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Old 01-16-2012, 10:54 AM
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Pontiac 428

Any experiences with stroking a 428 with a 455 crankshaft? What's the gain in HP? What extra machining besides boring +30 or 40? Any specific Cam requirements for roller rockers, need to run roller cam for street/strip/cruise use?

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Old 01-16-2012, 12:18 PM
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Quote:
Originally Posted by CETEN
Any experiences with stroking a 428 with a 455 crankshaft? What's the gain in HP? What extra machining besides boring +30 or 40? Any specific Cam requirements for roller rockers, need to run roller cam for street/strip/cruise use?
My first experiance with a stroked 428 was when I bought one in 1970. It had been built by CT Automotive, in California, using one if their welded stroker cranks (4.25"). It had JE Super Light pistons with stock cast rods. The crank eventually cracked so I started using offset ground 455 cranks until I went all out hard core racing. Now I have one forged 4.25" stroke crank and one 5.00" billet crank and I now use aliminum rods. I have three aftermarket (IA) blocks. One standard deck and two tall deck.
The only thing that you would need to change to make a 455 out of a 428 is the crank and the pistons. You can run roller rockers on any engine, but you will need an adjustable valve train, so if you have bottle neck rocker studs, you will need to change to screw in 7/16 studs with Poly Locks, and if you change cams, you will need valve springs to match the cam.

Bill

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Old 01-17-2012, 11:47 AM
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Using a 455 crank in a 428 bored .030" IS a "455". Why?

What is the application? We have many running the 4" stroke with great results. The rod "angle" (rod/stroke ratio) is much better for higher revs.

All factory 428 cranks are 'nodular' iron and can withstand over 700 HP. Same is true of the 455 cranks except the last version, which has no "N" on the cheek. The "103" (last three digits of the casting) cranks are nodular.

Tell us more.

Jim
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Old 01-17-2012, 12:51 PM
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There are guys who would be glad to swap you a 55 crank for your 28... Not that it much matters but I like the 428. A lot. In the right application it'll run very good.
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Old 01-25-2012, 10:42 AM
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Thanks for the comments. I'm a bit confused as to why the 455 crank also. The pistons I have are for .30 over, the rods are stock 428. The idea to stroke the motor came from the previous owner. I do not "race" serious, just what to build a street screamer. Since I have a few parts, I just want to get the most out of the engine since I have options and the cost is better to spend it up-front and do it right so that I will have a bullet proof engine. I have a BOP rear seal to replace the rope seal. Are there any other aftermarket oil leak secrets? I've always had leaks from my Pontiac Engines. Another opinion question, The "Dual Grind" Comp cam "CL51-224-4" hydraulic, that's a 274/286 lift, 230/236 Duration and they only offer a 106" center line. Any opinions on this as a street cam with power brakes and vacuum advance dist. Thanks, Chet
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Old 01-25-2012, 11:52 AM
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Chet,

Changing the stroke increases the displacement. There's a solid foundation for the term "no replacement for displacement". However, the 428 is no "punk". Rick Holladay runs 10.30s over 130 with his in a '65 GTO convertible, over 3,400 lbs. and a 4-speed. It's a "pump gas" engine.

Be absolutely certain to replace the connecting rods. A "stock" 428 rod is a casting, not a forging. It is also the SAME rod used in all other full-sized Pontiac V8s. It is the "weak link" in the chain. There are many good choices. The Eagle H-beam is considered the 'best for the money". For your application, though,.the RPM 5140 forgings are adequate. Most Pontiac vendors sell them, anywhere from $240 to $300 for a set.

XE274H (the cam you mention) is a good "replacement" for the Ram Air IV cam in lower compression engines (under 9.5:1).

The BOP seal is very good. We HAVE experienced ssues with "stock" blocks, though. The seal "groove" is not machined "close tolerance" because they knew a "rope" seal would be used. Sometimes, the Viton seal will leak because the groove isn't "round". We use the Best Gasket "GraphTite" seal. It's a graphite-impregnated rope. In aftermarket blocks, we use the BOP.

BOP also sells a 1-piece oil pan gasket. More often than not, the rear seal gets blamed for a pan leak. The rear "lip" is problematic, and the new gasket "cures" it.

Most important,. use no sealer between machined surfaces where a paper gasket is used. RTV causes more leaks than it fixes. If a little is "enough", a lot is NOT "better".

Jim
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Old 01-25-2012, 12:04 PM
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Quote:
Originally Posted by CETEN
Thanks for the comments. I'm a bit confused as to why the 455 crank also. The pistons I have are for .30 over, the rods are stock 428. The idea to stroke the motor came from the previous owner. I do not "race" serious, just what to build a street screamer. Since I have a few parts, I just want to get the most out of the engine since I have options and the cost is better to spend it up-front and do it right so that I will have a bullet proof engine. I have a BOP rear seal to replace the rope seal. Are there any other aftermarket oil leak secrets? I've always had leaks from my Pontiac Engines. Another opinion question, The "Dual Grind" Comp cam "CL51-224-4" hydraulic, that's a 274/286 lift, 230/236 Duration and they only offer a 106" center line. Any opinions on this as a street cam with power brakes and vacuum advance dist. Thanks, Chet
The choice of a 4.21" stroke crank over a 4.00" crank is for a little more torque v.s. more RPM. As far as I'm concerned, you have the ideal street/strip set up, except for the cam. I would tend to go with a cam with 110* to 112* centerline, but maybe Jim (Mr P-Body) will chime in with a better recomendation, as I haven't built a street engine since the early 70s.

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