Sbc compression ratio

Sbc compression ratio. 28 Compression Ratio 3. 75 cubic inches. #1 · Oct 3, 2008. 4:1 compression when I did the calculations. Sep 24, 2015 · TBI sbc 350 factory compression ratio. 050 is needed from the cam choice, and the lower the static CR is, the less dur is needed. I added in the 52 and 80 cc heads. 030-inch bore and 3. . 5:1 for use with aluminum heads to help prevent detonation. 5cc. 050" lift durations. 22 CR. 015 in the hole, a 042 gasket, and no eyebrows or dish is pretty close to 9. Open chamber BBC heads are usually abut 119cc. I was thumbing through Summit and was thinking that might give a little added boost. Instructions: Enter a value in the un-shaded boxes below as they pertain to your engine. 0:1 to 10. Oct 24, 2003 · classic_chevy_guy Discussion starter. 25:1. Based solely on our thermal efficiency formula, raising the compression to 12:1 should bump that figure to 397 ft-lbs. 94"/1. Remember you can use different thickness head gaskets to alter the CR. Feb 18, 2008 · Cam is . Because it is based on fixed values Taking those numbers, and doing some compression calculations, using a typical Felpro head gasket, assuming a Mahle flat top 2 valve relief piston with a 5. 7, so somewhere in that range real compression ratios are done by measure cc volumes of the combustion chamber, head gasket volume and effective dome volume using a burrett, plate, etc The ratio of the cylinder volume at IVC over the volume above the piston at TDC dictates the dynamic compression ratio. #2 · Oct 24, 2019 (Edited) The quality of pump gas isn't going to improve, so that's what you have to build to. 675"). 000". Oct 25, 2022 · from Fountain Valley, Ca. 019" steel shim head gaskets. The compression ratio of the engine varies depending on the specific model and can range anywhere from 8. '85 GMC C1500 SWB 355 sbc. 025 inch between the piston and deck with the former at TDC and 12 cc factory pistons the compression ratio with 64 cc Vortecs looks like this: 1) with a . This round will be: 400 . 5:1 for aluminum heads. A friend of mine has a very nice 406 with 12:1 compression that runs on pump gas that he swears is very easy to drive on the street. This makes a stack of 9. 52% boost in torque from that change alone. What I'm wondering is, can anyone tell me how much my compression ratio will change by going to a 64cc or a 58cc head. KB piston site has a great calculator for compression ratio if you know the piston cc’s, thickness/diameter of gaskets, piston to deck, bore , stroke, etc. 50" Valves, The Pistons are MOST likely stock dish one´s and it the engine is at std deck height. Jun 21, 2007 · As a general rule, the best available pump gas will work with an 8. 420/. 45 Aug 8, 2009 · Can anyone here tell me what the compression ratio is in my engine, it is 350 SBC from 1974 Chevy Blazer/Pickup truck. It doesn't give any lift figures or . 015. I've got flattops in my 383, with 64cc heads, and it was rated at 9. 020-inch yields a significant change in CR,” warns Stevenson. 03 x . 540. Here’s an example of a 350 with a 10. 18069 posts · Joined 2005. 5 cc Heads: 9. Mar 19, 2020 · Even with engines having fixed valve timing (non-VVT), the effective compression ratio changes as the engine speed and load change. A compression ratio of 9. Jul 24, 2010 · The . 000 + 9. On a street driven small block chevy with aluminum heads, what are the advantages or disadvantages of smaller (64cc) chambers versus larger (70cc) chambers. To get 8. 48-inch stroke. This is actually my second 400 sbc for the car, the first round was 400 with Vortec heads, Comp 280H cam, 9. Jun 6, 2020 · Working on a fresh rebuilt 350, and I did a compression test, all cylinders read 140 psi. 7") and piston compression distance (1. 047" quench. 0 is based on a standard . 2-9. Sep 1, 2002 · Then, for the June '01 issue, we tested another small-block with an XE268 camshaft, this time with a 9. 050 in the 220-225 range would be fine. The horsepower was rated at 165 for the 2 barrel, 175 for the 4 barrel, same as the 350's in '72 cars (bought a new Nova in '72, and 165 was the HP rating for the 2 barrel 350 in it), with 280 Jul 24, 2006 · Consider this, to make 600hp with a 383 you will need turbos that will flow 150cfm, translates to about 5-6psi. Mar 24, 2017 · If your engine has these pistons, expect the compression to be around 8. Compression Ratio =. 