rams horn exhaust info you might need



rams horn exhaust info you might need

Postby grumpyvette » October 22nd, 2008, 6:21 pm

theres three common versions, of the rams horn exhaust manifold design.
heres some threads to look thru, don,t ignore the sub links, keep in mind stock exhaust manifolds, even the rams horn corvette 2.5" versions start to be restrictive by 4000rpm, and on any headers a low restriction exhaust behind the manifolds or headers collectors are MANDATORY if you expect the headers to work anywhere near full potential.

viewtopic.php?f=56&t=1303

viewtopic.php?f=56&t=495

viewtopic.php?f=56&t=3155


http://www.naparts.net/Exhaust/Exhaust- ... 90544.html

the 2" exhaust found on several Chevy cars

http://www.performanceexhaustplus.com/p ... rod_id=125

Image

the 2.5" versions originally exclusive too corvettes

http://www.castheads.com/corvette_systems.php

the improved stainless aftermarket design

http://www.speedwaymotors.com/p/5425,41 ... folds.html
Image
http://www.speedwaymotors.com/Stainless ... ,5425.html
http://www.speedwaymotors.com/ProductSu ... s&deptId=0
Image
IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
grumpyvette

User avatar
Site Admin
Site Admin
 
Posts: 14105
Joined: September 14th, 2008, 1:40 pm
Location: florida

Re: rams horn exhaust

Postby dcairns » February 19th, 2010, 4:37 pm

For "newer" cars with alternators, Corvette Paragon has a correct reproductions of 2.5 inch rams horns. Only down side is the price.

Casting #3846563 2.5 inch rams horn. Correct for 1964 passenger 327/300 and Corvette 327/300,365 and 375 . The down

http://www.corvette-paragon.com/p-355237-exhaust-manifold-lh-2-12.aspx
Image

Image

Right hand casting 3797942. Correct for 1964 passenger 327/300/365/375 and Corvette 327/300 and 365.

http://www.corvette-paragon.com/p-357760-exhaust-manifold-wchoke-tube-rh-2-12.aspx

Image
Image

YOULL GENERALLY WANT TO USE AN EXHAUST PIPE DIAM. AT LEAST AS LARGE AS THE RAMS HORN MANIFOLD EXHAUST DIAM>



Image

There is a huge difference in flow potential between the 2.5 inch corvette exhaust design and standard pass car 2 inch rams horns.


Image

They fit and look just fine.

Image
Image
dcairns

 
Posts: 1
Joined: January 18th, 2010, 10:45 pm

Re: rams horn exhaust

Postby grumpyvette » February 19th, 2010, 5:11 pm

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

Image
your torque curve closely matches the cylinder fill and scavenge efficiency

READ THRU THESE RELATED LINKS
viewtopic.php?f=56&t=495

viewtopic.php?f=52&t=5154

viewtopic.php?f=52&t=1070

viewtopic.php?f=56&t=1503

viewtopic.php?f=56&t=1303

viewtopic.php?f=55&t=8485&p=29767&hilit=volumetric#p29767
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.


Image




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?


Image




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.


Image




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.


Image



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

Image

Image

your engines torque curve is almost always a good indication of the engine volumetric efficiency



viewtopic.php?f=56&t=495

viewtopic.php?f=56&t=1166

viewtopic.php?f=56&t=961

viewtopic.php?f=56&t=3155

viewtopic.php?f=56&t=1303
IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
grumpyvette

User avatar
Site Admin
Site Admin
 
Posts: 14105
Joined: September 14th, 2008, 1:40 pm
Location: florida

Re: rams horn exhaust info you might need

Postby 59Lenoir » July 6th, 2011, 1:54 pm

Image



so would it be worthwhile to put these on an otherwise stock 283/2bbl with soon-to-be-dual exhaust? There is a possibility of future cam/head/carb enhancment.
59Lenoir

 
Posts: 233
Joined: July 1st, 2011, 2:21 pm

Re: rams horn exhaust info you might need

Postby grumpyvette » July 6th, 2011, 1:58 pm

http://www.speedwaymotors.com/Dorman-25 ... ,9133.html

why not pay a good deal less, they are better than most stock manifolds but you can find cheap headers that still work reasonably well for under $250
IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
grumpyvette

User avatar
Site Admin
Site Admin
 
Posts: 14105
Joined: September 14th, 2008, 1:40 pm
Location: florida

Re: rams horn exhaust info you might need

Postby 59Lenoir » July 7th, 2011, 7:57 am

wow! thats a lot cheaper! Probably less that the cost of sandblastingg my originals! Thanks
not to sound like a "numbers-matching-weenie" but aren't these slightly differetn than my originals?
59Lenoir

 
Posts: 233
Joined: July 1st, 2011, 2:21 pm

Re: rams horn exhaust info you might need

Postby grumpyvette » July 7th, 2011, 8:19 am

they might be , I don,t know what they look like other than the picture and Id have to put them next to your originals and compare them, but at the price it seems like a decent deal

