
Guss and Reynold, I am happy to see that you guys are paying attention to the weight of the parts you are putting into your engines. Reducing reciprocating weight wherever possible will help the engines longevity and its ability to accelerate the vehicle. Below is a picture of the piston and wrist pins in my engine.
John What size piston is that? It looks like my 494 Bill Miller but it looks shorter. My Bill Miller's are 555 grams.
Ahh...I see "gas port technology" is still being used in racing applications...had wondered recently about this and what it might be worth in a Buick build. Something to think about...Thanks Staged70Lark
Gas Ported pistons Never thought about doin that with my motor. Bud of mine had Musi build a 380 chev for EZ St. that had gas ported pistons. Think they had low tension rings and cyl. pressure holds them rings tight. Not sure what thickness the top land has to be so the pressure goes thru the holes right. Can you give us some tips Staged 70? thanks ..fish
