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#21
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Can the chambers be opened up on the 48’s?
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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... |
#22
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I am certainly not a fan of loosing the quench. It seems like once the quench is around .070” for most engines the quench looses it’s effectiveness and increasing the quench distance more yet wasn’t noticeable over the marginal quench. Would rather make efforts to deal with the bad quench up front than try to nurse an engine along with to high of compression and a marginal quench. Poor quench higher compression engine I would keep at least 10 degrees more on the exhaust side. Doesn’t cure end gas issues, but it seems to help manage it. Going to act more like a open chamber. FWIW…We are every bit as high on compression for pump gas with open chamber heads and other engines with no quench.
Unless it was a unbelievable smoking deal on some 92-96 cc head, before letting those ported 48 heads go I would sell the flat pistons and get some pistons with a good dish. I know DSS has a nice 27 or 28 cc D dish.. 455 pistons in the photo look like nice pistons, selling them, buying dished pistons and not having to get the expensive thick Cometics would be what I would try to do first. I would do the thick cometics if that fell thru. Rather let the pistons go before I ground on another set of iron heads. Lots of guys don’t realize how much work it is when you do extensive porting. |
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#23
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Seems like there are certain quench ranges that cause issues too. For some reason quench from .070” to .09” range is worse than .09 to .14”. Then after sometime after .14” issues start to show up again. See that on open chamber stuff to where we milled the heads and quench end up in that .070” -.090” range, has some extra issues, each engine acts different though. Not sure the RA heads will be much different, my guess is they are going to respond similarly, I would keep out of that .07-.090 quench range.
Last edited by Jay S; 07-16-2021 at 10:18 AM. Reason: Aff |
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#24
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Keeping the #48 heads?
Can’t blame you for wanting to. If so resign yourself to cracking open your wallet to purchase some dished pistons and for the ensuing balancing job. Some new custom pistons will give you the opportunity to set the compression height to zero or whatever number is right for what you’re doing. Get ‘er done.
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1964 Tempest Coupe LS3/4L70E/3.42 1964 Le Mans Convertible 421 HO/TH350/2.56 2002 WS6 Convertible LS1/4L60E/3.23 |
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#25
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Trade them with someone for some # 64 heads
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72 lemans,455 e-head, UD 255/263 solid flat,3.73 gears,,,10" 4400 converter,, 6.68 at 101.8 mph,,1.44 60 ft.2007 (cam 271/278 roller)9"CC.4.11gear 6.41 at 106.32 mph 1.42 60 ft.(2009) SOLD,SOLD 1970 GTO 455 4 speed #matching,, 3.31 posi.Stock manifolds. # 64 heads.A factory mint tuquoise ,69' judge stripe car. 8.64 @ 87.3 mph on slippery street tires.Bad 2.25 60ft.Owned since 86' |
#26
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Mark,
In rough numbers every .001" of head gasket equals 0.22 cc's Is it possible to do a combination of things ? David Vizard talks about putting a radius on the valve relieves which he says helps improve flow. Opening up / soften the combustion chamber Finally increasing head gasket thickness. Stan
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Stan Weiss/World Wide Enterprises Offering Performance Software Since 1987 http://www.magneticlynx.com/carfor/carfor.htm David Vizard & Stan Weiss' IOP / Flow / Induction Optimization - Cam Selection Software http://www.magneticlynx.com/DV Download FREE 14 Trial IOP / Flow Software http://www.magneticlynx.com/DV/Flow_..._Day_Trial.php Pontiac Pump Gas List http://www.magneticlynx.com/carfor/pont_gas.htm Using PMD Block and Heads List http://www.magneticlynx.com/carfor/pont_pmd.htm |
#27
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Quote:
If like my 465 cid flat top 74 455 (undecked) 80's TRW forged.. with 62's that are 75-77 cc ish I can run a can of Torco Accelerator to maybe 10 gallons of 93 Super and it works never pushed it less than that and or I mix 50/50 93 and 110 race fuel
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63 Catalina coupe 455 budget drag car 11's 1/4 , 7.4 1/8th 66 Star Chief Executive 57k mile 69 Le Mans 2 dr HT 350 85k mile 15 sec 1/4 69 Firebird 400 Burgandy/Black 70 Olds Rallye 350 F85 4 speed 3.91's 70 Olds Cutlass Cruiser Red Wagon 350 101k miles 15 sec 1/4 12 sec w 455 74 Cheyenne Super C10 LWB Gen 6 454 w ZZ502 cam 3.07gear 13.1 1/4, 8.3 1/8 2020 RAM 1500 SLT 4x4 5.7 A8 Hemi 2007 Hummer H3 3.7 liter turd 2019 Chevy Spark petrol car 38 mpg |
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#28
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Quote:
Dang Slugs are at zero deck. |
#29
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I am slowly assembling a engine now that doesn't have cylinder chambers at all and my first gen second head bolt design Edelbrock RPM head chambers meet the edge of the cylinder,
No hang over either way, may want to settle on a head package before cylinder chamfer +.030 400 block You can occasionally get the thicker steel shim composite stock head gaskets on ebay I picked up 4 pretty cheap . |
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#30
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Dad successfully ran a flattop 455 (bored .040 over if I remember correctly) with a set of ported #12 heads. It was zero decked and a typical .039" head gasket.
