# Bob Hoover's HVX VW Engine Mods.

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#### Pops

##### Well-Known Member
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I'm just starting to do Bob Hoover's HVX engine mods for a 1973 VW Type 1 case. The case has been machined for 92 mm pistons and cylinders, welded behind #3 cylinder, welding sometimes tends to warp the case and good idea to have it checked and if warped have the main bearing saddles line bored. I had the case checked at a VW Type 1 only machine shop. Everything OK. Also cleared for a stroker crank if I wanted to make it a 2180 cc engine. Decided to use the stock 69mm crank for 1835 cc engine. I had great success in the HVX mod in the 1835 cc engine in the SSSC aircraft. With the increase oil flow to the rocker arms and heads I had no heat problems in a WOT climb as long as I wanted on a 100 deg OAT day. To get a better understanding of the Mods read all of this.
https://bobhooversblog.blogspot.com/2007/05/hvx-mods.html

The only down side that I have found is with the increase oil flow to the heads you will have a slightly lower oil pressure. But that is easy to take care of by going to the larger capacity oil pumps or what I did. The stock oil pump cover uses a .004 paper gasket, I made a new gasket of .002 gasket material from NAPA and raised the oil pressure about 8 to 10 pounds at cruise rpm of 2650/2700 rpm, went from 32 lbs to 42 pounds.

Can't beat that.

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#### Alan_VA

##### Active Member
Took some VW rods from the part box and weighted them. Look at the difference of weights. This is the reason you need a matched set of rods for long engine life and smooth running with more power. Two rods weighed --580 grams, Three rods weighed --585 grams, One rod weighed -- 590 grams, Two rods weighed --600 grams, One rod weighed-- 610 grams.
At the local VW only VW parts/ machine shop, they will swap you a set of rods that have a match total weight to within one gram, new wrist pins bushing installed, equal weight on each rod end and exact distance from center of the large and small hole of each rod. The last set I bought was \$15 each and a set of old rods.
Can't beat that.
(New guy here, trying to sort out the gems from the dross.) How closely does your shop balance the rods? IIRC, Bob Hoover was pretty insistent on that as well.

Alan