318 rebuild

[ndw2832]

Hello I have a 1970 Plymouth Satllite 4dr. with a stock 318 and am wondering what I would need to build up the engine to make at or above 400HP, while still running on pump gas. What kind of times would I expect with the hopped up 318 with all the goodies? Any replies will be appreciated.

[Secret Agent Toast]

From my limited experance, and what I've read here, a more realistic target for your 318 would be 300 HP. That can be had with semi-minor modifications. Some people are able to get 300 hp by simply adding a better intake, headers, better Carb, and some head work. and have it run off of pump gas.

When you start looking at 400 hp for a 318, i think you would want to rebuilt to whole engine to be able to take that kind of stress, just for starters. I would be rather nevous about a 30 year old 318 block producing 400+ HP without some kind of beefing up of it's internals.

If this car is gonna be a driver with some track action (which i'm assuming due to it's non-race 4-dr nature...) then you might wanna look at aiming at 300 HP, dropping in a special built 360 capapble of 400 HP while being safe and driveable, or swap to a 440 big block. Swapping to the big block would make it much cheaper to get to your goal of 400 HP, and would remain drivable too.

toast

[joey]

okay...i dont have much experience either...but i do have a rebuilt 318...of course i havent started it yet...but heres what i have

318 block bored .030 over
360 heads milled with 2.02/1.60 valves(3 angle job)
flat top pistons and rebuild, crank turned down .010
.443/.465 lift cam for low end torque
edelbrock performer dual plane intake manifold (torque)
holley 600cfm carb
will have 1 5/8 headers
mopar performance distributor and orange box

some say that the 360 heads will be too big and that my engine will be doggy under 3000 rpm....with a good stall converter i dont think i will have a problem...also they say my compression will be too low....between 7 and 8 to 1...but at least i will run on regular unleaded....

well thats what i had..and someone on here said i would have 300-350 hp..hope this helps

[rumblefish360]

Your compresion is killing you for starters. It needs to around 9-1 or better for that cam. (Although you didnt include duration.)
The performer is going to limit your top end in a big way. Go RPM, 9.5 compresion or better, Edel. heads or port out your current heads well and a beefer cam and a 650 cfm carb when you can.
Secret agent toast is right about a bigger engine. A 360 would be better to do this with. Because of the small displacement, it becomes a little harder to make a higher HP engine for the street and be happy with it.

[DusterBill]

A long while back Direct Connection listed recommendations for different power levels. For 400+ hp from a 318 they reccommended:

700-750 cfm holley or Thermoquad
Mopar W-5 intake (but based on recient test I would go Performer RPM)
camshaft with 224/230 duration @ 0.050
at least 0.450" lift
1 3/4" headers and 3 1/2" collector
ported 360 "high-swirl" heads
2.02/1.60 valvesupgraded ignition (super gold, MSD, ACCEL, etc.)

if you try to build this time bomb, upgrade the rod, and main bolts (switch to studs on the mains). Shot peen your rods. I would strongly consider the Edelbrock heads and get them ported. At a minimum get some keith black pistons, or some light weight forged pistons. Be sure to port and match the intake to the cylinder heads.

since you will need to turn 6500+ RPM try to lighten everything that moves. Realize you have no low end, so get some steep gears. Magnaflux your block, because you will be stressing the hell out of it. Better to spend a little to check your block than to split it.

[ndw2832]

Thankyou everyone for giving me all the info, it has been much help in my decision making process of what to do with my car. Keep the replies coming.

[Karl43]

Your engine will run fine with the 2.02's. I have a 68 Barracuda with 9.2:1 compression, 77 360 truck heads opened up to 2.02 and ported, MP 260/268/44 .430/.450 cam, stock 68 340 intake manifold, Holley 600 vac secondary List #80457, stock exhaust manifolds, Rhoades lifters, dual exhaust stainless steel 2 1/4" with an h-pipe and Dynomax mufflers. Old TRW 10.5:1 compression forged pistons.

It runs very strong throughout the RPM range from idle to 6500. I ran this with a milder cam and 1.88 valves for 170,000 miles and had to rebuild due to rounding a lobe off of my old cam. It gets over 17MPG and is a blast to drive. I used to get over 18.5 MPG with the smaller cam (and 2.76 axle). I do not know my exact MPG yet as my spedo is not working right now (I have changed to a 3.23 sure grip axle). I think that it might be getting better than before, but not sure until I get the spedo working again.

Your cam is a nice one for low/mid RPM on the street. The heads will allow it to breathe on the top end. You should be happy with your combination. Yours is pretty close to mine, except you have headers which will allow it to make more power and probably a little less compression (did you happen to measure your piston drop at TDC before installing the heads?). You may be a little low on compression. I used to run headers, but due to low ground clearance and crushing the primary pipes, I went back to stock exhaust manifolds. Don't change anything yet until you try it!!! This will be a great street motor capable of driving every day.

[5thAve]

If was doing this I'd start with a 360.

[Stans Customs]

Me too...a 360 would probably be cheaper (certainly easier) to get the horsepower, even though you've alredy started with the 318...IMHO

[goose]

The replies to this have all been pretty good. The main thing to keep in mind is that you WILL have to spin the 318 to a pretty high RPM to get the 400 HP. Everything that needs to be done to modify the engine to make the 400 HP is a result of making the engine work well at the high revs. High RPMs mean lots of cam and headwork. Lots of cam means high compression. Lots of headwork = $$$. You can use the higher-flow 360 heads to reduce the amount of headwork, but then your compression is not high enough to give good results with the high RPM cam. There are ways around this though. Also high RPM's mean higher stresses on the engine, so if you want it to last very long you will have to beef up the bottom end.

In the end, what you finally do to the engine depends on the amount of money you have. You could probably make the 400 HP for about $700 by putting in a hotter cam, mildly reworked "302" heads, a performer RPM manifold, some headers, and a 750 carb. That's assuming you do all your own work and get some deals on used parts. For an all-out effort I would imagine 3-4 grand on new hi-po parts including forged pistons and stronger short deck etc. Of course you could go to boosting the engine with a turbo or blower as well.