Does anyone have any actual and honest performance numbers comparing the 427 and 428 engines? I certainly know the factory horsepower ratings, etc., but I’m looking for the real world numbers.
During those several months in 1968 when someone could order either engine in their GTE, and assuming that they actually had a choice, which one would someone choose and why? For example, does anybody have any 0 to 60 or quarter-mile times?
Sorry if this has been asked and answered previously, but I don’t have the information.
If I had been old enough in 1968 to order a new GTE I would option it with the XR-7 package and the 428 CJ. Why the 428? Because it was available with a 4 speed, and in 1968 a real muscle car had a manual transmission.
The 1968 GTE 427 is strangled by the GT-390 exhaust manifold and the 600 cfm carb. I am assuming that the late run GTE’s came with the 428 Cobra Jet exhaust manifolds and the 735 cfm carb? Both engines used a very similar hydraulic camshaft. If the second sentence is true then it is a no brainer that the 428 GTE would run away from the 427 version. Maybe some later 427 GTE’s came with CJ exhaust manifolds? If so that would help.
I think the addition of the 735 and CJ exhaust manifolds would make them virtually the same. The 1968 427 with the cross bolt mains and side oiler system is certainly a better choice for high rpm work and longevity. And I have owned 2 Cobra Jets. And been around a lot of the earlier Medium and High riser versions of the 427. They were far more potent than a 428 CJ in stock form.
I just installed the GT-390 Exhaust manifolds and 2 inch H pipe on Bart’s GTE today. What a shame to choke off such a cool motor. Tomorrow I will go through the 600 cfm carb that we got from Royce. Also a shame to put that on a 427! Especially when Bart had a set of CJ exhaust manifolds and I have a good 735 that we could have bolted on.
Back in the day I had a 427 GTE and a 428CJ GT500KR. I found the 427 would pull hard to 6000rpms while the 428 pulled hard to 5500rpms. Raced them both at Mn drag ways and Twin city speedway. The 427 ran way better times.
I guess I am asking more about “back in the day” stock motor as produced by the factory (unless back in the day you would have bought it for immediate modification).
I am not asking about collectibility or value now, I am asking if you were at the dealer and had to check a box on the order form, which one?
You would think the 428CJ would be the obvious choice. The 428CJ could be bought in a standard cougar. Maybe Bill B could run the numbers, but I suspect that the buyer would save at least $1000 compared to buying a 427 in a standard GT-E. That is like saving 20K today. While the 428CJ is more fragile, for the average motorhead it would have been just fine.
Most folks in those days would have immediately put in an aftermarket radio and wheels. Headers would be fitted to probably 75% of muscle cars within a month or two of leaving the dealer. That saved money would easily pay for all those things and gas for a year.
Of course the opposite is what actually happened. 427 GT-E’s are much more common than 428CJ Cougars in '68.
Were they both totally stock? Same rear end gears? Same tranny? If so, I would love to go back in time and tune that KR. I had a KR in 1975 and it pulled hard way past 5,500 rpm. It was totally stock!
That’s part of the question as many were modified right away. The reason my Dad purchased the car was to street race so it was turned into a stroker. Based on that experience, I’d choose the 427 no question. But considering the car turned out to be so collectible and the huge process it’s been returning it to stock, I’m not sure about my decision would be the same. There’s a lot of variables to consider.
I own two '68 XR-7 Cougars 1. 428CJ C6 3.50 Traction Lok. Stock engine, glass pack type mufflers. 2. 427 C6 3.50 Taction Lok. Stock exhaust manifolds Magnaflow mufflers 735 CFM Holley Solid lifter cam but with the same cam profile as stock hydraulic. Service block, stock heads.
The 428CJ is stronger off the line, but the 427 will reel it in if you have enough room. Compared to a slightly modified 428 (the '68 XR-7 that I bought from Royce with the Jack Tarner built 428CJ) the CJ will just barely stay ahead of the 427. (I did this test with then owner of the 428 car, Bob Tufts) That Cougar would run in the high 13’s in Phoenix with temps in the low 90s. THe best quarter mile time for my CJ was with my very skilled nephew driving in Oklahoma in about 45 degree temps, he got to something like 13.6+. I was lucky to get 13.8 or so out of it. Both Cougars were running BFG TA radials. When Bob and I tested we were doing rolling starts from about 3 mph on the street. (Bob was a police detective with a get out of jail free card at the time).
If you have ever compared a an A code 289 4V with a J code 302 4V it is a very similar comparison, the 302 has more off the line but the 289 seems to build revs faster above about 3000 RPM. The 428 and 427 seem very similar to me.
Bill,
So both your Cougars have the same exhaust manifolds and the same carb, a 735? In that case I would vote for the 427 due to the shorter stroke and larger bore. The 427 should rev quicker.
I am unsure of what the creator of this thread wants. A compariosn of a stock GTE with a 600 CFM carb and the GT-390 exhaust manifolds, against the 428 Cobra Jet with the CJ exhaust manifolds and the 735 CFM carb. Maybe he will weigh in. But it is obvoious that the 428 GTE stock for stock should be the winner.
GTE was an auto with 3.89 and KR a 4 speed with 3.50 and traction bars. I said pulled hard not that that was max rpm. both cars at the time had about 30k miles.
For clarity, the exhaust manifolds on both of my cars are stock. 428 CJ has CJ manifolds, the 427 has the stock 390 style manifolds. If you hold the two manifolds in your hand you can easily see how much better the CJ manifolds are. I suspect the 600 CFM would slow the 427 down some on the top end. The original owner of my GT-E certainly thought so. He put a Holley 780 on it the day he brought it home.
The GT-E is now running a 735 CFM service replacement 428 CJ carb
other specs as below.
I am not saying that my experience is the right, or only, way this could turn out, but I do have two very similar cars with the two engines in question installed in them (nearly identical transmissions and rear axles.
427 C6 3.50 Taction Lok. Stock exhaust manifolds Magnaflow mufflers 735 CFM Holley Solid lifter cam but with the same cam profile as stock hydraulic. Service block, stock heads.
Later on I replaced the 600 on my 1st GTE with a 950 3Bbl. World of difference. That and some other mods got it into the high twelves on a good day when the engine was cool or low thirteens when things were not so advantageous.