'75 Dodge 440 - top speed only 50-55mph?

mattyj858 · January 05, 2016, 11:11 AM

Hello,

I am new to this forum and had a question about a 75 Winnebago Indian 23 w/ 440 motor 3 speed. The engine idles, shifts and operates really nice, no misfire or rough idle. My question is cruising or acceleration speed is really slow. I completely understand we are talking about a 10K lb vehicle but top end seems to be about 50/55 mph dry, no water or waste in tanks, unloaded. Seems I have to drive it with the gas peddle consonantly pegged to the floor. I have only driven on flat roads but looking to take a local trip soon that requires going over a 4,500' pass. With a 440 motor I would think the RV would have a bit more power behind it. Does this seem right? I don't see any air intake restriction, vacuum shows good pressure according to gauge.
Has stock gearing if that helps. Again I know this isn't a sports car but concerned there might be a power loss somewhere? I couldn't even consider passing another vehicle on flat ground.

Thanks
Matt

Rickf1985 · January 06, 2016, 06:20 PM

Well there is not much info to work with here since both of these problems can be many things but lets start here. Have you verified that the secondaries in the carburetor are opening? If not due to a bad diaphragm or misadjusted linkage then there is your power issue. Some people like to disable the secondary linkage to save gas. Make sure you vacuum lines to the vacuum advance are working and if possible check the flyweights in the distributor to make sure they are not frozen.

mattyj858 · January 06, 2016, 08:03 PM

Great thank you! I didn't even think to make sure the secondary's are working. The idle and neutral acceleration is really smooth. I'll double check for leaks and the flyweights as well. I have the feeling it's the secondary's.

Thanks again

LJ-TJ · January 06, 2016, 09:04 PM

Well I'm running a 1975 21footer with the 440. She runs sweet/loves 55 to 60 miles an hour and gets + - 8 miles to the gallon at those speeds. If you want a quick check on the secondaries opening the next time you go out just quickly mash the accelerator peddle down and trust me, if there opening you'll no it. It will sound like it's going to suck the dog house down through the carburetor. Hm?

mattyj858 · January 11, 2016, 11:04 AM

Thanks yes this is the small Indian so you were right. I think they bypassed the secondaires for a quick sale....

yogiberra · August 11, 2017, 07:14 PM

I have read this post several times to see if anyone has added discussion. I have a 1975 23 ft Indian, Dodge 440 as well...replaced the thermo-quad with an Edelbrock 500 cfm. All engine performance parameters are good,... I took the RV out to test the speed performance on the highway....I could only get to 52 mph...hmmm!..... okay, let's install a larger carb..... the new Edelbrock 750 cfm should get me more gas to the 440 dodge engine....well! still only get only 52 mph.....so now, I am thinking that the DANA 70 gear ratio of .458 is to low... I live in San Antonio, TX so we are mostly flat here! Oh! and yes the secondaries on all three carbs open up completely!

Rickf1985 · August 11, 2017, 07:47 PM

Are you running the stock ignition? No rev limiters have been added in? You should definitely have more speed available. It is possible that the exhaust is clogged, some older pipes were know to collapse internally and block things up. It will usually sound like a vacuum cleaner at the exhaust tip. It will not sound normal. Heat riser stuck shut? This will not usually cause that much of a restriction but it will cause overheating. You could have a timing issue, have you gone through all of the normal tune up stuff?

If it is single exhaust then I would bet there is a restriction where the Y pipe splits off.

Froggy1936 · August 11, 2017, 07:58 PM

Have you noticed 2 upshifts ? Sounds like mabey no 3rd gear ? Frank

Rickf1985 · August 11, 2017, 08:05 PM

Hadn't thought about that one! Man, 2nd gear at 55 with 4.56's!!!! SCREAMIN!

yogiberra · August 12, 2017, 01:07 AM

Thanks for the replies; I have stock ignition, plenty of exhaust air & heat coming out of each of the dual pipes; I am using a quiet road for my speed tests,... stop first so I can hear/feel second and third gear kick in......have vacuum gauge on dash, stays 10-15 mm Hg. I will re-tune again and perform speed test.

Xbird · August 12, 2017, 08:50 AM

minor but important item to add to the mix to check--throttle cable, are you getting WOT at the carb?

Rickf1985 · August 12, 2017, 11:10 AM

That vacuum reading is at idle or when you are trying to get your top speed? At idle it would be far to low and if it is when you are flat out it would be far to high. The throttle cable is a good idea if that is the reading at full throttle, it should be very close to zero at WOT. And around 18 at idle. That said, those dash gauges are far from accurate.

yellowrecve · August 12, 2017, 11:40 PM

Your Diff Ratio should give you about 3000RPM @ 60MPH. You have another 500 RPM available. More, but I don't like going much higher. I agree about the throttle lickage. The throttle may not be opening all the way.

yogiberra · August 29, 2017, 01:57 AM

Yes, I am get WOT at the throttle. I went back to my manual and found out my throttle linkage is not fully engaging at WOT. I'm a GMC man and got a rude awakening when I saw all the adjustments for the A-727 torque flight tranny. Now, that Hurricane Harvey has almost left us, I will start making throttle linkage adjustments tomorrow,....San Antonio is drying up a bit!!

Oz · October 10, 2017, 08:30 PM

Just a quick reply to the original question. Yes, 50-55 mph is well below top speed. The two, 74 Indians I had with everything stock except with 650cfm carb on the 2nd one already replaced made 65 - 71ish mph and still with pedal and rpm left. Didn't really want to go any faster, just wanted to see if it would make 70 for loading up for steep hills.

skloon · October 11, 2017, 01:12 PM

I had similar issues with a 400 turned out to be the plug wires. Two were bad. it idled fine but, under load, they didn't spark. oddly, it was still smooth but, the mileage sucked too

Sasquatch · October 12, 2017, 06:28 PM

I agree, something is wrong. I have a 76 Executive 26' coach on a Dodge M500 chassis with the 440/727 and 4.58 gearing combination. Even before I did all my mods it would run 65 easily on the highway and rev out to near 100 (too fast) if I wanted it to. This was with the original thermoquad on an Offenhouser dual port manifold. All else stock.

So, go back to basics and check everything. I would replace the plugs and wires. Then a new cap and rotor. They are all cheap enough to just do it. (make sure you get the right taper seat plugs if that is what your 440 needs). Check the air gap on the pickup coil in the distributor. Then, check the timing. Are you getting a full 38 degrees advance at 2500 rpm? Is your vacuum advance hooked to the carb or intake manifold? If it is on the carb, move it to the manifold and set all the timing again. Ported (carb) vacuum is WRONG. It was done for emissions and hurts power. Your coach should be able to maintain higher speeds even just on the primaries. I seldom got into my secondaries even when I had a carb.

Oh, you should also check cranking compression on the engine when you have it warmed up. Is the engine in good shape? Maybe you should do this first. A cheap compression guage from Harbor Freight is worth every penny.

So, something is amiss. By a process of elimination you should be able to track it down. The 440 is a very robust engine, but it was detuned very much from the factory for emissions reasons. But even with that, 55-60 should be able to be maintained easily. Should be able to push to 75-80 in a pinch for passing.

Once you find and correct the problem, and if you love the coach, some mods to the motor will net huge results. Headers, intake, cam, MSD ignition, and fuel injection will make it a screamer, even in low compression form. Mine runs like a scalded ape and still gets mid 7's in fuel mileage without babying it. I can get almost 9 under the right conditions, all while cruising at 65 mph, and still have plenty of passing power on tap if needed.

Sasquatch · October 12, 2017, 06:29 PM

Correction, I have 4:88 gearing

Rickf1985 · October 12, 2017, 07:26 PM

4.88 gears and what? 17.5 tires and a 3 speed Torqueflite. 100 mph? I put a calculator up on here somewhere a while back that would figure out your RPM on that combo but I am guessing it is around 6,000. D:oH! D:oH! I don't think you have near enough horsepower to overcome the wind resistance to get to 100 mph in a RV. And your power would be dropping off after 3600 rpm due to loss of torque curve.

Found it and I was close, I am guessing at 30" height on the tires. 5612 RPM

http://spicerparts.com/calculators/engine-rpm-calculator

Sasquatch · October 14, 2017, 10:48 PM

19.5 tires, and has seen an indicated 95 before, but for a very short burst just to see if it would. The motor, while still a low compression block, is far from stock. Fuel injection, cam, intake, headers, exhaust, ignition, etc. But I do not remember what the tach was reading, I know it was north of 4k, but I do not remember how much higher. Probably short of 5k though.

Before I get yelled at for going that speed in a 41 year old coach, it was a very short burst on a freeway in the middle of nowhere Idaho. Very little traffic, except for dad chasing me in his 2004 43' Monaco diesel pusher.... he lost. Also, the suspension and drive train are in fantastic shape and have been upgraded extensively. Air bags on all 4 corners, Bilsteins, all new brakes, sway bars, new power steering system, etc.

But my original post was for the reason of stating that even a stock 440 should easily do 60, even without getting in the secondaries, so something is wrong with his rig.