5:1 for use with iron heads and 10. 7 Head Gasket space + Deck Height space +. 510 lift 9. 000) Note: For pistons ABOVE the block @ TDC - value in box must be a NEGATIVE. 76 cc chamber, a flat top piston, . #5 · Aug 9, 2003. 020 steel shim head gasket. Nov 20, 2015 · Effective Compression Ratio (ECR) = [(Boost / 14. 8:1 with no problems even on 87 octane. + cc head is off a 400SB truck engine). 2L, small block. Jan 24, 2020 · So with a small-block Chevy with zero piston deck height, we’ll need a 0. 5cc) / 63. I don't have all the specs of the motor to figure the compression ratio, but I know it is 8. 854. Note: For pistons BELOW the block @ TDC - value in box must be a POSITIVE number (. 5:1 is considered high by today’s standards. 35 18cc -- 8. 2256 posts · Joined 2003. We also looked at the 5. Show more replies. 020 down in the hole. 5-points. 180 domed speedpro forged slugs in my 396 with same type design 063 lrg oval port closed chamber heads with 98 cc when i had themchecked has approx 9. So the now-restrictive exhaust increases the pumping losses seen on the exhaust strokes by about 80 hp. 030 x 0. #1 · Feb 20, 2009. Use (-) for Dome and (+) for Dish. In short, if it changes the amount of charge in the combustion Oct 3, 2008 · 6 posts · Joined 2008. 039 gasket. Chevrolet also made 64, 68 & 72 cc heads. 48 inches, respectively. The Chevrolet small-block engine is a series of gasoline -powered V8 automobile engines, produced by the Chevrolet division of General Motors between 1954 and 2003, using the same basic engine block. (The 52 cc head can be a 305HO, -601 head and the 80. I was leaning toward those heads anyway for the reasons you just stated. 0:1 with the preceding rod, stroke, and cam intake closing event, you would need about a Feb 3, 2015 · Both run on 91 octane ( same as the 87 octane you get in the USA) The key to running higher compression is having less timing and a air fuel ratio around 12. 110 c/l which may help bleed off some low speed pressure. 5 ratios away from where it needs to be. 050" with iron heads without any detonation problems. It was introduced in the 2014 C7 Chevy Corvette. Hi, I recently tore apart a 307 take out of a '70 Chevelle. As a guess …. 031 gasket. 03 x 4. 8 and Dynamic Compression Ratio will be about 7. 015" gasket and you'll be OK. I went pretty mild with the cam because this is supposed to be a cruiser. Use . 480 stroke - . 9 cc heads. Apr 20, 2018 · Compression Ratio = (626. 61 Compression Ratio 3. I bought a used SBC 421 a few years ago and never knew the compression ratio. 877 posts · Joined 2011. 170 Click "Calculate" for dimension results. SCOTT. 5:1 with vortecs. I suppose I could run a different head with a larger combustion chamber or aluminum heads. If you plan to change heads use the 64cc heads and make sure you have the steam holes drilled Sep 17, 2006 · The amount of compression ratio is not the only variable in pump gas compatibility. #2 · Mar 19, 2004. what would my Sep 20, 2007 · A 283 2 barrel head would have a chamber somewhere in the mid 60s. 84:1 cpr change so you can reasonably expect a 1. Google your cylinder head casting number, that should get you in the ballpark. 73:1 compression from the summit engine rebuild kit that they offer. Hope some of this helps. Nov 10, 2020 · Static compression ratio is affected by multiple variables including crankshaft stroke, piston-to-head clearance, head gasket thickness, and piston valve reliefs (if present) or the presence of a dish or dome in the piston. 5cc (500cc/8=62. 9:1 high. the motor runs great. Jan 25, 2018 · This is critical to accuracy of compression ratio since a difference in deck clearance of 0. 90; 76 cc = 7. I decked the block a little (10-15 thou off, block was slightly crooked), shaved the heads a little (machine shop measured at 93-94cc per) and used a regular fel-pro gasket, 39 Jun 5, 2012 · I agree with above, 8-8. Nov 16, 2018 · When building any engine, one of the most important factors to consider is compression ratio. Assuming the same compression ratio, runner size, etc, is there a horsepower or torque advantage one way or the other. On a 9. The reduced volume that gets compressed represents your dynamic compression ratio and it is always less than the static compression ratio. Cam duration was 280* intake and 288* exhaust. 7. 