"Pointless Incremental Improvements"

This phrase was coined by a car magazine editor a few years ago. They were doing a project car buildup with small bolt-on parts, and not getting the gains expected.

For example, the ads might say that this high flow air filter is good for 10 HP, and that high energy ignition is good for 10 HP, and these higher ratio rocker arms are good for 10 HP and those high flow exhaust manifolds are good for 20 HP etc., etc.

So if I do them all at once I will get 50 HP, right?

Well, not necessarily. If the original parts were not limiting engine output, such small changes won't make a difference, and they don't add up. You will only get as much power as the weakest link will allow. For example, if the stock ports in the cylinder heads are choking, changing every thing else before and after those ports cannot do much.

A skeptic might think that advertisers base their claims on engines that have lots of good parts but one poor component (the one the manufacturer wants to sell you). Change that component and you allow all the other good parts to work to their potential. The gains may be substantial but is it fair to say that they are due just to the new component? No, of course not.

In the case of boats, we hear comments on this board all the time that confirm the PII theory. High flow flame arresters, ignition upgrades and better exhaust manifolds often make little or no difference on a 400 HP engine with stock heads and cam. This suggests that Mercury provides a good combination of parts for stock heads. Change the heads and cam though, and you need all the other good stuff to make the 500+ HP you were after.

I'm just making these observations because of the frequent comments about no gains from exhaust improvements, and the recent comments about high flow flame arresters.

If someone has airflow data that shows Mercury's flame arrester flows 600 CFM (~400 HP) at a desirable pressure drop, then I would agree that an aftermarket flame arrester that flows 1000 CFM at the same pressure drop, is capable of supporting more HP. But that doesn't mean that the engine will use the extra capacity.

What are your experiences with minor bolt-on parts, and what do you think?

So, should I cancel my lifetime subscription to J.C. Whitney? Actually, when I'm discussing engine improvements with a customer I try to steer them away from the things you mentioned. I'd rather see someone on a limited budget buy the "dollar sense" items rather than trinkets (chrome valve covers are at the top of my "useless trinket" list). I do encourage people to buy roller rockers, especially with a camshaft upgrade.

[ 01-16-2002: Message edited by: Crazyhorse ]

Tomcat, it funny you mentioned the flame arrestors. When I rebuilt my SBC's I did everything I could to move the air. Port matched, clean up all the flash cleaned up the castings and short side rads etc. Put everything back together and ran them. After I broke them in I ran them up. Sitting there pleased with myself at 5000 rpms and the secondaries hadn't opened yet. So I hammer it and the engines said "Huh? You want more?" The only thing I didnt do was change the arrestors because I was out of money. Sometimes the cheap changes will get big gains too. It just a balancing act. Good thread.

Good post.

I am ALWAYS looking for something cheap to add some ponys, but half of the **** is not going to make a difference.

Why would I want to spend 1800 on a set of headers to gain 200 rpms. and thats for each engine!

I think that the reason this board is so helpful to me is people here have tried it and it separates the bull**** articles that we read from what really makes a difference.

I agree 100% with you tomcat. We should start another post on the top ten least inexpensive things that work.

I think for one prop labbing is worth it. Get the same rpms as adding headers at $175 a prop.

Any others??

Tomcat hit a lot of good points. I always chuckle when I see ads like "flows 40% better than stock" Well, as TC pointed out, stock may be 20% more than what the rest of the engine needs- so can you measure the gain on the dyno or GPS- not likely. Our boats compound this as it takes a lot of ponies to get each mph, coupled with the repeatability on any given day due to a myriad of variables....

A lot of people just need something to do, myself included. Some resort to dressing up their engine bay with trick looking parts that are hard to justify on a bang for buck meter. If it's their cash and if it makes them happy- so be it. A perfect example would be CMI's on a 310 hp 454- eye candy is all it will ever be.

What's unfortunate is people who somehow aquired unrealistic expectations and are faced with the disappointment of it not working out as expected.

Before my fast boat days I had an itch to make my tournament boat faster "I need it for barefooting" I told my wife. I bought a nice roller cam from a reputable california marine performance shop that would take my 350 mag from 275 to 360 hp. a little labor, a hotter coil the shop recommended, played with the jets, a better prop recommended by the prop shop. I was rewarded with a lumpy idle that really got the testosterone going, the same speed as I had before, a spare prop and a wife who 5 yrs later still remembers how much money I spent for no gains in speed. In hindsight I'm sure the power increase was close to the mark but a tournament hull is the wrong thing to throw power at and expect gains- way to much wetted surface area to get the flat waterski wakes.

If you are seriously in pursuit of performance gains there are many proven, reputable ways and shops to help you get there and there are no free rides. That's what's so great about this board, when the opinion dust settles the truth is usually self evident without undue influence from the advertising dollar.

tomcat,
You've got it exacly right. I tried to explain this to a freind who bought a 38' Scarab with 502s (410hp). After adding PFM headers, 500hp carb & intake, flame arrestor, and an MSD ignition to the tune of about $10K, the boat had the same top speed as before. I was trying to tell him a cam would improve this, but since you can't see it (it wasn't shiny or blue) he didn't think it was worth the extra couple hundred dollars.
Gary

and then their are boaters like me....a nice boat & you've done all the really important stuff to the engine, cam, rockers, heads, blower, headers, thru hulls, nose cones, hydraulic steering, etc....and the boat is at it or beyond its design maximum speed(75mph in my case). So all that is left is the "eye-candy" stuff...powder coating, stainless stuff, aluminum stuff...it's a guy and boating thing I think....we just gotta change something !! I know I'll NEVER go faster in this boat. But, what the hey!

Anyone know how you determine the "design maximum speed" of a hull, that 93 formula mentions? I would like to know the mph number for a 30' Scarab Panther.

BT

How bout that new vortech thingy thats supposed to swirl the air entering you carb or efi for better combustion. I expect a 20hp gain and 10mph.....not.

When I see manufactures claims of rediculous H.P. gains with, for example a flame arrestor, I would like to ask them if your claim is 10 h.p. with your arrestor, how much would I gain if I tried to run - just for a test of course - with no arrestor. If the stock arrestor is so restrictive , will that test send me to the century mark?? What a bunch of B.S. These companies have a lot of nerve with their claims. I questioned a reputable company who claims gains in h.p. with recalibrating you stock computer. When I questioned the guy over the phone as to what they do to the program to get the extra power, he told me that they richen the mixture, raise the rev limiter and ADVANCE the timing. Then I asked him, since when does advancing the timing give you more top end power? He claimed that it did. I said I guess that drag racers spend all that money on timing retard systems to lose top end power. Then he got the dial tone.