400 Stroker Build Documentary
 

I'm building a new 400 stroker engine to replace the 455 (41.5 X4.25 474) that was destroyed at Norwalk this year. I plan to use the same cam, heads, intake, carb and headers that was used on the 455.

Previous build was .060 over 455 converted to program engineering 4 bolt main caps, J&E pistons, Eagle 6.8 H beam rods, and 4.25 Ohio cast crank. Ultradyne solid roller 264/268 @ .050, 176/187 @ .200, .3944/.3944 Lobe Lift .592@1.5 Harland Sharp rocker arms, LSA 108, 1-7/8 Indian Adventures headers with Flowmaster merge collectors, Victor intake with 1050 dominator.

I am doing a documentary of my new build step by step to share on the board. I am by no means an expert engine builder just going to share my build with others. who may want to follow along. I'm starting with a 71 400 block purchased at Norwalk, it was supposed to be a STD bore but it looks to be bored .005 to a 4.125.

So far I have had the block hot tanked and used a wire wheel to clean off remaining paint and rust. Next step to de-burr sharp edges on the casting flash around the lifter bores, install a SD Performance lifter bore brace and hard block up to the water pump holes.

Replaced NEW SFI Balancer sounds like a good idea. Will try to keep up wit the Thread.

How much weight does hard block add?

Cool, I'll be watching/reading

Cylinders with hard block distort differently than cylinders without it.
So, you need to have a head or tq plate with the same head gasket you will use in the build torqued down while the hard block cures.
At least that was the way Whitmore did mine. He had his reasons.

Are you going to billet cap the block ?


Thin rings planned ? Power to be had there.

Glad you're posting the build, will be fun to follow along.

The block has been pre-cleaned, I drilled and tapped the lifter galleys 3/8 NPT, deburred the casting flash around the lifter bores and am currently fitting the SD Mega Brace.

Christmas came early this year, look what the UPS man brought me today from Butler Performance.

Definitely watching this!

It's standard bore. Pontiac literature showed 4.12 but
that isn't right. 4.125 *ISN'T oversized. Pete McCarthy
touched on this weirdness. The 428 is actually a 427,
the 350P is a 354, etc. HTH.

I cleaned every threaded hole in the block using a thread cleaning set, WD-40 and compressed air. I don't use a machine tap as it can remove metal and actually weaken the threads.

This block is a bit of a mystery I wish I knew the history of it. There is absolutely no ridge at the top of the bore. You can still see some hash marks in the bore and this block came out of a GTO. The block was very dirty with grease and grime and a lot of rust on the exterior of the block. There is evidence that the engine had been apart and/or rebuilt at some point by high temp silicone on the pan rail and in the rear main seal area. There are a couple bores that had enough rust that it would need to be bored to remove. If this is a standard bore it is a low mileage mystery.

We've built many Pontiac 400's using a 4.125 finished bore. If the bores are in good shape things work out perfect. Bolt on a torque plate and hone the cylinders to 4.125. Excellent selection of rings and leaves a lot of meat in the cylinder walls.

Recommended....

RACE ENGINEERING: "ULTIMATE" BLOCK FILLER
https://raceeng.com/race-engineering...25-each-bf-25/

Fast setup time
No need to vibrate block
Easy material to work with
Block machinable in 24 hours
Will not crack or separate with age

.

The counterweight will hit the block in the front more than likely. Easy fix. I have built allot of these and love them. It's my go to for a quick easy to duplicate build. 400 blocks are not easy to find but the easiest of what's left.

I am going to put in a plug for Butler Performance just because I think their rotating assembly package is a pretty good deal. The package includes the crank, rods, pistons, rings, wrist pins, and bearings. You select from the available cranks, rods, the piston overbore, type custom dish, dome, or flat top, choose your rings and bearings. After you select all your options the assembly is then balanced, and they provide the balance card in your shipment. They had EVERYTHING in stock and from the time I ordered it till it was on my front porch was about a week. In todays world that is saying something and the price is hard to beat.

Mega Brace installation complete, torqued to the full 40' lb with no lifter bore distortion. Dave provides excellent instructions with his Mega Brace if you follow the instructions, you can't go wrong. My cam is not a super aggressive cam and it's not necessarily in the category that needs a lifter bore brace but I feel better having it than not and the cost is very reasonable.

Whenever you are running solid lifters, flat tappet or roller it is recommended that some of the oil going to the top end be restricted and send it down to the rod and main bearings. This can be accomplished by installing restrictor plugs in the lifter bore or by using restrictor pushrods. I tapped the oil hole in the lifter bores 1/4-20 and installed 1/4-20 plugs drilled .060. No need to drill the holes, it is already sized to accept a 1/4-20 tap. Carefull you don't tap too deep go slow and check it doesn't take much. Make sure you test each bore with a lifter to make sure there is no interference after your done and put red loctite on the plugs.

Always use brass freeze plugs you don't want to pull your engine to replace a rusted leaking freeze plug. I clean each hole with a wire wheel on an air motor to make sure the surface is 100% clear of rust and clean metal. I then wipe it with lacquer thinner or brake cleaner to remove any contaminants. I then rough up the edge of the freeze plug with scotch brite. Then put a very thin layer of silicone on the I.D. of the hole in the block and the same on the mating surface of the freeze plug. I start the plug in the hole with a good size hammer then drive it the rest of the way with an aluminum rod working around evenly until it it's flush with the block. I know you may be thinking this is over kill but this is how I do it. The correct size freeze plugs for a Pontiac is 1-61/64".

I'm not sure hitting the brass plug on the sealing area flange to finish your install is such a good idea.