22:1. I think your compression is very good especially since the readings are so close cylinder to cylinder. Mar 19, 2004 · camaroman7d. 015"-. #4 · Jun 15, 2007. Apr 17, 2010 · 1150 posts · Joined 2009. 050 specs to the static compression ratio of the engine and/or vice versa. Cheap way : Shave the heads. Nov 19, 2008 · youll gain about 3% in hp increasing the effective static compression ratio one full point, so swapping from a 9:1 to a 10:1 cpr boost torque about 3%. It's supposed to be about 9. 387cc = 1 cubic inch. May 28, 2003 · I used the same piston in my 396 rebuild (66, 702 heads - 96cc), did the math, and the static compression ended up *around* 10:1. Get accurate compression without the guesswork! Get your engine's optimal compression ratio and total displacement in no time flat! Just complete your engine setup, click calculate, and you’re on your way to maximum performance. With the higher cr, you won't need as much boost to build the cylinder pressure. Aug 9, 2003 · 122 posts · Joined 2002. So as many of you may have seen I recently scrubbed the cylinder walls in my top end build due to inexperience during the initial start up. 043 inch thick composite gasket. I read the formula to determine the compression ratio and I don't really understand or have all the information. 039 thick head gasket it's 9. Apr 20, 2009 · Looking at a L-31 SBC shortblock, hydraulic roller block, 1 piece rear main seal, dished hyper pistons. 041 thickness you went with a . 015 head gasket, which will push the compression up to 9. 9cc’s – we’ll round that off to 209cc. Aug 28, 2011 · 65 Skylark. Its highest output was 300 hp and 380 lb-ft of torque, before it was slowly neutered for emissions. 480" Stroke w/58. 80 cc head = 7. 8 compression per speedpros piston catalog depending on amount of decking done on heads & block along with gasket thickness too. 7 inch rod, and a deck clearance of . Don't let it get lean anywhere. 5-to-1 is a 0. I'm a firm believer in matching the cam dur. 7:1. i have a 1976 400 sbc bored 40 over and decked with flat top pistons (4 small valve reliefs). The parts you choose for your build are designed to achieve a s Sep 9, 2019 · Pump gasoline has got worse over the years and it is not getting any better. Yes the heads are 64cc and combined with the factory 10cc dish pistons the compression ratio is 9. the heads were rolled a bit. If they are dished pistons I think they are 18cc cups, I'm not positive though, 58cc chambers are ok with dished or most 4 valve Jul 22, 2007 · A set of aluminum heads with 72cc chambers and 180cc runners would be just the ticket with the 268HE cam. 0 cc Dec 11, 2011 · I put together a 350 . 5:1 would be a better choice, but Jan 1, 2014 · 283-350 Chevys. they flow 330 at 700. My concern would be the stock block, get high-quality main caps and bolts to keep it together. A rule of thumb for automotive engines is that a 0. Today on vortec heads you can get that much (literally) on 9. 4:1 if your block is undecked and you're using a standard 0. 2:1 compression but it wiped a lobe. Run your numbers twice or three times to make sure you've not making any errors—but don't worry. 12. With a quench distance of . 039-inch thick head gasket to establish a proper piston-to-head clearance. Is there anything special you have to do prep-wise to run a copper head gasket? Thanks, Greg Apr 27, 2005 · Here`s where the fun part begins. Is anyone running a similar combo and with what compression ratio? With this roller cam and heads on a 350 Iam running 9. RobbyDD. 141 posts · Joined 2003. 4:1 , But once you go past 13:1 compression you need to run higher octane. 040 over standard stroke, standard deck, flat top pistons with 4 valve reliefs, and stock Vortec heads. 2341 posts · Joined 2015. May 2, 2014 · I'm building a late model chevy vortec 350 before I pull the trigger on any parts I need to know what is the ideal dynamic compression ratio for aluminum heads and 92-93 octane gas and what is the absolute limit and yes I'm building to keep a squish of . 789:1. Let’s plug in our 10:1 compression engine with a psi of boost into this equation: ECR = [(8 psi / 14. Jun 19, 2020 · 64CC vs 68CC SBC heads. IMO 10. 017" would look like this: . The result is a 110-hp increase at the flywheel. Sep 26, 2016 · stock compression height pistons piston dish/valve relief----compression 7cc -- 9. There are a number of ways to accomplish the task. The compression ratio will be approximately 11:1. It had hydraulic cam, a 4bbl Quadrajet carb, cast pistons, 4-bolt mains, and originally a 10. 