390 w/open chamber heads

[Treblig]

I have a 318 and a nice set of 360 heads. The heads are 596s ('80-'85) open chamber with 66-72 cc chamber. I will cc the heads and do a mild port job (open them up a little). So that I don't get any wild answers or questions about a drag motor build....I'm building a torque monster, nothing over 5500. I'll be running a 200R4 with 3.08s or maybe 3.42s. Don't think I'll need lower rear gears with the low first gear in the 200R4. This will be a daily driver and I plan to occasionally stomp on it just to see the look on peoples' faces.
My question is this....I've read a lot about quench and the closed chamber heads. I have a pair of 302s on my 318 (904 trans) and I wasn't impressed with the results. I mean it has a pretty good low end with the 308 gears but I want to be put back in my seat. With the open chamber 596 castings I'm not going to get any quench BUT since I have all that stroke I should have no problem getting good compression (9.5 to 1). In fact, I'll have to be careful not to get a high dome so that can't run on pump gas.
The 390 will go into a '69 Barracuda. I guess I'm worried about getting "ping" (detonation) since I won't have any quench. Has anyone built this combination before. No super high lift cam, no super high RPM, no super low gears, no quench. I want to be able to cruise on the highway and also come off the line like a batouttahell. Hoping for at least 325 horses!!
Forged steel 4' stroker crank
Ferrea SS valves 3.02, 1.88
SIR6123 5140 forged steel rods
2176 Performer intake
92-02 mag Truck exhaust on pass side, 340 exhaust on drivers
2 1/2 pipes (twice pipes with crossover) all the way back
Edelbrock carb
Port matched intake and exhaust
Haven't decided on pistons yet
Can't get cam made until I cc heads and get chamber volume

thanks in advance,
Treblig

 

[RustyRatRod]

The low first gear in the 200 is not the issue. The issue will be in overdrive with such highway gears. You will be constantly jumping in and out of overdrive. Geez guy, put 4.10s in it. You'll only have 2.74 final drive. That's what OD transmissions were designed for.

 

[70aarcuda]

Try 2.02 intake and 1.60 exhaust valves...those will fit...
get rid of Performer intake and get a Performer rpm at least...
pistons...not a large selection...Diamonds or Icons..

 

[Treblig]

RRR,

I haven't figured the final RPM in forth gear yet. I thought 4.10 gears would be too low. Geeez, I'll be pulling wheeelies!!!! I want to maintain about 2200 to 2800 RPM at 65-70 MPH. I'll have a torquer cam so I'll have plenty of low RPM power. What RPM do you think my engine would be doing with 4.10s and 70 MPH (think my rear tires are 28")...I'm not against 4.10s I just don't want high RPM at highway speeds.

Treblig

 

[skrews]

Don't think I'd pop for a forged steel crank with the kind of usage you're talking about. I go with a SCAT 9000 series crank myself. http://www.summitracing.com/parts/sca-936020/overview/ much less $.
The 596 heads would be my pick, with 2.02/1.6 valves. Have the bowls cut and blended for the bigger intake valve. The Performer with a proper port match will do OK, but a Performer RPM would definitely make more power. I don't think the RPM will fit the AC compressor you have in the pics though.
Don't go over board with the compression, 9.5 tops. Might want to talk to Mike at MRL, get you set up with a rotating kit.

 

[skrews]

Friend of mine has 4.30 with a 518 OD trans running 28" tires. Goes down the hiway quite nice. 4.10 would probably be even better.

 

[RustyRatRod]

RRR,

I haven't figured the final RPM in forth gear yet. I thought 4.10 gears would be too low. Geeez, I'll be pulling wheeelies!!!! I want to maintain about 2200 to 2800 RPM at 65-70 MPH. I'll have a torquer cam so I'll have plenty of low RPM power. What RPM do you think my engine would be doing with 4.10s and 70 MPH (think my rear tires are 28")...I'm not against 4.10s I just don't want high RPM at highway speeds.

Treblig

I just told you the final drive with 4.10s. 2.74. Plenty of online calculators out there to tell you what your RPM will be. Don't use 4.10. Use 2.74.

