[Will]

I have often heard of using oversize dowels to more accurately locate the maincaps (and reinforce them?).

By "oversize" are we talking larger diameter, or simply longer.

If larger diameter, do you then have to hone the cap and block holes to fit them? (Sounds ridiculously expensive).

If longer, are there any potential "gotchas" to be aware of?

Where does one find these oversized dowels?

It's obvious that a line hone would be necessary after altering the dowels.

[Will]

I have often heard of using oversize dowels to more accurately locate the maincaps (and reinforce them?).

By "oversize" are we talking larger diameter, or simply longer.

If larger diameter, do you then have to hone the cap and block holes to fit them? (Sounds ridiculously expensive).

If longer, are there any potential "gotchas" to be aware of?

Where does one find these oversized dowels?

It's obvious that a line hone would be necessary after altering the dowels.

[Bermuda Blue]

It is unlikely that installing new dowels will increase the strength of location properties of the caps on the block. It is very difficult to sheer a 5/16" pin. Actually, the diameter of the pontiac dowel is 3 thou. under 5/16" if i recall. Installation of new pins becomes neccessary when the dowels holes in the caps become elongated and oversized.

An oversized dowel is larger in diameter. The dowels could stick out of the block quit abit without causing problems but it would make putting the cap on more difficult

You may not feel it but allot of caps will move around even though the pins are locating them. Take a dial-bore gauge and measure from the block to the cap. them push on the cap back and forth toward a motor mount bosses. If the measurement changes, you have a problem. This may be one of the most overlooked aspects of building a pontiac motor and the cause of many failures. If the cap moves enough, the oil film will be sheared and any a spun bearing is not far behind.

Removing these dowels is a real PITA. If you break one off flush to the block you have a nightmare on your hands. Once the dowel is removed, the holes in the block are reaemed (not drilled!!) to the desired diameter (this can't be done correctly with a hand drill!!!). The approprate dowel is pressed in while the block is heated. The dowel has to be larger than the hole by at least 0.0002" to ensure a tight fit. Then the caps have to reamed to accept the new dowels. Sometimes this is not necesary if the cap holes are already oversized due to them "walking".

Done correctly, it is not necessary to align bore the block because the location of the dowels and dowel holes in the caps has not changed.

I use a 5/16" + .0002 dowel and ream the block holes 5/16 exactly. The holes in the caps have to be exactly the dowel diam. to enusure that they don't move and at the same time allow you to install them. This is a fine line.

I have some dowels ($1 each) if anyone wants some. But they are available at any good machine shop supply house.

[SCOTT ESTERLE]

What he said. We reamed the holes & caps with a hand drill but we carefully located all caps while doing this. We also had the block line bored after the fact. We used an old drill chuck to pull the dowels out of the block & some we had to heat & try & use vise grips. The ones that barely stick out of the block are a pain in the you know what. Just take your time.

[Half-Inch Stud]

Female grip-socketed Slide-hammer tool is used to remove my dowels...Driverside only.

Caps re-attached, torqued and Match-drilled for new, larger dowel.

Remove Caps.
Install Oversize Dowel in Driverside. End up taller than stock by about 1/8"
Ream Driverside Cap-hole for slipfit.
----------------------------------
Slide-hammer removal Passenger dowels.
Install Caps, torque and Match-drill passengerside
Remove Caps
Install oversize Dowels in Pass side. taller than stock by 1/8th inch
Ream Pass Cap hole for slipfit.
----------------------------------
Thrust Cap #4 done last during each process..
constantly inspecting parting line visually and by feel for any cliffs.

I think.

[Steve C.]

Will- is this inconjunction with the installation of aftermarket steel caps?

I found this of interest.
It's from a article in PE Mag/ March/April '02.
Picture shows a guy pointing at a main dowel in the block. Within the caption and in referance to installing steel caps, it says the process is more difficulit on a Pontiac than on other engines because the dowel pins used to align the main caps are like fingerprints - no two are exactly alike.
It goes on to say that the company doing the work installs oversize dowls (no size given) to ensure a tight fit and then cut's a "removal notch" on the side of the cap to facilitate removal.

( caption continues on with.. Once the new caps are fitted, the block is align-bored and the block surfaces are machined parallel to the crank centerline and the proper distance from the crank centerline )

[Will]

No plans for steel caps. When I go through the 440 again, I'm thinking I'll install new oversized dowels. Loose dowels is one of the possible causes of the bearing failures I'm experiencing. Just want to know what all is involved.

Thanks!

[PONTIAC DUDE]

I've installed 4 bolt factory caps on 2 bolt(4 bolt location) and only line honed.
The Pontiac block is better located then "MOST" factory block produced.

So I don't think the Pontiac block is like finger prints. They are just better machined from the factory. that's all.

Build it fast, build it right, build a Pontiac.

http://PontiacDude.cc

[Half-Inch Stud]

Agreed.

I've noticed excellent registration transfer with the #1 and rear main caps. Thrust cap is the least likely to hot-swap. #2 #3 spot-off by 2 or 3 mils tops. Certainly not practiced often.

I rather suggest 4-bolt cap swap-ons occur per my above-typed method using oversized dowels..INSTEAD of line-bore & line-hone.

Uhm, non-GM steel caps will need the traditional line bore...obvious.

"tbdET/1xxMPH/1.xx 60foot/28"/3.54:1/10"/469 #48/Flat HYD/DualQ-Jets/Offyl/3xx0Lbs
11.00/123MPH/1.50 60foot/29.5"/4.10:1/10"/469 #48/FlatHYD/DualQuad/Wenzler/3250Lbs
12.00/112MPH/1.61 60foot/26"/3.31:1/10"/469 #48/FlatHYD/Q-Jet/Torker/3650Lbs
12.70/103MPH/1.71 60foot/28"/4.10:1/12"/469 #48/FlatHYD/Q-Jet/Torker/3950Lbs"

[trim]

My number 1 cap has a very small amount of play in it with just pins holding it. Will the clamping force of the main bolts be enough to keep the cap from walking and creating a bearing problem? Can the oversized dowels be installed to tighten up the cap without removing the crank or the rods/pistons? The short block is all together, and I really don't want to totaly disasemble unless I have to.

[SCOTT ESTERLE]

I wouldn't do it unless you tear the motor down. It will be almost impossible to get them out of an assembled motor.

[Bermuda Blue]

the bolts which hold down the caps can not stop the cap from moving around. the dowels have to be tight. I think loose dowels and moving caps are one of the most common causes of bearing failure.

ive seen cracked dowel holes in caps do to severe cap movement. when the cap hammers agains the dowel it cracks.

[Half-Inch Stud]

Could lift a dowel or two up a little. Could replace the dowels.

Could leave it alone.

[Dick Duclow]

It's a good idea to use a longer dowel to help locate the caps (we use 1"). On high HP applications (1250 +) we had some cap walk on the original (first 50) run of blocks. As a result all subsequent blocks have 3/8" dowel pins.