phaze1todd Reader
April 4, 2011 9:50 p.m.

Been looking for information on the Shelby Cobra Mark I 260 motor because I want to "loosely" replicate it in my Fairlane.

For the most part I will go for aftermarket parts such as Edelbrock for the 4V intake, but I can't find information on how Carol raised compression. Did he deck or is there a higher dome piston for the 260?

novaderrik HalfDork
April 4, 2011 11:05 p.m.

probably dome pistons. that was the most common way to bump compression back then.

pres589 Dork
April 4, 2011 11:08 p.m.

Why not have heads milled for higher compression? I know that there's offset milling of the intake faces to deal with so the intake manifold will seal, but that seems better than going for less common "pop-up" pistons that also weigh more, with domes that will protrude farther into combustion space and possibly impede combustion times [read: increased spark lead requirements, less efficient burn].

And have the deck surface checked for true if you're really serious about the build.

jimbbski Reader
April 5, 2011 11:14 a.m.

The original 260 heads had tiny combustion chambers. I would bet Ford used dished pistons in stock 260's. Shelby would just need to go with flat tops to raise the compression ratio.

stuart in mn SuperDork
April 5, 2011 12:29 p.m.

If you're just concerned about appearance, I'd go for more cubic inches...a 289, 302 or even a 347 stroker properly dressed will look the same.

pres589 Dork
April 5, 2011 1:10 p.m.

Agree with stuart, plus 302 inch motors are dirt common compared to 260's.

novaderrik HalfDork
April 5, 2011 8:26 p.m.
stuart in mn wrote: If you're just concerned about appearance, I'd go for more cubic inches...a 289, 302 or even a 347 stroker properly dressed will look the same.

people are making 400's out of stock 302 blocks these days..

phaze1todd Reader
April 5, 2011 9:03 p.m.
stuart in mn wrote: If you're just concerned about appearance, I'd go for more cubic inches...a 289, 302 or even a 347 stroker properly dressed will look the same.

Thanks, all.

Don't want to spend that much time turning wrenches. Also, one thing leads to another, e.g., 5 bolt block leads to tranny swap, higher horsepower leads to rear end swap. . .

This things for cruise nights. Want cool looks and a little lump in the cam. Just thought it would be cool to have a Cobra replica motor in a car that came out the same year.

tuna55 Dork
April 5, 2011 9:40 p.m.
phaze1todd wrote:
stuart in mn wrote: If you're just concerned about appearance, I'd go for more cubic inches...a 289, 302 or even a 347 stroker properly dressed will look the same.

Thanks, all.

Don't want to spend that much time turning wrenches. Also, one thing leads to another, e.g., 5 bolt block leads to tranny swap, higher horsepower leads to rear end swap. . .

This things for cruise nights. Want cool looks and a little lump in the cam. Just thought it would be cool to have a Cobra replica motor in a car that came out the same year.

It's a good goal, just keep in mind you can get a 302 with a little lump by kicking over some rocks in your backyard vs trying to find the 260. Your goals are honorable, though.,

stan SuperDork
April 6, 2011 6:37 a.m.

You can get a lumpy 302 pretty cheap and easy these days.

Also, pictures would certainly help us help you...

pres589 Dork
April 6, 2011 6:53 a.m.

Unless you already have a 260 sitting there that has been magnafluxed and sonic tested so you know how much overbore can be done to clean it up for rebuilding, a 302 seems like a lot easier motor to build because there's so many more of them out there.

John Brown SuperDork
April 6, 2011 7:37 a.m.

I have seen more than one occasion where a late model 5.0L was put in place of a 260. It is a pretty painless swap with the hardest part being the timing cover, a proper cam gear, a 50oz imbalance flywheel and an aftermarket pulley.

TR8owner Reader
April 6, 2011 8:22 a.m.

I'd assume this is the same 260 that was in my Sunbeam Tiger? Unless the serial # match and you're going for complete originality, I'd be ditto on the 5.0. upgrade.

gjz30075 Reader
April 6, 2011 8:28 a.m.
John Brown wrote: I have seen more than one occasion where a late model 5.0L was put in place of a 260. It is a pretty painless swap with the hardest part being the timing cover, a proper cam gear, a 50oz imbalance flywheel and an aftermarket pulley.

You can still go after a late model block but use the early front cover, flywheel, crank, pulleys, etc to replicate the look. No need to use late model stuff because you have a late model block.

In fact, early 289s are all over craigslist and they have the 'look' you're looking for.

mblommel Reader
April 6, 2011 8:25 p.m.

Sounds like he already has a 260 in place with the early 5 bolt bellhousing pattern. IIRC you can't swap to a later 6 bolt block, e.g. late 289, 302, 5.0 etc. without swapping the tranny or at least the bellhousing.

mad_science New Reader
July 7, 2011 1:59 p.m.

A stock, un-special 260 runs about 8.5:1 compression with 54.5cc heads with teeny-tiny valves. (1.59/1.39)

289 heads were the same, volume-wise, but ran bigger valves (1.67/1.45).

HiPo (k-code) 289s had 49.2cc heads with the same size valves.

Source for all my info: http://mustangtek.com/heads/Heads.html

That's pretty much the only straightforward way to get a CR bump in a 260. They're hard to find and tend to be kinda spendy, but not ridiculously so because the 289 guys have no shortage of piston options to get high CRs with heads that flow better.

Later Ford and pretty much all aftermarket heads have way bigger combustion chambers (high 50s, mid-60s cc), which I'd assume offer better combustion and flow characteristics.

oldeskewltoy Reader
July 8, 2011 11:22 a.m.

Do to the 5 bolt bell.......

If memory serves me......there are some 289 that also used the 5 bolt pattern. That way you could keep the full look, and drivetrain and still have a few "lope" type engine build options

Woody SuperDork
July 8, 2011 11:29 a.m.
oldeskewltoy wrote: Do to the 5 bolt bell....... If memory serves me......there are some 289 that also used the 5 bolt pattern.

I think '64 1/2 D Code 289s did.

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