Leo001

If I'm running a stock engine or even a mildly modified motor, how much power am I giving up by using the stock rams horn manifolds? I did open the ports up a little and clean them up inside the runners with a grinder. I understand there are places that will get rams horn manifolds to flow almost as good as headers, but at what cost $$

Thanks

Fevre

The higher the eng output the greater the return you will get with headers, for a slightly modify base motor (assuming a L48) then you prolly won't see much diff. What is the rest of your exh system like?

Leo001

Right now the only mod is an Edlebrock Peformer intake. I'm unsure of how far I want to go with the orignal motor. The rear main has a small leak so I may just pull the motor this fall rebuild the short block, aftermarket heads (world product sportsman II ) mild cam and same intake.

mrvette

The man at Schoenfeld headers told me using any muffled exhaust after the header negates any gains from the header....just too much backpressure....

but the large gain IMO with headers, is appearance and LOSS of heat storage under the hood when car is first parked....those cast iron things retain heat like crazy in all that iron, and sit there with NO air circulation and bake hell out of anything around them....headers being less massive do not tend to do that nearly as bad.....

on a dark night, go for a run, several miles at higher speeds, pull over and look at the headers/manifolds with engine still running, see the orange glow...

case closed....

GENE

TTop Tony

FYI
I have a freind with a 63, 2.5 inch rams horn and a zz4 that pulls 13.5 in the quarter mile. I also drove in an original lt1 with rams head manifolds that was about the fastest car I've ever been in. I've never seen a dyno test of the two but I would guess rams head manifolds ain't too bad on a street car. Just my $.02

L79vette

I'll let you know soon. The ram horns are off, headers on, gotta finish pipes and hook everything back up, hope to chassis dyno next week. Made 281HP at the wheels with the 2.5" ram horns and X pipe. That's 340-345HP at the crank with full exhaust, all accessories, etc. Good for a mild 327 with stock heads, but I think the exhaust is choking it at higher RPM. I base this on the observation that power peaked at 281HP@5700RPM, but did not drop off much at all, staying at 270HP@6500RPM.

One thing that makes a big difference with ram horns is an X pipe. Look at http://www.castheads.com. This guy is using Y pipes, but to the engine it is the same. My car made 255HP with 2" ram horns and no crossover. Next test with 2.5", X pipe, LT1 intake, and 650 double pumper was 281HP. Can't separate out which components did what though.

Extrude Hone (www.extrudehone.com) will process your manifolds for $500 last time I looked. Way more spendy than headers, and I doubt you gain much. The problem is that the passages are too small, and there is no separation of the exhaust pulses so the next cylinder exhale is always pressurizing the manifold.

Chevy High Performance did a series on the Goodwrench 350, about as mild a motor as you can imagine. Going from log-type manifolds and mufflers to headers and mufflers they gained a lot, like 30lb-ft of torque at 3600RPM, and about 15HP at peak as I recall. The articles are online. This led me to conclude that the claims that exhaust systems kill header gains are untrue. Maybe if you run very small pipes or something.

Anyway, we shall see next week.


[Modified by L79vette, 4:56 PM 4/30/2004]

cardo0

Leo, I installed headers on mine and now realize I wasted a lot of time and headaches for maybe a small hp gain. You will need custom collector to pipe connectors as no one sells them. Also sparkplugs need some type of heat shielding as stock shields will no longer fit and the wires will burn up fast . And the starter/solenoid needs a better heat shield now as it will see more heat from all the added hot piping. AC compressor will need new spacers and brackets as stock pieces no longer fit as made.
David Vizard writes he tested the ram horn manifolds and reported they produce 75% of what a good header produces for a large camshaft. But for small street type cams the difference is much smaller. Now 2&1/2" ram manifolds are availible for less restriction. A company Brezenki or something spelled close to that sells ported ramhorns for restricted class racing.
Good luck. cardo0 :chevy

KenSny

The best flowing GM stock iron manifolds are the rams-horn style most commonly found in 2" dumps. You can find them in 2-1/2" dumps at swap meets if you have lots of time to look for them. Don't make the mistake of comparing magazine tests done on "log" type manifolds, these do NOT flow the same as the rams-horn manifolds. David Vizard, in one of his books, tells how to cleanup the rams-horn manifolds AND where not to grind away metal.

Bottom line, for a stock or mild motor the $$ spent on headers will not gain you much. I have installed headers on lots of my cars, even some that were considered mild builds. Done mostly for the "COOOOOOL" factor and because stock manifolds are considered "UNCOOOOL". Nowadays, I keep the rams-horns, money is better spent elsewhere.


[Modified by KenSny, 8:11 AM 5/1/2004]


[Modified by KenSny, 8:17 AM 5/1/2004]

carl a

i jet hot coated my ram horns and could tell the difference the first run.. it seems that by coating the ram horn inside made the exhaust flow faster. i like the way they look and wouldnt want to even try headers for all the problems installing them, amd running them...---------

L79vette

I have the Vizard book where he discsusses the ram horns. It is "How to Build Max Performance Chevy Small Blocks on a Budget". In it he refers over and over to Randy Brzezinski as the source for cast iron parts that really flow. He says that Brzezinski achieves about 2/3 the benefit of headers. But, if you go to Brzezinski's site ( http://www.castheads.com ), you'll find that he says the most critical thing for getting performance from exhaust manifolds is a merge collector. The ones he sells are Y pipes, but X pipes work on the same principle. Vizard shows merge pipes in the book, but does not note how critical they are for getting the best from exhaust manifolds. On one picture caption he says he typically sees a 10HP increase on a 250HP motor from a streamlined merge pipe. Brzezinski makes much larger claims for the merges.

Anyway, this trip to the dyno the only change will be header addition and jetting and timing adjustments if needed.

No doubt about troubles with header install. I'm planning a pretty radical induction setup soon, and figured the headers were necessary to get the most from it.

Solid LT1

The difference between a fully ported set of 2.5" dia rams horns and Hooker Super Comp 1.75" headers was about 10% of my power on my 1972 LT-1 motor during a dyno test of the motor (394HP manifolds/426HP Hookers.) The testing was done with a set of DynoMax Ultra Flow 2.5" mufflers on a simulated exhaust system. The difference at the Drags 12.60@113.8 MPH with rams horns (I had a lot of porting labor in them and broke over $90 of carbide burrs porting them, they were better than Brezinski manifolds) and 12.28@117 MPH with the Hookers (both runs through the mufflers.) I use Earl's pressure seal gaskets with the Hookers with good luck and the exhaust is way more "throaty" souding with the Hookers with considerable torque pick-up in the lower RPM ranges. I just wish the Hookers had more ground clearance because they have already suffered a few dents while in service especailly at the hands of my wife on parking lot speed bumps.

cardo0

Thanks for posting your numbers here LT1. I'm still under the impresson here that smaller cams are just fine with the ram-horns. A shorter cam will see/need/use less exh savaging and stop breating before it would have a significant effect. I guess if want to make big power you have to pay the price somewhere. :yesnod: