My 383 is weak!?

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1mopar4life

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I have a 83 Dodge D-150 pickup that my dad had swapped a 440 and later a 383 into that just seems weak.

Im not 100% certain on what parts are in the truck as I was only a few months old when the 383 was built and its been 20 years since dad had built the engine so bare with me here.

'69 model 383 Block
10:1 compression pistons
Mopar RV Cam
Stock 383 crank
440 heads with 1 5/8 headers (I think) run into true duals with glass packs
650 Holley 4bbl with vacumn secondaries
Factory big block Dizzy and Ignition with Orange Box Mopar brain box

The motor probably has less than 8K miles on it and was built with all brand new parts. Truck doesnt use any oil, engine sounds good but after about 3K RPM is just has nothing. It will wind out to around 4500-5000 RPM but it feels like it has a cylinder that is just dead. I have not got around to compression testing each cylinder. I am going to change the ignition system out to a full MSD setup but I feel like thats not the only problem. The truck has 2.92 gears which I will end up swapping to 3.23 or maybe in the 3.40 range. It doesn't get drove on the interstate, only on the 2 lane roads and cruising around town. I like to be able to crank it up and go anywhere I want in it but it just doesnt have the power it should. I want to really be able to break the 275s loose at a roll!

Thanks for the help guys,
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if the compression is good and the ignition is tweaked like you plan, i would say the cam is too mild

also the 10:1 pistons... maybe they are spec'ed for 10:1 but if the block wasnt decked you might only be at 9:1 or even less, depending on which heads you have on there.

but really, the mopar rv cam is more meant for mileage and low rpm torque not big power.
 
Thats what my dad had figured it would do well for when he built it. Its the cylinder feeling like its dead that has us baffled. After I get my Dart suspension and brakes squared away the engine may come out of the truck and have a hotter cam put in it as well as the MSD system. It acts like it lugs to pull the truck but it has a mountain of torque.
 
I think you might have a little different result than you think... If the pistons were "10:1" but they were installed in a '69 383 without the block and heads being blueprinted, and with the common head gaskets, you really have compression down around 8.8:1. Add to that the MP cam which if not degreed is probably off, and the 2. series gears, and it's going to be sluggish. You need to take compression readings first and post the results.
 
1mopar4life said:
Thats what my dad had figured it would do well for when he built it. Its the cylinder feeling like its dead that has us baffled. After I get my Dart suspension and brakes squared away the engine may come out of the truck and have a hotter cam put in it as well as the MSD system. It acts like it lugs to pull the truck but it has a mountain of torque.
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you can probably do the cam in the truck but it will take some patience a nice smooth careful glide to get the cam in without scoring the cam bearings. lots of white lithium grease on the bearings and insert section by section, get a new grip until you get it all the way in.
 
Throw a 3.55 rear in it, cheap at any pick a part, look for slant trucks.
It should wake it up real nice.
 
I had a 383 built just like you mentioned except it had a .484/.484 Mopar Performance cam, Performer intake, 750 cfm holley, headers, and it was nothing close to weak. Also it had stock 383 heads... I wonder if the 440 heads is killing it? It was however in a 68 Charger with 2800 stall converter, and 4.10 gears. If your motor has good compression and is running like it should (no bad cylinder, good spark plugs,etc... healthy) then you might should checking to giving it some more gear like previously mentioned. If you go bigger on the cam you might as well go with a stall converter so you will have good street manners with the truck in gear and idling. A stall converter will get it out of the hole quicker because you will building up more RPM coming off the line.

What gears are in the truck?
 
Thanks for the input so far guys. It has a 2.92 rear gear the deal is its got the small bolt pattern spindles and axles so I'll have to look for 84 and older trucks for parts which are very hard to come by here. Here's another question, will the axles from my pre-85 rear end work in a post 85 rear? If they will then this swap will be much more simple. What kind of RPM will I be running around 60mph with 3.55 gears? I am running around 2200rpm at 60mph with the 2.92s. I don't want to heat it up to where I can't afford to run around in it all weekend and pass anything but a gas station for sure. I'd like to be able to outrun late model 2wd bolt on Chevys and Furds. Around 9.0 in the 1/8th would be a good number to go for I suppose. What octane gas should I run with the setup I have? I usually run 91 octane but maybe I should be running 87?
 
