Tell me about my 383 Magnum engine build from 1989

[Coelacanth]

I'm a pretty mechanically adept guy but when it comes to internal engine work, it's not my forte. It's not my ANYte to be honest.

I had my '70 Charger's 383 Magnum rebuilt at a reputable shop in Edmonton, Alberta back in 1989, Campbell Automotive. They did a lot of race cars back in the day and are still in business today. My buddy and I did most of the work on our cars back then but engine-wise, nothing beyond swapping a 2-barrel manifold for a 4-barrel and adding a carb. I was a tad naive bringing my car to Campbell Auto but I trusted them.

Here are the 4 pages I scanned from the original build sheet. Balanced & blueprinted, Crane Cams hydraulic flat tappet cam #HMV-278-NC which has a lift of .467 intake, .494 exhaust, duration 278/290; I got this info from Summit:

https://www.summitracing.com/parts/...Ic2fvEjIcHfUdvV31Uyt64XuMUkbvZUlZQf0LcHHMnlBR

All you engine experts out there, I'd really like to hear more about this engine build; what are your thoughts? This was done as a mild street build. My car has about 30K miles on this engine. It's been garaged for the past 25-ish years and I last had it running 12 years ago, and hope to get it fired up again before winter, just to get me excited again.

 

[4mulas]

What do you want to know? All the info is there.

Looks like an average performance 383 with a slightly larger than stock cam which in a big car will be just ok. It’s bark will be worse than it’s bite.

The pistons look pretty far in the hole, probaly doesn’t have the highest compression that’s for sure

 

[Coelacanth]

What do you want to know? All the info is there.

The specs don't really mean much in terms of actual performance to the non-engine-rebuilder average Joe. I'm interested to know what the build is like in layman's terms. When I brought the car to them, I basically knew not much more than to say "I want my engine balanced & blueprinted, install this Mopar Performance electronic ignition kit, and have good street performance"...because I didn't know any better.

Knowing more might help me decide how to move forward with future engine improvements and suggestions. Thanks!

 

[Doorkicker]

Thanks for sharing. This is pretty cool. I love looking at this kind of stuff... especially from back in the 80's & 90's. I'm sure you're going to get a lot of opinions (it is the internet, but here are my quick reactions.

In short, all the numbers look pretty good! It looks like all the clearances are consistent and in the desired window, which explains the good oil psi. You have a stock heads (906) and stock springs, which should be fine for that lift. Definitely not a high RPM motor, as you can see the CAM is relatively mild (5k redline perhaps). Deck height is not bad, but that plus the 0.058 head gasket may not make for a high compression ratio. Rough numbers... for that bore, stroke, head chamber, and assuming flat pistons... that's about a 7.85 CR at 388 CI. The LOA (114 deg.) on the cam may not help with CR... dunno, but not a big deal honestly for this motor. I'm assuming he installed the cam dot to dot without timing.

I'm sure it sounds really nice and will let the smoke out of the tires just fine I think it looks like a good, solid daily driver motor that should do well. Just use top grade oil, oil filters, and air filters and it'll last you.

 

[Coelacanth]

Thanks guys, keep 'em coming. And if you were to change anything to step up performance a bit, internal engine-wise, share any suggestions. I still want the car to be a cruiser, not a bracket racer, but everyone looks to eke out a bit more juice when you goose. I currently have a 3.23 Sure-Grip but will be upgrading to 3.55's. Manifold is an Edelbrock Performer 383 and matching Eddy 750 carb. I rebuilt the carb this summer and added a K & N 14" x 3" air filter. I'll get rid of the Fram oil filter and install a Wix.

 

[Doorkicker]

The specs don't really mean much in terms of actual performance to the non-engine-rebuilder average Joe. I'm interested to know what the build is like in layman's terms. When I brought the car to them, I basically knew not much more than to say "I want my engine balanced & blueprinted, install this Mopar Performance electronic ignition kit, and have good street performance"...because I didn't know any better.

Knowing more might help me decide how to move forward with future engine improvements and suggestions. Thanks!

