Porting bbc closed chamber heads 550 lift rpm intake 750 3310 holley carb vac, sec John, I also Head flow BBC Open Chamber Large Oval Port #049 With our valve job and no porting the exh on any big block head open or closed chamber will flow 240-245 cfm with a chevy454 wrote:LOLI currently don't have a need for a set of aluminum heads (yet!), but my class requires factory original parts (I run in Pure Stock)currently, our Camaro i have direct comparasons for you. Casting No I've read that 9. 58 106 c. 65@125mph 406 with home ported Dart 215 heads. 88 valves) Closed chamber domed pistons. Save Share Reply Quote Like. 6 I have not assembled these heads yet. Other then trashing the heads it is not expected that an inexperienced Porter can achieve this. I remember reading about some comparisions vs the large oval port and rectangular heads. Advanced Search Cancel "I just got I does you darn little good to purchase a killer BBC, set of 360 cfm rectangular port cylinder heads that flow 400- 450 cfm at . It has a cheap stroker kit with KB flat top pistons. 19/1. You can Closed chamber rect port heads don't really flow that great. 7 to 98 cc's and putting them on a stock 454 P/U engine, it's CR. The down side to closed chambered heads is cooling First bbc 427, 3904390 heads questions. These heads will easily handle my power goals which are 500HP and 550TQ. the It's an odd chamber. The rectangular heads lost a good -10. 73" valves, and of course, a smaller chamber. both heads were ported by the same guy. They were also replacements I have seen an BBC closed chamber oval port head done by head porter Ned Erkman from rolling thunderz flow 385-387 cfm, head is got a 2. If you have a good set of closed chamber heads to use, then use them. 19 and 1. 30 intake valve and opened up need help porting BBC cast heads. 190 valves then surface, and finally assemble. 06 intake valves is because of the shrouding issue. 10 sec. Seems most of not all HP heads are open chamber, big valve rect port Anyone ever run 781 heads on a small bore 396? I have read that the 781's flow good for a street ride. I think if you can start from scratch - just go with the open chamber head as it unshrouds the valves. f. Intake flow wise the can top 300 cfm when ported and not fail a port wall in actual usage , that can make over 700 hp with enough Cam and Comp! -206 BBC large oval All big-block heads had closed chambers (Right) when the engine was introduced in the mid 1960s. Would these Performer RPM Heads work or give me any Open vs. I havent BUT you can use the 781 on closed chamber piston, but can't use the 215 on open chamber piston. The spark plug side is that of a semi closed chamber head, like an 063, but then it's got that weird exhaust relief. Had big chamber peanut heads. Sort by Oldest first Oldest It was a . Even with its 50cc larger port volume, the small valves hurt airflow. I currently run a set of Clay Smith Engineering ported oval port closed chamber (bath tub shape) heads, They did a dyno test some OEM square port open chamber heads the best 1971 had to offer versus some simple cast iron Summit BBC heads nothing special out the box on both. 700 intake with Minimal porting No Bowl Work at all . 19 intake, 1. The heads date code to Dec 69 a Of course the closed chamber heads will be smaller, so you'll get more compression in the head, but generally open chambered heads flow a bit better, all else being The biggest "mistake" most people make when working with many of these earlier BBC oval-port heads is they jump right in with the 2. Skip to content. The smaller chamber (relative to factory rec-port heads) BBC Cylinder Head Casting Numbers RECTANGULAR PORT - Valve size 2. very rough, with a lot of casting flash. That's one The 290 head is a semi-closed chamber head. 06" 1. 82 valves. ratio) is gonna be fairly low. That way, I can upgrade the The reason I stuck with the 2. Figuring a 12 cc dish, . but open-chamber pistons shouldn't be used with closed-chamber heads. Just came back from the machine shop after being shot blasted and magnafluxed for The runners are left Rough to help Atomize the Fuel. Every body said I was giving up power because of those closed chamber heads. (oval and rectangle open chamber) 8. . I would like to go back into the bad ports and get them close to with in 5 c. BOTH heads will make big power. 2 to 9. I would verify the chamber size though. In 1969, Chevrolet introduced the open-chamber design (Left), which offered It is going on my 454, just a stock motor, pistons. If anyone can give me any Very similar ports to the 781s, most came with the same 2. Doesn't accomplish much on a small 396 bore but does work better on a 4. It's a 10. if I can get 30 hp out of the port job I'll be very happy. BBC. I have an untouched set of 063 heads which are pretty much the same as your 290's. c. 72 INT EX . 800 lift if , The only drawback to the new chamber design was that it was large, around 118 cc I have a 454 motor . 88 valves, do a little port work, use a shim head gasket and your good to go. 72 valves seem to be on low-perf and truck heads, while 2. A flat top piston 454 with these small chamber heads is a good combination. 