GT500 VS GT500KR engine

The significant differences are heads, exhaust manifolds and ram induction. The intakes and carbs are also different #'s but basically the same from a performance standpoint. The gamed the additional horsepower from allowing the engine to breath better. Rated @ 335 hp but were probably closer to 400 as opposed to 360 from the GT 500's PI engine. Other than badging other signicant differences are cast iron tailshaft on the automatics and staggered rear shocks on the 4 spds. they also had trac loc rears except the AC automatics.

 

I'll take the easy ones.

In Ram Air, there is a direct connection between the hood scoop or cowl intake and the air cleaner.

PI engine means Police Interceptor.

robin

 

The heads were C80E N based on the 427 med riser heads. The intake was similar to alumium PI intake but much heavier cast. The carbs were Holley 4bbl, I believe 735 cfm. The GT 500 PI and the CJ use the identical short block except camshaft. The 428 PI used the same heads/exhaust manifolds as the 390 GT. Nothing wrong with the 360hp the PI puts out, it will snap your neck just fine.

 

actually the CJ Block is Beefier with external and internal Ribbing and a couple of other tricks not found on the standard FE engines (FE= "Ford Edsel")

 

A bit of trivia for you. The 428CJ was introduced mid-year 1968 and was the brain child of the TASCA Ford racing team. KR stands for "King of the Road" and rumor how the name evolve was Carroll Shelby heard GM was thinking about using this name in one of their big block Chevy's. Carroll the beloved competetor beat them to the punch.

Doc

 

Actually the 68 PI blocks did have the extra webbing, U1 crank and C7AE rods like the CJ's. Some even have the infamous "C" on the back of the block. I have one sitting in my garage, a Jan (pre CJ) build car with original motor.
As far as the development of the CJ, I had a chance to hang out with Bob Tasca Sr. recently and pick his brain a little. His exact words to Ford were they were embarrassed by the performance of the 390 GT at the track comparred to the performance of the big block camaros and mopars. When Bob speaks, Ford listens.

 

On the same note, my 428 P.I. has an allum. intake which is supposed to be much lighter than a 428 C.J. cast iron intake. If they were going for more performace then why use the heavier cast iron intake ? --S.

 

2 thoughts, one there were a lot of problems with aluminum manifolds... stripped bolts @ valve covers etc. With the type of modifications this motor was expected to see (valve covers on/off) the cast would hold up better. The other is they knew carb/manifold would get changed to something more orientated to the type of racing it was going to be used for (tunnnel rams,etc.) This explains why C8OF AA/AB carbs are so rare, most of them probably didn't stay on the cars long. It actually is a pretty good manifold from a performance point.

 

When my engine was being rebuilt, the under side of the intake [ allum. ] was corrided with a hole about the size of an apple. The consences was the exhaust gate ? or butterfly was missing from the exhaust manifold for along time, which had something to do with when the car was started , the air flow went thru, or around ,or whatever the intake ?? So I put one on when the engine was going in the car. The only thing it leaked exhaust & I could not stand the noise any longer, so I took it off. If it took 30 years to get to get to this point it will out last me. Had someone cut out the bad & weld in a new patch,--good as new.---S.

 

That is very common with the PI intakes. Some people block off the exhaust crossover and deal with the slower carb warmup. There also were a lot of corrosion issue from electrolysis between the metals and the added influence of antifreeze. As a rule I coat every bolt that goes into or passes thru the manifold w/ antiseize.
By the way I was reading your post about pinging. Do you know what springs and jets he used?

 

My prob. was advancing too quick ,too soon ,timing set @ 6 degrees as per manual etc.etc. Alot of people agreed on the heavier spring for the dist. I don't know what # spring he used. same for the jets in carb. larger than the 72's ??? I believe that were in there before. He was telling me all this & I was'nt paying too much atten. then , just interested seeing how the car performed. What he did say was having to RETARD the timing, & when I heard that I thot it would be a dog. Engine was bored 30 over, decked squared, etc. etc. Also with C.R. of 10-5 to 1 to begin with when new ,I thot it might be someweres around 11-to 1 now. & not fixable unless I did what you were doing with the Sonoco 105 & so forth. When I was fooling with it myself, retarding it less than the 6 degrees was against my thinking. Shows how much I know. I even got one of those adjustable Vacuum advance canisters which helped some. Sometime later I'l will put the original back in. Try this,fordmuscle.com "Timing is Everything" ---S.

 

Cobra jet short blocks were actualy blue printed at the factory, in the top side oil gallary next to each cylinder you will find a number painted , pistons and rods were weighed and matched.It's to bad that Ford had to put the thermactor system on these engines as new emission laws came into effect, this is why so many CJ cars are missing the systems and the cost to replace it is so high.
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