I don't recall the exact compression ratio (I'm sure it was pushing close to 12:1 or so) but I do remember it pumped 210-215psi. He ran a Harold Ultradyne solid flat tappet in it that was pretty healthy, duration in the 250/260 range. That engine ran on the street for a few years on Sunoco 94 octane and I was able to make it work. But the tune had to be spot on and routinely checked. It would not have worked with todays 91. Anytime he went to the dragstrip with it he did mix a little 110 in the tank for good measure. These days with more knowledgeable people and better parts I've pushed the pump gas deal with a few engines on the crappy 91 we have now. One is 11:1 with iron heads and a pretty healthy camshaft running on 91 octane for 5 years now (daily driven to 50k miles so far) and it acts like it would run on less. I keep the tune pretty spot on but I don't have to monitor it like it's life or death. My bird I also drive regularly and it's 10.13:1 with it's #12 heads and does fine on 91 with a very small 068 cam (albeit a 400) put about 25k miles on it in the last 3 years. Neither car acts finicky even in the AZ summer heat but I don't know if I'd push the issue any more than that. Aluminum heads I would, but iron heads that's about as far as I want to go. I don't think pump gas is going to get any better in the coming years. Last edited by Formulajones; 07-16-2021 at 10:21 PM. |
#31
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Quote:
Since 2003 i have had 9.00:1 and have relied on munerous little things and a big cam to realize good results, in either compression. Fear going back to Hi-Comp though. Is 10:1 to 10.5:1 of any use? I suppose a chart is helpful: Correction welcomed! Octane. Compr on a 455 (Race/Tow-Street) 87. 9.0:9.5:1 89. 9.5-9.7:1 91. 9.7-10.1:1 93-94. 10.2-10.7:1
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12.24/111.6MPH/1.76 60'/28"/3.54:1/SP-TH400/469 R96A/236-244-112LC/1050&TorkerI//3850Lbs//15MPG/89oct Sold 2003: 12.00/112MPH/1.61 60'/26"x3.31:1/10"/469 #48/245-255-110LSA/Q-Jet-Torker/3650Lbs//18MPG 94oct Sold 1994: 11.00/123MPH/1.50 60'/29.5"x4.10:1/10"/469 #48/245-255-110LSA/Dual600s-Wenzler/3250Lbs//94oct |
#32
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I would not at all go to the point that 10.0-10.5 is of not any use in a 455. There are just to many factors to narrow the compression ranges in a chart like that, to me the higher octanes on the list are getting to high with respect to the lower octanes, ranges look to wide for the 87 and the 92,93.
I did a SR cam 9:0 462 with ported D ports that wants 91, I think it is borderline in some conditions to want 93, he is gunning for 10s 1/4 mile. Even though it is 9:0, you would swear it has 11:1. IRC, I think I have less cylinder pressure on my 461 at 11:1 than he would have. He is going after all the mid range he can find to launch his car, wants to drive it to the track. My car is a semi daily driver and I wanted efficiency @ low rpms, not a huge mid range, or crazy low end tq, but strong power up high. All things I did so my 4 speed would have a longer life. Complete different combos, same CID, 2 points different on SCR, basically the same octane. FWIW. Power is in the heads. Compression more for efficiency. As long as the compression is adequate for the chosen cam, there is much more power with better head flow than compression. Nothing wrong with 9:0, depends on the rest of the combo. Not enough info in this thread to begin to determine where the perfect SCR should be. If in doubt, stay on the low side and sleep better at night. Last edited by Jay S; 07-17-2021 at 10:46 AM. Reason: r |
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#33
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This graph roughly shows cranking compression for 9:1, 10:1, and 11:1 CR verses IVC for a 455 + 030.
