moparchris
Well-Known Member
roadrunnerh said:
One thing I would complain about the MP cams is that the older grinds (the 484 and 509 specifically) have terrible vacuum at idle. There is definitely better stuff out there today.
383 project: The tear-down
- Thread starter roadrunnerh
- Start date
One thing I would complain about the MP cams is that the older grinds (the 484 and 509 specifically) have terrible vacuum at idle. There is definitely better stuff out there today.
roadrunnerh
Well-Known Member
Here is a rebuild I read that piqued my interest.
http://www.moparmusclemagazine.com/techarticles/mopp_0209_383_engine_restore/index.html
What do ya think fellas?
http://www.moparmusclemagazine.com/techarticles/mopp_0209_383_engine_restore/index.html
What do ya think fellas?
mcmopar
Well-Known Member
I used that very article when recamming my 383. The cam they chose is a little big for a 383 so I went with the Comp XE275HL-10 which has timing events of 231-237 duration (intake-exhaust) with a 110 degree lobe c/l and .525" lift. Its still a little too big for my taste and idle vacuum is at about 10.5". If you have power brakes you may well need a vacuum canister (I installed one in my car).
The other problem with this cam I and others have had is that the idle circuit is rich - so much so that it can really make your eyes water. I have tried many ways to make it stink less but to no avail. At highway speeds my jetting is right on the money. I am running a Holley 750 vac. secondary carb modded to 4 corner idle with 4.5 power valves on both ends.
Gas mileage for me on the highway with 3.55 gears is anywhere from 10-13.5 mpg depending on how fast you want to run, headwind, etc. This past year I drove the car from Orlando to Ocala for the Big Daddy show and on Sat. it got about 13.5 mpg up and back. Sunday it got about 11 mpg with no other difference other than a fair headwind going up. I tried to keep speeds the same; 60-65 mph each day. The power is superb, though, at highways speeds. It feels soooo good and sounds great through the 3" exhaust. It also has a nice, rumpety idle if that is what you are looking for.
I'm toning it down to a milder cam to try and get rid of the idle richness, increase idle vacuum and make the car smoother running. I shouldn't lose too much horsepower - perhaps 20 or so which to me is worth it.
Comp has some milder sticks that would be worth looking at if you aren't going to run headers, a better than stock intake and carb and ported heads.
The other problem with this cam I and others have had is that the idle circuit is rich - so much so that it can really make your eyes water. I have tried many ways to make it stink less but to no avail. At highway speeds my jetting is right on the money. I am running a Holley 750 vac. secondary carb modded to 4 corner idle with 4.5 power valves on both ends.
Gas mileage for me on the highway with 3.55 gears is anywhere from 10-13.5 mpg depending on how fast you want to run, headwind, etc. This past year I drove the car from Orlando to Ocala for the Big Daddy show and on Sat. it got about 13.5 mpg up and back. Sunday it got about 11 mpg with no other difference other than a fair headwind going up. I tried to keep speeds the same; 60-65 mph each day. The power is superb, though, at highways speeds. It feels soooo good and sounds great through the 3" exhaust. It also has a nice, rumpety idle if that is what you are looking for.
I'm toning it down to a milder cam to try and get rid of the idle richness, increase idle vacuum and make the car smoother running. I shouldn't lose too much horsepower - perhaps 20 or so which to me is worth it.
Comp has some milder sticks that would be worth looking at if you aren't going to run headers, a better than stock intake and carb and ported heads.
mcmopar said:
Oh c'mon, John, you're really making far too much of this. I've been behind your car cruising at idle for extended periods of time and it really is no worse than getting caught in a trench under a Nazi mustard gas cloud... :lmao: :lmao: :lmao:
:jester:
O.M.T.
mcmopar
Well-Known Member
ACME A12 said:
:lmao: :lmao: :lmao: :lmao: That good huh? :lmao: :lmao: :lmao:
I know i'm new here,but have some experience in this.The hyperuetectic pistons need alot of gap on the top ring.So what I would do is use either the childs and albert zero gap rings,or total seal rings.Use the gap rec.by piston manu.and then add a couple more thou.With that type of ring the extra gap won't hurt ring seal.And i'm a big fan of zero decking the block.Of course you need pistons that have a comp.hght that will allow it.There are pistons out there that allow you to run a 440 rod and still retain the 3.38 stroke.( when I do my next engine I am going to do that)Hone the block with torque plates and your ring seal will be less than 2%.And don't get to loose on piston to wall clearance with those pistons,a bit on the brittle side.My :cents:
CompSyn
Well-Known Member
jjl said:
I'm now leaning towards doing a 383 with the stock stroke and 440 length connecting rod. I have a numbers matching 69 383 RR. Anyway, the 440 rod puts the rod ratio at 2.01:1 which I'm to understand is the holy grail of rod ratios plus you get a lighter piston with that rod combo. So I bought a set of K1 h-beam rods with the lightweight 2.200"/0.990" journal sizing and Big Block Mopar rod widths to perfectly fit on the stock crankshaft. For pistons, Diamond supports Big Block Mopars nicely with some nice off the shelf piston choices for most of the popular rod/stroke combos talked about here. The only thing is I still feel tempted to do either a 383/432 stroker or 400/451 stroker as I have all the parts to go either way. It's tough as I appreciate the nostalgia and history behind the 383 Road Runner engine and want to honor the 383 callouts on my Road Runner hood. Decisions... Decisions...