61; and finally an. But, in my case, running a true measured 11. 480" Stroke w/60. Mar 1, 1998 · Whether you decide to cut the heads for a compression increase or to budget for an aftermarket version, it's wise to keep the ratio around 9:1 for iron heads and 9. Share. Cam profile is also plays a big role along with the load on the engine. 5 to 1. 050 and low . 5:1 with aluminum cylinder heads. On a final note, these calculations Apr 12, 2010 · This is the volume between the crown of the piston and the deck of the block with the piston at top dead center. Now, if we increase the bore diameter to 4. You need to know what heads/cc you have to begin with, decode your heads casting number, then cc your chambers to confirm if your heads have already been milled or not. Piston Top volume + Combustion chamber volume. If you run the higher compression it will be better off the bottle but will be harder on parts when on the bottle. Compressed Volume + Displacement. #3 · Oct 26, 2014. 71 Regarding the cam, that's a function of vehicle weight, transmission type, overall gearing, and intended usage. 26@106mph with no work other than a valve job to the heads. The 4 eyebrow relief style usually contains 4-6cc. L-29 461 BBC 11. A standard TO4E will flow 550cfm at 25psi around 6000rpm. 5:1 and a 191/196 cam. In theory, forcing air and fuel in as small a combustion chamber as possible (measured in volume) will yield maximum engine compression and horsepower. 75:1 static compression ratio that produced a cranking compression of 175 psi. 1:1 jumps to a more impressive 10. 25 compression. so even with a zero deck height, it would still be . Apr 15, 2012 · Let’s use a 2 litre 4 cylinder engine to illustrate both methods. 1:1 compression ratio: 4. . Feb 20, 2009 · 15 posts · Joined 2001. 67 Chevelle owned since high school. Focus on ignition curve and fuel curves. Some sit at different height in relationship to the head surface. As mentioned, it depends on the total package. OEM deck height is . Compression Distance: 1. Mine are flat top 4 relief pistons, but may not be the same as yours. R. 0 down to 9. 155-inch bore, our original 10. 442 lift because of the limitations with stock Vortec heads. General rule of thumb for acceptable dynamic compression ratio to run safely on pump gas is 8:1 maximum for engines with cast iron cylinder heads and 8. 0 cc Heads: 9. 3:1 with 64cc heads. 480" Stroke w/68. 5:1. 0:1. Static Versus Dynamic Compression. Aug 1, 2008 · Using stock 5. 79. 625"), rod length (5. 3:1. Oct 6, 2008 · The heads are aluminum but what is the limit with pump gas. 2. 0 cc Heads: 10. On the good side you don't need premium gas. The conversion is 16. 232 @ . I went with a Lunati cam with 204/214 duration at . Pro Street 1983 Chevy Monte Carlo Feb 3, 2023 · SBC Compression Ratio. 050. Dynamic: 8. Jun 16, 2011 · Unknown member. The 9. 5:1 or slightly less, there are many factors as well as this is a ball park figure without exact measurements and a compression calculator. 030 x 4. by T-flow » Tue May 25, 2010 12:02 pm. 5:1 If you use a 72 cc chamber it's 8. Using a manometer is much simpler, as you won’t have to open the engine block. The new LT1 is the Gen. Aug 4, 2006 · What would the effect be on the compression ratio if instead of a . 10@118mph 9-30-22. swapping from a 76cc head to a 58cc head is a 1. Since the formula is long and tedious, click this link for an Omni compression ratio online calculator. 5 decrease, which may be fine for eliminating Nov 24, 2006 · The 350 LT-1s n 1971 were rated at 330 gross HP which translates to about 280 by today's standards, and to get that it relied on 11:1 compression and a solid lifter lumpy cam. 8 to 1 ran great on pump gas and pulled off a 12. 4 and 8. Check the changes in compression ratio if you enter these numbers, or use a . 550 lift Crower cam 234/244 @ . I would bet that 350 has a smogger cam and flattop pistons. The head gasket that came on a 283 would have been . 589 posts · Joined 2011. 665:1. 5cc) to give a static compression ratio of 8:1 – the old school method. Like. AFR does make a very effecient head but that and 91 octane will only go so far. 75 x 16. 020 destroked" meaning, it has . 