[sjdiesel]

So I pulled my 400 appart today to begin the rebuild and this is what I find


Looks like its a 4 bolt block with 2 bolt main caps?? WTF??

[Bruce Meyer]

# 4 main cap is broken around the dowel.

[sjdiesel]

Yes saw that too. No pieces in the engine tho. Thought it was odd to see 2 bolt caps on a 4 bolt engine....

[Bruce Meyer]

That's fairly normal to have 2 bolt block drilled for 4 bolt.

[sjdiesel]

Originally Posted by Bruce Meyer

That's fairly normal to have 2 bolt block drilled for 4 bolt.

Really? So should since I have to replace the #4 cap and have it align honed should I just go ahead and get a set of 4 bolt main caps??

[Bruce Meyer]

I don't see why not.

[mchell]

Originally Posted by sjdiesel

Really? So should since I have to replace the #4 cap and have it align honed should I just go ahead and get a set of 4 bolt main caps??

common to see them drilled for 4 bolt mains.......unless you're planning to make buhkoo power I wouldn't waste my money on 4 bolt mains....

[Tim Corcoran]

I would say that depends on your budget and how much power the new build will be putting out. If you are not going over 575hp I would say just replace the broken cap. If you do decide to get new 4 bolt caps it is pretty pricey to do the machine work and you will need a top notch machinest to make sure the job is done right.

[sjdiesel]

Originally Posted by mchell

common to see them drilled for 4 bolt mains.......unless you're planning to make buhkoo power I wouldn't waste my money on 4 bolt mains....

Don't know what kind of power that is but I'm planning on stroking this motor with KRE heads and a roller cam.

[sjdiesel]

Originally Posted by Tim Corcoran

I would say that depends on your budget and how much power the new build will be putting out. If you are not going over 575hp I would say just replace the broken cap. If you do decide to get new 4 bolt caps it is pretty pricey to do the machine work and you will need a top notch machinest to make sure the job is done right.

Now correct me if I'm wrong but won't I need to have the block align honed if I replace just the one bad cap?

[The Boss]

Originally Posted by sjdiesel

Now correct me if I'm wrong but won't I need to have the block align honed if I replace just the one bad cap?

Yes.

[Old Man Taylor]

Since you need to align hone it anyway, I would use the two bolt caps but change to studs instead of bolts - after replacing the #4 cap.

[android 211]

The factory had a machine that drilled all the holes at the same time.

[Don Chapman]

If it were a 455 or 428 block it would be very common to see 2 bolt caps and drilled for 4 bolt. But this is a 400 block, most are drilled only for 2 bolt mains.

[1971WARBIRD]

it is harder to find blocks that are only drilled for 2 bolts. they are out there but you have to look.
alot of guys building for more power like the 2 bolt blocks as they can be drilled for splayed caps, which to a point help hold the block together.
as far as power, a friend of mine has ran a 2 bolt 455 in the mid 10's for years, in a full bodied 67 GTO.

[Nicks67GTO]

Originally Posted by sjdiesel

So I pulled my 400 appart today to begin the rebuild and this is what I find


Looks like its a 4 bolt block with 2 bolt main caps?? WTF??

Several things....

-How sure are you that its a 400? What are the numbers and codes on it? I think this is common with the 455's. I know mine is this way.

-The #3 cap looks to have the left hand hole drilled dangerously close to the edge of the block. Im not sure I would mess with that and install 4 bolt caps??

-Since you are rebuilding i would fix the #4 cap but the break isnt catastrophic. I had the same deal on my current 455. Someone got stupid and smashed a dowel and broke the cap edge. I pulled the cap, filed down the rough break and reinstalled it and its been running good for 2 years now.

[Nicks67GTO]

Originally Posted by Tim Corcoran

I would say that depends on your budget and how much power the new build will be putting out. If you are not going over 575hp I would say just replace the broken cap. If you do decide to get new 4 bolt caps it is pretty pricey to do the machine work and you will need a top notch machinest to make sure the job is done right.

I dont want to argue but as a 19 year old kid I fit my own steel splayed main caps on a 2 bolt small block 350 chevy. I just filed the inner ridge on the caps until the fit tight on the inside of the recess on the middle 2 bolts and torqued them down. {Filing woul be unnecessary on a Pontiac} Then used a drilling bushing {many times this is supplied with the caps} to drill out the splayed bolt holes right into the water jackets {whoops} Then I drilled the holes out a touch at the top with a larger drill bit and angle relieved the holes around the top with a cheap bit to relieve stress, tapped them and used white locktite sealer when i final torqued the mains after it was align bored. I did it in the garage and it cost me nothing. I drove the wheels off that engine, it saw above 8000 RPM many times. I never had the slightest issue with any of it. If I could do it at 19, its do-able for most guys if they want to take the time.

[Sammy B]

First, the timing set looks like it isn't mounted property. (Sorry, couldn't help it.) And, yeah, that hole does look pretty close to the edge. Weird.

[70pontiaction]

The displacement is cast into the side of the block.
Upper right side of photo clearly says "400"

I've had quite a few 400s like this - usually 68/69,
but I don't remember the engine codes.

One was an original, virgin 69 RAIII WS engine I
tore apart for the 1st time, replaced the rings
and bearings, did a valve job, buttoned it up
and drove the snot out of it. Ran great for
about 10k miles before I sold it.

All three 67s I had apart were drilled 2 bolts.
Couple of 71/72s same thing - only 2 bolts.
70s WS, WW, YZ were 4 bolt with caps.
Two 1970 WTs were 4 bolt with 2 bolt caps.
Several 1970 YSs were 2 bolts only.

I think this is more common on 455s. Of the
dozen or so I've had far enough down to see
inside, almost all were drilled for 4bolts.

I agree that 2 bolt caps are sufficient for up
to 7k rpms - 575 HP. But do get studs.

[sjdiesel]

Ok guys thanks for the info.

I am 100% sure it's a 400. Can't remember the casting numbers but it is a 1971 year block.

That hole being close to the edge is odd. I will check later. Maybe it is the pic angle??

So I guess the real question is how hard will it be to find just one cap??