Got the engine full disassembled

[eagleone1983]

I finally got my '67 383 fully disassembled so I can take the parts to a shop to have them inspected and machined as needed. During the disassembly and upon bumping casting numbers I found that the engine has '67 440 hp heads casting number 2780915. I also have a '78 400 that is currently in the roadrunner and I haven't checked to see what kind of heads are in that possibly 452s or 906s. Which would be my better option? The only difference I see between them is closed/open chamber respectively. My plans with the motor is hopefully acheiveing 450-500hp as far a torque I have no idea what I can get out of it. I've never built nor do I know much about building engines :edgy:.

 

[Deleted member 214]

The 915s would give you more compression, maybe half a point????? which equals more power. They also can create quench between the top of the pistons at top dead center and the flat part of the combustion chamber. That's a good thing if done right, but a better motorhead than I will have to explain it.

 

[dantrap]

The 915 is the way to go if your looking to make more power. Just have your builder install hardened seats during your rebuild. While they are at the shop some pocket porting along with bronze guides and stainless valves. Make sure you use the recomended valve springs and retainers for your cam. The only problem is by the time you spend all the cash to redo the 40+ year old heads your close to the cost of a new alum. set. Good luck with your build.

 

[Meep-Meep]

915's are the best production heads in my opinion and for all the reasons stated by Greg70. Yeah, the Max Wedge is up there in the food chain, but these are easier and cheaper to get. The non obvious difference between these and the 452's is the intake port. The 915 and 906 have the same port with a hump on the floor. In the old DC books they say to not mess with the short side radius when pocket porting so I'm thinking this hump together with the corresponding roof promotes a nice laminar flow as the fuel mixture turns the corner into the valve pocket. I have also read the hump can hurt you on the flow bench but what it really boils down to is wet flow. By the way, the Source heads and the Edelbrocks don't have a flat floor like the 452's, so maybe there is something to the hump.

I have seen 915 heads factory installed on early 383's but they are not the hi-po heads. They will have the small 1.6" exhaust valves. The factory hi-po heads will have an "HP" stamped on the end with the bolt holes. No matter what they are still the same head casting just the exhaust valve is smaller. You will need hard seats for the unleaded gas so that would be the time to go with the 1.74" valves. Quench is essential to minimize detonation to run the crap they call gas these days. Head work is expensive so if you have to put a lot of money in guides, seats, etc... You might be ahead of the game by using the 440Source heads.

Years ago I ran a 383 with the 915 heads, zero deck flat tops, .528" MoPar cam, Torker, 3310 Holley and it pushed a 3700 lb 68 RR 12.65 @ 107 with 8" slicks and a 4.88 Dana. That's with a stock converter stalling at 1800 and the power steering hooked up, and the car still was turning the slicks about a half turn on launch. Optimizing the suspension I think I should have gone 12.40.

 

[eagleone1983]

12.65 seconds sounds good to me. I just want to make sure that some kid in a Honda with one of those annoying bumble bee exhaust isn't going to make a fool out of me or Mopar. When I bought the motor the guy said the heads had just had a valve job as far as anything else with the heads I'm not sure. I really wouldn't even know what I was looking for. The valve area and valves look pretty clean except for one cylinder which had more carbon build up than the others. I'm going to take off early from work today so I can get the heads and block to the machine shop. If head work really is going to be more expensive than just buying 440 source stealth heads (I'm guessing those are the heads you are referring to) then I'll probably just get those.

 

[Meep-Meep]

The real problem when comparing to a Civic is the weight. Even though our cars are not as heavy as people think, they are still heavier than a tin can.

For my 68 RR I used the formula in the DC book, plugged some real numbers in to it and calculated 370 HP. I'm guessing that's applied, or rear wheel HP. Factor out the drive train (TF) and this could very well be over 400 at the crank, and that's with no "trick" aftermarket parts except forged pistons, cam, intake, carb and headers.

 

[Patrick]

915's are the best production heads in my opinion and for all the reasons stated by Greg70. Yeah, the Max Wedge is up there in the food chain, but these are easier and cheaper to get. The non obvious difference between these and the 452's is the intake port. The 915 and 906 have the same port with a hump on the floor. In the old DC books they say to not mess with the short side radius when pocket porting so I'm thinking this hump together with the corresponding roof promotes a nice laminar flow as the fuel mixture turns the corner into the valve pocket. I have also read the hump can hurt you on the flow bench but what it really boils down to is wet flow. By the way, the Source heads and the Edelbrocks don't have a flat floor like the 452's, so maybe there is something to the hump.

I have seen 915 heads factory installed on early 383's but they are not the hi-po heads. They will have the small 1.6" exhaust valves. The factory hi-po heads will have an "HP" stamped on the end with the bolt holes. No matter what they are still the same head casting just the exhaust valve is smaller. You will need hard seats for the unleaded gas so that would be the time to go with the 1.74" valves. Quench is essential to minimize detonation to run the crap they call gas these days. Head work is expensive so if you have to put a lot of money in guides, seats, etc... You might be ahead of the game by using the 440Source heads.