A couple thoughts: First would be to make sure it's hitting on all 8, and that each cylinder is healthy with a compression check. If it's healthy, ignition would be next on my list. I think Mopars RV grind is only around .430" lift, which comes in at a bit less if using the stock rockers, and will fall flat really quick. 383's are actually not alot of fun to get compression out of, but if it has flat top, no valve relief pistons, you should be around 9.0 to 1, which is OK for what you are doing.
I didn't see mention of an intake, so I will assume stock? If so I really like the Performer RPM. The regular Performer is OK, but unless you get one cheap, it's just too close to a stocker for me. I would do the RPM, go to a 750 carb, and try at least the stock Magnum cam grind. I didn't see mention of converter either, and if it's too tight, you won't be into your power band at all at a launch. at least an 11" converter would help. A little more gear would be good, 3.23's maybe considering your driving requirements.
Oh, and there is really no such thing as "440 heads" They may have come off a 440, but Chrysler generally used them on the full range of vehicles in a particular year. For instance, many made a big deal out of the "906" cylinder heads, because HP 440's had them. Well so does my '68 Newport with a 383 2 bbl. Good luck.
 
Thanks Cuda, I believe it has a Performer RPM intake by the look of it but it has all been painted in the past so I'm not exactly sure. I have a stock stall converter in it as well. I am certainly going to upgrade the ignition as well as swap the cam out and change the rear end for one with better gear. I just have to decide which cam will do best with the combo I have in it.
 
If it's a Performer RPM it will be cast into one of the front intake runners, unless it was ground off for some reason. There is a great article online, Google "383 resto to rad". They built a stock 383, dyno'd it, and then added bolt on parts one by one and gave the results. The version with carb, intake, headers and stock Magnum grind cam might interest you. It made just over 400 HP, and would still work very well with the taller gears you wish to run.
 
1mopar4life said:
Thanks Cuda, I believe it has a Performer RPM intake by the look of it but it has all been painted in the past so I'm not exactly sure. I have a stock stall converter in it as well. I am certainly going to upgrade the ignition as well as swap the cam out and change the rear end for one with better gear. I just have to decide which cam will do best with the combo I have in it.
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First thing that needs to be said is that 383's love to rev, maybe not as high as a good flowing 340 but I take mine and the ones before it to 6200 all the time and that's where they perform. A 383 is not a lugging engine thats what 440/motorhome engines are for and sadly this 383 has been built as a small scale 440 and it don't like it much. Next there is nothing wrong with the orange box ignitions, cept you should carry a spare box and it will go strong to the low 6000 range. MSD's are good for engines pumping a lot more HP, fuel, and RPM than this engine will ever see and I doubt you'll ever feel a difference putting an MSD on this engine if it was already running good and strong. So we need to know what heads are on this engine. As mentioned before all BB heads will fit either the 383 or 400 or 440 whether they are the 915's, 906's, 452's, 902's and there are a few more so remove the tappet covers off of both heads and give us the last three numbers of the casting number. For all we know you may have a couple small exhaust valve 915's or 516's or one of each, yea you can mix and match them. All these heads had there own good and bad points. Next if you haven't got an RPM Performer then get one, the 383's love them and for what you're building anything else will not match up formula wise. Holley 750 minimum either the vacuum secondaries or double pumper, I prefer the DP'r cuss I build these engines to ignite off the line ie. no stumble. Next, minimum 1 3/4 " primary header pipes with 3" collector and with that truck that shouldn't be a problem. Comp or better cam with an effective lift of .480" to .510" lots to choose from. Next 9 1/2" 3000 stall converter. Rear gears of 3.55 are the minimum I'd go, good on the highway (60mph at 2700 RPM) with a fairly tall 275x60 tire but again the 383 would probably love the 3.91 even more. Put her all together and get the timing just right, start at initial of 12deg with full centifugal at 38 and all in between 2200 and 2400 RPM, and proceed to melt the tires off that truck. Here's the article mentioned that highlights the potential of the 383 without having to spend a ton of money. Don't forget that if you really want to make her rev then you'll have to invest on good roller rockers cuss the accuracy of the stamped steel is laughable. Example, they're supposed to be 1.5 ratio but infact I've physically measured them and got 1.42-1.46 and that's brand new out of the box.

http://www.moparmusclemagazine.com/techarticles/mopp_0209_383_engine_restore/index.html
 
I asked my dad about the engine and he said it has 452 heads on it and an edelbrock intake on it. I'll see if it is the Performer or RPM Performer tomorrow. I did read over and save the build you guys had mentioned and will look at a cam around those specs for my engine. I do have headers as well but not sure on the size. It seems I have the makings of a powerhouse of an engine just need a few parts. I may get around to checking the compression on each cylinder this weekend if I can find my tool. Hopefully that will come back good so all I'll need to do is look at the ignition system. I would like to go to a Edelbrock carb too. My Dart doesn't smell horrible but both my pickups with Holleys just smell awful and if you idle anywhere you smell awful too from the fumes around the trucks.
 
383 is awesome. Get rid of that wet noodle cam and it'll wake up. The 452 heads are good factory heads with hardened seat's,only thing better is aftermarket.They will support 500 h.p no problem,with some basic porting.

There were a lot of 396 chevelle owners who had thier pride wounded by a 383 road runner back when the cars were new!
 
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