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Old 09-02-2010, 09:43 PM   #1
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Car: 1986 chevy camaro z28 coupe
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2500 rpm at 55 mph, is that normal?

I did a swap to a 350 and i think i have 3 23 gears but i could be wrong. The speedo needle fell off so i am checking speed with a garmin. I idle at 1500 rpms in park and 1000 in drive. The cam is pretty lopey.

My question is, everything i read shows cruising in 4th on the 700r4, I should be at much lower rpm's.

I just cant seem to find what I need to know by searching and I dont know much about gears and trannys.
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Old 09-02-2010, 09:46 PM   #2
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Re: 2500 rpm at 55 mph, is that normal?

first off, what cam? that idle is stupid high.

sounds like you are not getting to OD, did you remove the lockup wiring?
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Old 09-02-2010, 10:04 PM   #3
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Re: 2500 rpm at 55 mph, is that normal?

If my idle is any lower, it dies and I have checked everywhere for vac leaks, many times over. I am getting in OD, I can feel the shifts. I dont know much about the cam just that it was the power 2 cam from phoenix engines, I bought a long block there and did the swap myself, learning as I go. I dont know what the lockup wiring is.

I pretty much just slammed the engine against the tranny and bolted over what i could from the tired 305 i pulled out.
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Old 09-02-2010, 10:44 PM   #4
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Car: 1987 Trans Am
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Re: 2500 rpm at 55 mph, is that normal?

with a 355 and 2.73 gears and the 700R4, at 2k rpm I'm doing 80mi/hr and 1k rpm, I'm at 40mi/hr. Even when I was having OD issues (torque converter lockup issues), I only lost about 100/200rpm (70mi/hr at 2k rpm)...
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Old 09-03-2010, 12:42 AM   #5
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Re: 2500 rpm at 55 mph, is that normal?

is there something i maybe should have changed with the engine swap that i didnt that may cause this problem? I am not sure how to trouble shoot this. The car has good power and breaks the tires loose when i hit 2nd gear around 35 mph i think. the tranny never slips or anything. I have a couple holes in the cat. conv. and some air pipes that arent plugged coming off the ex. manifolds but other than that, everything seems to be fine. Any advice on how to figure this out is greatly appreciated.
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Old 09-03-2010, 01:02 AM   #6
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Re: 2500 rpm at 55 mph, is that normal?

86TA is correct... your idle is way to high.. you need to tune your prom.. or another issue
if you need you idle @ 1500
i can get my CC 290 <> 112 cl on 1.6 rockers down to 500 rpm
you should have no problem
your RPM does seem a lil high for 55
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Old 09-03-2010, 01:46 AM   #7
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Re: 2500 rpm at 55 mph, is that normal?

not using a prom, I am carb'd with a edelbrock 1406, the previous engine was supposedly a 305 tpi but converted to carb when PO had problems. I ran it with the 305 before the swap and the rpm's were nothing like they are now

EDIT: will the rough lopey cam require a high idle rpm? I dont think the idle is too high because the car doesnt diesel when you shut it off. While the engine is still cold it does lunge at a redlight. Its kinda cool though, when everyone else is stopped still and your car is rocking like crazy!
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Old 09-03-2010, 11:00 AM   #8
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Re: 2500 rpm at 55 mph, is that normal?

Is your tach just off? A lot of the tachs in these cars read high. I couldn't believe how far mine was.
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Old 09-03-2010, 11:19 AM   #9
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Re: 2500 rpm at 55 mph, is that normal?

Quote:
Originally Posted by DAVEY420 View Post
Is your tach just off? A lot of the tachs in these cars read high. I couldn't believe how far mine was.
This is what I was thinking. My car with a decent but not huge cam will idle at 700 no problem and can go to 600 although it gets a little rough.

I would find a place that you can borrow a timing gun that also reads rpm's. I think your high idle and high cruise rpm may be related.

Does it sound like its idling at 1500?
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Old 09-03-2010, 11:41 AM   #10
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Re: 2500 rpm at 55 mph, is that normal?

Quote:
Originally Posted by matts86cam View Post
EDIT: will the rough lopey cam require a high idle rpm? I dont think the idle is too high because the car doesnt diesel when you shut it off. While the engine is still cold it does lunge at a redlight. Its kinda cool though, when everyone else is stopped still and your car is rocking like crazy!
yeah well, its not running right. i gaurentee you the cam is no where near large enough to need an idle that high. You have a vacume leak, or the carb is not tuned right, or both. no reason for your idle to be more that 700 in park. my 86 has a good sized cam. comp xr288hr-10, (about .555 intake, .576 exhaust with 1.6 rockers),and it only idles at 900, but will work at a lower rpm too.

all that extra lunge and rocking will eventually take its toll on the trans.

but, do you know that the tach is correct? it may be off and reading high, so you may not really be at 1500rpms at idle, or 2500 at 55mph.
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Old 09-03-2010, 05:45 PM   #11
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Re: 2500 rpm at 55 mph, is that normal?

