Harv's Repco HighPower crossflow head thread

[Harv]

Checked in on the progress going on for the head. Head and roller rockers now in the same location.

Water jacket plugs out of the top – glad they could get them out, as I couldn’t even with a cheater bar. Solid (not allan-head) plugs being sought to allow the extra rocker shaft support to be added (as luck would have it, the additional support is right on top of the plug rather than an open area of the head).

My Crow retainers are not going to cut the mustard – their shape precludes the roller tip getting contact, so new bespoke retainers are needed. Bit of a shame I spent so much effort trying to work out an off-the-shelf spring/collet/retainer set, but I did learn a lot as I went along.

Patience, grasshopper.

Cheers,
Harv

[Harv]

Head measured - 47cc before surfacing.

Cheers,
Harv

[Errol62]

About 8.5:1 assuming 0.060” overbore, zero deck height, flat tops and 0.050” gasket.


FB ute fixer upper, EK van on rotisserie

[Harv]

A little more squeeze, as the forged slugs have a little lump. About 9.5:1... then some breathing from the Norman

Cheers,
Harv

[Harv]

Copper head gaskets arrived today from Gasket Solutions (same mob that makes the improved cooling gaskets for the normal head).

IMG_1312.jpeg (3.03 MiB) Viewed 739 times

Cheers,
Harv

[Harv]

Head has finally come home, and I've started dummy assembling. Most of it is intuitive, but suspect I will learn more as I go. Photos and learnings to follow .

The bare head is a chunky bit of kit, and weighs some 24.5kg. Like most, mine has had a working life. I can see where some casting porosity/void has been weld filled:

Repaired casting goober between numbers 2 and 3.jpg (1.1 MiB) Viewed 486 times

Little wonder these things often leaked water, and that mine was Loctited. Two of the rocker pedestal mounts have also needed thread inserts:

thread inserts near numbers 1 and 2 and machining examples.jpg (1.86 MiB) Viewed 486 times

At the bottom of that photo, below number one and number two inlet valves you can see some significant machining work near the rocker pedestals. This is required at each pedestal to allow the roller rockers to clear. They are definitely not a "buy them online and bolt them in" deal. Experience has shown that each Repco head was hand finished from the factory, and needs unique machining. My thanks and kudos to Craig and the guys from HSD who made this work.

The exhaust rocker shafts are quite long, and tend to flex (a lot) under load. A common way to sort this is to install two additional rocker pedestals. One is a (relatively) easy drill and tap, the other needs a casting plug removed and a threaded brass insert fitted to the head:

Brass insert for six-post upgrade.jpg (974.45 KiB) Viewed 486 times

Cheers,
Harv

[Harv]

Time to throw the springs in. These are double springs, and have an uninstalled height of 1.643". The HSD guys machined up some valve seat inserts. This gives more flexibility on spring choice as the spring pocket depth can be varied (without shims) and so can the inner and outer seat diameters. Assembly looks like this:

spring and retainer assemblies.jpg (1.13 MiB) Viewed 485 times

Note to self: inlet and exhaust inserts are different. When I forget this like a durn fool idjit and mix them up, the diagram below will help:

Spring seat inserts.jpg (13.87 KiB) Viewed 485 times

Valves and springs in place:

Valves installed in head.jpg (1.25 MiB) Viewed 485 times

Springs installed in head.jpg (2.43 MiB) Viewed 485 times

Cheers,
Harv

[Harv]

The rocker pedestals are held on with studs. I'm going to replace these with ARP fasteners, so just dummying up for now. Will post details on the ARP stuff once it arrives. Four of the exhaust pedestal studs go through not only the pedestals but the rocker cover too (with two nuts - one on the pedestal, one on the rocker). Studs are 4" long, 5/16" thread, -18UNC one end and -24UNF the other. I’ve used ARP AG4.400-12G stainless bolts, supplied 4.4” and cut to suit. These should look neat poking up through the rocker cover. They are stainless, so antisieze needed to prevent galling.

