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cobra jet identification

April 3 2007 at 1:02 AM
Eric  (Login psudokiller)

ok im pretty sure i have a 428 in my truck, so now i need to figure out if its a cobra jet, police interceptor, or just a pass car 428, so what are tale tale signs from the outside to tell weather or not its a cobra jet or pi block, also i was wondering if anyone knows how to figure out compression ratio and cc volume.

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(Login Kevin66.)

Difficult task!

April 3 2007, 2:38 AM 

Eric, it's very difficult to make all of these determinations by just looking at the outside of the engine.

In the first place, parts could have been...and probably were...changed in the 37+ years since the last of these motors was factory assembled.

Next, there's a great deal of 'grey area' when it comes to determining exactly which specific engine a part (casting number, etc) should have come on. Many of the 410 Merc, 428 Passenger, and 428 Police Interceptor engines used blocks, cranks, rods, pistons, and heads, with the same casting numbers.

The head casting numbers you gave earlier indicate they were not CJ heads, and there isn't enough difference between the passenger and PI heads to worry about. Nor is there any significant difference between a lot of the other parts.

The CJ's and PI's used a better connecting rod than the 410/428 Pass engines, but even those standard rods are more than adequate for most usage when equipped with premium rod bolts during a rebuild.

The early PI engines got a solid lifter cam from the 410 HP 427 engines, and the later ones used a 390GT/428CJ-type hydraulic cam. The 410 & 428 Pass motors used very mild hydraulic cams.

The CJ's used a high-rise, cast iron intake manifold (C8OE-C), and a 735cfm Holley 4-Bbl carb. The PI's used a high-rise aluminum intake, and a 600cfm Holley. The Pass engines used an Autolite or Motorcraft carb, on a low-rise cast iron intake.

Get some of the numbers off of the components of your motor, and post them here. As best they can, people will identify what it's likely they came off of originally. But the only way to positively know what you have, is to at least partly dismantle the motor for a look!

All of the 410/428 motors were rated at 10.5:1 or 10.6:1 compression ratios, and probably delivered closer to 10:1. Calculating your actual ratio would require a knowledge of the combustion chamber cc's, piston dish, deck height, head gasket thickness, and swept volume of the cylinders.

"In theory, theory and reality are the same. In reality, they are not!"

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(Login scf100)


April 3 2007, 3:23 AM 

no way to tell if its a cj block while in truck...

go here


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Rod C
(Login MT63AFX)

Keep in mind when trying to identify FE castings 1) the block has two.....................

April 3 2007, 5:14 AM 

.................patterns pressed into the two flasks/molds, (Cope/top and Drag/bottom) that form the exterior side walls. On the patterns are removable plates for date and shift "clock" with the main engineering number and plant ID being a permanent, machined part of the pattern. These external patterns are quite interchangeable among all the FEs from the 60s on. The end castings are made with bulkhead cores and it appears Ford had a few, not many, for the front and back, with back having added the provisions for the Side-Oiler. These cores were also interchangeable , to a degree. When production called for the "A" to be scratched into the bulkhead core to signify a certain 428, it was done on an existing generic core before being placed in the mold, as well as the "C" scratching and originally it is scratched, not welded, not cast. As with any birthday present, "shaking it" tells you nothing of what's inside 'till you OPEN IT, LOL. What differentiates FE blocks is the different INTERNAL cores used: bore cores, water jacket cores, cam area cores, and crankcase cores. Now imagine assembling this menagerie/myriad of sand cores, under time/quantity pressures from management, or take a whiz, or a "drink", or a "puff", or just plain ignorance and you could end up with 427 water jackets placed over a 352 block cores, LOL, (poetic license). That's how I see it from a Former Ford Foundry worker's point of view, Rod.

Mickey Thompson's 63 1/2 AFX Hi-Rise 427 Lgt/Wgt Galaxie,
1957 C-600 Cab-over carhauler w/390-4V, 2-speed rear-end
FGCofA member #4908
MCGC member #75

"There will ALWAYS be an FE in my LiFE"

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(Login ScotiaFE)

It is only a

April 3 2007, 6:17 AM 

Cobra Jet if you have Cobra Jet heads on it. A Low Riser is a Low Riser. A Medium Riser is a Medium Riser. A High Riser is a High Riser. A Tunnel Port is a Tunnel Port. A SOHC is a SOHC. If you you don't have the heads you don't have the heads.

A Edelbrock is a AlumaJet. LOL

1968 Mustang Fastback Hotrod 428

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(Login RM428)

Re: It is only a

April 3 2007, 10:37 AM 

Although I agree that the heads are the MAIN differance on a Cobra Jet vs a TBird 428, the other differences DO exist.One of my 428`s I have was a new 428CJ "Service" short block, that was bought from a Ford dealer in the mid 70`s, and installed into a 1966 F100 pickup, using the trucks original 352 heads. I bought the whole engine from the truck in the mid 80`s, after pulling the oil pan for inspection (1UB crank, 13/32" rod bolts, extra main webbing etc). I gave the guy his $350.00, brought it home, and popped out 1 piston for a look see. It has the factory cast "428 Super" pistons, and the crank and bores are standard size, with the bearings being OE Ford "DAB" 1974 dated. So basically, it was a CJ short block when it was new, still a CJ short block when it ran around with the 352 heads for a decade, and when I eventually freshen it up for the 59, using C8OE-N heads, it will still be a 428CJ, although of a more "pure" pedigree once the correct heads are on it. So, without taking at least the oil pan and a head off, and doing some measuring and numbers checking, you will be hard pressed to tell exactly what the engine is.

428 powered Fairmont drag car, Best ET:10.20@131.59MPH, best 60 ft: 1.32
59 Meteor 2 dr. sedan 332, Ford O Matic
74 F350 ramp truck 390 4speed

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