The specs are basically stock. The bore 030 over is common to ensure a good cylinder wall and seal with the rings and makes for a good fit with the pistons, but not really done for performance. The heads were shaved at 0.005 to ensure a good seat to block and gasket. Like I said in the other post, the good news is that the clearances are pretty spot on, what you want from a good machine shop. You appear to have a forged crank that has very, very close stock dimensions, straight, and everything balanced. He probably only polished it, so that's stock and solid. No mention of piston or rod details, but I'm assuming stock because the wrist pins were pressed in (I could be wrong).

The only thing that is non-stock (from what I can see) is the cam. By today's standards, that's a somewhat mild cam... meaning not a huge amount of lift or duration and the lobe separation angle (LOA) is a touch wide (IMHO) for a muscle car. It'll make for a smooth(er) idle for sure and you likely have good low-end torque. The compression ratio is likely stock too... it was the start of the 70's!

I bet it sounds great, idles nice, great vacuum, and will feel good when you press the peddle. It's a good motor (looking at the specs). Not a drag car... not big HP. But that's not what it was built for. Gut says.. I think you got what you asked for - good street performance. In the late 80's... the years where 300 HP on the street was mind blowing and it was all about burnouts... you got that

Anyway... just a fella's $0.02.

 

[Coelacanth]

Appreciate the feedback, Doorkicker. I was told back then it would probably be around 350 hp...a bump over the OEM 335 hp rating.

 

[Doorkicker]

Thanks guys, keep 'em coming. And if you were to change anything to step up performance a bit, internal engine-wise, share any suggestions. I still want the car to be a cruiser, not a bracket racer, but everyone looks to eke out a bit more juice when you goose. I currently have a 3.23 Sure-Grip but will be upgrading to 3.55's. Manifold is an Edelbrock Performer 383 and matching Eddy 750 carb. I rebuilt the carb this summer and added a K & N 14" x 3" air filter. I'll get rid of the Fram oil filter and install a Wix.

Keep in mind when you go to the 3.55 your cruse RPM will increase a bit and the engine isn't really setup for anything over 5k. But the change will certainly help a lot in burnouts BTW... the eddy intake - great choice for the motor imho.

As far as improvements... gut reaction, drive it around a lot and then decide how far it is off from where you want to be. Then think about what you want with that baseline and shoot just a bit past... and you'll be happy for a long (or longer) time. For example, does great burnouts, but not great acceleration, or no top end power to pass people, or you float the valves at 4500 rpm... etc.

From a pure performance perspective... you have a couple things to think about.

Compression ratio is not necessarily optimal. So, you'll always be fighting that. If you don't want to change pistons (which I suspect is not really an option), then you can look at everything from new head gaskets (very minor improvement) to putting on new heads altogether (fast, easy, not inexpensive). Although the 906's are very good heads, they're not the best flowing head in the world (edited: Correction, the 906's flow good and they're actually in demand. When I first wrote this I was thinking that with a new head you'd can get a smaller chamber to increase CR, as well as having the option to increase flow with port size and valve size.). But, if you go in the new heads direction (recommended), you have to improve the cam. The cam IS the heart of the motor and pretty much defines how the motor performs. Get more lift to support the new head flow and more duration to move the power up and get more RPM range. You could actually get quite far with just a new cam... which is a super easy install.

Honestly, it all comes down to what you really want from the engine, and the best way to figure that out is get out there and drive it a bunch and find out if it's a little too much, a little too little, or just right. And then money ;)

 

[Doorkicker]

Appreciate the feedback, Doorkicker. I was told back then it would probably be around 350 hp...a bump over the OEM 335 hp rating.

I'd say 350 HP is very realistic. Of course, it depends on other things... like fuel system (carb, intake), ignition system (especially timing!), and how all that may translate to the ground.

 

[RemCharger]

Looks like a well measured build. The ring gaps are a bit tight, forget the juice. The headgasket # is weird enough, I'd wonder if it's a misprint ( .038)? Easy to check, find a spot between the head and block you can stick a feeler gauge in. I would think 5500 should be closer to max, depending if the stock springs will hang in there.
Edmonton has a great track. I would utilize that before doing any mods to have a baseline. I would think you might be in the 14.5- 14.2 area.