020 off the top of the piston, where a normal 350 piston would have a 1. It could be as low as 8. Dart SHP 180cc runner/64cc chamber. Piston makers have charts to give approx compression with each size piston and they list the various cc's of the domes. Is there anyone else running that kind of compression on the street. I don't know how true this is. Those 76cc heads (Most likely what you have) kill compression, throw in a dished piston and you end up on the low end of the C. #2 · Apr 17, 2010. Jan 16, 2015 · For instance, a mildly modified 9:1 350 small-block Chevy makes about 380 ft-lbs of torque. Victor makes a . May 19, 2024 · Using Summit’s free online compression ratio calculator, the program gives us a compression ratio of 10. 00 inches by 3. i dont want any more than 550hp/550lb-ft, and so i think that 9. 017 x 16. 7:1 ratio. Have you tried to figure out the dynamic compression ratio? I run a 11:1 cr sbc with a 244 degree cam @ 0. I believe the heads were original to the engine and the Sep 3, 2022 · Lat year I ran a dished piston 400 with a set of 64 cc Vortec heads and the compression was right around 9. Mar 6, 2007 · I've seen pump gas 10. Compression Ht. In practice that number is usually exceeded and the bigger the cam, the bigger the gain. 040 head gasket thickness - 76 cc head volume should give you a CID of 349. RSR static compression ratio calculator. #5 · Dec 1, 2012. i think it might have longer than stock rods as well but not sure so i put a pic to show where my piston comes up to. 7) +1] x 10. 9-13. Calculate the required thickness of the thicker head gasket based on the desired new compression ratio. -----67 RS RAGTOP # matching 4X4 Chevy truck 4X4 Suburban Oct 25, 2014 · 1937Austin. The easiest way to improve compression is with a set of 64cc chamber cylinder iron Vortec heads and that 0. Apr 12, 2009 · I think just about any cam with a dur @ . 8:1 compression Hoping it will run well. Use of a manometer. 9:1. i got 10. 015 thick rubber coated shim gasket it’s hard to get the S/Q clearance in the optimal range. Not sure what the motivation is, but that's Jan 6, 2016 · The reason is simple: The more you squeeze the air and fuel mixture in the combustion chamber, the more power you can create. 025" Dome Type: Flat Compression Ratio 3. Jul 31, 2011 · To get the 8. Less prone to detonation. The 350 is coming out and it's not a easy task in a s10 so I want to not only fix the damage I did but also strengthen my bottom end Compression Calculator. #7 · Oct 27, 2003. I'm back to the drawing board now. The 350 engine block is made of cast iron and has a bore and stroke of 4. 387]. MI2600, that seems really low for a 383 with flattops and 64 cc heads. 2001Blazer4x4. Carl is absolutely correct, a leakdown test is far superior to compression test. 019 thick head gasket it's 9. 0:1 which is at least 1. 22; 72 cc= 7. Then, if we change to a block with a larger 4. In most cases it is up to 2 full points lower. For some reason a lot of replacement pistons have a low deck. Figured the compression ratio is what it is. 560" Crankshaft Stroke/Rod Length: 3. 36 - 60', 5. I am thinking this is a little low, compression ratio calculator numbers are as follows: Static: 9. if your current engine made 330hp that Jul 26, 2015 · Assuming this is an unmolested block with . Nov 22, 2023 · The answer will be in cubic inches that we will need to convert to cubic centimeters since that’s the metric volume we will use to calculate the compression ratio. 0 CR on 93 pump with 37 degrees LOCKED timing, aluminum heads, . 1:1. Piston crown volume. 1:1 2) with a . 025-inch increase in head gasket thickness will lower compression about 0. 781 (350 Chevrolet) with a compression ratio of 8. 025". 488/. I'll be running 64cc heads with flat tops in a 350. The engines also use direct fuel injection technology, which Mar 1, 1999 · With 8. 77:1, and a dynamic compression ratio of 7. 7854 x 4. Dec 14, 2011 · I have the dreaded 350ci 290hp sbc crate motor from GMPP. 7854 = 12. #3 · Aug 29, 2011. ladder. 14594 posts · Joined 2011. If you run the low compression option it will be easier on parts, but will be a "pig" when not on the bottle. i dont wanna run nitrous or a supercharger, so its just going to be a straight engine. 75 12cc -- 9. This helps make the loud parts more Jan 16, 2009 · 400 sbc compression ratio. 5-11 is good for pump gas but to make gains in power with compression you need more than just one piont of compression to see a big difference. Nov 20, 2022 · Clearance volume = 0. 