ibstewrat

I have a 1968, 318 bought in a 1967 Barracuda. It was supposed to be the original 273 engine but is not. I have disassembled and found it is bored .040 over with J.P. pistons? They are .100 below deck and the engine is in good shape. The heads are 2843675 castings (original?) in good shape with no mods.

I'm looking to rebuild using these components with some work to the heads and a new cam. Cost is a big concern. I can't find any info on the piston brand, but rings are available in this size. It seems this engine was not run much following the .040 bore because there is no wear ridge in the cylinders and they are round and true. The intake is an old Edelbrock 340 Torker , not sure if I will replace it.

The goal is to make about 325 hp and run on pump gas.

The trans is a 904 with an 8 1/4 rear end.

Any suggestions would be greatly appreciated.

Silverick

Welcome to the forum. There is a lot of Mopar knowledge here.

I found this link for J. P. Pistons and it's a start. I had a Torker on a 383 Magnum and it really worked well, especially when the secondaries opened up! Sounds like it's going to be a fun car!

http://www.jp.com.au/JPPistons.html

ibstewrat

OK
Thanks

Archer

i --

OK are you talking about 325 HP at the flywheel or rear wheels, big difference.

If you mean at the rear wheels, you're looking a 400 HP engine (+/-) and for anything more than cruising around town, you may want to think about changing the trany to a 727 and the rear to something bigger than an 8 1/4, like an 8 3/4.

The older Edelbrock Torkers were large single plenum, slightly curved runner manifolds and designed for around 3000 - 5500/6000 rpm. (Sorry, not sure about the newer ones.) You'll need a decent sized cam and headers to make that efficient. You'll have to upgrade the exhaust system as well. You didn't mention the rear gear ratio and that has to be factored in.

Not trying to discourage you, because I did the same thing to a 318 a number of years ago and it worked out really well. Just trying to help get a game plan set up, so you can get in to it on a step by step basis and not kill your bank account all at once.

Archer

ibstewrat

I'm looking for 325 HP at the flywheel. Certainly it will take headers and 2 1/4 to 2 1/2 " exhaust with a balance tube.

I don't know what gear ratio is in the 8 1/4 rear end. It did have old school traction bars. I'm looking to make this into a nice street car. I'm not looking for a 12 second car but want it to be fast and fun.

I hoping to get the engine rebuilt this winter. I think some work on the heads like larger valves, a little bowl work and porting. But I'm not sure what cam and intake I should consider to get to that 325 mark. I don't want it difficult to drive due to too much cam.

Thanks
Tim

Archer

Tim -

Ya gotta figure out the rear gears first, shouldn't be too difficult if you can jack the car up by the differential and manually rotate the tires and count the relative number of drive shaft rotations.

Also, you're right on keeping it relatively mild, else the tranny and converter will need to be swapped.

Regarding the heads, the easiest thing to do would be find a pair of HP 340 heads and clean them up (that's what I did). Probably still have the heads somewhere...

I'm still using the old school traction bars, BTW ... kinda cool.

The Torker is OK, but as I said, it's a high(er) RPM manifold. A dual plane would be more streetable.

The trick is still to have the engine/tranny (convert) and rear work the same rpm range. Again, the nice thing is, you don't have to do it all at once, but it's better if you have a long term plan.

Archer

condor74

I would not use the the torquer for that kind of power. In order to get that kind of power out of a 318 you are going to have to spin it fast. That manifold was orignially designed to make torque not high horsepower. I am also not really familure with your pistons. Are they forged or cast? Hopefully they are forged but if they are cast they can still be used. You just wont be able to use any nitrous and I be careful with pinging. I would figure first on boosting compression. Deck the block or the heads to get the compression close to 10 to 1. Make sure you have the rotating assembly balanced. Cam selection will be important also. I would figure on something that makes good power from 3000 to 6500 RPM.
Once you get your short block in order you need to turn your attention to the heads. I would use 360 heads with 2.02 intake valves installed. A nice pocket port job will help move the air. I would use an Edelbrock Victor JR manifold for peak power but you will get better driveability with the Performer RPM. A good set of steal tube headers and a high flow exhaust are needed as well. That should get you close to your power goals. If you start with a 360 with the same type mods you will be even better.

Unless someone swapped the axle out of the car at some point that is not the original axle. The only 2 options I am aware of in those cars are the 7 1/4 and the 8 3/4. if you have the latter you are fine..If you have the 7 1/4 it will break. It came stock with almost all low performance engines unless you got a towing package.

Good luck.

theomahamoparguy

the biggest problem I see is the pistons. I would look for a set of KB 167's
in the .040 oversize otherwise, you will have a hard time making the HP.
.100 is just too far down. are you sure they are that far down?

ibstewrat

Yea they are down .100 I measured several times.

I want to end up at 9 to 1 compression so I can use pump gas. If I swap to 360 heads it will make that even harder to reach.
If I change pistons to flat deck such as the KB's it will be expensive.
Could I get the heads milled .010 to help? They are going for bigger valves and hardened seats and some porting.

Also the rear end gearing will be 3.91 or 3.73.

Thanks
Tim

twalace

Your heads are the same as on my car and are listed as 1968-74 318 with 1.78" intake & 1.50" exhaust.

theomahamoparguy

there are available cheap pistons that have a 1.755 compression height. If you shave the block .025 then the piston will be down about .042 (or there abouts). that is alot better than .100. should end up somewhere about 8.8 or so with the 360 heads. A nother trick would be to use the somewhat more flat valves sold by Mopar. they are about 15-16$ a piece for the intakes. this would make the chamber smaller 'cause the original valves are tulip style and they add volume to the chamber. you could shave the heads a bit but .010 wont add up to much more compression.

cudaracer

Where does one find all these spare heads anyway?

I keep reading that 2 in valves are not good except in very high rpms.

TVLynn

The 904 trans will work If rebuilt right !! I would just get a set of 360 heads, Just do a clean up and valve job.. MAKE sure to check the valve to cylinder clearance- with the motor being .040 it will probably be ok.. You can remove .050 from the heads To get some compression. Your machinist needs to know to remove material from the intake side of the head also.. Not sure I think it is .008 for every .010, or custom fit the intake manifold, Also do not use the intake manifold end seals if you do this - use some gasket maker. With the required machine work ! It may be cheaper to just replace the pistons...


Nothing real easy,I built a 360 for my Coronet I had .050 machined from the block for a zero deck clearance plus some from the heads Worked fine with the stock pistons and 284/484 cam. If you use the stock oil pan USE a stock oil pump !!!!