I am pretty sure my carb needs tuned a little better, I played with it for a long time adjusting then test driving etc. I have it now where it wont backfire when you rev it up but i am sure someone skilled could do much better. Its hard to find a mechanic that works with carbs where I live though and all my family members that know are 700 miles away. I cant afford to spend two weeks rebuilding it myself learning as i go because i sold my DD.

Now that I think about it, there might be a vac leak in the brakes or something, when I hit the brakes, the idle raises about 50-100 rpms but otherwise, my idle doesnt surge.

I have never had a car with a lopey idle before so its hard to tell if i am truly at 1500 at idle. The exhaust leak doesnt help either. When I am at 55 mph it sure does sound like 2500 rpms is right. The engine builder said I would max out at 6000 rpms with the engine and thats where she redlines.

I didnt know how to check the rpms until BUILT91Z28 mentioned you could do it with a timing light. I will probably have it done at the shop next week when I go in for an alignment, I just put new springs on.

Hey 86TA, you said that lunging isn't good for the tranny, would lowering the idle fix that?

I really appreciate the help you guys are giving me, I have only been in WI for a few years now and I am the most experienced mechanic I know, scary hunh! I must add that I swapped an engine by myself with help from only reading and asking guys here in the forum as i went. You guys rock!
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Old 09-03-2010, 08:45 PM   #12
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Re: 2500 rpm at 55 mph, is that normal?

If all this is is some "readings" from that wavy pointer thing in the dash that moves when the engine speed changes, they're wrong. Like most of the rest of them. It's a "trim option", not a piece of test equipment or even an instrument.

That's the way they usually fail in these cars: they read high. I've seen em where they read literally pegged at idle. Most of em are at least a little high, some ALOT high. Sounds like yours is a fairly moderately messed up one, could be a great deal worse, in fact probably eventually will be.

Ignore it. The gears and the RPMs are what they are in spite of it. If you really want to know what they are, you'll change the diff fluid like you should have long since done anyway, and you'll make a point of looking at the gears while the cover is off, and then you'll know. Likwise, you'll use a piece of actual test equipment to measure the engine RPM, and that will put that mystery to rest as well. Not much point in speculating about it on here.
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Roughly paraphrased into modern English, and applied to figuring out what's wrong with your car:

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Old 09-03-2010, 11:52 PM   #13
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Re: 2500 rpm at 55 mph, is that normal?

Quote:
Originally Posted by sofakingdom View Post
If all this is is some "readings" from that wavy pointer thing in the dash that moves when the engine speed changes, they're wrong. Like most of the rest of them. It's a "trim option", not a piece of test equipment or even an instrument.

That's the way they usually fail in these cars: they read high. I've seen em where they read literally pegged at idle. Most of em are at least a little high, some ALOT high. Sounds like yours is a fairly moderately messed up one, could be a great deal worse, in fact probably eventually will be.

Ignore it. The gears and the RPMs are what they are in spite of it. If you really want to know what they are, you'll change the diff fluid like you should have long since done anyway, and you'll make a point of looking at the gears while the cover is off, and then you'll know. Likwise, you'll use a piece of actual test equipment to measure the engine RPM, and that will put that mystery to rest as well. Not much point in speculating about it on here.
good advice, i will use some test equipment this coming week. I never really thought of changing the differential fluid before, didnt know that people do it but now I do. probably count the teeth to see what size gear it is? I'll do some searching. I gotta say though the reason I speculate on here is truly because I just dont know where to start when it comes to transmissions and gears. Thanks for everything guys, i'll repost in a week or two when i figure it out.
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Old 09-04-2010, 07:47 AM   #14
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Re: 2500 rpm at 55 mph, is that normal?

Yup; count the teeth. In fact the ring usually has the tooth count stamped on it, around the edge; It'll say something like 15:42, which would be 2.73 (42 15).

You're right about the fluid. It's supposed to be changed every so many miles, 50 or 60k or thereabouts, I forget. I just do mine immeditaely whenever I buy a new used car and then every 4 or 5 years or so after that, whenever it's convenient. Failure to change it, or even check it, is one of the reasons you see so many people with rear end problems. (their car's, that is; although I suppose having problems with your car's rear end is a pain in your own rear end too)
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Roughly paraphrased into modern English, and applied to figuring out what's wrong with your car:

The simplest explanation that fits all the facts is probably the right one.
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Old 09-04-2010, 12:43 PM   #15
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Re: 2500 rpm at 55 mph, is that normal?

looking @ the stamping is fool proof... 9 bolters NO gaskets for you..
>>>Posi<<<
you can jack up the diff. 2 wheels off the ground. Trans in neutral. mark a line on the drive shaft. mark a line vertical on the tire turn the drive shaft till the tire mark ends exactly
where it started!!!! count the marked line on the drive shaft.... example 3.5 turns
close to 350 gear

my tac was 2,000 off... I used my scan tool to verify!! took the bezel off and matched
the gauge with my scan tool
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Old 09-04-2010, 01:10 PM   #16
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Re: 2500 rpm at 55 mph, is that normal?

After going from all factory guages to all electric Autometer guages, I wouldnt trust any factory guage. Every guage read different than my Autometers, which I do trust.
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