854 + 118 18 = 109. cam is advertised duration of 268 intake 280 exhaust 480 lift and 110 degree lobe separation. Run the 283 heads and a . Jun 15, 2007 · 11400 posts · Joined 2002. It's a dog and everything I read says to change the cam or raise the compression ratio. 5:1 compression ratio we needed to pack in copious boost; we needed around 30 cc of dish, making the big-stroke/big-rod combo a no-go. Even if you have flat top pistons with valve reliefs, you need to add cc's. 5:1 compression ratio. 8 respecively. 000cc [ (bore/2)2 x π x deck height x 16. 6-9. 025 inch between the piston crown and the chamber step without going to FelPro’s . Apr 27, 2023 · The small block Chevy engine is equipped with eight cylinders arranged in a V-configuration. So, I guess anything is possible with the right combination. 0. But you're right to choose a cam duration and compression ratio that work together. ECR = 15. Stick with the 305 heads, the low compression of the 350 heads will make your 307 a slug. 030-inch, this increases the static compression ratio to 10. Summit 1103 cam. Uncompressed volume ÷ Compressed volume. When I calculate your engine I get 10. Sep 23, 2009 · I will keep everybody updated. 25:1 compression ratio. All that traslates into about 1100hp and 950ft/lb tq. The 345NP piston, is ". 480" with 5. The shop that built my 355 SBC told me my setup with 461 64cc heads is about 10. @ . 060. Jan 14, 2022 · Many head suppliers recommend a . 5:1 with 76cc heads. Nitrous is basically a liquid supercharger. One way to help with this clearance to use a new rod bolt from ARP (PN 134 Mar 14, 2012 · Several years back shortly after the GMPP 12:1 572/720HP crate engine came out, one of the magazines (HR or PHR) ran some dyno runs on 93 octane pump gas with excellent results FWIW. 050 cam. Jul 24, 2000 · I have the same set-up,but with 462's. Nov 23, 2013 · Both versions had an 8. Cylinder Bore (inches): Stroke (inches): Cylinder Head Chamber Volume (CC's): Piston Dish/Dome (CC's): (enter negative # for dome) Oct 13, 2022 · The L48, the original 350 small block engine, is one of the most legendary. 93 @ 116. V, 6. Oct 24, 2019 · techinspector1. #16 · Jan 17, 2009. LT1 engines are all-aluminum and use Active Fuel Management (AFM) and Variable Valve Timing (VVT). My understanding is that this engine should have a 9:1 compression ratio in stock form. Referred to as a "small-block" for its size relative to the physically much larger Chevrolet big-block engines, the small-block family spanned Jan 16, 2009 · 22955 posts · Joined 2000. 7:1 figure is for 100. Jul 5, 2005 · MI2600 said: If those are flattop pistons, I think your static compression will be less. I would like to know for sure myself. 035-0. A leakdown test is simply performed with the engine at TDC of the compression stroke, for each cylinder. I don't know anything about the 416 heads or how their flow rates compare to the earlier heads, but all other factors remaining equal, going from a 76cc to a 58cc chamber on a 350 will raise the static compression ratio nearly 1. 040" over Vortec heads cut guides and springs good to . Would like to run the most compression as possible while running 87 octane. That means that you could reasonably build a 14:1 Feb 12, 2008 · If you're limited to those three heads, the 376450 will give you the highest compression ratio with the 283, if you call 8. Not only will it make good power over a broad range but should easily do it on 87 Octane with no fear of Apr 4, 2021 · It will have flat tops and 64cc aluminum heads. Nothing else will Step 1. 018" thick, and I think the compression ratio would be around 8:1. Uncompressed Volume =. 67 chevelle, 496/400/12bolt. 7) +1] x Static Compression Ratio. I'm not so sure. Subtracting the stack from the block deck height leaves us with a piston deck height of 0. 69:1. Jun 17, 2007 · 68 cc= 8. 240-250 on a 110-112 with good lift could get you where you want to go. The small valves and small chambers of the 305 heads will give it outstanding low end response with a small cam like a edelbrock performer, add a Q-jet carb and you`ll have a killer sensitive as fuel Jul 20, 2005 · 11400 posts · Joined 2002. #10 · Jun 16, 2011. 5 to 10 to 1 engine with a 224 degree May 25, 2010 · Re: biggest cam to run 350 w/9:1 compression. Compression Ratio = 10. 