Years ago I ran a 383 with the 915 heads, zero deck flat tops, .528" MoPar cam, Torker, 3310 Holley and it pushed a 3700 lb 68 RR 12.65 @ 107 with 8" slicks and a 4.88 Dana. That's with a stock converter stalling at 1800 and the power steering hooked up, and the car still was turning the slicks about a half turn on launch. Optimizing the suspension I think I should have gone 12.40.

The 915 was the 383 four barrel head in 66&67 as well as the 440 head. The reason you only clean that little hump in the chamber is you'll hit the water jacket.

 

[eagleone1983]

Well I dropped off the block, heads, pistons, crank, and cam at the machinist yesterday. They are going to be measuring everything and letting me know where it all stands. I wasn't sure exactly what to bring them so I just brought that stuff. The cam most definitly will be replaced anyway but I just wanted them to find out what type of cam it is. I told them that I had other heads although I still haven't had time to find out what they are. The told me with the closed chamber 915s I'll have to choose my pistons carefully so we don't get crazy on the compression. Any suggestions?

 

[Meep-Meep]

My 383 as described above ran on pump 92 but that was before the gas really went to hell. Not sure how it would react now. It's not just the compression but how you go about getting it. The quench area is your friend!! I don't remember what the compression height is on my forged replacement pistons but they are .005" in the hole max. Closed chamber with up to .040" in the hole should be good too and might drop the ratio by 1/4-1/2 point. You can run the calcs yourself based on published info to get an idea, but ultimately you should cc everything.

I know there is a water jacket under the hump in the intake port but didn't know that was the only reason to not mess with the short side radius. Makes sense.

 

[eagleone1983]

I talked to the head of the shop today although he is not the machinist doing the work he told me things might get a little crazy to try and make 450-500 hp with the 915 heads. I'll be talking to the machinist when he gets back from vacation on Tuesday. He also advised me that we might be getting pretty close to not being able to pass emissions with the 383 pulling that many horses. Luckily I have a way around that . If I do get aftermarket heads are the 440source stealth heads the way to go? I've heard mixed reviews mainly good ones.

 

[69 Runner]

pass emissions? Since when does a car thi old have to pass emissions?

 

[Deleted member 214]

He's in California, remember...

 

[69 Runner]

I'd move:edgy:

 

[Meep-Meep]

In CA the cut off for emissions is 1975. What is this 383 going in? My 383 used to pass the CA emissions (before the exemption) with a .528" cam, but I had to tweak it a bit. What I did was set the valve lash about .004" looser on I & E to kill the excess overlap plus install a DP4B and a factory AVS. I remember the readings were about 3% on the CO and 350 PPM on HC and the pass requirement was 6% and 600 PPM. My old 67 bug was allowed 1200 PPM!!

I think breaking well into the 400 HP barrier with 915's (or any production head) on a 383 is no problem. With the advent of cheap aluminum heads the only decision you will have to think about is the cost. The max HP should be in the 6000 RPM range and the max torque I'm guessing will be about 450 ft/lbs or more at about 4000 RPM. Stock 383 Road Runner engine rating is 335 HP @ 5200 RPM and 425 lb/ft @ 3500 RPM. Proper cam, compression, intake, carb, gearing, etc.. and you will be scrambling for ways to hook it up!

 

[eagleone1983]

No not Cali...I'm in Utah and we have emissions out here as well. I'm not sure what the cut off for emissions here is but they definitely told me my '69 Runner has to pass. My other option is using the 452 heads I currently have in the car if the 915s become more of a problem then they are worth.

 

[69 Runner]

The 452s will have a chamber that's about 92cc's. They have induction hardened seats, which will probably be lost during a valve job. They have flatter intake runners than a 906, but have more short side radius in the exhaust than a 906.

I'd be surprised if your car had to make any emissions other than for it's year of manufacture. And because of the cleaner gas and oil, it should do that easily.

 

[CtownChris]

Utah requires cars 1967 and newer to pass emissions.
Only older then that are exempt.

 

[eagleone1983]

Runner, I know nothing about heads so would my best bet be the 915s or the 452s? You are also correct I only have to meet emissions from 1969.

 

[eagleone1983]

Well I just got off the phone with the builder and he told me that I might be running into trouble trying to produce 450-500 hp out of my 383 using the 915 heads due to flow. He gave me the "no replacement for displacement" speech and said I'd end up throwing a lot of money in the heads to give me the kind of hp numbers I'm looking for. He's going to be running some budget numbers for me and see what we come up with. He also was talking to me about building a possible 451 stoker since I currently have a 400 in the roadrunner and he has a 440 crank.

 

[69 Runner]

Like he said, there's no replacement......

However, one thing he might be forgetting is that a 906/452/915 whatever is a BIGGER head on a 383 than it is on a 440. That's right. It's all relative. And since the 383 is (obviously) smaller than a 440, then what the heads flow is more relative to the engine's size. My old 69 Bee with it's number's matching 383 put 375 to the ground using 346's, a DP4B, .474/280 cam, 9.9:1 comp, and 625 cfm AVS.

So yeah, you can get that much HP out of a "lowly" 383. You just have to match all the parts. As far as the heads go, some people swear by the 915s thinking they are the be-all-end-all production head. Personally I don't think they're any better than anything else.

The last thing I'll say is it will be easier to make the power you want without using a bunch of compression if you go with a bigger motor. But it's fun to say "It's just a 383" when you kick someone's ***