Swapping '69 273 with '84 318 Into My 1969 Dart

[CudaRay]

The Enginetech gasket kit has head gaskets with a smaller fire ring for 318. I recall 4.08n vs 4.125 or 4.140. In your application the felpro gaskets will drop the compression 1/4 point or more.

See: Enginetech ENGCR318-29

You could advance the cam 4* while your making the swap as well.

So are my calculations wrong at the ~8.5:1 ratio with those fel-pro gaskets? I'm okay with that number for the money I have in this, but at 8.25:1 or even less...that's not great considering the 273 was 9:1 or so.

Noted on the advance, although I'll need to learn how to do that, haha.

As far as those gaskets, I wasn't able to find the thickness on them. I guess my problem is, I don't quite understand yet just how much better the smaller ring and that potential small amount of thickness will make in practice.

 

[4spdragtop]

You used a -ve number for piston "dome" volume? You're using domed pistons?
Also 0.10 deck clearance?

I guess I'm hoping with the dual-plane intake, 4bbl, headers, and mopar orange ignition module it will at least be equivalent to what the 273 was.

It was running lean when I was driving it, so I may not even notice the difference if the 318 is tuned well. I have no further performance mods in mind after those, it'll just be cosmetics.

The gaskets I got were fel-pro, and I want to say they are 039. I couldn't justify 4x the price for a $500 engine, haha.

-edit-
The calculations I just made with compression show a compression ratio of 8.5:1, which isn't bad. The stock gaskets seem to have been .069, so I imagine that could make a difference? I could be doing something very wrong though, as I've never messed with compression ratios.

View attachment 1716471355

 

[CudaRay]

You used a -ve number for piston "dome" volume? You're using domed pistons?
Also 0.10 deck clearance?

I'm going off of information I can find with research. What should those numbers look like in reality then?

 

[AJ/FormS]

No, for 318s, the stock gaskets were usually steel shim, .020.
The .069 number would be the deck clearance, which is how far below the decks your pistons are.
.069 is about 13.57cc, which has to be ADDED to the head volume.
OPEN chamber 318 heads usually come in around 70cc.
IDK; about heart-chambers, or Magnums, nor about the early 273/318 closed chamber heads, which seem to vary between 57 to 63cc, IIRC.
039 FelPros, which are actually 4.18inches round-bores, to fit the 4"Plus bores, come in at 8.8cc, and don't forget the Crevice volume of about 1cc.
This totals 70 +13.37 +8.8 +1=93.17, before you add for piston dish. This makes your SCR to be 7.99, BEFORE adding the dish, if any.
Some of those smogger-318 pistons have huge dishes.
And don't forget, Google says yur at 1300ft elevation. That's gunna cost you ~6psi CCP, (Cranking cylinder Pressure). Which is equal to about 3/10ths of a point of Scr.
So, even if your 318 was at 8/1 Scr, and was situated at sealevel;
by the time you get to 1300ft, it's making the same pressure as if the SCR had been reduced to 7.7/1@sealevel.
Pressure is heat, makes torque and times rpm, makes power. The less pressure you have, the less potential to make POWER.
This is not always a big deal, say for a grocery-getter. But, with a stock converter and short gears in the back, when you need POWER, it just will not be there, until the engine is running up on the shift indicator; and once you hit Second gear, it's all over.
These are all glitches that cam be overcome with gearing and stall, at added cost.
And
we don't even know if the coming 318, is still worth installing.

 

[AJ/FormS]

your torque converter register will be too small for the 318. Perhaps someone manufactures a bushing or you may have a lathe to spin one up.

Are you sure? The 273 is a 1969 model.

 

[Illahe]

So are my calculations wrong at the ~8.5:1 ratio with those fel-pro gaskets? I'm okay with that number for the money I have in this, but at 8.25:1 or even less...that's not great considering the 273 was 9:1 or so.

Noted on the advance, although I'll need to learn how to do that, haha.

As far as those gaskets, I wasn't able to find the thickness on them. I guess my problem is, I don't quite understand yet just how much better the smaller ring and that potential small amount of thickness will make in practice.

Call Competition products, They should have the specs.

 

[4spdragtop]

You need to know what pistons are in the 318. A truck 318 unless modded will not have pistons that come outta the hole.
Pistons play a major role in comp ratio. Any guess is just a guess.

I'm going off of information I can find with research. What should those numbers look like in reality then?

 

[Illahe]

Are you sure? The 273 is a 1969 model.

The 273 steel crank I have has the small register, which I had machined to the 318-360 register diameter . I've never read about any of them having the larger register. Do you have one you could measure..?

 

[junkyardhero]

your torque converter register will be too small for the 318. Perhaps someone manufactures a bushing or you may have a lathe to spin one up.

68/9 should be the big register, no?

yes, somebody makes the adapter ring. i just bought one off member @slant six a few weeks ago

 

[Illahe]

68/9 should be the big register, no?

yes, somebody makes the adapter ring. i just bought one off member @slant six a few weeks ago

I'm going off the 273 steel crankshaft I had machined for the larger register.

 

[junkyardhero]

I'm going off the 273 steel crankshaft I had machined for the larger register.

hold plz...

thank you for staying on the line.... while we were experiencing difficulties in procuring a measuring device.

the 68 273 i have here is large register.

