More HP out of my 318

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72lidart

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Right now I have a completely rebuilt 72 318 that runs excellent but I would like some more power without breaking the bank. Right now it is a stock bore, eddy performer intake and cam, holley 650 carb, 302 heads with 1.88 intake and 1.50 exhaust valves, heads were gasket matched to the intake and some bowl blending done. Mopar orange box. The car is a 4 speed with 3:55 gears. At this time I am running crappy stock exhaust manifolds with TTI 2 1/2 exhaust with H pipe. My questions are:

1. Will TTI headers make a huge difference with the 318 (I've read so many conflicting articles that I do not know what to believe).
2. Should I go with a hotter cam and if so any suggestions. I really love the streetability of the car right now but I am willing to compromise some to get some more power.
3. After reading up on the 302 heads, should I have left the smaller intake valves and went to the larger exhaust valves and if so could I rectify the problem by going with the larger exhaust valves. ( Will it make a big difference).
4. Is the 650 carb too much/too little for this setup.
I have a 340 with J heads that will eventually get built up, but not for a while. I figure I will use this 318 for a while since it only has about 2000 miles on it. So if I go get some more power for a reasonable price right now it will be worth it. I can eventually pull it and find another a body to put it in.
 
Headers make a big difference, however, there not going to set the world on fire. Headers make the biggest difference on an engine with that has been hopped up more so than a stocker.

You never mentioned what cam is in there now.

According to a buddy of mine, the exhaust valve should have gone to 1.60 and the intake would probably have been better left stock, but that is also build depedent. The 1.88 installed isn't the end of the world and not a huge issue to cry over.

A 650 is a good size. The engine probably isn't useing it to it's fullest capicity. Again, a build dependent item. Also driving style.
 
318 exhaust log exhaust manifolds are restrictive, the TTI's would be an excellent choice, and will work great on the 340 later...and the best thing is, they don't hang through the steering like the cheap brands do. A good 2.5 dual exhaust set up with an H or better yet, X pipe will wake it up a bunch.
A faster advance curve in the distributor can't hurt, if you haven't done that already. I assume you ditched the points...
If memory serves, a 1.50 ex valve would be SMALLER than what it came with, should be a 1.58 stock....smaller isn't better....
Keep reading, you've come to the right place.
alan627b
Ah,I see you've got the exhaust already, you just need to get the headers....sorry I jumped the gun.
 
Yea, but you made good sense Alan. The 318 exhaust valve stock are 1.5 and the 340/360's are 1.60.
 
I bought a cheap set of used headers out of a guy's trunk back in my youth. Took the front suspension apart as I was told I'd need to do. Imagine my surprise when after it was all together, the steering didn't go through it. They tucked up high enough that you would have to drag the frame on the ground to smash them!
I had a 2.5 inch dual exhaust added, with a crossover pipe and resonators for a firebird instead of mufflers.God it was loud.
I had this on a stock as dirt 72 Duster, 318/904/8.25 rear with 2.76 gears. I'd added electronic ignition, double roller chain and an hv oil pump and distributor drive, windage tray, and made an open air cleaner by cutting away the sides off the stock one. Low budget.
My usual competiton was my buddy's 78 Camaro LT, 350/turbo 350/ 10 bolt with 2.41 gears. I went from losing by 2-3 car lengths to beating him by 2 length's!
Best $30 I'd spent!
That's how I came to believe 318 manifolds have to be horribly restrictive, it just putting the exhaust on made that much difference! They got worse as the years rolled by, I believe...
I have another set of what I think are the same wierd headers, they can be ID'd by the slip fit tube on the passenger side, where they don't really need one. Odd, since they don't come apart!
They are 1 5/8 tube, with only a 2.5" collector instead of the usual 3" that are commonly used. Maybe they are old Dougs or Casler headers....
To make a long story short, buy the TTI's....
alan627b
 
The real revenge came when the buddy went out and bought headers too, and actually slowed down! Then I was beating him by 3-4 lenghths! I think it leaned him out and lost power. He then went on a money spending campaign, that I won't describe here.
he he he
alan627b
 
I think with your heads being done and your intake and carb that you would benefit a lot from a set of headers. +15 hp or more?
 
Like Alan mentioned, an electronic ignition and windage tray would be good bolt-on hp helpers. A viscous fan is another bolt-on that`s a relatively inexpensive improvement. As far as getting power to the pavement, a pinion snubber , long shocks, and a set of leaf spring clamps are all bolt-ons that`ll help you get down the road faster without breaking the bank. If you`re running a stock 2 bbl. cam in your 318, well that is something you`ll definitely have to address.
 
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