Gas washing pistons?

I was chatting with an engine builder the other day, although not my engine builder, and he mentioned that he always tries to convince customers to go with fuel injection over carbs because of the damage done to engines from gas washing. Fuel injectors shut off when you take your foot off the gas. I'd love to get some feedback on this. For a vehicle like mine with the 440 that gets 3000 miles a year of cruising, how concerned should I be, and what should I look for?

these cars were, and some still are, everyday regular passenger vehicles that were driven as the only means to get around , with carburetors. it wasn't uncommon to see them hit 120, even 150,000+ plus miles before dying. I would say your concern should be zero. I know mine is. unless i smell fuel in the oil from some other source.

LOL... 42 years on my Bee's 383's rebuild, 50 now as far as I know on my Birds 440 warranty engine..

At that rate Mark you'll be about 75-80 before needing another rebuild.

Sounds like that clown is trying to sell you an EFI system! 440'

A fuel injection can fuel wash a bore in exactly the same way as a carburettor will if is not tuned right.
Tune them right - a carburettor is no real problem.

Its all bs, if carb is tuned properly and you dont flood the engine at start or fouled plugs you will be fine with carbs. Bigger chance your mechanical fuel diaphram pump leaks and drips fuel into oil since the chinese make our fuel pumps.

steve340 said:

A fuel injection can fuel wash a bore in exactly the same way as a carburettor will if is not tuned right.
Tune them right - a carburettor is no real problem.

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I get diesels with destroyed pistons and cylinders that had injector problems and they took out the cylinder by washing the oil away.

Had a 6=8 intake on a ford 300 with a holley carb. Way too much Carb. for the engine and it washed the cylinders down and froze up on me. Yes the rite carb for the car's motor. Seen 300 thou. on Carb motor's. No issue.

Mark1972 said:

I was chatting with an engine builder the other day, although not my engine builder, and he mentioned that he always tries to convince customers to go with fuel injection over carbs because of the damage done to engines from gas washing. Fuel injectors shut off when you take your foot off the gas. I'd love to get some feedback on this. For a vehicle like mine with the 440 that gets 3000 miles a year of cruising, how concerned should I be, and what should I look for?

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If you take your foot off the gas with a carburetor, it still "shuts off the gas", except for the idle circuit. With the high manifold vacuum, any bit of gas that comes in will flash into vapor right away, especially once the engine is warm. Besides, many things can contribute to a fuel rich mixture with injection as well.

As always, thanks all. I learn something everytime I ask a question. I'll take an oil sample and look for signs of gas in the oil. I've also used an oil analysis shop in the past for industrial equipment, and can send them a couple of ounces to check.

You will usually only notice fuel wash upon tear down. That being said, the fewer miles you drive the less it will affect the engine. Carburetors are not exact 100 percent of the time. There will be liquid fuel in the cylinders a good bit of the time on the best tuned carb, especially during engine load changes (the basis of the highway miles are better idea). Tear apart an older carburated engine with 70 to100 thousand miles and you'll find a fairly thick ring land at the top of the cylinder bores even if it was well maintained. In late model FI engines it is very common to see the crosshatch pattern left from the factory machine process, and no ring land in the cylinder. And this can definitely NOT be attributed to the higher quality oils used these days (sarcasm fully intended). But, no more miles than you drive it, keeping it tuned and running the snot out of it occasionally, shouldn't be a problem.

Just me, but all these years it just kills me to see and read about all the guys that just have to have a double pumper and also CFM ratings thats damn near twice as much as they need for proper performance for their street combo. I've seen so many small blocks with 850-dp's it's mind boggling. When I was a kid many cars had multiple carbs and my first car was a 63 ford with a 406 tri power. Now ya know the rest of the story.

318 factory dual quads were an option in the late 50's...how's this for carberrration...

Would ya believe a factory 5.2 L Magnum throttle body flows 635 cfm?

I’ll stick with my well tuned carter avs! May even run cleaner than some folks set ups with fuel injection. I’ve seen some horrible installations and tunes no change for me as long as I can always get a tuning kit.

cryplydog said:

Just me, but all these years it just kills me to see and read about all the guys that just have to have a double pumper and also CFM ratings thats damn near twice as much as they need for proper performance for their street combo. I've seen so many small blocks with 850-dp's it's mind boggling. When I was a kid many cars had multiple carbs and my first car was a 63 ford with a 406 tri power. Now ya know the rest of the story.

