Re: rams horn exhaust
http://www.mre-books.com/chevy/engines/parts_interchange/exhaust.html
3747042 - RH rams horn ex manifold
1965 Passenger 283/195hp
1965 Corvette 327/250hp & 300hp auto trans w/ac
1966/67 Passenger 283/195hp and 220hp w/o A.I.R.
1966/67 Passenger 327/275hp w/o A.I.R
1966/67 Corvette 327/300;350hp w/o A.I.R.
1968 Passenger 307/200hp with auto trans
1968 Passenger 327/250 and 275hp
On the LH, the closest number I can find is 3932473 which is curved outlet type:
1969 Passenger 327/235hp w/auto with A.I.R.
1969 Passenger 350/250,255,300hp manual trans with A.I.R
1969 casting was tapped for A.I.R
1970 Passenger 350/250,300hp w/o A.I.R.
1970 Passenger 400/265hp
1970 casting was not tapped for A.I.R.
thanks for posting the additional source, info on those manifolds as IM sure that info helps, as those original manifolds are becoming harder to find
HERES INFO DCARINS POSTED
but before you decide that RAMS HORN EXHAUST is all you need,
be aware that it makes a HUGE difference what rpm,your engine will be expected to make power in,your engines displacement, your cam timing and how restrictive the exhaust system is behind the headers or exhaust manifolds. at low and mid rpms a well designed exhaust with 2.5" pipes may act like an extended header collector and you can make reasonably good torque, but look closely at the graphs and the rpm range they were plotted over, notice the RAMS HORN EXHAUST makes for decent results but its EFFICIENCY is falling rapidly as ENGINE RPMS INCREASE
if your engine had a fairly larger 383-406 displacement, a decent cam with a fairly tight LSA lets say something with about 240 degrees or more at .050 lift or more and compression up at or over about 10:1 you would be strangling an engine designed to produce power up in the 6500rpm range.
RAMS HORN MANIFOLDS work very well at off idle to about 4000rpm but headers usually produce better power above 4000rpm
but if the exhaust system behind the headers or the cam timing is not set up to maximize the higher rpm port flow rates and cylinder head flow or intake flow rates,are restrictive theres not much to be gained with headers, remember headers by design must operate with near zero back pressure to maximize cylinder scavenging
look closely at the dyno results posted lower in this thread, notice the restrictive exhaust has already made the torque start dropping off by about 3500rpm and remember the torque curve closely follows the cylinder fill or volumetric efficiency, so its obvious the rams horn exhaust or the exhaust behind them are restricting flow
your torque curve closely matches the cylinder fill and scavenge efficiency
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I had my newly built, mild 383 run on a dyno. It is going in my 64 Impala, so good torque was important as was keeping the idle civilized enough for power brakes and air conditioning. Given those constraints and the stock block, heads and intake manifold tow work with, it came out rather well.
YouTube Video of some of the dyno runs
One of the things I wanted to test was the headers vs stock rams horns exhaust manifold topic that seems to come up from time to time. Since this engine is made of stock castings, overall breathing ability is rather limited. So the headers never really get a chance to show much advantage at the extreme top end. The rams horns are reproduction 2.5 inch manifolds that have the correct casting numbers on them. They were mildly ported and the anti-reversion bumps removed.
I have to say, that in my test conditions, using the rams horns is a no brainer. Why deal the disadvantages of headers for such a small gain?
What made a bigger impact on performance was adding the 2.5 to 2 inch reducers to the pipes, to simulate what actually happens at the muffler on the stock exhaust system on the 64 Impala. It also points out that an all 2.5 inch exhaust system would be an advantage.
And just for fun I did a run with the stock air cleaner and filter in place, along with the 2.5 to 2 inch reducers on the exhaust (trying to simulate how it will be once installed in the Impala). On a 64 Impala the air cleaner horn has a remarkably small opening and I was expecting it to really cause a hit on the performance.
