Rhodetd

I'm sure this has been covered before, but I couldn't find the thread. For a mildly built 455 would a person be better off with W/Z manifolds or headers? I'm looking at hooker 3902's. The cost is pretty much the same, and I'm wondering if the extra performance of the headers is worth the hassle. I was also looking at the Mondello HD-57P ceramic but can't find any reviews. It sounds like the hookers are the best option under $500. It's a 70 supreme that sees only street use. Motor should be in the 400hp/500tq neighborhood. Thanks for any input.

Fun71

With the description above, I think you posted this in the wrong section. A mildly built 455 that sees only street use doesn't really fit with the "Racing and High Performance" section.

With that said, I always opt for headers over manifolds unless going for a factory resto or noon-performance daily driver use.

70cutty

Headers all the way and stay away from Mondello.

nonhog

I think member My442 (forgive me if I'm wrong) did a dyno test.
Headers vs. W/Z. Like 20HP better w/headers?

oldcutlass

I was reading on another site with a BBC (I know not oranges to oranges) there was a dyno test using early Corvette manifolds vs headers and there was a 9+% difference in favor of the headers. The Corvette manifolds flow better than the w/z manifolds so I'll assume the difference to be even worse.

olds 307 and 403

Nothing a like at all. Chebby and Pontiac had much better HO manifolds than Olds.

joe_padavano

First, yes, this topic has been covered about a bazillion times since the first hot rods were built.

Second, building horsepower requires a total system design where all parts of the engine are matched. You need to get air in and out of the engine and a single part by itself won't produce meaningful gains.

Third, it's been shown repeatedly that correctly designed LONG TUBE headers produce about a 20-25 HP gain, depending on how bad the stock manifolds were. More importantly, if you ever plan to improve breathing with intake, carb, and cam mods, you MUST improve the exhaust side to get any benefits from those other mods.

Your call on what you plan to do ultimately and the size of your wallet.

My442

Correct on a mild street build.

The higher the horsepower, the bigger the impact.

joe_padavano

Exactly. More HP means moving more air in and out of the engine, so headers will have a greater impact as flow rates go up.

coldwar

This fellow has been honest in describing his use for the car. Most guys want us to think they are going to the Nationals or to Pinks or something like that when in reality they will putt-putt to shows and the burger stand with their 9:1cr engine.

Let's also consider the Oldsmobile engineers made extensive use of the dyno in development of parts. In consideration of the port design and available room with clutch linkage and steering box, the 308 and 328 cams and 10:1 static C.R., the W-Z manifolds do a great job. The benefits of headers with a modded engine are known but require tuning, clearance, stock exhaust mods and seasonal maintenance especially when mufflers are used, to see results. Many guys will tell you they haven't touched them once installed but you hear them pfft pffting around shows and the burger stand, and they look like rusty crap when not coated, and dented up on the bottom. Maybe add a crossover or 'h' pipe for a few more ponies (proven).

Unless you must have perfect appearing manifolds with no pits, you ought to find used manifolds for a lot less then repros at $500.

cutlassefi

I couldn't disagree more.
Manifolds will cost you a minimum of 30hp on anything that makes 400 or better. And yes I've had my headers for 12 years, no issues.
The engineers went the route of least resistance, period. Adding headers is one of the few things that improve power AND efficiency. Do you think they had the fastener and gasket tech we do today back then? Not hardly. And ultimate hp wasn't as difficult to achieve back then as well, not with 100+ octane fuel available everywhere for .25/gal.

Thanks.

joe_padavano

Mark is pretty much spot-on. Factory engineers in the 1960s cared about lowest production cost, easiest installation on the assembly line, and lowest chance of warranty call-backs as their primary requirements. The engineers knew that serious racers would ditch the manifolds for headers as one of the first things they did before heading to the track, since even NHRA Stock classes allowed this.

coldwar

Here's what this guy in question said he was doing. You guys go worry about super stock and least resistance and lowest cost and serious racers (eyes rolling). Like I said see you at the Nationals and Pinks ( eyes rolling again). I'll be out on the streets with this guy.

70cutty

If you read the question again you will notice that The guy (op) was asking if he would be better off with headers or w/z manifolds and the answer is he would be better off with headers plain and simple.

oldcutlass

I like headers and we all agree that for performance they are better. What the OP needs to decide, since he's building a cruiser is whats best for him. Is it worth the gain or not? On one hand most headers don't drop right in and may require some mild massaging to install with the periodic bolt tightening and gasket changes. Or on the other, the simplicity in installation and maintenance vs the loss in power that the butt dyno may/may not feel while cruising around with manifolds.

Fun71

I will be out on the street as well, with headers, just as I have been since 1982.

I have not had any of the issues you mentioned (leaking, loosening bolts, rusting through, etc.) in the 34 years they have been on my car.

olds 307 and 403

Olds knew the stock SBO manifolds sucked but knew most would toss them in favor of headers for the track. I am sure if the W/Z would have fit, they would have got the nod. Even the W/Z manifolds were a small number for the BBO, let alone on the tiny 350 performance sales. Bolts do come loose but not that often and stainless or even ceramic coating has made headers last longer. Plus Copper or Aluminum gaskets last nearly forever without blowing out. Probably helps that most Olds are no longer driven in salty winter conditions.

Fun71

In my case, even though mine is daily driven it has never been in a location that has "salty winter conditions".

onetogofast

Engine=air pump. More in and more out is more efficient and more power. More in and a cork Stuck in the out causes less fun and less power noise!

android 211

Its been demonstrated that on some engines a tight LSA works better with headers as they help to scavenge the cylinder of exhaust. Since manifolds are a restriction a wide LSA like at least 112 or better 114 works to make power. Many of the Olds cams were ground on a 113. If you're going to install headers then you should fill the crossover and weld up the divider to make best use. Remember you might have to relocate a brake line bacause one header tube rubs on it. I have that problem on my stalled '72 455 442 project. If you have a stick the pipes might interfere with the clutch linkge. Buy a box of ynomat for the extra heat.

Rhodetd

Thanks for all in input, think I'm going to go with the Hooker 3902's. Even though it will only see street use, I've bought to many performance parts to skimp now. Still can't justify ARH's, so cheaper headers will have to do.

Cincinnati Rick

I went with the HD-57P-S stainless headers from Mondellos. They fit really well and sound great. Flanges on the headers are heavy duty. My only complaint was the collector flange (adapters for the exhaust pipes) were a little wimpy.
You'll be happy you went with headers!

I have purchased a lot of stuff from Lynn at Mondellos. Everything has been exactly as promised. It's not the first time I've heard people on this forum bash him but really haven't seen any reason for it. Did you have a bad experience with them?

Rick

Fun71

I did.Was flat out lied to when I asked about a part fitting my engine, then when I sent it back because it couldn't possibly fit I was told there were two different block designs in 1970 and I must have "the other one" and I was given store credit instead of a refund.

Cincinnati Rick

Kenneth,
That's unfortunate to hear. At least they offered the store credit and didn't stick you with a part you couldn't use. If I order anything else from him I'll make sure that I can get a refund if it doesn't fit before I place the order. Thanks for sharing your experience.

Rick