Hello, I'm currently doing a new motor build for the ol 3rd gen and I would be interested in a hp and torque evaluation and a couple of questions.

1978 4 bolt 350 010 punched .030 over
The bottom end is an eagle 383 rotating assembly
Pistons are flat tops with -5cc valve reliefs
The heads are aluminum Dart heads, 200cc intake with 2.02 intake and 1.78 exhaust on a 65cc chamber
Cam is a hydraulic flat tappet .450 lift intake and exhaust. 214/214 duration at .050 and a 106 lsa
Intake is an old victor jr that was laying around
Carb is a Holley 750 vacuum secondary
Headers are 1 5/8 (yes I am aware quite small)
10.5-1 Compression hopefully
This motor does not need to pass emissions since it's in Michigan
Planning on running it on 87 octanes, is this safe? I personally think so since my dad had a 355 with pop up pistons with the same heads on 93 (yes I'm aware quite sketchy but it never detonated) that compression ratio is 11.5-1
Also, what is the limit of the 700r4 with a shift kit and servo? And the 10 bolt with the axle housing welded and a new Detroit locker eventually and 3.45 gears
And how do I get the converter to lock without the ecm? I've heard about lock up kits but don't know a good way to work them.

Thanks, Sean also btw this will be my first build so I'm excited and have these questions.

 

That should end up closer to 10.8-11.0 to 1.

would not use that cam, too small. You will be creating to much cylinder pressure at low rpms and have detonation problems potentially with pump gas.

i would recommend spending money on retrofit roller lifters and get a roller cam. Something closer to 230 deg duration especially with a vic jr intake

 

Is this a plan or do you have these parts already?
I'm with Orr. The compression is approaching 11:1 and that cam is mis-matched.

 

Basically have all the parts already except the rotating assembly and the machined block I'm waiting for it to get back. But yeah it's the largest cam on summit for a stock converter

 

You need to add a converter to your list then

or get rid of the flat tops and victor jr and a get a dish and a performer rpm dual plane

you got good intake and heads to make serious power, might as well use them. So i would up the cam and add a 3000 stall atleast. I mean anything over 2000 will help alot, else its gonna want to push thru the stall at idle in gear and be a jumpy car

 

The static compression ratio is fine.

The dynamic compression ratio, however is too high with that small camshaft.
A performance camshaft better suited for the engine displacement and those heads will lower the dynamic compression ratio, and should be fine.

 

I'm right in the middle of spec'ing my own 383. I'm looking at that 10.8:1 CR with the flat top piston too and it's just not going to work with my compliment of parts. The cam gets pretty big and I don't have the heads to support it. This is forcing me to look into what's available in a dished piston so I can get the CR closer to 10:1 on one side or the other.
So, you have to ask yourself, is this going to more of maximum effort where there's more RPM involved to work with the heads and big cam or do you tone it down to something more "streetable"?
That cam, even with a 15cc dish is still going to build considerable cylinder pressure and I'd venture to say that your 87 octane target isn't going to work.
Do you have part numbers for the heads and cam?

 

I hear what you're saying.
That'll take a sizable cam to lower the compression enough to use 87 octane though.
Comps XE288HR (I have the specs so I'll use it as an example) will take that 11:1 SCR and get you 8.4 DCR. That could be a handful in any number of ways. Especially for a novice. Tuning would be critical. And even with aluminium heads, I'd say regular gas is a stretch. Unless you kill the timing.

 

Why do your heads have 1.78" exhaust valves?
Are these some previous racer heads that you got a "deal" on?
Your combination of parts is not well matched and needs more work.

 

I dont care what cam you put in it at 11:1 static, it likely wont want 87 oct gas. Sure it will drive but under peak power/trq, cylinder fill is still a function of how well your induction system works, it still gonna flow enough air to make power and that is cylinder pressure

 

Ah ok I see. I'll work on it and find a better way.

 

I think we are approaching the engine build from the wrong angle. What is the goal of the car? Street/strip car, Sunday cruiser, or daily driver. I see you are wanting to run the car on 87 pump gas, so I am assuming that the car will be street driven.

 

Street I gotta be able to drive it as a near daily. But I do go down to the track occasionally. However the track is 3 hours away.

 

Your car sounds more like a 97/3 car. It will spend 97% of its life on the street and 3% of it's life on a racetrack. This is the part where you need to be honest with yourself. What do you want out of this car as a whole? From there, we can help assemble a parts list that will fit the goals for your car (IE: RPM range, peak torque location, peak Horsepower location, and fuel octane rating)

To be brutally honest, utilizing your current parts list, you will be VERY disappointed in power production and longevity. To start, the Victor Jr intake will be a dog down low. You can expect losses of 30 Ft-Lb or more under 4500 RPM. There have been several back-to-back comparisons showing the loss by every car magazine, so take your pick. A performer RPM, or Air Gap RPM would be a much better match for an engine that is mostly street driven.

Now for the cylinder heads. Do you have a part number for the cylinder heads you are running? I cannot find a Dart head with 65cc chambers. Everything I'm seeing is 64cc. Like those above me have stated, you could get away with that much compression, but you need 93 octane AND a larger cam with more overlap to bleed off the pressure, as your dynamic cylinder compression is well over the 8.0 to 1 guideline for pump gas.

Next is compression ratio. What is the deck to piston clearance? What is your cylinder head gasket thickness? Cylinder head gasket bore? All of these factor into the static and dynamic compression ratio and effect the quinch. For you engine, I would target 0.045 In of quinch. Any tighter, and you risk damaging parts. Any less, and you're leaving performance on the table. As far as static compression, I believe you are way to high for your purpose. something around 9.7/1 static CR should allow you to run 87 gas with a carb (as long as you are conservatives on the timing and can dial it in at cruising speeds with no detonation.)