 

[Treblig]

70aarcuda,

You said replace my Performer intake and get a Performer rpm?? If I'm not going to high RPM won't it help to use the intake I have (2176).

skrews,

Why do you say that the RPM will make more power...more flow??? Will I need more flow with a torque motor (no high RPMs)?

thanks,


RRR can't make up his mind, I said that 4.10 gears weren't out of the question, I just want a lower cruising RPM. Can't stand to hear my motor wind at highway speeds.

Thanks,
Treblig

 

[skrews]

Just do a deep port match on the Performer. The Performers ports are somewhat in between the 318 and 360 size. I doubt the difference between the two would be noticed once this is done for how you're running it.

 

[340sFastback]

In fact, I'll have to be careful not to get a high dome so that can't run on pump gas.

The standard off the shelf Icon dish pistons will get you around 9.5 compression with a 4" stroke and those heads. You can mill the heads and pay attention to head gasket thickness to further fine tune the compression. Make sure you work with someone knowledgeable to select the right cam.

 

[frosty_the_punk]

IF you only want 325 horses the performer manifold will be fine.

First thing to do is to take your cylinder heads to a machine shop,

bring your wallet because your heads will probably going to need surface grinding, new valve guides pressed in, spring pads will probably need to be machined. new valve seats, new valves, guide seals, retainers and collets.

For your power goals it's not necessary to port the heads whatsoever.

2.02"/1.6" valves will fit, anything larger would be unnecessary and may require notching of the bore (can't confirm this).

If you are going to CC your cylinder heads, do it after it is completely assembled as you will run it. Bigger valves make a smaller combustion chamber and vice versa.

Regarding cam selection, I strongly recommend building the motor around your camshaft, not the other way around.

The Lunati 60403 is a popular grind. It's seemingly a benchmark by which other street/strip hydraulic flat tappet camshafts are compared. It would create great torque in a 318 stroker but still give a hint of that hot-cam idle sound.

There are some youtube videos of this camshaft that will give you an idea.

A cast crankshaft is probably better suited to your requirements, just make sure it's not made by a brand name that Starts with E and rhymes with "legal" and "regal".

 

[frosty_the_punk]

Just to give you an idea. my 10.4:1 318 made 352hp @ 5700rpm. standard stroke. Just rebuilt 2.02"/1.6" valves in J heads with no port work.

A stroker would make those kinda numbers with less compression and less cam, while making substantially more torque through the whole rev range.

 

[frosty_the_punk]

My question is this....I've read a lot about quench and the closed chamber heads. With the open chamber 596 castings I'm not going to get any quench BUT since I have all that stroke I should have no problem getting good compression (9.5 to 1). In fact, I'll have to be careful not to get a high dome so that can't run on pump gas.

The 390 will go into a '69 Barracuda. I guess I'm worried about getting "ping" (detonation) since I won't have any quench.

strokers usually don't need dome pistons, in fact dished pistons are the most common type for stroker engines.

Let me try to explain why.

As I'm sure you know, compression ratio is a comparison between a piston's displacement and the size of the combustion chamber.

for example if you have an engine with 10:1 compression in a standard stroke 318 you have 39.75cubic inches of swept displacement per cylinder. and an effective chamber volume of 3.975 cubic inches.

If you stroke that motor to 390 you suddenly have a displacement of 48.750 and in order to maintain a compression ratio of 10:1 you would need a chamber volume of 4.875cubic inches.

Obviously 4.875 is bigger than 3.975. Therefore if using the same cylinder heads, the stroker motor will need to have the piston further down the bore at top dead center, allowing the remaining bore above the piston to act as part of the combustion chamber.

For this reason you will need pistons that are specifically designed for a stroker engine.

9.5:1 will be fine with an open chamber, all day, every day. towing, racing, cruising. whatever. They make these pistons and you can get them off the shelf.

