hey guys I need some help and the more specific the info the better. I am not very familiar with the differences between a 428 and a 427. I have heard the terms cobra jet and super cobra jet but i always thought that these pertained to the 429 block. so I geuss the really question is what are the differences between a 428 and a 427 FE block?

Secondly out of the 428, 427, and 429 which is the better engine to build for 450+ hp. I want to build one for a cobra kit car but unsure the best for the application so any info that you could give i will greatly appreciate. Thanks in advanced.

 

[font size="1" color="#FF0000"]LAST EDITED ON 09-Apr-01 AT 06:29 PM (EST)[/font][p] The difference between the 427 and 428 blocks is the bore and that the 427 has crossbolts to help prevent main bearing cap walk at sustained high RPM the 428 has a 4.13" bore and a 3.98" stroke while the 427 has a 4.23" bore and a 3.78" bore. The 427 is better for high RPM as it can be made with steel cranks as opposed to the 428 cast crank. Both engine can easily be made to produce 450hp with stock parts. The terms Cobra Jet and Super Cobra Jet as far as the block is concerned indicate a reinforced block on the main webs, a heavier rotating mass, better rods, the SCJ has 427 LeMans Rods which can and do go to 7500+RPM without failure. Also the 427 can be had in center-oiler and sideoiler versions, the sideoiler just puts the oil into the passages at a point between the cam and main bearings, while the centeroiler makes the oil pass between a groove in the cam bearing and the block before going to the main bearings. If you want your car correct either a 427 or 428 will work because a lot of the '427' cobra's were actually 428's. The 429 will work too, but if you are going to use a 429 block I'd get a stroker 460 kit for it since it will work just fine and give you a LOT more torque and can still be badged as a regular 429 without anyone knowing any better. And of the engines with a complete edelbrock Performer RPM package are pushing or over 450hp if you add a hotter can and run at least 10-11:1 compression with the aluminum heads you'll have a very potent engine

 

There was indeed a 428 cobra jet and super cobra jet (essentially the 428 cj with a numerically higher gear ratio in the rear end and a few other speciallized options for lower 1/4 mile et).

Prices for a complete 427 or 428 Cobra Jet are going to be high, but you'll probably pay more for the 427, especially if it is considered exotic, like the tunnel port or side oiler 427s were. Also, the 427 is not exactly street friendly. Compression ratios were out of this world, so you might find running on street gas difficult. 427 valve trains were also solid, so you have to fiddle with that every so often and there's more noise than with the 428 cj set-up.

The 427 was made from 1963 to around 1968, but the 428 was only around from 1966 to 1970, I believe. But I still think the 428 was more common because it was more of a mainstream engine. The 428 cj was a fairly hot engine, more than the factory ratings will tell you. Mustangs with the 428cj ran the 1/4 mile in the high 13/low 14 second range, so a Cobra kit car with a bone stock 428 cj should be pretty exciting. And it has the added benefit of looking just like a 427 on the outside (valve covers, manifolds, and other external bits will interchange), so you could trick everyone into thinking you had a 427.

As for the 429, it's heavier than even an FE block. You could bore it way out and stroke it to a pretty high displacement and make really big power, but the weight would make your little Cobra a handful in the corners. The FE is relatively light with aluminum heads and intake and tubular exhaust manifolds.