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Then there is Valve Overlap

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by rexrich2k

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23 replies

by rexrich2k

When I was an engine builder I had lots of extra parts to mess with so I was able to experiment around a bit.

A few ways to get a lot better power and not spend much more..

Carbureted engine; I cut piece of micro wire 1/8in screen to fit under the carb and between the manifold. Doing this would mix the fuel & air far better and made a huge difference in Torque, specially in the 700 to 2000 rpm range. I thought it would most likely kill high rpm performance but it seemed to have no negative effect at all.

The best poor man Torque and HP maker is of course milling the head and deck. Getting the most out of Pump Gas I found that 10.5 ~ 11.5/1 was the best ratio depending on the engine.

Then one other thing most people get wrong.. More Oxygen makes more power.. In most cases using the lowest Octane fuel you can get without pre-detonation (85 Octane) would get much better Torque and crisper HP. To aid in this I would polish out any potential hot spots in the combustion chamber, e.g., all edges, around the spark plugs and exhaust valves.

Spend a little money; Balancing the engine and porting & manifold port matching the runners. A mild Cam can help a lot too.

So doing these cheap things can really make your car engine a lot more fun. I did these things and still pass smog in Cal.

by hal 9000

Where you remove the Production Tolerances and return the engine to what the designer envisaged.

It will of course always make more power as you start with the [b]Ideal[/b] and then the shop floor introduces [b]Tolerances[/b] which kill of power. They then decide what they can get away with and have an acceptable level of Power and build accordingly.

The one big way to improve combustion is to Introduce Oxygen into the Induction system as it drastically improves combustion and hence power but if you don't have a motor designed for Nitrous Induction it's going to kill the thing quite quickly, or at least drastically shorten it's life. Here I do mean oxygen as apposed to Atmosphere gas which has a much lower % of oxygen.

With Force Feeding engines you push more of a charge into the chamber so you have more fuel air mix to burn and as it is at a Positive Pressure rather than a negative pressure you get more power simply because there is more to burn per power stroke. Again you need the motor designed for this with lower compression that would otherwise be used as you now have a higher pressure inside the chamber and considerably higher combustion pressures involved.

Though with any production engine scraping more power out of it and still using it as a daily driver is self defeating they tend not to mix all that well.

Col

by rexrich2k

"production engine scraping more power"

For the daily driver in most cases it will not hurt the engine to do some of the things I mentioned in my last post. Just don't let it Ping and keep up on maintenance. I had only 2 problems when doing these mods..
1. I would break the rear Axels a lot.
2. The high compression and low octane was hard on the Starting system. So I went through Starters fast. Then when I solved that problem.. The Battery blew up. ahaha! But MAN once I fixed those things the engine couldn't wait to start!! I could just touch the ignition and the engine would fired up! All the starter had to do was engage and that was it. :o very fun

Using Nitrous is ok but risky, its too easy to just add a little more ~ and a little more ~ and finally ~ Boom!

For the Street Car and this is why I like to separate HP from Torque, you don't really need more HP. For the most part you get more speed but that can lead to Tickets and Speeding crashes, not good!

But more Torque on the other hand gives you that feeling of big power and in most cases you are going to be showing off Light to Light, more Torque can make you the winner of that race without having to do too much speeding.

I've have had a few cars that would just Lurch Hard to the speed limit in a second and that's a blast in its self. So I've found that Chic's dig Big Torque more than HP, and that's a good reason too ;p

by aidemzo_adanac

It was initially a way to make European engines more appealing in the days when big blocks were storming America. People looking at the 351's 400's etc found that a little 4 cylinder was more aggressive (especially tonewise) with a turbo charger, plus engines were horribly inefficient then, well they still are but were even worse.

These days, it's a cool rally driver feeling, along with those disgusting, tuned exhaust tips you can buy for $50.

There are higher end sports cars where turbo is a definite benefit but for the most part, it's just a way of making a small engine sell for more in certain models.

by robo_dev

that I am fitting to my engine may actually do harm? :) :)

When I was stupid and young, one of my fellow stupid and young friends rigged up a large tank of nitrous oxide to his mother's 1976 Plymouth Volare wagon.