Rocker cover studs installed in head.jpg (1.81 MiB) Viewed 484 times

ARP rocker cover stud.jpg (2.48 MiB) Viewed 484 times

Rocker cover studs installed in head.jpg (1.81 MiB) Viewed 484 times

The oil supply comes up from the block like a normal grey motor, and through one of the inlet shaft pedestals between number four and number five. You can see the mounting pipe sticking up through the pedestal in the photo below - the other pedestals are bare. A little rubber washer is needed to seal the pedestal to the shaft so the oil does not leak out:

seal for oil supply from pedestal to shaft.jpg (1.46 MiB) Viewed 484 times

The oil flows though the hollow inlet shaft, and there is a crossover pipe to let it also flow to the hollow exhaust shaft (I'll take more photos of this later). Oil flows along the shafts to each rocker. The shafts had small chamfered holes drilled to feed each rocker bushing:

oil exit hole from shaft to rocker.jpg (1.05 MiB) Viewed 484 times

The rocker bushes have a groove down the middle to receive and distribute the oil:

rocker bushes and oil groove.jpg (746.04 KiB) Viewed 484 times

The oil then flows sideways out of the rocker bush and dribbles out the gap between the bush and the shaft spacers. Will draw a better diagram later. As far as I can see, the roller tip is splash-fed.


Random photo of one of the exhaust pedestals:

Exhaust pedestal.jpg (773.71 KiB) Viewed 484 times

Cheers,
Harv

[Blacky]

Hhhhmmmm, rocker cover studs - I need some longer ones to put my fancy hold down bolts back on - have you seen what our old mate Greedybitz is asking for them ?

[Harv]

Hhhhmmmm, rocker cover studs - I need some longer ones to put my fancy hold down bolts back on - have you seen what our old mate Greedybitz is asking for them ?

$120 for two studs... they would want to make coffee and sweep floors too at that price. If I had some I'd send 'em to you, but every motor in the spares department has the rocker cover held on with only hope and gravity.

Some more info on the valve train.

Collets are Crow 4133 single groove machined valve locks, 7-degree to suit 0.343" valve stems.
Springs are Crow 2836 dual race springs to suit Nissan A12, 3K Toyota and E13 Mazda (and apparently also Repco HighPower ). 1.134"OD for the outer, 0.383"ID for the outer, 0.612" ID for the inner, outer is right-hand wound, 1.638" free length, 320lb/inch, 0.800" at coil bind.
No valve stems seals run on the originals, and none that have been found to work well in the last half century.
No torque settings for the rockers.
Valve lash is cam dependent (mine is 0.014" cold).

Head original colour is the subject of much debate. It is very likely that they were not painted at all, but research (even on the Repco-owned cars) has not landed a definitive answer. I'm planning on Duplicolor engine enamel in Cast Iron, with the block done in Duplicolor Holden Engine Grey. All masked up and rattlecaning tomorrow, weather permitting.

Cheers,
Harv

[Harv]

Last lot of progress before I went back to work.

The inlet shaft pedestals have a 45-thou thick spacer placed under each to lift the inlet rocker shaft to the correct roller rocker geometry. Care needs to be taken in assembling these are the bolt holes in the pedestals (and the spacers) are offset. The pencil in the photos below are pointing to the short side of the spacer and pedestals.

offset pedestal cap.jpg (2.27 MiB) Viewed 343 times

offset inlet pedestal spacer.jpg (2.49 MiB) Viewed 343 times

inlet pedestal spacer in place.jpg (861.25 KiB) Viewed 343 times

The assembly looks like the below:

inlet shaft pedestal assembly.jpg (1.78 MiB) Viewed 343 times

Note that the rockers did have some studs and nuts. I thought I would get cute and use ARP bolts (ARP 641-1250 5/16-18x1.25”). This proved to make the assembly job unbearably fiddly, and the bolt heads are borderline too large for the task (tend to rub on the rocker arms). I will instead use some ARP studs (ARP 100-3219, 5/16-18/24x1.75” OAL) for final assembly.

