383 Rev Limit question

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02sixxer

02sixxer

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I have a 383 with a few addons and want to know where it sould be reved to. This is my first Big Block and First Mopar.

The engine has a .509 purple shaft hyd cam, with matching lifters, 915 heads stock (i believe), MSD Ignition 6a, Pro Billet Distributor, Team G Intake, 850 Demon carb, Unknow pistons (will find out when I pull the heads), or current compression, previous owner only ran 111 octane so I believe it has a rather high cr.

Next question, with head work what where should it be revved too.

Head work would connsist of new springs (what would be reccomended), 1.6 Roller rockers, I would like to have it machined for larger valves i believe I have the 1.60 exh valves and would like to increase to 1.80, the intake valves are 2.08 how much larger should I go if I go to 1.8 exh. I dont think I will have the money for a port or polish. If so I would just by a pair of edy's.

Thanks for the help as I said this is my first time with Mopar and a Big Block. Right now it runs strong and sounds great. If you need additional info ask and if i know i will answer. Also i think the exhaust migh be a little small it a true dual with a cross over flowmaster delta flow mufflers but only 2.5 inches. I thought it should of been 3".
 
6,500 wouldn't concern me a bit. The hydraulic lifters will likely be what limits you. Thats plenty of cam in my opinion, so head flow will prolly be what will limit your power. 2.5" exhaust isn't bad, I would prefer the 3" myself. Good luck.
 
Not having the money for a new set of aluminum heads at this point, and probably not having the money to port the current ones either would you reccomend changing the valves and if so what valve size would you replace the small valves of the 915's with?

I figured that the heads would limit the engine more than anything right now. Far as I know they are stock.
 
If your 915's have the 1.60" exhaust as you suspect, I would go with a minimum of a 1.74" exhaust. It's important to have the bowl area under the valve opened up afterwards. Just sticking a bigger valve in and leaving the port under it restricted doesn't help much. If moneys tight, maybe do a little bowl work yourself using the MP porting templates?
 
First off, 2.5" is WAY enough for a 383 built how you describe. That size exhaust will flow 600 HP and do it well. Unless that exhaust system is just JUNK, I wouldn't worry about it. 2.5" is fine. You have a bit of a mismatch with those heads in the mix, though. That 509 cam is a BIG hydraulic. That cam, Team G and 85O wanna flow WAY more than those heads can take. LOL You put some ported Eddys on that thing and it'll be just a beast of a 383. I take for granted you have headers? You didn't say unless I missed it.
 
You can (Or should be able to) get the iron heads done for less than Edelbrock heads. The new springs should be MoPars own. They have springs to match there cams.
P5249848 for .480 - .540 lift,
P2806077 for .500 - .610 lift.
Your lift of .509 with 1.6 rockers is; .54293333333333333..........
I'd run the second spring for more control with the 1.6 rockers.
Going the next valve size up is adviseable like mentioned above You really do not need a larger intake valve. A larger exhaust valve would be good. Have the machinest bowl port and gasket match the head.
The MP porting template for the B/RB stock head is P4120437
Also, DO NOT be bothered "Polishing" the head. It is sooo not needed. Save it for when your racing for the money with serious hardware on top.

IMO, dump the Team G and use ethier a RPM or M1 single plane intake.

The cams basic RPM range is 2600 - 6000 RPM's. Shift at 6200 and cross the finish line at 6500. for a beginer. Adjust shift points upwards at 200 rpm jumps to see how it performs in MPH and et. (Mostly et.)

You also mentioned that the previous owner only ran 111 octane. This would suggest it has indeed a very high compresion ratio and I think it nuts to run one. But! One of 2 things may happen here. Ethier it does indeed have a high ratio or the previous owner is an idiot who ran the 111 gas for no other reason but stupidness. (My fav excess, I like the smell of it.)

OH, your exhaust @ 2-1/2 is fine. 3 would be better, but it's not reall worth the $$$ to change unless your on the track with the like gear,stall, tire size/style/compound, car weight, etc.........
 
Thanks everyone, this helps quite a bit.

I think it has a rather high cr, the owner was building the car to be a strip car. Thats why I think he went out of his way to tell me he was running 111 and that he reccomends that I stay with race fuel.

thanks for the part numbers. When I pull the heads I will post up some pics
 
You may just be an open chamber set of heads away from a pump gas engine. The bonus to such a swap, aside from not having to run race fuel, is a set of say, #452 heads will already have the larger exhaust. It shouldn't be too hard to find someone willing to swap a set for your 915's.
 
power wise, how much difference would the open chamber heads make. Right now, the previous owner stated the car was slightly over 500hp, however, i have not seen a dyno on it. So if the cobo dont look that storng dont slaughter me. Like I said to begin with, first mopar.

are the 452's the only open chambers receomended, what about 906's.
 