I would advise playing around with the specs utilizing a dynamic Compression Ratio Calculator and a cam timing calculator before making any changes to parts.

 

Daily driver i would definitely go Hydraulic roller cam. Todays oils arent for flat tappets. You want longevity and reliability you want rollers

sounds like you need to drop down to a dish piston and get a dual plane intake

 

Thank you for all this information. Yes the victor jr is not ideal but its what was laying around off my dads old nova. But ill consider the dual plane. And yes if im honest im not really aiming for fast. Im aiming for faster than it is right now. How much are retro fit roller lifters? Ive heard a little bit about it but not much. And the piston to deck clearance is .025 and the head gasket thickness atm is .039 but can be changed. I messed up the head sizes, its a 2.02 intake and a 1.6 exhaust and they are 64cc.

 

That would be ideal, however dropping to a dish seems like its gonna lose power. Note the rotating assembly hasnt been ordered yet and i can get dish pistons.

 

If you dont have the rotating assembly then the block is getting machined and deck clearance can be redone to 0-0.005 or so if you want to allow for more clean up in the future

resurface the heads, use a .041” mls gasket.

then its up to you. Compression and bigger cam 93 oct. make big power and be a bit more radical driving. Need converter to go with. Off idle to 3000 ish rpm will be alot softer But strong above 4000 to 6500.

or go dish low compression, smaller cam and dual plane, possibly use 87-89 oct, be very torquey off idle. Might be ok with stock converter or mild stall speed. Wont be near as fast up top but be fun due to the low rpm torque feel

 

It's the compression ratio you need to dial in. So, it's not so much that the dished piston is going to cost you power, it's that it will give you CR that's workable. A flat top piston and the 11:1 it'll give isn't going to make for some street friendly regular fuel cruiser. It'll take a cam that'll make the whole thing just a little unlivable.
FWIW, I've been working on a 383 spec for a while. Lots of data and measurements taken along the way.
Not to get into specifics about the rotating assembly such as the crankshaft material, connecting rod type or length, I see Eagle has several dished options. 12, 16, 18, etc.
With the .025" deck and a slighter thinner head gasket at .026, the 12 cc dish is going to land right on 10:1. That's an excellent value to work with and can make 500 HP if you want it to. That's all in the rest of the supporting parts.
But if you really want to cruise trouble free, take that 10:1 and go with a cam that'll let you run 87 octane. Still plenty of power available with those heads, that CR and an intake to match.

 

 

I think ill go the dish route. Thanks for your imput. But my thought was to get it running pretty ok in time for the race season then buy parts to make it better for example a 2500ish stall and a bigger cam. But for now I think ill stick with dish pistons and 10-1 compression

 

This sounds like a good base to start with, then maybe ill go a bit more radical afterwards. Thanks btw

 

You got good heads so it will make power even with lower comp and smaller cam as above said. 10:1 is nice compromise

my 11:1 383 may have been fine with 89 oct, never really tried wot on it tho but i think i could have tuned it. 93 just was worth it to me For as much (or little) as i drive the car. But my cam was 230/245 on a 109 lsa. Hyd roller. Efi so i could properly control timing and fuel. Tune helps

cam around 220-224 deg at .050 for a hyd roller be great. If you must stay flat tappet maybe add a few deg more. Good overall compromise of manners and power.

you can make a nasty radical cam live fine if you want. But its a loud car and gotta keep an eye on tune up and valvetrain parts. Aggressive lobes and rpm will wear things fastsr

 

Not going to lie, might have been inhaling a little bit of paint fumes when I decided for a cam with a 106 lsa however people on summit gave it good ratings and good vacuum and it could work with a stock converter. Mine is a 224/224 on a 106lsa and its flat tappet but sadly my block isnt a roller one. But one quick question, why go with a dish piston with a thin head gasket and not a flat top with a thicker head gasket? Is there something im missing here? Thanks

 

piston to deck clearance. Sometimes called quench height. It is said ideally it should be .040-.050”. So a zero deck block and a standArd .041” gasket is perfect. If pistons in the hole .020-.025, shoot for a .015-.028 type gasket. too mucH clearance can actually cause detonation and hurt power. Real excessive clearance like over .100” things may start to behave normally again just with super low compression. Kind of a weird phenomenon.

keep that quench height near .040-.050 and 10:1 comp it will be a very good street deal. If 11:1 you will want a bigger cam

 

As stated, the tighter piston to head clearance can offer some resistance to detonation. That can be helpful with your wanting to use low octane fuel.
Something to watch out for though is the piston dish shape. It's better to have a D-shaped dish so that at least part of piston crown works like a flat top and takes advantage of the flat part of head and gives you that quench. Eagle should have some pretty decent pictures of what they offer in their kits.
Of course in a perfect world, you'd have a cylinder head with a larger chamber and a flat top piston. Then all is good. But like me, I'm forced to use small chamber heads (because I have them). Such is life.
As for a 106 LSA cam, some cam guys prefer it for the larger cubic inches. Lots of torque possible all else being equal. But you have to pay attention to the duration with that tight of a lobe spread. Otherwise things get unmanageable with respect to overlap.

 

I think this article will help with explaining the benefits of quench area and reason why it is so important. It also touches on MLS head gaskets.
https://www.enginelabs.com/engine-te...ston-and-head/