| FAQ |
| Members List |
| Social Groups |
| Calendar |
| Search |
| Today's Posts |
|
#1
11-15-2017, 09:50 PM
|
|||
|
|||
Deck Height/Pistons out of hole
Have a question regarding deck height and what is acceptable as far as pistons being out of the hole.
Block has a current deck height of 10.215 and my rotating assembly comes to 10.220 (4.25 stroke, 6.8" rods and 1.295 CH). This would leave the pistons 0.005 out of the hole, is that safe to do? Would I just run a thicker head gasket to get the recommended quench? Thanks!
__________________
1970 Trans Am, numbers matching, White, Auto, A/C, Owned since I was 15. 1973 Trans Am, numbers matching, Brewster Green, Saddle interior...Sold :-( 1978 Trans Am 400-4spd, non-numbers matching 400, Low compression daily driver, 9.66@73.5mph 1/8 mile....Sold :-( |
|
#2
11-15-2017, 10:03 PM
|
||||
|
||||
|
You will be fine with .005 above the deck.
6.8" steel rods will never have a growth issue. .042 Gasket will be fine too. Tom V.
__________________
"Engineers do stuff for reasons" Tom Vaught Despite small distractions, there are those who will go Forward, Learning, Sharing Knowledge, Doing what they can to help others move forward. |
|
#3
11-15-2017, 10:19 PM
|
||||
|
||||
|
Built my street 421 with pistons .007-.008 above the deck and a .045 gasket.
__________________
1964 Tempest Coupe LS3/4L70E/3.42 1964 Le Mans Convertible 421 HO/TH350/2.56 2002 WS6 Convertible LS1/4L60E/3.23 |
|
#4
11-15-2017, 11:27 PM
|
|||
|
|||
|
.005 above the deck is acceptable. You’ll have better squish.
__________________
“It takes considerable knowledge just to realize the extent of your own ignorance.” Dr. Thomas Sowell |
|
#5
11-16-2017, 01:03 AM
|
||||
|
||||
|
You will be just fine with it .005" above the deck with a steel rod. You can even run a .042" gasket. Quench will be excellent without any problems at all. .037" Quench will be fine for a steel rod street engine.
__________________
1978 Trans Am Pump Gas 461 Stroker |
|
#6
11-16-2017, 05:36 AM
|
||||
|
||||
|
I wish mine was .005 out of the hole ... wouldn't have to spend $90 on .039 gaskets instead of $40 for .045.
|
|
#7
11-16-2017, 09:11 AM
|
||||
|
||||
|
Not an unusual practice. A pretty talented engine builder I knew actually built several 350 sbc's on purpose this way. They would shoot for 11:1 compression with a flat top piston. He liked the flat tops for better flame travel. So to get the target 11:1 compression he wanted, he'd build it with pistons slightly above deck. He always made respectable power with his engines and they always put up good numbers. He would just tell people "eh it's just a little flat top motor" LOL
Yeah, a lot more going on than he would lead people to believe. |
|
#8
11-16-2017, 09:24 AM
|
||||
|
||||
|
When SS cars make 580 to 600 hp with heads only flowing 240 cfm, you would not loose a bet by saying that there's a ton more going on there then meets the eye!
__________________
Wernher Von Braun warned before his retirement from NASA back in 1972, that the next world war would be against the ETs! And he was not talking about 1/8 or 1/4 mile ETs! 1) 1940s 100% silver 4 cup tea server set. Two dry rotted 14 x 10 Micky Thompson slicks. 1) un-mailed in gift coupon from a 1972 box of corn flakes. Two pairs of brown leather flip flops, never seen more then 2 mph. Education is what your left with once you forget things! |
|
#9
11-16-2017, 12:42 PM
|
|||
|
|||
|
Awesome, thanks guys for the input, makes me feel a whole lot better about it!
__________________
1970 Trans Am, numbers matching, White, Auto, A/C, Owned since I was 15. 1973 Trans Am, numbers matching, Brewster Green, Saddle interior...Sold :-( 1978 Trans Am 400-4spd, non-numbers matching 400, Low compression daily driver, 9.66@73.5mph 1/8 mile....Sold :-( |
|
#10
11-16-2017, 03:47 PM
|
||||
|
||||
|
I've heard that lots of dirt track guys run 'em out of the hole, in the classes that specify a flat top piston & a certain head. So, I assume this is a common practice in any type of racing in which it would increase performance.
|
|
#11
11-16-2017, 04:12 PM
|
||||
|
||||
|
I'm sure that .005 out would be fine with a .039 head gasket, also...