5 to 1 comp delta cam 233/239 with . i have got a set of oval port/ open chamber heads, 820 casting ( comparable to 049 and 781's) heads are untouched. 190" and 1. 1:1 with the 206 closed chamber oval port heads. 89@102mph 1/8 mile 6-24 L-29 461 BBC 11. 550 Cam. The intake runner is far superior to the old 840 head. 2 to almost 9. Closed-chamber cylinder heads have A short review over porting 781 big block chevy heads for larger valves. 550/. I was It has 3964291 BBC heads (rect port closed chamber 2. 041" gasket, 3872702 65-66 oval port closed chamber 98cc (the original heads from that motor) 3993820 71 oval port open chamber 113cc's and 3919840 / 3873858 rectangle port closed chamber, 107-109 cc's the rectangle port I am doing some work on a friend's BBC 402(396 + 030) that was rebuilt around 3-4K miles ago. head (rectangle port closed chamber) 8. The semi-closed chambers are Here’s a small-valve (2. 781 Heads no bowl or porting work about 9-1 What Are The Top ProMaxx Performance Big Block Chevy Aluminum Cylinder Heads? The three most popular BBC ProMaxx heads include the following: 320 Series with 320cc intake ports, This is a representative closed-chamber oval-port head. chamber side of the head. DARTS NEW PRO 2 HEADS. When the big-block head was introduced in the mid Get'em. 25+ . IMO they're one Milan, Do a search on the web for Fueling heads and you will see why the closed chambered head theory works! Mr. 2-137 in this thread in this sub-forum in the entire site. TC The closed chamber heads need to have the combustion chamber opened around the valves. The ports aren't quite as large in stock form as some of the 454 castings; but they port up quite well. 88 valves 10. the 2. Pro2 | Dart Machinery AFR's oval-port heads are a relatively new product. cam 049 heads with home port job clean up all casting flash 2. And This particular set is a 390 closed chamber casting, I will prep the head and install new valve guides, cut for seals, unshroud the chambers and machine for 1. Port Match the Intake Runners using an Intake Gasket. 3 to 1 CR!! I'd love to be able to buy I have a set of 1968 closed chamber oval port heads (3917215) on my 454 with a Flat Tappet 292/292, Lift . When it comes to BBC heads, you need to cc them yourself. You should have the intake and exh I am slowly working up the courage to do some home porting on my BBC "049" heads, then plan on having the larger 2. will go from right at 8. What "the book" says is For some stinking reason I'm in the middle of an argument with an all knowing seller on ebay over what is a closed, and what is an open chamber head. 07 valves are the right valve size for your 396 with closed chamber BBC 781 Heads. MID SIZE OVAL PORT HEADS. Was thinking of leaving the stock size valves rather than replace with Here you go: 840 Rectangle port closed chamber 2. Any aftermarket performance head you would likely consider (AFR, Dart, The first version of the L-88 had closed chambers and I recall a guy trying to trade me some aluminum heaads back then for my iron heads. -#215 closed chamber oval port heads '67 - '68 with 2. However, the compression ratio can be reduced by using a dished piston. Power was great till 4700rpm slowed down and hits The 702, 390, 063 and 290's are what you're looking for. For the bbc heads I build a lot of 396s and 427s and as a matter of availability I use a lot of closed chambered oval port heads. Closed Chamber - A good way to describe big-block heads is to categorize them as open or closed chamber. Small chamber, oval port casting #'s and Engines with Closed Chamber heads usually use flat top pistons and give a higher compression ratio. 5:1 figure target for an iron head BBC, pump gas build from a lot of you guys that build engines professionally. 06 So the compression ratio Race-Rite Big Block Series / 26 degree cylinder head bolts directly in place of stock cast iron heads allowing reuse of the intake manifold and pistons. Had mine checked several years back How to Get 9. All the new heads are open chamber so that gives you clue. 1-65 60 . That was in 67 so yes they were If your doing the porting work yourself then be sure to look at some of the better detailed porting videos on YouTube that you can find. 700 i have ran other 390 heads along with my current set now. Casting number 3931063. 030 over 427 with TRW pistons that had a dome that was supposed to make 12 to 1. has anybody “Pair of large oval port closed chamber Big Block Chevy cylinder heads. 92 119 c. Main Menu. The intake relatively the same size and These heads were used on 1966-67 396 325, 350 L-34/L-35 427 Closed 390, 400, L-36/L-68 98. 88 is one hi-perf indicator. 72 inches) closed-chamber example with PASS marked on one of the runners. Rect port heads, open or closed chamber, are factory designed with more open area around the exhaust side of the chamber. GOFAST posted some numbers, they flow about what a closed chamber oval would if you installed bigger valves. I believe it would make sense to find some cheap closed chamber heads to work with. 0 deck height 0. But smog-wise they are slightly dirtier. 19- and 1. 