 

[Doorkicker]

Looks like a well measured build. The ring gaps are a bit tight, forget the juice. The headgasket # is weird enough, I'd wonder if it's a misprint ( .038)? Easy to check, find a spot between the head and block you can stick a feeler gauge in. I would think 5500 should be closer to max, depending if the stock springs will hang in there.
Edmonton has a great track. I would utilize that before doing any mods to have a baseline. I would think you might be in the 14.5- 14.2 area.

stupid question... where did you see the ring gaps in the paperwork?

 

[RemCharger]

Not stupid at all

stupid question... where did you see the ring gaps in the paperwork?

 

[BSB67]

I agree it looks like a good/quality build. A little uncertainty regarding head work, i.e., quality of valve grind and bowl work. But those are probably details that aren’t that important now.

Personally, from a performance perspective, I don’t like the compression ratio and that cam with the low compression ratio. If the CR was higher, the cam would be fine. I’d keep the intake.

So the question to you is what is your budget and goal. On the low end, a different cam. On the high end pistons and heads, or in the middle, heads and cam.

 

[496 polara]

The single biggest improvement IMO would be a head swap with a thinner head gasket. Something like the Edelbrock E street with 75cc chambers and a thinner head gasket would likely wake everything up significantly. No cam break in to worry about either.

 

[Coelacanth]

The single biggest improvement IMO would be a head swap with a thinner head gasket. Something like the Edelbrock E street with 75cc chambers and a thinner head gasket would likely wake everything up significantly. No cam break in to worry about either.

Found a nice review on these heads here; thanks for the recommendation! I think I'll take it if I happen to fall into some money!

https://www.motortrend.com/how-to/installing-and-testing-the-edelbrock-e-street-cylinder-heads/

 

[#41]

I do see "mild port 2 heads". Who knows what they did, but it probably didn't hurt. Stock rods are resized, crank reused, 30 over, moderate cam and associated gear, ..... a pretty standard rebuild. After 30,000 miles, they obviously did it right. Nice to have that paperwork.

But wow, $3811? I'm not sure what the translation into Canadian was back then, but I had a 71 440 long block get the same treatment in 1989 for $1000 US + tax out the door. The only appreciable difference was that I ported my own 906 heads before dropping them off at the machine shop.

I also ran that engine for about 30k miles, but before I sold the car I went to swap out the ported heads for stock ones and found that running unleaded gas for 21 years had severely sunken the exhaust valve seats.

 

[Coelacanth]

But wow, $3811? I'm not sure what the translation into Canadian was back then, but I had a 71 440 long block get the same treatment in 1989 for $1000 US + tax out the door. The only appreciable difference was that I ported my own 906 heads before dropping them off at the machine shop.

I know, Campbell Automotive was an expensive machine shop then, and probably still is today. However, they were known as a reputable shop that knew their stuff when it came to building engines for racers (not that I was one by any means), and you pay for that kind of knowledge and expertise. Sure, lots of shops might've done it for a lot less, but unless you "knew a guy you could trust"--and I didn't--it's a risky venture. Also this was a price for driving the car to the shop and leaving it, it wasn't a motor already pulled. No doubt pulling the motor is a big factor in the labor cost.

 

[#41]

Also this was a price for driving the car to the shop and leaving it, it wasn't a motor already pulled. No doubt pulling the motor is a big factor in the labor cost.

That explains a lot. 30k miles and 25 years later I'd say you got your money's worth.

 

[BSB67]

And they bought everything, intake, valve covers, fluids including gas…, if I’m reading it correctly

 

[BSB67]

Pulled up my invoices from 1990. Machine shop work and associated parts was $1,470 in Ohio. I did the assembly and bought everything else myself. I have a stack of Mancini and Jegs invoice for that build too. I bet it was $2,500 before it rolled out the driveway.