He had no nozzle or even valve, so he simply ran this piece of rubber hose into the air intake and had the tank in the front seat. He simultaneously floored the throttle then opened the valve on the tank while driving and dumped about ten lbs of NOX into the air intake all at once.

The engine stalled on the first try, but after several attempts, it did seem like a small amount of extra power was there. The next week the car blew a head gasket, which may or may not have been the result of my friend's experimentation.

by slayer_

Just re-aim them into the air box.
So want more power, turn up the fan.
Want cold air intake, turn on the A/C.
Etc. lol

by aidemzo_adanac

Pop the hood and vent the snorkel BEFORE your MAF. Unfortunately modern cars have too many limitations, even if you juice them they computer accommodates the change and adjusts AFM accordingly to manage emissions and slow you down.

by rexrich2k

I wouldn't have but I had no choice, I only get take off line options on the longer conversations now. :\

You wouldn't get anything from the fan but the cold air could give a little HP. Yeah but the freakin pump takes more than that to make it cold lol So dry ice on the ol fuel line again :)

Im a carpenter now so that sucks cause having engine parts all over is such a great life! It really makes you appreciate the way they work. Best thing man will ever invent.

by hal 9000

With [b]Sacrifices to the Gods of Speed?[/b]

I have a piston with the head of a Valve through it but that's a very special thing as it's from a GP Racing Bike and the closing rocker broke and didn't pull up the valve. Only doing about 15K RPM at the time and just maybe Valve Springs would have been some help but they added weight and didn't really do anything when the valve gear was intact. Makes a great Paperweight and along with an sodium cooled exhaust valve from a Merlin Motor is a great conversation piece.

I used to have a Fuel Tank from a bike that had been bounced down the track and mangled as a spare for the road bike so I could continue riding it when it's tank was off for repainting or whatever. The son in law pulled all of the bends out of it and made it look new. :_|

Back in the day I really enjoyed racing and what killed it for me was being put on a Gas Turbine Project for a Race Special being developed. Took all of the fun out of the design, though at the time I jumped at the chance to work that project.

I still have a few broken bits though today they are only the smaller bits as things like heads which have been destroyed when the Turbo self destructs and sheds its blades are way too bulky to keep. :(

Col

by rexrich2k

Yep broken valve spring was most likely the culprit in that valve going through the piston. Only other thing I can think of is if the valve seized up in it's guide. :o

I did use defenses for both on my engines, one was to use the lightest Valves and Spring Retainers I could. The other was to Knurl the valve guides. But the trick was to not run the Knurl all the way through the guide. I would only run the Knurl through till about a 1/4 in to the Port end of the guide. This would keep the oil in the guide, not letting it run all the way through guide and so keeping the valve cooler, cleaner and much better lubricated.

It's cool you are so much in engines! :)
How did you get interested in them?
Where did you learn what you know about them?
Do you work in that industry now?

My favorite engine tech these days is Top Fuel and Formula 1. The tech that makes these engines do what they do is so interesting! :D

by robo_dev

Unless if you count forgetting to put some parts back on, or shearing off really expensive bolts as 'modding' :) then I've got whole boxes of mods......

I did help to build a Datsun 510 race car though, but the engine and tranny was built by somebody else.

My favorite is the touring-car championships like the BTCC, but F1 is amazing stuff.

by rexrich2k

Datsun 510s were a lot better cars than they got cred for. Those tiny 4 bangers were fun to work on too. I did get to re-machine a few of them, but never had one. I would like to have one now, in fact that would be the perfect project car! :D

Oh bro I could sit for hours and watch the BTCC!! My freaken favorite for sure! :)

by hal 9000

As used by the McLaren team once?

When McLaren was using those I used to test them for that team. OK it was a while ago now and by that time I was very much on the side lines only doing a bit of Part Time Work but I always got strange looks when I went and picked up those play toys.