[Harv]

The exhaust pedestals do not use the spacers. They are fastened using the rocker cover studs noted above, and some more ARP bolts (ARP 641-2500 5/16-18UNCx2½ “).

exhaust pedestal fastener.jpg (1.2 MiB) Viewed 342 times

With the inlet and exhaust shafts in place, the twin shafts make the head look like a hemi head:

Looks almost like a hemi head.jpg (1.81 MiB) Viewed 342 times

Interestingly, the Repco head has some hemi (hemispherical) design. A true hemi head has a spherical combustion chamber. The Repco head has an almost spherical inlet valve surround, and an additional recessed almost spherical exhaust valve surround:

combustion chamber shape.jpg (1014.09 KiB) Viewed 342 times

The use of multiple spheres was called “polyspherical” (or “poly”) in the Chrysler motors, though it was used to make the hemi head simpler and go to a single rocker set. All up, the Repco may not be a pure hemi, but the canted valves, twin shafts and chamber shape are getting close to it.

Some exhaust manifold studs were in order (ARP 420-1402 3/8-16/24x1.67”OAL).

exhaust manifold studs.jpg (1.44 MiB) Viewed 342 times

[Harv]

The front coolant port will get a simple water neck, and a pair of fasteners (ARP 613-0500 3/8-16UNCx½”):

front coolant port.jpg (1.11 MiB) Viewed 341 times

water neck.jpg (1.1 MiB) Viewed 341 times

I’m not going to run a water pump, and in theory could run the block dry as the methanol will run cold. I’m a little nervous of heat-damaging the head, so will run the block and head water filled to buffer out any temperature shocks. Temperature gauge to keep an eye on the warm up, and if it gets out of hand the radiator cap will lift and blow some coolant to the catch can. Stupid me had the water neck made up a long time ago… the decided to put the catch can on the other side. Some piping elegance will be required.

The rear coolant port will get a rectangular cover fastened by four bolts (ARP 611-0625 ¼-20UNCx0.625”).

rear coolant port.jpg (1.04 MiB) Viewed 341 times

rear coolant port cover.jpg (1.01 MiB) Viewed 341 times

There are coolant plugs between numbers 2 and 3 exhaust valves (1/3-NPT – this will have a temperature sender fitted), behind #6 exhaust valve (1/8-NPT) and between numbers 4 and 5 exhaust valves (1/2-NPT).

temperature sender plug.jpg (1.39 MiB) Viewed 341 times

small coolant plug.jpg (1.19 MiB) Viewed 341 times

large coolant plug.jpg (1.48 MiB) Viewed 341 times

[Harv]

As promised earlier, a better diagram of the oil supply. Oil comes up from the block in a pipe just like a standard grey motor, and connects to the bottom of the head behind the rocker cover (green line in the diagram below). It flows up through one of the inlet pedestals, then along the hollow inlet rocker shaft (red line). At each inlet rocker it squirts into the groove in the rocker arm bronze shaft bushing then squirts out each side of the rocker arm and returns to the sump. Oil flows from the inlet rocker shaft via the crossover pipe (blue line) before running along the hollow exhaust rocker shaft (purple line) and out the sides of each exhaust rocker.

oil flow.jpg (2.38 MiB) Viewed 340 times

To cap off the end of the shafts, 1/8-NPT plugs are used"

shaft end plugs.jpg (1.03 MiB) Viewed 340 times

Cheers,
Harv

[Errol62]

Jeez mate, every time you say ARP I hear ker-ching, ker-ching…..
Looks a good breathing design that would be nice on a street car, albeit prototype quality fiddly finish, if that makes sense.


FB ute fixer upper, EK van on rotisserie