 

[Treblig]

Frosty The Punk,
Thanks for the great advise!! I already have the intake (actually two intakes) so not having to spend money on another one helps with the heads, crank and pistons. Will probably follow most of your advise on the heads except I've read that you it's better to CC the heads before valve job so that you don't accidently nick a seat as you smooth and CC each chamber?? I know the pistons are expensive and I've planned for that. It's nice to know that a cast crank will be OK I just wasn't sure about which manufacture (I had heard some bad things about regal, beagal or whatever it is). I just hope the cast crack can handle it off the line...I installed a narrowed Chevy 10 bolt posi with 12 bolt 30 spine axles and I have 10" thread tires so I'm going to get lots of "GRAB"
I have also read about "swept displacement" on the strokers so I agree with you on that. That's why I need to get my chamber volume before I order the cam.
As for the cam I was thinking of ordering one custom from Hughs, they seem to know what they're doing with Mopars?? this way the cam will be made for the engine with the torque and RPM range I'm looking for.
I already have the 2.02 and 1.88 SS valves, I've always heard that Mopars need all the help they can get on the exhaust side so that's why I went with 1.88s???
Sure is nice having all this knowledge to draw from. I'm a Chevy man but I love my Barracuda because I had one back in the 70's. I hated selling it back then. It was an old 273 4 speed, I could lite the tires up big time (off the line) but then it would fall on its' face after the tires stopped spinning and I'm determined to make a better Barracuda now that I can afford it!!!

I also appreciate everyone not wanting me to build a drag car. I'm going to be taking my daughter to school in this thing so it has to be tame enough for that but I still a young kid inside of me that wants to have some fun after I drop her off!!!

treblig in tex

 

[Treblig]

340sfastback,

Just out of curiosity, why would I mill the heads?? I know it will decrease the chamber volume but with all my "swept displacement" I'll get all the compression I need. There's no way I could cut them enough to get any quench because they are open chamber. But then again, I'm not an expert?? Let me know where I'm thinking wrong here as I am not a MOPAR expert.
I'm not disagreeing...just need more info, THANKS.

Treblig

 

[frosty_the_punk]

I should clarify, when i say CC the chambers. i am referring to the process of measuring the chambers for determining overall volume for the compression ratio.

you are correct, if you are going to cut the chambers to make them all equal you should do it before you get the new valve seats installed

Once they are all equal, they will stay equal no matter what valves are installed.

But changing from 1.88" to 2.02" intake valves will remove about 3.5cc from the chamber.

I don't know where you read that a 1.88" valve can be fitted to the exhaust of a mopar small block. But with factory cylinder heads that's definitely not possible.

unless you are building an all out race motor 2.02" and 1.6" is all you'll need. In fact, even race motors tend to keep the 1.6" exhaust valve and put a 2.08 in the intake.

 

[Treblig]

OK Frosty The Punk...you got me. I got the 1.88 intake mixed in my head with the 2.02. You're right, I have a new set of Ferrea 2.02 intake and 1.6 exhaust valves as the pics will show.
I worry a little about the rockers. I have a set of adjustable rockers but everything I read says that they are not very accurate as far as being consistent on the 1.5". But since I'm not building a race car I hope it doesn't hurt me too much. Also I guess I'll have to buy some of those adjustable (dummy) push rods to get the correct length then buy a set of the ones I need. That part I'm not sure how to do since I can't actually do a push rod length test until I have the cam. I can't order the cam until I finish the heads. Then assemble the engine (mock up) with cam and lifters to get the push rod length.
How do you make sure the lifters are properly pumped up in order to get the proper push rod length without starting the engine?????????


Thanks,
Treblig in Tex

 

[moper]

A 4" I built 6 years ago has 596s and dished SRP pistons. The 3.94 bore choices are less but go with dished and set the compression by the chamber size and head gasket because you can use anything. 9.8:1 is fine with a cam in the 240° @ .050 range which is a small cam for these engines. That combo makes about 450hp, instant torque, and get's 17mpg with 3.23s and no overdrive. It also is done at 5500. You must run enough cam if you build compression into it and with open chambered heads you have nothing helping you. So go low static and at least 240° @ .050 and you're fine. You don;t need special rockers, solid cams, or anything else. I would hwoever recommend the RPM if you can use it with that AC. It is a much better intake and will make more torque and power on it.