 

[CudaRay]

I appreciate everyone's help thus far, thanks for working with a complete newbie.

I am struggling to understand the compression situation. All the information I can find on these pistons are flat top, at most a 4cc dish. If I was to use a steel shim at .028, assuming a deck height of .069, 70cc for heads, and 4cc for the pistons, I am getting 8:1. Taking into consideration altitude as mentioned it will be even less.

With flat pistons, and .020 shims (as claimed with Fel-Pro 375-SFL8553SP) I am getting 8.44:1 before taking altitude into consideration.

I am just looking to get ~230hp out of this to match what I suspect the 273 had on a good day. And again, I'll be using a edelbrock performer intake and 4bbl carb to help out with that. Headers as well if they'll fit.

Am i getting closer on this, or still way off?

-edit-

If I continued with .020 or even .028 gaskets, would I be in a good enough spot to just run it and swap some low cc heads on it later?

 

[junkyardhero]

re: compression

i think you've got enough on your plate with the swap as is. i'd knock it together with felpro 1008's and send it.

if you're feeling frisky down the line do heads or a cam or both.

 

[Illahe]

I appreciate everyone's help thus far, thanks for working with a complete newbie.

I am struggling to understand the compression situation. All the information I can find on these pistons are flat top, at most a 4cc dish. If I was to use a steel shim at .028, assuming a deck height of .069, 70cc for heads, and 4cc for the pistons, I am getting 8:1. Taking into consideration altitude as mentioned it will be even less.

With flat pistons, and .020 shims (as claimed with Fel-Pro 375-SFL8553SP) I am getting 8.44:1 before taking altitude into consideration.

I am just looking to get ~230hp out of this to match what I suspect the 273 had on a good day. And again, I'll be using a edelbrock performer intake and 4bbl carb to help out with that. Headers as well if they'll fit.

Am i getting closer on this, or still way off?

If your 318 is factory (1984) your pistons should be pn 3698571 with no valve reliefs (flat) and a 1.74" Compression height. considering an aftermarket performance piston is 1.81" compression height that's close to "zero deck" you get the picture.

FWIW I have an 80's 318 like yours that has been "re-ringed" and uses the 1.74" compression height pistons along with 2843675 casting 318 heads which have 1.78/1.50 valves and 69cc chambers. Turning a Delta Cams 211/218 cam 425/435 lift on 112lsa with a cast spreadbore intake and a 800 cfm Quadrajet calibrated for 4700'.

The engine pulls my 1/2 ton Power Wagon down the interstate at 85+ with no more than 1/3 throttle. It doesn't blaze the tire, but its got plenty of power to pull the 5000# pig around with 3.55:1 and 29" tires. We use it at 7000' and it wheels fine. No reason to hate on a 318.

Good luck with your project.

 

[CudaRay]

If your 318 is factory (1984) your pistons should be pn 3698571 with no valve reliefs (flat) and a 1.74" Compression height. considering an aftermarket performance piston is 1.81" compression height that's close to "zero deck" you get the picture.

FWIW I have an 80's 318 like yours that has been "re-ringed" and uses the 1.74" compression height pistons along with 2843675 casting 318 heads which have 1.78/1.50 valves and 69cc chambers. Turning a Delta Cams 211/218 cam 425/435 lift on 112lsa with a cast spreadbore intake and a 800 cfm Quadrajet calibrated for 4700'.

The engine pulls my 1/2 ton Power Wagon down the interstate at 85+ with no more than 1/3 throttle. It doesn't blaze the tire, but its got plenty of power to pull that pig around. We use it at 7000' and it wheels fine. No reason to hate on a 318.

Good luck with your project.

This makes me feel much better about the power in a sub 3000lb dart even with those few performance mods. Thank you very much for that information.

 

[CudaRay]

re: compression

i think you've got enough on your plate with the swap as is. i'd knock it together with felpro 1008's and send it.

if you're feeling frisky down the line do heads or a cam or both.

That sounds like a plan, haha. Thank you so much for all of your help!

-edit-

I ended up spending the extra money, these seem to be the smallest bore while also being a .027 thickness, might as well get the good stuff. Cometic C5633-027

 

[Illahe]

This makes me feel much better about the power in a sub 3000lb dart even with those few performance mods. Thank you very much for that information.

This makes me feel much better about the power in a sub 3000lb dart even with those few performance mods. Thank you very much for that information.

No sweat!

 

[CudaRay]

If anyone is watching this thread or sees it in the future, here is what I ended up doing on top of the Edelbrock Performer Intake, 4bbl carb, and Hedman long tubes.

318 with the following new parts:
Main Bearings
Rod Bearings
Cam Bearings
XE256H Cam & Lifters
901-16 Valve Springs
Piston Rings
Freeze Plugs
Oil Pump
Timing chain/gears
Harmonic Balancer
Aluminum Radiator
Swaped 3769973 Heads

Also done:
Smog Delete
A/C Compressor Delete

At time of writing, I have the block completely stripped and am about 1/4 through cleaning/inspecting everything. It turn out the 273 on the car was actually a 1976 318 with the 273 valve covers, oil pan, and water pump swapped on.

I will report back when the project is completed, or if anything else comes up. Thanks again for everyone's help, this engine is going to make way more power than it did before I released the expensive sounds.