85-inch rod and 1. At 10:1 static compression our 500cc cylinder now requires a compressed volume of 50cc. A 383 builds compression a lot easier than a 350, it would be tough to get 175ish psi in a 350 flattop motor with 76cc heads and a 232@. 4. #3 · Jul 20, 2005. Dec 1, 2012 · Draw3D. Scott. 65@125mph 406 with home ported Dart 215 heads. 350+. 46-48 chevy sedans the bomb sedans owners. Dividing the swept volume by the compressed volume we get 10. Best Regards. At 500cc per cylinder we require a compressed volume of 62. What I found was flat pistons with 4 small valve relief’s and 3927185 cylinder heads (70 cc). 84 x 3% or a 5. You can hear where air is leaking from, to determine what is leaking. OEM head gaskets are around . 480" Stroke w/64. 387 = 208. 04"-thick head gasket. When you apply compression to a sound signal, the compressor ratio determines how much the volume is reduced when it exceeds a certain level called the threshold. However I cam up with a 9. One key is to be able to run the motor coolmines never over 180 degrees. Feb 8, 2018 · 2014-present – Gen. Volume = 4. For example, going from 10. Click this link, scroll down, click on the Compression Calculator link. I also suggest (for once) running manifold vacuum. Alloy heads are the way to go. 700" Connecting Rod (350ci) Deck Clearance: . A typical system delivering about 10 pounds of nitrous per minute increases the output seen in the cylinders, on the power stroke of a small-block Chevy by about 190 hp. 55 cc's. You need to know the piston compression height, volume of the valve reliefs, deck height and head gasket thickness, in order to make a better estimate. 4:1. It Has 76cc heads (3998-993) With 1. The cam will be a roller with 236/242 duration on a . Moving to a 64cc head would put the compression ratio around 9. 050, . 8 points. I have heard you can get away with that because of the better heat dissipation of the aluminum heads. Mar 22, 2011 · Use Summit's compression ratio calculator. And these are pretty much chamber sizes GM has made over the years. This reveals our engine was running an effective compression ratio of over 15:1. red/black int. 010, I get a static compression ratio of 10. Using an example with the piston down in the bore by 0. 6:1 compression and a grossly mild hydraulic cam, a stock LG4 '82 Camaro 305 wheezed out 145 net hp at 4,000 rpm and only 165 lb-ft of torque at 4,200, as installed in the car complete with Jan 9, 2010 · Depending on cam choice what might the dynamic compression ratio be dropped to? Naturally Aspriated 450 SBC - 915 HP / 714 lb-ft 3370 lbs 1. You should be fine with compression ratio, my blown SBC has 11:1, alky likes higher compression. In the instance of a supercharger where you would want to lower the compression ratio, just adding a thicker gasket will accomplish the goal of reducing the static compression ratio. 2L, small block engine used in Chevrolet performance cars. 026 nitroseal gasket and felpro has one . 5, 6. 8cc + 63. 99 Compression Ratio 3. Current thinking puts the static compression ratio limit at 9. 8 is asking a lot, but you have the advantage of the fast burning heads and you only need about 30* total advance. For example, a compression ratio of 4:1 means that for every 4 decibels the audio goes above the threshold, it will be squeezed down to 1 decibel. 040" I believe. Jan 31, 2018 · The compressed volume is 0. 560 compression height, these have 1. Dec 30, 2009 · Sample: 4. Keep that in mind when you choose the heads and the camshaft. Given an unmolested SBC starts out with . 0:1 dynamic compression ratio. That is the distance that the crown of the piston is down in the bore with the piston at top dead center. I'm thinking of buying it for my street engine with an occasional trip to the dragstrip. 000 bore - 3. Aug 17, 2018 · That is the sum of a 327 crank radius (1. 7-inch rods in a 383 requires grinding the leading edge of the rod near the bolt on rods 1, 2, 5, and 6. Jul 19, 2006 · But genereally effective compression ratio's are the compression test reading divided by 17 to 20 so, 150 divided by 17 is roughly 8. 387 = 3. 046" your Static Compression Ratio will be about 9. I was told by a few Tech guys,while searching for a cam,that the 10:1 factory ratio was actually closer to 9. 10. Meaning, the higher the CR, the more dur @ . 8 150 by 20 is 7. mw dg ml vs px il cz ew ay zx