__________________
1977 Black Trans Am 180 HP Auto, essentially base model T/A. I'm the original owner, purchased May 7, 1977. Shut it off Shut it off Buddy, I just shut your Prius down... 
|
|
#12
11-17-2017, 06:14 AM
|
||||
|
||||
|
+2, great place to be far as quench distance goes.......Cliff
__________________
If you can read this, thank a teacher. If you can read this in English, thank a Veteran! https://cliffshighperformance.com/ 73 Ventura, SOLD 455, 3740lbs, 11.30's at 120mph, 1977 Pontiac Q-jet, HO intake, HEI, 10" converter, 3.42 gears, DOT's, 7.20's at 96mph and still WAY under the roll bar rule. Best ET to date 7.18 at 97MPH (1/8th mile), |
|
#13
11-17-2017, 05:52 PM
|
||||
|
||||
|
I assembled my 455 with 5C's at about .005. It has run reliably for 15k that way.
__________________
-- James Work '67 GTO Convertible "Koerner Built 413 500 hp with a Victor!.. I'll run a stock intake." '75 Formula 400 - Daily Driver - Running with my Home Built 455 and TH400 Details here: http://forums.maxperformanceinc.com/...d.php?t=588372 |
|
#14
11-17-2017, 07:51 PM
|
||||
|
||||
|
Recent 455 I bought was 0.012-0.015 out and a 0.039 gasket had head kisses on the pistons.
__________________
Skip Fix 1978 Trans Am original owner 10.99 @ 124 pump gas 455 E heads, NO Bird ever! 1981 Black SE Trans Am stockish 6X 400ci, turbo 301 on a stand 1965 GTO 4 barrel 3 speed project 2004 GTO Pulse Red stock motor computer tune 13.43@103.4 1964 Impala SS 409/470ci 600 HP stroker project 1979 Camaro IAII Edelbrock head 500" 695 HP 10.33@132 3595lbs |
|
#15
11-17-2017, 08:17 PM
|
||||
|
||||
 Quote:
|
|
#16
11-18-2017, 06:49 AM
|
||||
|
||||
|
Recent 455 I bought was 0.012-0.015 out and a 0.039 gasket had head kisses on the pistons.
Not surprised, I wouldn't go less than .030" quench on one of these engines for any reason. I know a few builders who don't mind closer to .025" with steel rods, but that's pushing the limits IMHO. All of our Pontiac engine builds since the later 1990's have been in the .035-.039" range with zero issues anyplace. WAY back when I first got into Pontiac engine builds I let a machinist and Pontiac "guru" talk me into using those POS 8 valve relief pistons at .032" in the holes for a 1967 400 build. Talk about a running hot, overheating, gutless TURD. We teamed that junk up with an Ultradyne cam and it pinged everyplace but at idle speed, and when you fired it up the temps climbed quickly to 180, 190, 200, 210, 220, and right on past 230 and there was NOTHING you could do about it. Lessons learned with these things that I'll never forget!.........Cliff
__________________
If you can read this, thank a teacher. If you can read this in English, thank a Veteran! https://cliffshighperformance.com/ 73 Ventura, SOLD 455, 3740lbs, 11.30's at 120mph, 1977 Pontiac Q-jet, HO intake, HEI, 10" converter, 3.42 gears, DOT's, 7.20's at 96mph and still WAY under the roll bar rule. Best ET to date 7.18 at 97MPH (1/8th mile), |
|
#17
11-18-2017, 12:26 PM
|
||||
|
||||
|
Yep eagle rods but nice 6X chamber outlines on the pistons.
__________________
Skip Fix 1978 Trans Am original owner 10.99 @ 124 pump gas 455 E heads, NO Bird ever! 1981 Black SE Trans Am stockish 6X 400ci, turbo 301 on a stand 1965 GTO 4 barrel 3 speed project 2004 GTO Pulse Red stock motor computer tune 13.43@103.4 1964 Impala SS 409/470ci 600 HP stroker project 1979 Camaro IAII Edelbrock head 500" 695 HP 10.33@132 3595lbs |
|
#18
11-18-2017, 04:45 PM
|
|||
|
|||
|
I'd think you'd need really tight piston-bore clearances also if you're going to push the limits on your quench distance.
__________________
---------------------------- '72 Formula 400 Lucerne Blue, Blue Deluxe interior - My first car! '73 Firebird 350/4-speed Black on Black, mix & match. |
|
#19
11-18-2017, 05:41 PM
|
|||
|
|||
|
Quote:
|
|
#20
11-21-2017, 09:40 PM
|
||||
|
||||
|
Built my street 462 with pistons .007-.008 above the deck and a .045 gasket....no issue at all.
__________________
Jim Moshier 1971 Grand Prix 462ci SD Performance 6x heads 1962 Catalina 389 1968 Firebird 400-455 I haven't decided "If we ever forget that we're one nation under GOD, then we will be a nation gone under." - Ronald Reagan |
| Reply |
|
|
The PY Online Forums is the largest online gathering of Pontiac enthusiasts anywhere in the world. Founded in 1991, it was also the first online forum for people to gather and talk about their Pontiacs. Since then, it has become the mecca of Pontiac technical data and knowledge that no other place can surpass.
Linear Mode
