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Original Message
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| RE: 360 mods |
| By Dave Shoe - 01/01/2001 2:31:26 PM; IP 216.243.158.102 |
First off, you've got the good heads for that motor (I correctly assume they are C8AE-H castings, check between the center sparkplugs to be sure). These are small runner "emissions" heads, which are shaped really efficiently for torquey small displacement FEs that don't need to hit the 11-second bracket. Nearly all FEs since 1968 got this head (or the approximately identical D2TE-AA), and most since 1966 did.
390GT and 428PI heads are identical to yours except for stiffer valve springs because of the hotter GT/PI cam. Some 390GT and 428PIs got nice pre-emissions-style C6AE-R castings (available in '66-'67 only) with large runners, but most did not, and all from the last year of the 390GT motor, '68, got the high-velocity "emissions" runners. To be sure, the 390GT is not a motor you want to pattern your's after, as it was choked at the intake manifold, and was especially stuffy at the exhaust. Also, the lame 390IP of 1969 (which replaced the 390GT and came in GT-optioned 390 cars) was no different from your motor, except it had 30 extra cubes, a little more compression, a larger Autolite carb, and some marketing hype tossed inot the weird "Improved Performance" (over stock) name.
Note: all '65-earlier FE heads have larger pre-emissions runners, much like C6AE-R and CJ heads.
An Edelbrock Performer manifold is not a good way to go, as it's just an aluminum version of a stock manifold, IMO. You want the Edelbrock Performer RPM or an iron 428CJ or alum 428 PI intake to open up the intake side. A 600 CFM 4V Autolite carb (not a 450 CFM 4V Autolite) is probably the best carb for your motor. Those things kicked ass in the 428PI motors of that year. alternately, a 600CFM Holley would fit just right. I don't play with other carbs, so I can't give my patented bad advice for any others. Beware, most 428PI intakes are worn out and overpriced, so the Ed RPM or CJ iron route is generally best.
On the exhaust side, you want headers (your log exhausts are actually better breathing than stock 390GT manifolds). The most important parameter to know here is that you've got "emissions" heads which have the low-exit exhaust port (same size port, just lower on the head), so you need the low-exit style of header flange on your headers, or else you are asking for gasket leaks (bad gasket crush) and non-optimal performance (severe turbulence at the 5/16" port mismatch). FPA (fordpowertrain.com) probably has the best headers (quality and design) for your application. Hooker and Hedman do not have any headers with your emission flange, even though their book claims the headers will fit. Be sure to order the low-flange type, as FPA offers both types. Don't worry about the mufflers - keep quiet ones on for drivability. You won't find any performance improvement with loud mufflers. Hey, the power comes at the headers.
You can easily add CJ-sized valves to your heads for a little more flow.
I'm not a Camshaft guru, and there are many folk with great advise in this area, so I won't chime in here. Wait a minute...Yes I will. Obviously, when replacing a camshaft, you'll have to replace the lifters, as they lose their sphericity after only a short time and become set to a specific cam. A warmer cam will also require stiffer springs, which means you'll have to toss your low-perf valve rotators and install regular retainers, which means your valves will need to be replaced due to valve lock positioning, dot, dot, dot. You'll want to but a "cam kit", as well as some nice cheapo CJ-sized valves if you wanna actually complete the job. I guess I'm saying you can expect to replace the cam, lifters, timing chain, valves, springs, retainers, and locks. Pretty standard and cheap stuff, but not always what you'd see in the planning stages.
One more thing, modern camshafts are far superior to '60s cam grinds. For one, they have faster ramp speeds because improved valve spring material allows faster ramps. The problem is these faster ramps cause added rockershaft flexing. This is no idle problem, as many FE folk, myself included, know all about breaking rockershafts. Flexing shafts also reduce power. The basic fix is not a stiffer shaft, but a rockershaft end-support kit (FPP is one place to look). Next, rockershaft dowel kits not only stabilize the rockers by replacing the wimpy separator springs, but they also stiffen the shaft and don't cost all that much. Optionally, a stiffer shaft can be purchased after doing the prior two upgrades, but you certainly don't need to replace the shaft (unless it happens to be worn out, not likely) in your application.
I will advise that desktop dyno numbers can mask some parts-ordering mistakes. For example, the software doesn't differentiate when installing the wrong-style header flange. Be careful when ordering parts that you look past the computer and make sure you get the right parts for your application.
All JMO,
Shoe. |
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