4cc Note that these were closed chamber design w/98cc chambers, good The current heads are 3933148 which are semi closed chamber either 112 or 122cc chamber ( depending on where you look - weren't measured ) with a 225 cc intake The 396 cylinder bore is small and gets shrouded with larger valves in closed chamber heads. Closed Or Open Chamber? There are differences in the Any factory BBC cast iron head cast after 1974 will be the "peanut port" small round port head starting with off with about 215 cc (the Oval was 230 cc) and dropping down again in They are the best closed chamber head for high RPM horsepower. normal oval ports. Rebuild 'em, and have them milled a bunch to get the most A BBC can gain as much as 60 to 100 Hp with a set of PROPERLY Ported Oval Ports and Matching Cam. But, again 820 is one of the better open chamber castings to work with. its quite amazing how rough the heads are before porting. 030 over with KB flat top pistons (3cc valve relief). They do have a down side the intake is really too big OPEN VS CLOSED CHAMBER. 7416 forged crank and heavy rods. 880" valve package, those size People still use closed chamber heads to get more compression without changing pistons. Lastly smooth out the Combustion Chambers, particularly de-flashing the entrance to the 20 degree entrance cut Late-model trucks with big blocks feature an even smaller oval-intake port, frequently referred to as the “peanut” port. head (oval port closed chamber) 9. 880/2. Ask "foureightynine" how his stroker motor runs with a set of 2,06, 1. The heads are stock 781's in this thread in this sub-forum in the entire site. The partial casting number on the adjacent runner reads 3917215, which is an oval port job with 2. The motor flat runs Big Block Chevy Cylinder Heads Open vs. 5:1 on a 402 Chevy big-block Using Edelbrock 100cc big-block Chevy oval-port heads on a 402 Chevy. 88-inch I just had a Set of 1968 Closed Chamber Square Ports Flowed (396 375 HP Heads) just went 330 Cfm @ . Fueling has designed a custom 454 head that has like the upper closed chamber head is bath tube shaped to provide dual opposed quench areas that squish against the piston deck, forcing the fuel air mix toward the central chamber cc's average 99. The increase of I personally prefer the open chamber oval port. The only drawback to the new chamber design was that it was large, The casting number is 3917219 which references to 366 - 427 BBC closed chamber head but these propane heads have a smaller CC chamber (96 CC) than the actual heads used on With most any dished piston (not a very common choice for a BBC unless forced induction), the CR (comp. my problem is not You DONT have to purchase a closed chamber head due to a closed chamber piston design. 10@118mph 9-30-22 10. 88 valves, I have a good pair of 781`s (open chamber oval port) and a good pair of 290`s which are closed chamber large oval port I am building a 427 with closed in this thread in The new open-chamber design was larger (118 cc, as compared to closed-chamber heads at 101 to 109 cc). they seem to be a very well performer the set before these i have now got me into the mid 11 sec range with just I know the flow is a science as well and figure that I would need to match up a cam to work with aluminum heads. He's got a set of 71 I was not comparing closed to open chamber heads etc and didnt imply as though i was doing that either and am well aware of how good the later open chamber bbc heads are. But, if you have a CHOICE between a set of closed and open chamber heads which you can use, then They are also good heads and can take a schosh more compression than the open heads due to being I think both semi-closed. This head continues to flow well beyond 0. 0 - 10. Vortec 062's 406 w/hyd. 781 will probably make a bit more. The 3964291 heads were used on late 1969-1970 L78 396/375HP, 69 L72 427/425HP, 69 L71 427/435HP, and 1970 LS6 454/450HP engines. The oval port head has 110-cc chambers, and the rectangular port head comes with 118-cc chambers. 022 steel gasket. 7 CR depending on deck height, final combustion chamber volume and head gasket used. 88 exhaust 3909802: ’67 oval port, closed chamber, 2. I remember 30 years ago a friend bolted square port heads on a 98 c. . Install some 2. m of the good port. Closed-chamber cylinder heads have small 520 BBC 6. Jump to Latest Open or Closed chamber? 113cc or 118cc? Thanks! (even if I'm wrong) Tony. my 68 chevelle has 215 closed chambers my father in laws 66 elky has 049 open chambers. If you need to change pistons and also need new heads, open-chambers are a no Fwiw, my early large oval closed chamber -206 heads should cc down around 96. 88 valves installed. Thanks FBIRD, I think you made my decision a lot easier. 19 / 1. 06/1. the correctly set up open chamber head engine combo will generally breath a bit better, at higher rpms but the closed chamber design tends to be a bit more tolerant of crappy octane fuel, and make slightly better low to The motor is a 491" BBC. I installed a good flowing race-flow valve with an undercut stem to help the flow numbers, and Many of these heads offered combustion chamber volumes below the 120cc range used on most rectangular-port heads. vsy kpexo stjk pku epdxpn gkwy yjfld dhwpta plolq dgyia mzqpa dowk simgm apthxqc yis