Surprisingly, the air cleaner/filter had little impact. This is probably highlighting how restricted the intake manifold is. I am thinking it might be worth porting the intake a bit to pick up some more power higher up the RPM range. I don’t think a mild port would have much if any effect on idle quality, since it is a 383 breathing through a 327’s intake.
thats very impressive info, but I must point out, BEFORE you go thinking rams horn exhaust manifolds are almost as effective as headers,.....you need to remember that its the complete combo, not just the swap from headers from rams horn exhaust manifolds alone that can maximize the results keep in mind a great deal of what you can expect to gain from use of headers is dependent on having the exhaust headers tuned to scavenge the cylinders and thats dependent on both the header primary length , diameter,and collectors length and diameter,being correctly matched to the engines displacement, compression and cam timing, and having an exhaust system that has LESS than 1 PSI in back pressure, the best headers in the world feeding into an exhaust system with significant back pressure will result in little gains if any over a rams horn manifold.
Id also point out that when you see a dyno torque curve on a 383 sbc like that that falls rapidly from only 3500rpm, the cam used was very obviously too low in duration for the application and/or the exhaust was restrictive and hurting power (probably the case here) because theres a rapid drop in torque as the engine rpms build , thats almost always an indicator of a restricted air flow rate, it can be because the cams not allowing the intake ports to flow to their full potential but it can be because as the rpms build so does the volume of exhaust gases which increases the effect of any restricted exhaust, because of the rapid build-up in back pressure
your engines torque curve is almost always a good indication of the engine volumetric efficiency
Chevy Exhaust Manifolds Casting Numbers
Use these casting numbers to identify the exhaust manifolds you have.
Casting Number Years Engine Side Comments
336706 74-78 350 RH
336707 74-78 350 LH
336708 74-78 350 RH
336709 74-78 350 RH Camaro & Z-28 with A.I.R.
336710 74-78 307, 350 & 400 LH Chevelle,Camaro,Z-28,Nova and Passenger with A.I.R.
346222 74-80 307, 350 & 400 RH Chevelle,Camaro, Nova and Passenger with A.I.R.
346247 75-77 262, 350&400 LH Chevelle,Camaro Monte Carlo and Passenger 110,145,155,175HP 346248 75-77 262, 350&400 RH Chevelle,Camaro, Monte Carlo and Passenger 110,145,155,175 HP
354432 75-76 262 RH 110 HP
354433 75-76 262 LH 110 HP
364753 76-80 307, 350 & 400 LH Camaro, Monte Carlo, Malibu and Passenger
372243 74-83 307, 350 & 400 RH Corvette and Replacement manifold
462697 77-79 267 & 305 LH Monte Carlo and Malibu
462698 77-83 267 & 305 RH Monte Carlo and Malibu
474008 78-82 267, 305 & 350 RH
745994 80-86 267 & 305 LH
3704791 55-56 265 LH Corvette and Passenger 195 HP
3704792 55-56 265 RH Corvette and Passenger 195 HP
3725563 56 265 LH & RH Corvette and Passenger 210 HP 2-Bolt Flange
3731557 56 265 LH Corvette and Passenger 225 HP
3731558 56 265 RH Corvette and Passenger 225 HP
3732498 58 283 RH Corvette FI
3733975 57 283 LH Corvette and Passenger 220, 245, 250, 270 & 283 HP
