66 Mild Performance Specifics


New Member
Jul 6, 2004
Hi all, I need some of your experienced help/opinions on narrowing down some add-on potential performance equipment for a 66 289-2V C4 Auto. The car is a 41,000 mile coupe that was "restored" MCA/factory-like 10 years ago for serious but non-councours shows. It did its duty on that circuit but soon deteriorated somewhat w/o the shelter of a garage and after it was forced into 10,000 mile + daily driving during some hard times a few years ago. Today, I just want to make it a nice, peppy, fun as well as reliable clean/sharp occasional driver. Othe than the GT-Style exhaust, the car is factory and has not been torn down to the short block. To repair an oil leak, the intake and timing cover are now removed. The 2V carb leaks gas and needs replacement or a better rebuild than the one I unsuccessfully gave it.

Since the carb needs replacement/rebuilt, at minimum I want to change to a 4V, and have purchased a used Ford Motorsport dual plane. The lead wire from the distributor to the coil broke off and I'll likely replace that with a Pertronix set-up. Since most everything is basically accessible at this point, here's what else I have in mind: Cylinder Heads: The stock heads will need hardened seats at some point (right?), thus they will have to be pulled to replace them eventually. Is it wise to pull, then put fresh heads on a 40,000 mile 40-year old stock motor? I've seen several pairs of heads on Ebay for sale, both aluminum and iron. Since aluminum heads seem overly pricey (but not completely ruled out yet), I'm leaning towards factory iron heads that have been ported/polished, have new higher lift springs, are fitted for guideplates and with 1.94/1.60 valves, magnafluxed, etc. I'm thinking that with the 2V factory pistons that I'll need to keep compression up and stick with the early smaller combusion chambers (yes?). Will standard rocker arms due, or should I replace these (I know I'll need hardened pushrods with guideplates)?

Second, is the camshaft. A new timing chain is likely in order for the engine regardless, at this point...so why not? I'm thinking of the Comp Cams 268 or 270 models, or the Edelbrock performer series. How difficult is it to successfully install a camshaft?

Third, is carburetion. I'd like to go (have heard good things) with the Autolite but the 480cfm 1.08 model is over $500 w/o a core. I don't like Holleys and have heard that Edelbrocks wear out quickly. I'm thinking of the Demon Road Jr. Without the new cam and heads, I'd go with the 525cfm, but what about w/ the cam-head combo mentioned above. 525 or 625 cfm? Road Demon or Junior model? Any experiences/opinions on Demon carbs as to their reliability and bolt-on prowess out of the box? What about an Autolite 4100 600cfm 1.12 instead for the cam-head combo?

Finally, exhaust. IF the new cam and heads are installed, AND you didn't want to cut into the firewall/shock towers, would you go with the HI-PO manifolds, tri-Y headers, or something more special (Hooker headers Comp series).

Another note, the car has a 8" rear end w/2.80 gears now but will be upgraded to 3.25-3.89 range.

Whew! Thanks for any advice/opinions you can provide.
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wow, looks like you've got a lot going on there.....

for the carb, go with the Autolite 4100, 600 cfm version. You can buy these at swap meets(or e-bay) for 70 bucks or so, and rebuild them for $25. Great carb, no hassles. Edelbrocks are a good bolt on and go carb, I've never heard of them wearing out like you said. Holleys are better for performance, but be prepared to do more tuning to get it working just right.

If I were you, I would probably get some headers. With the added air and fuel coming in, you need to make sure it can get out. Lots of options here...If you want to keep the original look get some repro 'K' code manifolds. Tri-y headers could also be considered factory as they are what Shelby used. They work well on mild small blocks and strengthen mid-range power. Hooker and Hedman both make good longtubes if thats what your after.

For the heads, again lots of options. It looks like you want to stay with the cast iron. When its all said and done, it all costs about the same. You could get your heads rebuilt, ported, add bigger valves, srew in studs and guideplates, and have hardened seats installed. All this would cost in the neighborhood of $600 or so. Or you go get a set or world products windsor jr. or windsor sr. heads for a few bucks more and be better off. Don't forget GT40's or GT40Ps. They peform well and can be bought at reasonable prices. GT40P's require special headers, but I do recall hearing that the 'K' code manifolds work with them.

For the cam, it sounds like you're on the right track. Keep it mild with a strong emphasis on low end and mid range power. Be sure to use a good double roller timing set. CompCams makes a good set that is affordable, around $40 I think. I don't know what transmission you have, but it you plan to keep the stock torque converter make note of which cams will still work ok with it.

If you don't have overdrive and do a good bit of highway driving you'll want to keep your rear gear under 3.55, 3.25 is a good all around gear for sporty driving with comfortable cruising.

Since you're replacing the oil pan gasket, get a one pice rubber gasket for say a 93 5.0 mustang. Seems like the multi-piece cork/rubber gaskets always leak just enough to make a mess. A blind monkey with one arm could install the one piece rubber gasket and it would never leak.

With 600 autolite, motorsport intake, xe268 or edlebrock performer cam, hi-po manifolds or tri-y's, and upgraded heads, you should have a strong runner assuming the short block is in good shape. I would expect close to 300 horses depending on what heads you go with.