The above mentioned Piston/Valve was where a Closing Rocker broke and as there where no Valve Springs used it was a straight Mechanical Failure which theoretically should never have happened as the Colet's should pulled off the valve before enough force was applied to break the rocker. Desmodronic Valve Systems have quite a few advantages like no valve float possible but they do have several disadvantages, like when things go wrong they are spectacular. :^0

Unfortunately for me I'm a Mechanical Engineer who used to be involved in designing race cars once upon a time in the dim distant past and then continued with the design to engines and complete cars, not just a chassis. I spent a bit of time in Germany working for a company who makes sports cars in their R&D section so I did have a few people who knew me and quite silly thought I was good at what I did. Silly Fools. :D

Today I just play with things when I have some spare time which isn't often these days. I started this company to work a day or 2 a week and spend the rest of my time with my play toys. That lasted all of 12 hours when on the first day I had 12 people who used to work for me approach me with a long list of clients so instead of working 3 hours a week I'm now working 100 Hours a Week and don't have any time for my Play Toys. :_|

Col

by rexrich2k

I would love to get back into the auto stuff! :( Sounds like you have earned it though. Im that the type that loves to make things better mechanical and some electronic. I never got a degree because I suck at scholastics but my dad was a arrow space engineer, so I think I just inherited it from him. I am all hands with a 140 IQ :o

"no Valve Springs used it was a straight Mechanical Failure" hmm what? So it had a *Rocker and Cam, but no Springs?? Then not an electric or hydraulic, actuator? ..

Ah very cool! *Desmodronic Valve Systems* Yes that would tear up some stuff when it didn't work as it should. lol

But its got a valve stem guide, so it still could Seize, even just long enough to strip the Keeper's/Colet's off, then see ya, valve float.. bang! :)
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Ilmor engine. Wow cool, you have gotten into the high performance nitty gritty.
Yes Im sure McLaren doesn't like *strangers* mulling around their tech lol
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You must have some really interesting toys!

Well let me know if you need an uninhibited by higher education, semi engineer / machinist to help with that work load. Sounds like you have a good thing going! :)

by rexrich2k

..Elude on that question! Welp I don't have a Shelf to the Speed Gods anymore, but I did get the.. All Time High Honor award to the Gods of Speed, club!

How you ask; I gave a sweet (Brand New, one exhaust & one intake) set of, Manley - Swirl polished and Back-Cut Machined (by me), Over sized Chevy 350 Valves to my Girl Friend for her B-Day :)

Welp she's gone now and I don't know what happen to the valves. But I'm in like Flint with the Gods of Speed! :D

by aidemzo_adanac

HP means nothing in the engine, it's the BHP to rear wheels that matters, which is also a result of torque.

A lot of people buy cars based on HP though, we call such morons the hoods up gang. They are always parked in a Canadian Tire parking lot with the hood up as they pour can after can of the latest super goo into their engines

by rexrich2k

Today is a sad reality when you lived the big block days. Now days if you have the big money it takes you can engineer a spectacular engine as opposed to the 60s tech though.

A good example for this is the Top Fuel engine; Being relatively the same size, the early 70s TF engine would be lucky to produce 2000 HP but now 8000+ :o

by hal 9000

Where they claimed that the Average Power Drill is used about 12 minutes and then stored. I know I don't use my Power Drills that often as I simply prefer Pedestal Drills when I have to drill something but even the crappy cordless Makita has had several battery charges put through it and as it comes with 2 batteries it gets flattened several times a year. Though if I have to use a drill I tend to use Electric Drills as they have more power and I simply never trust batteries.

But having said that as the woman on the TV said you don't need a Drill of any sort you just want the hole so I thought of going to the local hardware store and asking where I could buy holes. :^0

Col

by aidemzo_adanac

I have air tools in my shop but I use my DeWalt 18V cordless drill so much I've actually run through a few batteries now (over 10 years). They are solid enough to last quite a few years but I drive thousands of screws a year, literally thousands and thousands. When out on the road, corded tools are not an option, cordless have become the contractors dream now. I don't know anyone, professional or casual who still has a corded drill. My radio charges the batteries on site so I just keep on charged and one running.

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