[Kingsnake]

I recently spun a main bearing so Im looking for ideas to do to my matching # motor.
I guess what Im asking is what are some ways to beef the motor up? It is a 1970 formula motor, it already is 30 over, has 6x8 heads, and the bottom end is balanced. Im going to replace all the bearings, rod, main, and cam. What are the Best bearings to use? Someone told me I should clearance the heads to take a 1.65 rockers. Are the any little tricks to help prolong the life of the motor. Any resonable input would be greatly appreciated. I want performance but I want the block to be as safe as possible.
Thanks, Chris

[Brian D'Amico]

I feel that Federal Mogul's are a good replacement bearing.

Yes... if you are going to use 1:65 rockers.. you need to elongate the push rod holes so that they fit correctly.

No real "tricks" except I've heard that having an engine balanced helps reduce problem in the future... (you already have that one covered)

As far as beefing up you engine.. A stroker kit is the best bang for the buck.. but a smaller chamber (hi-commpression) head like a 72cc would really wake up your 400. With the 6X's you're probably running around 8:1 cr... with a 72cc head (like 12's 13's 16's 670's ect..) you could bump that up to 9.5 or 10:1. Not sure if you want to go that route with a #'s matching engine.. just my .02

[Kingsnake]

What about oiling problems? Do the 400's not have the same problems as the 455's?

[Will]

455s don't have any real problems in street applications. Neither do 400s or any other Pontiac engine. The only time you need to get worried about oiling problems is when you're really planning to start spinning the engine and making serious power. For a sub-6000 RPM street engine just pay attention to clearances, make sure the crank grind is good (all journals concentric, properly polished, not "barreled", mains all on the same centerline) and run a 60 psi oil pump and good quality oil filter like a Wix or Napa Gold (same filter, different label).

Those 6X-8 heads are kinda big for a 400. As mentioned your compression is pretty low with them. On an overbored 400 that's been zero-decked a set of 6X-4, 5C-4 or 4X -?? (several different 4X castings and can't remember the ones with the favorable chamber sizes) can all be worked to deliver compression ratios in the 9-9.5:1 range. You may even keep your eyes open for a set of small valve heads like #11 or #17 as these have chambers in the mid 80cc range which is perfect for a 9.5:1 street 400. Just have them machined for larger valves and screw-in studs and they'll be just as good as any of the more desireable casting numbers and can usually be picked up dirt cheap which helps offset the additional machining costs.

If the machine work is done right and you don't over-rev the engine, your bottom end will be plenty safe no matter what bearings you use.

[sccc51106]

Just did a set of # 11 heads for my 406. Had everything done except tapping the rocker studs

[INJUNTOM]

seems like you should have #12 or 13 heads. what are on it?

[SWEETJUDGE]

OIL OIL OIL, Cross drill the crank, GOOD soft babbet bearings, block the bypass in the filter housing. RAM AIR IV oil pump MS54DS i think. OIL be there or sieze

[sixtee8gto]

You are having your crank turned and bearings to fit?

[Kingsnake]

Yes the crank will be done over fresh. I think Im going to get some roller lifters and 1.65 roller lifters. As for bearings I have hear good things about clevitt dont know much about fed. mougl. It had a set of high compression heads on it that we took of because my uncle said I would have to run race fuel, I would like to bump up the compression a little so I will keep a eye open for some of those #'s

[chiphead]

Any of those 72-75 CC heads are gonna put you over the limit for pump fuel. The trick is to have the TRW forged pistons dished by your machinist. Then you can run the correct cylinder head (if you still have them) or another 72CC head and choose what CR you want. I would suggest 9.3:1 with zero deck.

If your engine spun a main bearing, have the block saddle and cap true checked. Spinning a main bearing is serious and the block must be checked for damage with dial bore gauges and micrometers. Sometimes its the block saddle/main cap that made the bearing seize in the first place. Determine if the engine's main saddles need to be line-honed. This ensures proper fitment of the main inserts. Its not just bearing insert to journal thats important. Its bearing "crush". That is how much the block and cap pre-load the bearing when it torqued to spec. Not enough bearing "crush", and she'll spin a bearing every time.

If you want to protect your numbers matching block, use good rods. Do NOT re-use your stock connecting rods. They can fail at moderate RPM and ruin the block. For the cost of having your stockers rebuild, you can just about buy new CAT or SCAT or other quality steel con rod.

Use the Federal Mogul 3/4 groove main bearings, part number 4040M in the correct undersize. Blueprint the M54DS oil pump. Use a factory windage tray, a good pickup and a good 6 quart stock oil pan with the baffle. Shoot for .002" clearance on rods and mains. .007" on crank end-play. Rod side-clearance will depend on what rods you use. Piston to wall depends on what pistons. Ring end gap depends on what pistons/rings and bore size used.

I can tell you that once you see the prices for a roller cam setup for Pontiac, you will go back to a flat-tappet cam. Not really worth it either unless you're going for BIG power.

Use the Spott's tool to elongate the pushrod holes in head. It should remove the proper amount of material from heads pushrod passages. I used a die grinder, and did not remove enough material. So I have to go back to 1.5 rockers or pull the heads off my 400.

Pontiac engines are very powerful and reliable when built and tuned properly. However you must assemble it correctly, take your time to pay attention to small details, follow the advice given on boards like this, and use good parts for the engine to live long and run well.

[Will]

Main contributors to spun bearings and broken rods (not necessarily in order of importance):

#1 - over-revving. Remember, this is an old Pontiac V8, not a ricer 4-cylinder.

#2 - Poor quality machine work. More common than you might think. Many, many shops employ people who are just there for the paycheck and don't really give a rat's ass about quality. If it's within a thousandth or two, that's good enough for them, but it shouldn't be good enough for you. Crank grinding is almost an art. Around here it's really difficult to get a good crank grind done. This doesn't seem to be as much of a problem in other areas of the country. I've gotten cranks back that had journals that weren't round, that had main journals that weren't all cut on the same centerline, and that looked like they'd been polished with 100 grit sandpaper. Other critical clearances are in the main saddles. The allowable tolerance on the size of a main journal is only .0005"!!! That's the tightest tolerance of any part of the entire engine. If your main bores are all in line with each other and all the same size, DON'T have them align-honed or bored.

#3 - reusing stock rod bolts. For God's sake, don't do this! If you're on a really tight budget, buy some ARP bolts and have the stock rods magnafluxed and resized. This is cheaper than even the cheapest new forged rods, but not by much. If you obey #1 above, resized rods with new ARP bolts will be okay for most street applications.

#4 - Compression ratio too high for gas used (detonation). Running a true 10:1 compression ratio with a smallish cam is just asking for a spun rod bearing or even a broken crank. Detonation can occur even at much lower compression ratios if there are other problems in the engine, such as oil burning, overheating, and improper spark timing just to name a few. Best bet to avoid this problem is to err a little on the low side compression-wise (you really won't give up that much power), keep the engine cool and let it breathe fresh air from outside the engine compartment, keep load off it at low RPMs, and run an appropriate cam for the application.

Contrary to popular belief the Pontiac oiling system is NOT inherently weak. Many millions of Pontiac V8s have led long and happy lives while making plenty of tire smoking torque without any real modifications to the oiling system (though you definitely should run the 60 psi pump).