BTW, I do have a pair of hedman (per previous owner) fenderwell headers, ther are 1.75 inch tubes comming into a 3"
 
There are several open chamber heads, including the 906s's, 346's, 452's, etc. I mentioned the 452's as they are pretty easy to come up with, and had hardened exhaust seats from the factory. If your 915's are stock, and have the smaller 1.60 exhaust valve, I would expect a small power gain going with any of the open chamber designs, even though you will lose some compression.
 
wow, i thought i would lose power.but just compression

and be able to run pump fuel. wow whats the down side
 
When you get the heads off, you will have a better idea of whats going on. If it's around 11:1, the open chamber swap might be a good direction to go. If it's much higher, that swap might still leave you with too high compression for pump gas. The 915's are a much sought after head, due to it having the larger ports of the 906's, with the more efficient closed chamber design. The often encountered small exhaust valve is their biggest downfall. The open chambered designs have a better balance of intake and exhaust flow in stock form. It's probably only about a 1/2 point compression drop from one design to the other, and my guess at it making a bit more is based solely on the better airflow of the newer casting numbers. I'll try and figure out exactly how much compression you would lose and get back to you.
 
It's actually almost a full point, about .9 of a compression point, which is a healthy chunk. A better flowing head might make up for that, but only the track would really be able to tell you.
 
I appreciate all the help, I will be pulling the engine in two weeks to have the car painted at that time i am pulling the heads to see what has been done. I dont even know if the pistons are over sized or std. I dont know if they are flat top, dome, dish, any thing. I know it runs very well and seems to be very quick. I expected less low end quickness from a big block. Comparing to my chevy an 86 Monte Carlo SS with a 350 pushing 450hp and running 4:11 gears, the duster seems to be quicker with 3.89 gears and it has a ford 9" rear.

when I pull the heads I will take photos and post them just so you can see what I am working with. I cant figure the CR because I dont know whats under the heads. It would be ideal to run pump fuel instead of $8 a gallon race fuel. Not knowing the CR i dont want to risk putting pump fuel in when I was told to runn 11 or 110 by previous owner.
 
I'd say that before going much further, like switching to 1.6 rockers, you're going to need to find out exactly what you got. First I'd be surprised that your friend would build this strip engine and stay with the small exhaust valves originally found on the 915's instead of fitting the 1.74's. This was usually the first change racers made to these heads and the 516's that also had the small valves. Next would be what type of pistons are in it, flat top, flat top with valve reliefs or raised dome and what is the deck height, zero deck or slightly below. These items will come into play when you measure your piston to valve clearance and therefore if you can go with 1.6 rockers. What rockers are in the engine now, good roller rockers will get you 10-20 HP over the stamped steel because the stamped steel were rarily 1.5 from the factory and were actually in the mid 1.4's which robbed you of valve lift.
As said before ditch the Weiand and if it's a strickly strip engine go with the M1 or a little street the RPM Performer and that 850 is plenty of carb for that 383 maybe to much but time at the strip will tell. The Weiand has cast in restrictions on 4 of the 8 runners to make way for the manifold to head bolts. I got one for sale if you know of anyone that wants one.
Also if you're going to be spinning this thing at 6500 to 7000 rpm you're going to need a high volume oil pump and deep oil pan, 7 quart minimum.
 
When I pull the engine and start figuring out how it was built I will find out if I can go with the 1.6 rockers or just stay with a 1.5.

I want the car to be streetable but not for long driving just local things here and there, maybe 500-1000 mile a year and to be a strip car. Right now its set up for the strip with 28x 10.5 MT slicks and 4 inch front tires both on weld rims. I plan to get a set of street tires and rims for anything local.

i cant wait to have time to pull the engine just to see what I am dealing with.
 
383s take more money and an eye for detail to build and get big power from. My impression is this one might have a lot more left in it depending on the execution. but that was why I said pull a head and then post some pics. At this point, I wouldnt use that cam at all for a street car regardless of what it's got for pistons or machining.
 
Moper, thanks. I wish I could pull it thiss weekend but I will be out of town and next i work. So it will be a lil over 2 wks before I can but I will definitely post pics of everything.
 
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