[gtospieg]

I'm having my 400 align bored and my machinist is having a difficult time finding the correct dowel pins for the main caps. The part # is Pioneer PF-601-25(.309 diameter). If anybody knows where these are available please let me know. Thanks.

[400 Lemans]

http://www.precisionautomotivespecia...owel-Pins.html

[Bermuda Blue]

would love to know why pontiac went with such a wacky diameter. I have measured 0.3090 to 0.3093".

0.30965" as claimed on linked website may be more accurate than my measurements.

That's a great price on those dowels if the tolerance really is +/- 0.00005"

[chiphead]

I put a set in my 434 stroker when I built it. Swapping the pins will require a line-hone, as the longer dowels engage further into the caps, and may shift them a bit. The shop should make sure the caps fit properly before line-honing, as its difficult to get the caps on and off with the longer dowels. Only a line-hone is required, a line bore is not required unless the caps are being changed.

[blueghoast]

I just went to the hardware store and bought some 5/16 dowel rod and
made my own and I didn't do a line hone on mine no problems at all
FWIW.

GT

[gtospieg]

Thanks for the responses/info. The block will need to be align bored.

[74Grandville]

Originally Posted by chiphead

I put a set in my 434 stroker when I built it. Swapping the pins will require a line-hone, as the longer dowels engage further into the caps, and may shift them a bit. The shop should make sure the caps fit properly before line-honing, as its difficult to get the caps on and off with the longer dowels. Only a line-hone is required, a line bore is not required unless the caps are being changed.

I think if you notice the caps “shifting” they are probably just recentering on the deeper part of the hole. the initial part of the hole in the cap is probably elongated and making the cap loose.


Sent from my iPhone using Tapatalk

[Tim Corcoran]

Originally Posted by 400 Lemans

http://www.precisionautomotivespecia...owel-Pins.html

I used these same extra long dowel pins from Precision Automotive Specialties on my engine. They fit perfect no drilling or reaming they are a great product. I recommend anyone doing a rebuild or fresh engine to use these. They provide much better stability of your main caps. In addition you can add in some studs with more clamping force and this improves the durability of your engine.

[rolling money pits]

Originally Posted by Tim Corcoran

I used these same extra long dowel pins from Precision Automotive Specialties on my engine. They fit perfect no drilling or reaming they are a great product. I recommend anyone doing a rebuild or fresh engine to use these. They provide much better stability of your main caps. In addition you can add in some studs with more clamping force and this improves the durability of your engine.

My block was align honed, using studs, but with factory dowel pins.

If I were to spring for the precision ones, would the block need another align hone?

[chiphead]

The supplier of the pins makes is sound like you should line hone. The only way to know is to install the pins, fit the caps and measure the housing bore. If you measure them before and after the the pin swap, you'll know if it shifted the caps any.

The long dowel is how I knew my block was at a shop that wears clown shoes. The shop couldn't get the stock pins to come out, they wanted to drill them out. They broke a pin puller trying to get one out. I said "hold on I'll get them out.". I picked the block up the next day. I bought the cal-van pin puller and got them out myself. Patience, heat and some kroil got them right out. I had to weld a nut on one to pull it out, but no drilling required. Buncha bozos.

[Tim Corcoran]

Putting in the same size dowel pins as your factory pins shouldn't move the caps unless the holes in the caps are worn enough to oblong the holes. Ideally the replacement long pins should have been installed prior to the line hone. As Chiphead said measuring the bores after installation of the new pins can verify if the bore size is still good.

[Bermuda Blue]

[QUOTE=If I were to spring for the precision ones, would the block need another align hone?[/QUOTE]

If the existing dowels are well extended into the caps and have aprox 1/4" or more of engagement, its highly unlikely an align hone will be required. Keep in mind the dowels have a taper on the ends and the tapered section does not count as an "engaged" portion of the dowel. Where you run into trouble is when the dowel is sunk into the block and barely engages the cap.

If the dowels are presently well engaged with the cap its probably not necessary to change them

[Mr Twister]

Thanks for the tip. Mine are on order. I'm doing a 2 bolt to 4 bolt conversion soon.

[rolling money pits]

K. Thx. At some point I’ll measure the protrusion of the existing dowels….if that figure is over X amount, I *should* be ok? I currently don’t have any bore gauges and such, altho those are on the shopping list.

[Tim Corcoran]

The reason I changed the dowel pins on my new build is some of the pins had very little engagement into the caps especially the front cap. I was not comfortable with the limited engagement especially since this engine will be raced and will make over 650 HP. If you have adequate engagement and it's not a race engine you should be OK with the factory pins. On the other hand if you are building a new engine and plan to do a line hone anyhow these extra long pins are highly recommended.