Stan
__________________
Stan Weiss/World Wide Enterprises Offering Performance Software Since 1987 http://www.magneticlynx.com/carfor/carfor.htm David Vizard & Stan Weiss' IOP / Flow / Induction Optimization - Cam Selection Software http://www.magneticlynx.com/DV Download FREE 14 Trial IOP / Flow Software http://www.magneticlynx.com/DV/Flow_..._Day_Trial.php Pontiac Pump Gas List http://www.magneticlynx.com/carfor/pont_gas.htm Using PMD Block and Heads List http://www.magneticlynx.com/carfor/pont_pmd.htm |
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#34
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@ Jay; my 9.0:1 is all joy on 87, 1/4 mile on 89 due to the cam (combo below), butt hay the little things going on like cutting the Sparkplug GND lugs back, HEL finness, Phat Carb Primaries. And then aluminum water pump, alum water crossover, such things of no consequence really. I really dont tink the loud stereo is part of the deal though.
So, Flat HYD cam is likely a keynote thing. Solid Roller is gonna give those static compression woes huh. Rollercams not in my recipe book. Got grandkids here so chart comprehension will have to wait. Stan, I has an Isky 245/245 104 LC 4* adv for 100/108 provide 285-300PSI cranking pressure on a RamIII 455 combo awhile back. The idle pulsations were spectacular.
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12.24/111.6MPH/1.76 60'/28"/3.54:1/SP-TH400/469 R96A/236-244-112LC/1050&TorkerI//3850Lbs//15MPG/89oct Sold 2003: 12.00/112MPH/1.61 60'/26"x3.31:1/10"/469 #48/245-255-110LSA/Q-Jet-Torker/3650Lbs//18MPG 94oct Sold 1994: 11.00/123MPH/1.50 60'/29.5"x4.10:1/10"/469 #48/245-255-110LSA/Dual600s-Wenzler/3250Lbs//94oct Last edited by Half-Inch Stud; 07-17-2021 at 02:41 PM. |
#35
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Just open up the chambers.
Thats what I did to my 670's to 87cc and they work fine with premium pump gas. I think it was around 10:2:1 comp. I ran a 575-lift solid roller with 262 dur@50 on a 110 lobe seperation. GT |
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#36
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48s at 78 cc with Ram IV Valves. Not brave enough to eggshell up to 87cc.
My latest thought is to finish the shortblock, Top-end it, & break-in the cam on a super hobo stabilized engine Stand. Let it lay until Towncar engine is out and begging ready for the 455. Meanwhile money gets committed to Dished slugs, or thick headgaskets. Possibly sell the Spare as a run-in flattop forged-crank shortblock. And look for a dished shortblock.
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12.24/111.6MPH/1.76 60'/28"/3.54:1/SP-TH400/469 R96A/236-244-112LC/1050&TorkerI//3850Lbs//15MPG/89oct Sold 2003: 12.00/112MPH/1.61 60'/26"x3.31:1/10"/469 #48/245-255-110LSA/Q-Jet-Torker/3650Lbs//18MPG 94oct Sold 1994: 11.00/123MPH/1.50 60'/29.5"x4.10:1/10"/469 #48/245-255-110LSA/Dual600s-Wenzler/3250Lbs//94oct |
#37
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this conversation sounds very similar to my latest delima.....455 CAST piston ZERO deck motor and a selection of heads all with there own problem. The 7M5's...not enough exhaust bolt holes and 114 cc, the small valve 4X @98 cc then my lovely #62 @ 74 cc.....either get no compression (or header bolt holes) no flow with great compression, or TOO much compression with great flow.;.....lol
decided to work the 4X into a decent head. budget budget budget... |
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#38
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Quote:
The valve reliefs in the piston photo look big and deep. How many cc they? Kinda sounding like the compression is more like 11.0, not 12. Might not have that far to 10 scr with the parts you have. Connect the valve relief and make it more like a tear shaped trough, and unshroud the intake a little more. Little things like what Stan mentioned a few post earlier add up. |
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#39
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Quote:
48s have been unshrouded;
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12.24/111.6MPH/1.76 60'/28"/3.54:1/SP-TH400/469 R96A/236-244-112LC/1050&TorkerI//3850Lbs//15MPG/89oct Sold 2003: 12.00/112MPH/1.61 60'/26"x3.31:1/10"/469 #48/245-255-110LSA/Q-Jet-Torker/3650Lbs//18MPG 94oct Sold 1994: 11.00/123MPH/1.50 60'/29.5"x4.10:1/10"/469 #48/245-255-110LSA/Dual600s-Wenzler/3250Lbs//94oct Last edited by Half-Inch Stud; 07-19-2021 at 06:57 PM. |
#40
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Getting ready to Slug the Rods. Super-lightweight assy. Sharpie is a key scribe for coordinating these things. Spiralocks!!!
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