 

[Treblig]

Thanks Moper...that's some really good real world info!!! You said "17mpg with 3.23s and no overdrive. It also is done at 5500", you're describing exactly what I am looking for...who needs 6500/7000 RPM when you have overdrive unless you want to go 200 miles an hour.
I'm going to have to do some calculating to see how correct RRR was when he said to run 4.10s. You gave me some cam specs but if I have someone like Hughes make a cam for my set-up shouldn't I end up with exactly what I want in the engine performance?? Or is it a lot cheaper just to but what you describe??
As for the RPM intake, couldn't I mildly port the performer and call it even. Remember, I don't need tons of flow by keeping my RPMs under 6K?? Or does the RPM intake greatly increase torque at low speeds?? Plus it leaves me a couple of hundred $$$ extra for those heads, crank and pistons (I already have the rods and valves).

Treblig

 

[txstang84]

Treblig, RRR's point was that AFTER the overdrive, your final ratio would be 2.74 if you were running 4.10s out back. That's the beauty of OD, as it brings down the effective final drive. I don't know if I'd personally go with 4.10s, but 3.55s or 3.73s will make it a ton of fun to drive around town without revving high on the highway @ 70-75mph. 3.23s with no OD are still 3.23s, and flaring to how ever much your converter slips to...


Regarding the intake, a performer can be ported, but you're really limiting the breathing of the engine itself. The performer intake has a smaller volume in the runners to improve low engine speed port velocity and this is especially useful for 273s, and 318s--which is what that intake was designed for. You're planning to significantly increase your displacement and that intake isn't intended to feed that engine up to your max intended RPM, especially when coupled with a cam over 220* at 0.050"...an RPM intake would be light years better, and will actually allow the engine to breath better. I have an RPM intake on my bone stock 5.2 Magnum, and I experienced NO loss of low engine speed torque...and if that's the case with a stock 5.2, imagine what it can be with a correctly built 390...

 

[dirty white boy]

how do you connect a 700r4 to a mopar motor???

 

[Treblig]

Dirty white boy (love that handle!!!), there are two threads, one is "200R4 update" and the other is "Will GM 200R4 work with factory floor shift console". In the second one I am working out all the kinks for installing a 200R4 in my '69 Barracuda with auto floor shift. In the first thread MoParToYa actually installed a 200R4 into an a body. Enjoy!!!


Treblig

 

[Treblig]

Txstang84,

You are both correct...my humble apologies to RRR. I used an online speed/RPM calculator and found that with 26" tires, 4.10 gears, at 70 MPH I would be spinning at 2596. With 3.90s I would be spinning at 2470 at 70 MPH. With 3.90s at 140 MPH I would only be turning the engine at 4939.

That's means my Cuda will do 185 on the top end LOL!!! So "RRR" was pretty much right on the money, I had no idea overdrive would help that much!!!!

I thought the Performer was also made for the 360??? I'm not disagreeing (done learned that lesson)!!!

Treblig

 

[RustyRatRod]

No apology necessary. We're all learnin and if we ain't, something's wrong. lol

 

[txstang84]

It can, yes, by association, but the fact is if you pull the intake off and compare it to the ports on your J heads, you'll see the significant difference in port sizes. I know Edelbrock says it'll fit up to and including a 360, but it's really designed for engines utilizing the smaller 273/318 port heads...which will physically bolt onto any LA Mopar...by that rationale, they could be bolted to a 426 stroker, but that doesn't mean it's a good match for the displacement, compression ratio, cam timing, etc.

When you read the full description from the Edelbrock website for the different intake manifolds, they give you some rough parameters to match up parts. Yes, Edelbrock says it's intended usage is for the idle to 5500 rpm range, but again, that's for a smaller displacement group that have to maintain some runner velocity to enhance low engine speed torque.

When you add stroke (displacement), it changes the breathing (demand) of the engine. Based on what moper said above, you're going to need more cam to satisfy that 4" stroke...other things that have to be increased are the breathing capability-that's where your intake, carb, and heads come in--along with capability to expel those spent gases through the exhaust.

With a 390, you're essentially building a big block in a small package, the only thing you're not swinging is the big weight of typical big block parts, but the demands of an engine that size are still very much the same...and strangling a 390 ci engine with an intake designed to feed an engine 80 ci smaller will limit your breathing all around-not just the top end.

It is your engine, and feel free to do with it as you please, and it still won't be a turd or anything like that, but it'll definitely be way below potential.