What if I want to build my 318 up a smidge

rumblefish360 · Oct 15, 2017

TTI makes Poly headers.

The advertised compression ratio is 9.2-1 but! As we have seen, this is not always the case. Rebuilding the engine? If needed, should be done with thought and talking with the piston manufacturer to achieve what you want.

Again, for a street driven ride, I would yield at a pump gas friendly ratio for the octane available. This is a variable that can change with cam selection. Overall, a safe ratio is 9.0-1 with 9.5-1 being the maximum I would push for 93 octane. 91 should be possible but I do not know for sure since I have 93 available and FWIW, live at sea level.

Larger cams bleed off compression so a higher ratio may possibly be used, with caution!!!

Belle66 · Oct 15, 2017

There is a Facebook group called Polyspherical AKA Poly 318. I strongly recommend joining and asking there. Lotsa good people to help.

rumblefish360 · Oct 15, 2017

You’ll probably find Gary there.

Belle66 · Oct 15, 2017

rumblefish360 said:
You’ll probably find Gary there.

Guaranteed! His advice, expertise and patience helped me with my current poly and an "almost stock" one being built.

oldmopar! · Oct 15, 2017

PurpleBeeper said:
Agreed....I'm not sure what your gear options were back in '64, but if you can get something around 3.55's in there, even 3.23's, you'd end up faster with no engine modifications than if you left those 2.90 gears in there and did all the modifications you listed in my opinion. Gears are your best "bang for the buck"

WileERobby said:
You posted you wanted the combo for the street. You got to make up your mind. A good middle ground is 3.55

I now will change my plans around to proceed with the rear end first. Sounds like 3.55 gears are favored so I will aim for that.

rumblefish360 said:
All of your plans are now about to be laid to waste after you read my post on how most(90%) of your plan will fail in a spectacular pit of misery.

Your “Poly” 318 sahres a few things with the “LA” 318. But let’s start with what it doesn’t share.

Intake manifold
Cam
Rocker arms
Pistons
Heads
Exhaust

For intake manifolds, there is the OE 4bbl. And the in line dual quad. The aftermarket aluminum intakes are the easy to get (LMAO!) Weiand 4bbl. There is also the 3 Deuce by Weiand or Edelbrock (P600)
Chrysler Power has a brand new intake for the poly. It is like the “RPM” that Edelbrock does.

Cam, go to “Racer Brown” for a cam. Crane can also help you. You can not use an LA cam due to the engines valve lay out.

“E” equals exhaust, “I” equals intake

Ploy - eieieiei
LA ei ie ei ie

You can install the LA cam in the poly but it will NEVER FIRE.
You only have the OE rocker arms to work with.

The only manufacturer of pistons for the old obsolete engines I know of is a company called “Egge.” The only do cast pistons.

You only have the OE head to work with.

Exhaust, it is ether the exhaust manifolds or headers from tti.

Rumblefish: you're very knowledgable with 318 poly and LA. But then I got confused. Are you suggesting some LA parts are superior and more appropriate for my engine build and not get aftermarket parts? Is the LA engine a direction that I should be looking at?

oldmopar! · Oct 16, 2017

rumblefish360 said:
You’ll probably find Gary there.

Belle66 said:
Guaranteed! His advice, expertise and patience helped me with my current poly and an "almost stock" one being built.

I will seek him out. Thanks for the recommendations guys. Keep the good and the ugly coming. I rather learn it on the forums than to deal with it on the freeway with a blown motor or trashed tranny because I frankensteined this plymouth.

rumblefish360 · Oct 16, 2017

oldmopar! said:
Rumblefish: you're very knowledgable with 318 poly and LA. But then I got confused. Are you suggesting some LA parts are superior and more appropriate for my engine build and not get aftermarket parts? Is the LA engine a direction that I should be looking at?

I never suggested that. If I did, you would t be asking if I did. I’d tell you straight out. Many LA parts interchange. This makes parts searching easier. Upgrade your parts as needed.

oldmopar! · Oct 16, 2017

ok. gotcha. thanks again

dvw · Oct 16, 2017

Save time and money. Bolt in a junkyard 360 magnum with a cam upgrade and a Performer RPM.
Doug

PurpleBeeper · Oct 23, 2017

oldmopar! said:
rear is a 8.75 from a 70' roadrunner.
no cover on the back of the rear end

I think that is good news. You would be OK with 3.23 gears too & they are MUCH easier to find than 3.55's. I "suggest" you find a posi center section. The swap takes only about 6-8 hrs. Besides the "pumpkin"/"chunk"/"center section" all you really need is a gasket kit (cheap) and some new gear lube (cheap). And fyi - without overdrive, 3.91 gears make the engine rev so high on the highway you'd swear the engine was about to explode (as me how I know).... like 4000+ rpm "cruising"

After that, see how it runs & see if you need more "umph" before deciding on motor upgrades/motor swap in my opinion. Also, don't forget to change the speedometer gear in the transmission (I "think" you can do that on a '64).