3733976 57 283 RH Corvette and Passenger 220, 245, 250, 270 & 283 HP
3737902 62-65 327 RH 300, 340, 360, 365 & 375 HP 2.5" Outlet
3746563 65 327 LH 300 HP
3747038 58-65 283 & 327 RH Corvette and Passenger 220, 250 & 300 HP 1.9" Outlet
3747042 58-68 283, 307 & 327 RH Corvette and Passenger 195, 200, 220, 250, 270, 275, 290, 300 & 350 HP 1.9" Outlet
3747938 64 327 LH & RH 250 & 300 HP
3747942 65 327 LH & RH 250, 350 & 365 HP
3749965 58-63 283 & 327 LH Corvette and Passenger 230,245,250,270,275,290,300 & 315 HP
3750556 58-65 283 & 327 RH Corvette and Passenger 230,245 250,270,275,290,300 & 315 HP
3780728 64-67 327 LH Chevy II
3790729 64-67 283 & 327 LH 195, 220, 250, 270, 275, 300 & 350 HP 2.0" Outlet Chevy II
3790730 64-65 283 & 327 RH 220, 250 & 300 HP 1.9" Outlet Chevy II
3791162 65-66 283 & 327 RH Chevy II with AC
3791182 66-67 283 & 327 RH Passenger with AC
3797901 62-63 327 LH Corvette 300, 340 & 360 HP
3797902 62-65 327 RH Corvette 300, 340, 360, 365 & 375 HP 2.5" Outlet
3797942 63-65 327 LH & RH Corvette 300, 360, 365 & 375 HP 2.5" Outlet
3834947 64-68 283, 307 & 327 LH Chevelle 195, 200, 210, 220, 250, 275, 295, 300, 325, 350 & 365 HP 2.0" Outlet
3836968 55-56 265 RH Corvette and Passenger 195 HP
3837069 55 265 LH Corvette and Passenger 195 HP
3840715 64 283 & 327 LH Chevelle
3840912 64-68 283, 307, 327 & 350 RH Chevelle, Camaro and Nova 195, 200, 210, 220, 250, 275, 295, 300, 325, 350 & 365 HP 1.9" Outlet
3846559 64-71 327 & 350 LH Corvette 250, 270, 300 & 350 HP 2.0" Outlet
3846563 64-65 327 LH Corvette 300, 350 & 365 HP 2.5" Outlet
3846659 66 327 LH 350 HP
3849288 64-67 283 & 327 RH 195, 220, 275 & 350 HP 1.9" Outlet Chevy II
3849290 64-67 283 & 327 RH 195, 220, 275 & 350 HP 1.9" Outlet Chevy II with AC
3855163 65-68 283, 307 & 327 LH Passenger and Truck 195, 200,220,250 & 275 HP 2.0" Outlet
3872723 66-67 283 & 327 LH 195, 220, 275 & 350 HP 2.0" Outlet Chevy II A.I.R.
3872729 66 283 & 327 LH Chevelle 195,220, 275 & 350 HP 2.0" Outlet A.I.R.
3872730 66-68 283, 302, 307 & 327 RH Chevelle, Camaro & Z-28 200, 210, 220, 250, 275, 290, 325 & 350 HP 1.9" Outlet A.I.R.
3872738 66-67 283 & 327 RH 195, 220, 275 & 350 HP 1.9" Outlet Chevy II
3872741 66-68 283, 307 & 327 LH Passenger 195, 200, 220, 250 & 275 HP 2.0" Outlet A.I.R.
3872765 67-71 327 & 350 LH Corvette 300, 330, 350 & 370 HP 2.0" Outlet A.I.R.
3872778 66-68 283, 307 & 327 RH Corvette, Passenger and Truck 195, 200, 250, 275, 300 & 350 HP 1.9" Outlet A.I.R.
3887186 66 283 RH 220 HP 1.9" Outlet
3890424 64-67 283 & 327 RH Chevy II
3892679 66-68 283, 302, 307, 327 & 350 LH Chevelle, Camaro and Z-28 195, 200, 210, 220, 250, 275, 290, 295 & 325 HP 2.0" Outlet
3892683 66-68 283, 302, 307, 327 & 350 LH Chevelle, Camaro and Z-28 195, 200, 210, 220, 250, 275, 290, 295 & 325 HP 2.0" Outlet
3893604 66-68 283 & 327 RH Passenger A.I.R.
3893608 67-68 283, 302, 307, 327 & 350 RH Chevelle, Camaro and Z-28 195, 200, 210, 250, 275, 290, 295 & 325 HP 1.9" Outlet
3896956 67-68 283 & 327 RH Truck
3905364 69-72 307, 350 & 400 RH Truck
3932376 69-70 307, 327, 350 & 400 RH Chevelle and Camaro 200, 210, 250, 255, 265 & 300 HP 1.9" Outlet
3932461 69-74 327 & 350 LH & RH Corvette 190, 195, 200, 235, 255, 300, 330 & 350 HP 1.9" Outlet A.I.R.
