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HT4100 4.1, 4.5, 4.9 Discussion, What's so great about the 4.9 engine? in Cadillac Engine Technical Discussion; update-- 13mpg on hard city driving!...
  1. #31
    elwesso's Avatar
    elwesso is offline Cadillac Owners Master
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    Re: What's so great about the 4.9 engine?

    update-- 13mpg on hard city driving!

  2. #32
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    Re: What's so great about the 4.9 engine?

    Ha, my good ol' 4.9L gets 16MPG city, not sure about highway, but it should be marginally better!

  3. #33
    elwesso's Avatar
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    Re: What's so great about the 4.9 engine?

    Yeah, yeah, we'll take it to the track and then see who is talking!

    I need to do a few more items to get my gas mileage up, and then I may get 17......

  4. #34
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    Re: What's so great about the 4.9 engine?

    Quote Originally Posted by Katshot
    The '89 should net you approx. 20mpg highway/ 16mpg city.
    If it's got over 120K miles, it needs a timing chain and gears and a PROPERLY rebuilt carb. Those two items should make it feel like new again for you. If not, your mechanic screwed up. I've personally done close to 100 if not more of these and I'm telling you that they run GREAT if done right. Matter of fact, if done right, they'll run BETTER than new.
    And the Bronco should do better than that to. My '95 with the HO 351 got about 12-14 around town. I never checked it on the highway.
    havn't heard about the timing chain... I'll have to mention it. The carb needs to be fixed, the place is really good, but somethign went wrong... Richie with hsi '87 is getting 16-18mpg on his car (307 also) with 170k miles....I dunno how the 307 get get more power, the engine (car) is severly underpowered (mostly becuase of the port size int he heads) but I guess every bit helps

    the '85 is carburated, and that turck has every single extra and heavy duty thing avaible for it, I think it has 4.11 rear end, crusing at 65-70 on the highway and the engine is around 3500rpm..... geared very low.

    But that truck is rusting/rotting ut bad, the whole body is shifted, floorboards are pretty much nonexistant, engine is tired, 1 or 2 of the major bolts that hold the body on are gone etc...

    he has a '88 with the 302 fuel injection that we just rebuilt... I guess he is going to fix it up and sell it, and them work on the '90 with the 351 fuelinjection (blown engine) and then use that as his normal truck.

  5. #35
    ckucia is offline Cadillac Owners Fanatic
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    Re: What's so great about the 4.9 engine?

    Quote Originally Posted by 03EscaladeAWD
    I see. They should make more cars without 4 valves. I personally like pushrods too. 99% of people dont rev up to 6000+ rpm daily, so its not really neccessary to have the extra hp up high. So how is gas mileage better with 4 valves if more air can flow through 2 valves?
    I'm speculating here, but I believe the gas mileage improvements come from the higher-rpm capability, not the higher number of valves.

  6. #36
    92EldoTC's Avatar
    92EldoTC is offline Cadillac Owners Enthusiast
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    Re: What's so great about the 4.9 engine?

    just be sure to maintain it properly.
    clicked on a link from craigslist.
    A newer sts with 253,000 miles.
    Keep the maintanance up and they'll go long time.

  7. #37
    Po Pimp is offline Cadillac Owners Fanatic
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    Re: What's so great about the 4.9 engine?

    Early question:

    Why do 4 valve engines have less low torque then 2 valve engines?

    The 1 intake valve arrangement takes full advantage of what is know as the "bottle neck effect". Normally this is not really talked about unless you are discussing carburetors. Air increase speed when forced through a small space. It is forced through a smaller spot when it encounters the throttle body, then in the intake runner, this shape is pretty much the same (in a 1 valve), and finally into the smallest spot when it hits the intake port. The two valve arrangement differs once it gets into the head. This area is enlarged to accomidate the extra valve. This means you would have to have more air speed (only capable when the car speed increases) to over come this dead spot, so to speak. This same spot is an advantage at higer rpms because the air is building pressure making it pour into the cylinder in less time which helps because the valves are opened for a smaller amount of time.

    While this is not true for every car as designs are different but is something you will see in most cars.

  8. #38
    Barrie1 is offline Cadillac Owners Member
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    Re: What's so great about the 4.9 engine?

    Is it possible for the timing chain to start to hit the timing cover on a reg basis and create a tapping sound as My 1991 4.9 Fleetwood has a noise that has just started. It sounds like its coming from the bottom end of the engine so I putting it on a hoist on Monday to know for sure.

  9. #39
    lenny lincoln is offline Cadillac Owners Fanatic
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    Re: What's so great about the 4.9 engine?

    4.9 150-200k no drip trail. 40-100k NS drip trails and alot of owners with lighter pockets. The northstar was the biggest piece of crap next to the 368 motor. I would never own a NS caddy if a alittle old lady with 20k deville sold it to me for 2k.

  10. #40
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    Re: What's so great about the 4.9 engine?

    Quote Originally Posted by 2dfx View Post
    Ha, my good ol' 4.9L gets 16MPG city, not sure about highway, but it should be marginally better!

    18.8 mpg city (those are my calculation after fillup) . She sould get about 27-30 highway

  11. #41
    92EldoTC's Avatar
    92EldoTC is offline Cadillac Owners Enthusiast
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    Re: What's so great about the 4.9 engine?

    the earlier N*'s remind me of the old 4-6-8 digital fuel injected caddy engines from the 80's.

    Lots of problems that were improved upon later down the line.

    Think about it and it makes perfect sense, cadillac motor car company will put out a bug prone engine first and realize and fix the problem later.

    As dependable as the 4.9's were when they first hit the market in '91, the 4.9's in 95 were even more dependable than the earlier 4.9's.

    Same with the N*. The earlier ones were crap while the later '97-98 and beyond were free from most of the problems that plagued the earlier motors.

  12. #42
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    Re: What's so great about the 4.9 engine?

    I have to agree. I'm just on the verge of 180K with mine and the motor itself has just been bullet-proof. With a lot of parkway driving in the DC area, I'm getting 19.6 mpg -- this also with the basic upgrades on this forum: CAI, high-voltage igniton, less-restrictive muffler. Just had the tranny rebuilt, but even that was because I didn't notice a leak and it ran low on fluid for too long. I'm a 4.9 believer.

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