General: 1968 US Combi Being Outfitted with Vintage Performance Parts

[kishor]

Originally Posted by Vintagewrench

Have finished machining the B18 cast iron conversion guides (bronze is not needed in this application, and really is only necessary for racing applications) to be used with B20 valves which have .312-inch (5/16″) diameter stems that are hard chromed and smaller than the original .343-inch (11/32″) stems for improved air flow. The end of the intake guides have also been tapered for better airflow through the port. The top end of the guides were machined for modern valve seals. Valves with chrome-plate stems and finely machined guide id's with a honed finish will last a very long time in street and highway use.

The new B20 exhaust and intake valves are in the center of the photo above shown in comparison to the B18 guides and valves on the left and the right. The dark spots near the valve head will disappear after a second blending angle is cut on the back side of the head for improved flow, after the new valve seats have been established in the head.

Both sides of the valve heads and the end of the stem where it meets the head have been lightened somewhat (compare them to an untouched valve below) by machining the two sides in the lathe and then swirl polishing the backside of the head. The 42MM B20 intake valve heads have been turned down to 41MM which is larger than the original 40MM B18 intake valve heads. B18 and B20 exhaust valve heads are both the same size.

Next up, install the guides in the head and machine and press in exhaust valve seats, and cut larger intake valve seats. And finally, relieve the combustion chambers, and do some very minor porting behind the valve seats.

Delete the DOT in the following link and replace it with a period to learn more about what was involved and view pictures of how the guides were machined @ http://theoldmotorDOTcom/?p=165294

Good morning to you

You are doing a sterling job on that motor. Fantastic. Please keep us posted on the progress

Ta
kassiemotors@yahoo.com

Kasssie

[tdz840]

Originally Posted by Vintagewrench

No, they are as machined and CP-Carillo does offer ceramic coasting at an extra cost. The Company's pistons are used by most all high-level motor sports racing teams here in the US, but their products are priced accordingly.

I use them on customers vintage racing engines if possible and my own cars because of the engine shop discount I get. They are also the only forged piston manufacturer here with forging blanks long enough to make a zero deck height Volvo piston which when used w/a thin .032 multi layer steel Cometic head gasket allows the Volvo "squish band" combustion camber to work better than it did when new and produce more power and less detonation.

Check out this video to learn more:

https://www.youtube.com/watch?v=1Wt-jdHqsv4

I fitted a set of Ross Forged pistons but 92mm. I had to deck the block to achieve the correct squish
Russ

[Derek UK]

Will swirl polishing the back of the exhaust valve, rather than mirror polishing, lead to more carbon build up over time. Discuss.

[Derek UK]

Originally Posted by tdz840

I fitted a set of Ross Forged pistons but 92mm. I had to deck the block to achieve the correct squish
Russ

Were your Ross pistons accurate enough to give the same deck height for all? Sometimes that have to be matched before calculating how much the block needs to be skimmed. All very tedious if you are going for the last fraction of power, but that's what blue printing is all about.

[Vintagewrench]

Originally Posted by kishor

Good morning to you

You are doing a sterling job on that motor. Fantastic. Please keep us posted on the progress

Ta
kassiemotors@yahoo.com

Kasssie

Kasssie, Thank you!!

[Vintagewrench]

Originally Posted by Derek UK

Will swirl polishing the back of the exhaust valve, rather than mirror polishing, lead to more carbon build up over time. Discuss.

Derek, From what I have learned talking with other engine builders and observed from several vintage racing engines built here that have also seen a lot of miles on the track and on long tours, it does not appear to be an issue at all. Carbon build up seems to be about the same on valves w/polished, swirl polished, and left as manufactured surfaces.

Swirl polishing is mainly used to quickly remove under head material to blend in the stem to the head for improved flow, for weight reduction and to remove any irregularities that are stress risers that can lead to the formation of cracks.

As you know the key to eliminating carbon build up is to spend the time needed to get the mixture correct and to keep oil out of the combustion chamber with modern rings and valve stem seals.

And speaking of rings, the wide and heavy three piece oil rings fitted to most original and aftermarket B18 and B20 pistons flutter at TDC and BDC and wear the cylinder walls in a corrugated pattern that causes increased oil consumption.

Next time you remove pistons from one of these engines it is more than likely that you can see these ripples that form on the cylinder walls from the ring flutter.

[tdz840]

Originally Posted by Derek UK

Were your Ross pistons accurate enough to give the same deck height for all? Sometimes that have to be matched before calculating how much the block needs to be skimmed. All very tedious if you are going for the last fraction of power, but that's what blue printing is all about.

Derek
Two pistons were the same height but the difference was only 2 thou over the 4 pistons. It averaged out around 0.033".
I had them ceramic coated so it would have meant removing the coating so I accepted the difference.
Russ

[Vintagewrench]

Originally Posted by tdz840

Derek
Two pistons were the same height but the difference was only 2 thou over the 4 pistons. It averaged out around 0.033".
I had them ceramic coated so it would have meant removing the coating so I accepted the difference.
Russ

Volvo's machine work on the B18 and B20 engine components was done to a very high standard. When the top of the block to crankshaft measurements were checked on both the front and rear of this B18 block it was within .001" front to rear. The stroke of the crank and the center-to-center distances of the rods where also all plus or minus .001"