3932465 69-70 327, 350 & 400 RH Passenger 235, 250, 255, 265, 300 & 350 HP 1.9" Outlet
3932469 69-70 327 & 350 LH Passenger 235, 250, 255 & 300 HP 2.0" Outlet
3932473 69-70 327, 350 & 400 LH Passenger 235, 250, 255, 265 & 300 HP 2.0" Outlet
3932481 69 350 RH Corvette
3940972 67 350 RH Camaro 295 HP
3942527 69-70 302, 307, 327 & 350 LH Chevelle, Camaro, Z-28 and Nova 200, 210, 250, 255, 290, 300 & 360 HP 2.0" Outlet A.I.R.
3942529 69-70 302, 307, 327, 350 & 400 LH Chevelle, Camaro and Nova 200, 210, 250, 255, 290 & 300 HP 2.0" Outlet
3946826 69-70 302, 307, 327 & 350 RH Chevelle, Camaro, Z-28 and Nova200, 210, 250, 255, 290, 300 & 360 HP 1.9" Outlet A.I.R.
3959562 72-74 307, 350 & 400 RH Chevelle, Camaro and Z-28 115, 130, 145, 150, 160, 165, 170, 175, 180, 185 & 245 HP 2.0" Outlet A.I.R.
3973432 70-74 307, 350 & 400 RH Chevelle, Camaro, Nova and Passenger 115, 130, 150, 165, 170, 175, 180, 200, 245, 250, 255, 270 & 300 HP 2.0" Outlet
3986330 69-73 302, 307, 327 & 350 RH Camaro and Z-28 200, 210, 245, 250, 255, 290, 300, 330 & 360 HP 1.9" Outlet A.I.R.
3989036 71-75 350 LH & RH Corvette and Passenger 165, 195, 200, 205 & 270 HP 2.0" Outlet with and without A.I.R.
3989041 69-74 302, 307, 327, 350 & 400 LH Camaro, Z-28 and Nova 115, 130, 145, 150, 160, 165, 170, 180, 185, 200, 210, 245, 250, 255, 290, 300, 330 & 360 HP 2.0" Outlet with and without A.I.R.
3989043 70-73 307, 350 & 400 LH Chevelle, Camaro, Nova and Passenger 105, 115, 130, 145, 150, 165, 175, 185, 200, 245, 250, 255, 270 & 300 HP 2.0" Outlet with and without A.I.R.
3989055 69-72 307, 350 & 400 LH
3997742 71-78 307 & 350 RH 2.0" Outlet
3998902 72-78 307 & 350 RH
10045315 88-94 305 & 350 LH
10045317 88-94 305 & 350 LH
10045317 88-94 305 & 350 LH
10046123 87-92 305 & 350 LH
10046139 84-85 350 LH
10046140 84-85 350 RH
10055734 87-91 350 RH
10092901 89-91 350 LH
10092903 89-94 350 LH
10092905 89-94 350 LH
10108437 87-93 305 & 350 RH
10128448 91-93 305 & 350 LH
10128483 91-93 305 & 350 LH
10166144 91-94 350 RH
10166145 87-90 305 & 350 LH
10166147 89-94 305 & 350 LH
10166158 89-94 305 & 350 RH
10168494 94 265 & 350 LH
10207656 93-94 350 LH
10207657 93 350 RH
10433037 82-86 305 LH
12550621 94 265 RH
12550622 91 350 RH
14007400 80-86 267 & 305 LH
14014437 80-84 305 LH
14014438 80-84 305 RH
14014459 81-86 305 & 350 LH
14014500 79-86 267, 305 & 350 RH
14022625 80-81 305 LH
14031361 82-86 305 RH
14031376 81-86 350 RH
14034069 81-86 350 RH
14034075 81-86 305 & 350 LH
14043373 82-86 305 LH
14050233 83-86 305 & 350 LH
14050282 83-87 305 & 350 RH
14050287 82-86 305 LH
14057029 84-85 350 LH
14057030 84-85 350 RH
