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Will not roll over a rock 454 w/turbo 400
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slowtogo
New User
Oct 26, 2008, 10:33 AM
Post #1 of 4
(2018 views)
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Will not roll over a rock 454 w/turbo 400
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I have a 83 34 foot motorhome with a 454 and t-400, it runs down the road pretty good, passed emissions with flying colors, gets about 6MPG and will pull a grade at 40MPH. the trouble is it will not pull over a rock from a dead stop. if i put a 4x4 in front of the wheel, it seams to rev only to ~1000RPM (just a guess, i dont have a tach) while in gear. if i put in nutral it zings right on up. also going down the road, it seams to kick down and pull about as expected. Could the converter be locking up to soon??
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Oct 26, 2008, 11:14 AM
Post #2 of 4
(1995 views)
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Re: Will not roll over a rock 454 w/turbo 400
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That's a pretty low stall speed IMO. That meaning when engine will stop increading RPMs against the torque converter - hence a stale mate. Guess is most would run up to 1,500 - 1,800 or so.
Whatever got you to do this test?
Does this even have cat converter(s)? Sounds pretty HD and some were exempt at that level.
One way to test for any exhaust restriction is to take a manifold vacuum reading with a "T" in line to actual manifold vacuum. Should read about 18 or so at idle. Rev to 2,000 and hold it should read the same. When you rev quick and let go you'll see higher Hgs (vacuum) and it will return to norms. If it runs lower at no-load raised idle than plain idle a restriction is the likely cause but doens't say exactly what by just that. Converters would be a first likely spot but with these tricks and who knows where this thing has been look for bent exhaust parts!
T
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slowtogo
New User
Oct 26, 2008, 11:44 AM
Post #3 of 4
(1992 views)
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Re: Will not roll over a rock 454 w/turbo 400
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it has cat converters on it, but i never even thought about them. as to the RPM, this is just a guess, i do not have a tach. i just went out and checked vac (it has a gauge of some type on the dash) it shows 25 at an idle, when i rev it up, it drops to 15 but comes right back up if i hold the fast idle. Holding on the breaks has the same effect as the 4x4 in front of the tire, i am going to test drive again now and see if i can down shift it. the unit has 60K miles on it, and the previous owner had the tranny replaced at 50K. i found out i had trouble when i tried to pull the boat trailer away from the dock. (it was a pretty sad site) i had to have someone pull me out, yet driving to the lake (and then back to the house) it seamed to be OK,
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Oct 26, 2008, 3:43 PM
Post #4 of 4
(1982 views)
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Re: Will not roll over a rock 454 w/turbo 400
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Whatever that gauge is and it might be a vacuum gauge as they used those back when for "economy" gauges - when high vacuum you were in the most efficient zone. 25 might be a spike # but it shouldn't stay there at idle or if a vacuum reading it's not accurate. Max possible vacuum at sea level is 29.92 Hg if you must know and an engine doesn't do that or even close. Most would be 18ish as said.
You may not have a problem with this you know. A Chev 454 in 83 was a gutless wonder for it's displacement compared to older stuff or stuff for marine use. Since you have converters the chassis was subject to emissions rules and around about 1973 to mid 80s horsepower took a big hit for emissions reasons depending on what the engine was installed in. I would have thought the chassis for a 34 foot land yacht would have some exemptions but who knows?
If this is problematic for you there should be a higher stall torque converter for it to hit a stronger power band kinda like the effect of a lower gear - more revs of engine vs wheel revolutions. Torque converter really can't lock up at too low of a speed or engine would stall. I think a 700R trans would show D321 on your shifter in 1983 - the "3" was just not allowing torque converter lock up at all if I recall. Later they just labelled the same on your shifter to (OD)then D21 I think??
T
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