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I agree with your premise re over carburating an engine....unless it's designed that way with correctly sized carbs and related parts....
My first experience with a REAL muscle car was a 1962 Galaxy 300 2 dr sedan, diarrhea brown in color no PS or PB or radio, but with a 4 speed transmission AND a 406/405 HP engine and 3.50 something rear. Firing it up for the first time, hearing the clatter of the mechanical operated valves, slipping into 1st gear, and accelerating to 80+ mph on highway roards, banging thru the gears, being pushed back into the seat, with brute force, listening to the roar of the tripower Holley's gulping air is an experience I've never forgotten ....ALMOST (but not quite) as wonderful as sex.....although some may disagree??
And beating 1963 Impala Super Sport powered by a 409/425 HP 4 speed car at 100 mph by 1/2 car length, with my old and ugly Ford.....something to be said of Ford's published HP rating for the engine.....just like Mopar's published optimistic HP rating of the Hemi....
Anyway, just my opinion of course.
BOB RENTON

Ron H said:

318 factory dual quads were an option in the late 50's...how's this for carberrration...

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That may be the case but when you establish the CFM of those earlier carbs the total flow isn't that great and was an option to increase gas into the engines at a time when the advancements in carburation was still being developed. We have to remember that big cfm carbs came in the 60's (Im generalising here). A couple of early WCfb Carbs on an early Poly probably only flowed 650 cfm tops. The longer carb development went the sooner larger CFM ones came on the market and to a certain extent 2 x 4 barrel manifolds fell away. Easier to install 1 x 800 than do 2 x 500 cfm. and lets remember that the upper end of the cfm flow only occurs on a vacuum secondary when you are up in RPM.
Cheers Brett

3000 miles a year times 20 years = 60,000 miles, a half-life for an engine. Even if in 20 years you left the carb rich enough to somehow wash the oil off the cylinders, The rest of the car will have succumbed to old age anyhow.

Gas-wash is the least of my worries, and I do have a 750DP on my 367. And it has currently got over 100,000 miles on her and still spins the tires to 80 mph. Tire-wear is my principle concern, along with hydro-planing.

The thing about carbs is, just like everything; the flow rating was generated under a very specific test set-up. Unless the carb is way too small, it will flow whatever your engine can. If your combo flows 500 thru a 600 carb, it will not flow any more thru a 700.
If you try to pull the 500 thru a 450, you might just get it, cuz you have only exceeded the rating, not the carb's ability to flow at a new and different rating.
A too-big carb is not guaranteed to gas-wash your cylinders.
Rather
the inability of the tuner to match, and limit, the fuel supply to the demand, is. And never underestimate the worth of proper timing. The V-can is your friend. It is vitally important to most street combos.
If a guy can neither tune a carb, nor tune the timing, to the combo; that is a bad recipe for the poor,poor, engine.

But in all fairness, the price of carbs is skyrocketing, and the price of EFI is not. The day may be fast approaching, that EFI can be almost be justified by anyone who has no fuel-system at all.
As for my 367, the 750DP carb on it, is circa mid 70s, and does whatever I tell it to; so until it rebels, it can stay.
BTW
Is a 750 too big for my 367? Why yes it is. By the formula, my engine requires a 638 at 100% VE. At 88% that becomes 562. So it would seem, that a 600 would be plenty. So I bolted one on, after having already been running a 780Vsec. What a joke that was. So then I bolted on a 750DP, which killed the 780Vsec. By the formula, a 750 should be good for 8000 rpm, at 88% VE . Well, I'm not gonna try and prove that, but it does pretty good at 7200.
If I had an 850, do you think I would leave it on the Bench in my shop? Hah. In a heartbeat I would bolt it on, just to see what would happen,lol.

If someone offered to gave me everything I needed to convert my fuel system over to EFI, I don't think I could accept it. I like to drive my car now, not work on it anymore. Since it seems to work perfectly with the 750DP, I'm not interested in starting over.
I'm not condemning EFI, not at all. If you got the cash for it, and have a tuner that wants to get into it, then fine have at it. It is possible to have a funtastic car when it's done. I just think that for most of us, EFI is waaay over-hyped. Many many years ago it was on my wish-list. That ended when I bolted the 750DP on.

Double pumpers rock. I wouldn't want to go back to a Vac sec. Seems like most of the DP naysayers have never actually had one.