14060630 81-86 350 RH
14060633 81-86 305 & 350 LH
14067365 77-86 267, 305, 350 & 400 LH
14068667 85-88 350 LH
14068670 85-88 350 RH
14071200 83-86 305 RH
14075611 83-86 305 LH
14079295 85-86 305 & 350 LH
14079296 85-86 305 & 350 RH
14087511 86-91 350 LH
14087512 86-91 350 RH
14093653 87-90 305 & 350 LH
14093654 87-90 305 & 350 RH
14093655 87-90 305 & 350 LH
14093658 88-94 305 & 350 RH
14093660 87-90 305 & 350 RH
14093682 87-90 305 & 350 RH
14094045 87-90 305 & 350 LH
14094063 87-92 305 & 350 LH
14094064 87-92 305 & 350 RH
14094065 85-88 350 RH
14101054 87-88 305 & 350 RH
14102016 88-94 305 & 350 RH
14102018 89-94 305 & 350 RH
14103206 87-91 305 & 350 RH
14103207 87-91 305 & 350 LH
329225 73-76 454 LH Chevelle and Passenger with and without A.I.R.
353028 73-76 454 LH Chevelle and Passenger with and without A.I.R.
353030 73-76 454 LH Police
3732793 58-61 348 LH Passenger
3732794 58-61 348 RH Passenger
3767583 59-61 348 & 409 LH Passenger
3767584 59-61 348 & 409 RH Passenger
3814682 62-64 409 RH Passenger
3814683 62-64 409 LH Passenger
3822925 62-64 409 LH Passenger & Z-11
3822926 62-64 409 RH Passenger & Z-11
3855161 65 409 LH Passenger 340 & 400 HP
3855162 65 409 RH Passenger 340 & 400 HP
3856297 65 396 LH 325 HP
3856301 65 396 LH 425 HP Corvette
3856302 65 396 RH 425 HP Corvette
3856306 65 396 RH Passenger 325 HP
3857297 65 396 LH Passenger 325 HP
3868874 65-66 396 RH Chevelle 325, 360 & 375 HP Z-16
3869925 65 396 LH Chevelle 375 HP Z-16
3872770 66 396 RH
3880827 66-69 427 & 454 LH Corvette
3880828 66-72 427 & 454 RH Corvette 270,365,390 &425 HP with and without A.I.R. LS-5 & LS-6
3880869 70-72 454 LH Corvette 365 & 425 HP with and without A.I.R. LS-5 & LS-6
3883827 66 427 LH Passenger
3883828 66 427 RH Passenger
3883999 66 396 LH Chevelle 325, 360 & 375 HP
3884504 66-67 396 & 427 RH Passenger 325, 385 & 390 HP
3892307 66-67 396 & 427 LH Passenger 325 & 390 HP
3902401 67 396 LH Chevelle
3904399 66 396 LH
3909879 67-70 396, 427 & 454 LH Chevelle, Camaro and Nova 325, 350, 375, 425, 430 & 450 HP LS-6 COPO
3909880 67 396 RH Chevelle and Camaro 325, 350 & 375 HP
3914613 68-70 396 & 427 LH Passenger 265, 325, 335, 345, 390 & 425 HP
3916178 68-70 396, 427 & 454 RH Chevelle, Camaro, Nova and Passenger 325, 350, 375, 425, 430 & 450 HP COPO LS-5 & LS-6
3969869 70-74 454 LH Corvette 270, 365 & 390 HP with and without A.I.R. LS-5
3989310 71-72 402 & 454 RH Chevelle, Camaro, Monte Carlo and Passenger
3989343 71-72 402 & 454 LH Chevelle, Camaro, Monte Carlo and Passenger
3994045 73-75 454 LH Police
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