THERE ARE STAINLESS BLOCK HUGGER HEADERS
http://www.kmjent.com/cart/product.php?productid=564

http://www.ecklerscorvette.com/corvette ... -1974.html
Image
keep in mind the big block chevy also had some preferred exhaust manifold casting designs
IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
grumpyvette

User avatar
Site Admin
Site Admin
 
Posts: 14105
Joined: September 14th, 2008, 1:40 pm
Location: florida

Re: rams horn exhaust info you might need

Postby bob » July 7th, 2011, 9:34 am

why run rams horn exhaust when headers are both fairly cheap and produce better results?? just asking, curious?
bob

 

Re: rams horn exhaust info you might need

Postby 59Lenoir » July 7th, 2011, 10:55 am

I'm trying to keep things relatively stock-looking under the hood, even if it's at the expense of power; I'm not really looking for a hot rod, just 'a little better' than stock if possible.
Also, aren't you more likely to be plagued by hot-start problems with headers?
59Lenoir

 
Posts: 233
Joined: July 1st, 2011, 2:21 pm

Re: rams horn exhaust info you might need

Postby grumpyvette » August 15th, 2013, 5:00 pm

http://www.powerblocktv.com/episodes/HP ... mance-mods

you might find this interesting

AND for anyone who thinks headers are not an important component in your engines efficiency ,heres a rather interesting dyno test where carefully ported rams horn type exhaust manifolds were tested against a set of 1 3/4" headers, the result with this particular engine combo was that the engine made just over 500 hp with headers but LOST 95 hp once the cast exhaust manifolds were installed replacing the headers


http://www.yenko.net/ubbthreads/ubbthre ... /415017/16

Image

THERE IT IS!!! 504 HP @ 7400 rpm! That was my goal with headers, and once I realized we were off quite a bit on the camshaft I was pretty doubtful we would see it. Again, keep in mind the cam in this engine as supposed to be designed to run with ported exhaust manifolds, and was to have a "stock" idle. The idle went out the window as soon as the engine fired for the first time, and w/o giving away any camshaft details, the LSA on this cam has been a concern to me since I received it, but I was placing my trust in someone else's expertise. It's not a big issue, I didn't expect them to hit a bulls-eye the first time around, that's all part of the deal when building engines like this.

Now that we'd hit my power goal with the headers, it was time to try the manifolds.

As much as it pains me to say this, as I feared once I realized the cam wasn't right, the manifold test was a bust. The engine flat-out HATED the manifolds...it lost 95 horsepower with the manifolds installed. eek However, even though the engine was obviously unhappy with the manifolds, peak power still came in @ 7200 rpm. As such, that will have to be re-tested during the next round of testing.

504 HP from 306" is just under 1.68 HP/CI, and 397 lb.ft of torque is 1.29 lb/CI. That's pretty stout considering how much there is still left on the table with this build.

Last comments regarding the dyno sheets: This time the air/fuel ratios are correct, but the VE figures are nowhere close. I calculated VE using Pipemax software and it showed roughly 94% VE to match the actual dyno numbers.

So that's it for now on this build, but rest assured, there will be more to come! Along those lines, I'd like to hear what you would like to see me do with this engine project--stick with the "F.A.S.T." theme?...go balls-out with headers?...tame it down a little with a more "practical" set of heads and cam?
IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
grumpyvette

User avatar
Site Admin
Site Admin
 
Posts: 14105
Joined: September 14th, 2008, 1:40 pm
Location: florida

Re: rams horn exhaust info you might need

Postby 87vette81big » August 17th, 2013, 12:59 pm

Grumpy something just don't look right with the above Water Brake Engine Dyno sheet printout.
Volumemetric efficiency never exceeded 77.6%.
An engine making 1.68 Hp per cubic inch of 306ci peaking Hp @ 7400Rpms & 504 Hp & headers should have VE ar least 90-95%.
Data appears skewed.
Left alot in the table.
Small CFM carb used ?
87vette81big

User avatar
 
Posts: 3278
Joined: February 28th, 2012, 12:34 am
Location: Central Illinois

Re: rams horn exhaust info you might need

Postby grumpyvette » August 17th, 2013, 3:34 pm

if you read the notes posted he stated that 74% ve was obviously calculated wrong and when he recalculated he got 94% VE
IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
grumpyvette

User avatar
Site Admin
Site Admin
 
Posts: 14105
Joined: September 14th, 2008, 1:40 pm
Location: florida

Re: rams horn exhaust info you might need

Postby 87vette81big » August 17th, 2013, 4:04 pm

Yes I read the notations Grumpy.

Old dyno test from '99.
Interesting writeup none the less.
87vette81big

User avatar
 
Posts: 3278
Joined: February 28th, 2012, 12:34 am
Location: Central Illinois


Return to Exhaust and Mufflers

Who is online

Users browsing this forum: No registered users and 3 guests