Mild Torque 318 suggestions wide open!
comments in the quote
I'm embarking on a sl6 to 318 swap. (automatic 904)
My wife says this car MUST be quiet -no headers. It must idle nice. It must have AC. It must not overheat. It must be fine with 70 mph. That said, I can spend some cash on this build no problem but don't want a fiddly exotic tuning nightmare. I think I'll shoot for 250 HP and as much torque as possible to get it off the line with my 276 gearset.
To hit all these targets you need a 360
I'm gong to rebuild the 318. plan on bumping the compression up with pistons
Heads? 360 heads and intake- stock
5-650 vac secondary carb to retain a bit of mileage.
slant torque converter might be a good idea?
Bast option on exhaust? like a high flow cast iron manifold.
what cam to use? power just off idle-retain torque- sounds like an 80's truck cam but cam choices are infinite and I'm not "in the know" about them.
what kind of head mods would be most effective? I thought just a bowl polish and knock back the heart tip? Full porting would just slow the charge and cost torque?
Going to an aluminum radiator with dual electric fans-Griffin makes the best ones I've seen around. What's wrong with a mechanical set-up?
Of course I have electronic ignition and such. I just need to talk to my engine guy soon and bat around ideas
Other worthwhile mods? Am I off base for my goals? 360, hi-flow exhaust,4bbl, no cam, and done.
EDIT -NO Magnum Swap. I've got a 318, it's good, it fits, unless someone wants to trade?
So you want to keep the teener, kindof shooting yourself in the foot then, but here's my 2 cents
Static compression ratio of 9.8:1.
Effective stroke is 2.74 inches.
Your dynamic compression ratio is 8.27:1 .
Your dynamic cranking pressure is 166.91 PSI.
V/P (Volume to Pressure Index) is
134
This is about the best compromise your gonna get on pump gas
The cam I used was a 252/260/114 in at 110. It has 32 degrees of overlap so will run fine with logs. I won't make a lotta power, but also won't suck a lotta gas. The VP of 134 is not all that bad.
Here's the same specs and cam in a 360
Static compression ratio of 9.8:1.
Effective stroke is 2.97 inches.
Your dynamic compression ratio is 8.30:1 .
Your dynamic cranking pressure is 167.70 PSI.
V/P (Volume to Pressure Index) is
153
Notice the VP is 153/134=14% higher.
The 360 will feel that same 14% more powerful in the lower rpms. Of course it is also 13.2% bigger, so it will just feel more powerful all thru the rev range.
The beauty of the 360 is that you can downsize the cam if you wanted to make better fuel mileage.
Or you could upsize it a lot, before the VP falls to the same 134.
Heres an example with a 272/280/110 cam, in at 106, still with the 360
Static compression ratio of 10:1.
Effective stroke is 2.84 inches.
Your dynamic compression ratio is 8.14:1 .
Your dynamic cranking pressure is 163.52 PSI.
V/P (Volume to Pressure Index) is
143
Notice the VP has fallen to just 143
Yet the cam is a very generous size that really wants headers. Again this is about the best compromise for a warmed up 360 still running pump gas and iron heads.So now the bottom end is feeling like 143/134=6.7% stronger than the optimized 318, yet making a huge buncha more horsepower than the 318. My guess is nearly a hundred more ponies.
Course you don't have to install this big a cam; your 360 can be optimized for almost any size cam. I just used a 272 for illustrative purposes.
Here's a 360 optimized for a 240/248/114 cam (teener cam)
Static compression ratio of 9.3:1.
Effective stroke is 3.10 inches.
Your dynamic compression ratio is 8.19:1 .
Your dynamic cranking pressure is 164.83 PSI.
V/P (Volume to Pressure Index) is
157
This will be a tire frier. Of course the cam is done around 4500, kindof perfect for those 2.76s; 1st is good to 50, and second to 85, and tops out at 4500=125. No need for headers, just duals.
Oh sorry, I forgot; the teener is staying.
Well in that case your best course of action is to get rid of 400 pounds.In my case, I drive alone.That solves a lotta problems for me. LOL
Here's an interesting comparo; a 440 with a 272 cam
Static compression ratio of 9.3:1.
Effective stroke is 3.10 inches.
Your dynamic compression ratio is 8.19:1 .
Your dynamic cranking pressure is 164.83 PSI.
V/P (Volume to Pressure Index) is
157
Notice the 157VP? Tire frier