Although the car might be faster/cheaper with a 360, it will be "cooler" with a poly 318 in my opinion....your choice though.... 360's are "cool" too.

YY1 · Oct 23, 2017

attention member "purplebeeper"

You are hereby suspended from using the image of the RoadRunner for your avatar for using the term "posi" to describe a Mopar Sure Grip unit.

Please turn yourself in to the moderators immediately.

Belle66 · Oct 23, 2017

Wait, you don't use a posi for a sure grip?

rumblefish360 · Oct 23, 2017

dvw said:
Save time and money. Bolt in a junkyard 360 magnum with a cam upgrade and a Performer RPM.
Doug

While this makes sense on many many levels, it doesn’t really answer your question or help now does it?

I swapped a ‘00-5.9 into my ‘79 B body Dodge Magnum. EZ-PZ, nice and easy. Installed Hooker Super Comps into a 2-1/2 exhaust, rpm intake, 650 Edelbrock AVS, junk yard distributor with Chrome box ignition. A 727/3.55-9-1/4 rear back it all up. It is an excellent street cruiser. Good power. It gets up and goes very well. FWIW, the car is under 3600. A good bit lighter than the Durango’s that are known good movers.

oldmopar! · Nov 7, 2017

i would love to go with a 360 even a 340 but the 318 poly was there 1st and has never left the engine bay.

Got a 489 case off craigslists for cheap and sent it to The Rear End Shop in Livermore.
They put a trutrac with 3.55 gears and the works. :steering:

Challenger340 · Nov 7, 2017

Once upon a time a few years ago, there were NO parts, or very limited parts at best, to even contemplate a Poly build ? Even though the cylinder head configuration had obvious potential, and the bottom end fundamentals were there.... just was nothing to work with ?
Nowadays, what a difference a few years can make ?
A very decent Intake Manifold is available, and tti Headers are now there, IMO, everything else is surmountable for some decent power.
I wouldn't hesitate to build a Poly tomorrow if the need arose. And although some of the Poly parts are still pricey vrs LA stuff.... I'll give the "eye candy" effect to the Poly hands down as worth the investment !

idrivemopar · Nov 7, 2017

I like my trutrac!!! Just an FYI, if you are using green bearings, keep on eye on them, mine leaked out all the grease from inside, so I put Timkens back in!!!

oldmopar! · Nov 7, 2017

idrivemopar said:
I like my trutrac!!! Just an FYI, if you are using green bearings, keep on eye on them, mine leaked out all the grease from inside, so I put Timkens back in!!!

thanks for the tip. I am using BCA bearings. I havent heard anything negative about them from the mechanics I’ve spoken to.

And of course the Timkens are great. Are they holding up well for you?

oldmopar! · Nov 7, 2017

idrivemopar said:
I like my trutrac!!!

I was told the trutrac requires little to no maintenance. Just drive it! And regular differential gear oils. No synthetic.

idrivemopar · Nov 7, 2017

No issues with Timken's, and if they lose grease, that easy, just re-grease, cant do that with sealed bearings. They say no synthetic, but I am running synthetic. That makes no sense to me why, its only gears inside. I think once I do my next change in the spring, I may switch to regular 90 weight.

rumblefish360 · Nov 7, 2017

Challenger340 said:
Once upon a time a few years ago, there were NO parts, or very limited parts at best, to even contemplate a Poly build ? Even though the cylinder head configuration had obvious potential, and the bottom end fundamentals were there.... just was nothing to work with ?
Nowadays, what a difference a few years can make ?
A very decent Intake Manifold is available, and tti Headers are now there, IMO, everything else is surmountable for some decent power.
I wouldn't hesitate to build a Poly tomorrow if the need arose. And although some of the Poly parts are still pricey vrs LA stuff.... I'll give the "eye candy" effect to the Poly hands down as worth the investment !

Really, way back when, the only part that hot riders really could have used are headers. Intakes were made for this engine as well as most everything else. Intake selection was crummy. Edelbrock and Weiand has a 3 x 2 set up and Weiand has a single 4bbl. The factory 4bbl. was around but not sought after and the in-line 2 x 4 was and is still priceless.

Racer Brown, Competition Cams, Crane Cams used to have cams on the shelf. Crane will still make you one. Chrysler Power has a few on hand.

Only tti makes headers.

What if I want to build my 318 up a smidge

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