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Offset grinding means you take down the diameter of the rod journal but the centre of that diameter is ground into it further out in the throw from original, so when first grinding/turning it down, the journal will be wobbling in the grinder/lathe and more material is removed from the inside than out. The theoretical maximum you can increase the stroke by is double whatever the difference in pin diameter is. So a Clevo/400m is 2.311, the usual chev pin is 2.100, difference is 0.211, so is the maximum throw. Double that and you get stroke increase - 0.422. There is a limit to how much throw you can grind into it, determined by main/rod journal overlap (strength), rod to block and camshaft clearance, rod angle and thus rod/stroke ratio. As far as taking meat off the counterweight goes, crank balancers only like to drill them for some reason. It's easier to work out the amount of metal to be removed when it's directly opposite the crank throw so I guess that's why. It would be more beneficial to remove metal from either end of the counterweight as you would be able to remove heaps more to get the same result (reducing rotating mass in the crank), but calculating that wouldn't be easy. Sent from my CPH1920 using Tapatalk

These days, machine work like that is as expensive as a brand new stroker kit, with a steel crank and H-beam rods Sent from my CPH1920 using Tapatalk

Hahaha 8 inch rods and an extra 100kg of engine... Sounds worth it Sent from my CPH1920 using Tapatalk

I think he's going to carve up a perfectly good 400 crank for nothing. The biggest feasible stroke an 8.2 deck Windsor can handle is 3.4", which with an overbore gives you 347, and already these don't have a great rod/stroke length. The pistons are very short to clear the crank weights, oil consumption and piston wear becomes a problem due to piston rocking and ring stability. The ideal 302 stroker is the 331 with a 3.25 stroke, this having a much better rod/stroke ratio. Any longer stroke than 3.4 and your rods need to be impossibly short, and I don't think the bottom of the bores will clear the crank or the rods. If he's using a 351W block, that is a whole different story. That deck is 9.5", taller than a clevo at 9.2". The mains are the same size as a 400, and with an offset grind and a bore, you can go beyond 408 cubes to say around 427, etc. With a 4.125 bore, you can go right out to 454 and beyond. Maybe if he's talking about a "Boss 302" type engine, he really means a 351W with clevo heads? That's what they call a "Clevor". Sent from my CPH1920 using Tapatalk

I have never used a machine shop, let alone recently so I couldn't tell you how much a sonic check would cost. Best place to find out would be to ask your old mate, I'm sure he's got connections somewhere. Sent from my CPH1920 using Tapatalk

In Oz, they used to take the 351 crank and offset grind to a chev rod size and make it a 377. I think Eagle and Scat were the big brand kits to get in the day, and they didn't really come along till the late 90s? The US aftermarket didn't really tool up for clevos like they did for 5.0s as they only built them for 5 years or so there. Sent from my CPH1920 using Tapatalk

Regarding line boring the block... I don't have a clevo and a 400 block to compare, to know if the main cap bolts are the same distance apart for each but if the 400 is wider, then boring the clevo out to suit 3.0" mains might have the tunnel bore too close to the bolt holes and end up with cracking issues or ripping them out altogether. Sent from my CPH1920 using Tapatalk

That was pretty common in the day, start with a 400 crank and grind the mains down 1/4” for a cheap clevo stroker crank. I think they used to chop quite a bit off the counterweights too, as they're too big for shorter stroker rods and shorter, lighter aftermarket pistons. The reason why Ford went with such big mains (as with 351Ws) compared to clevos is because they were designed as a truck engine, to be able to slog it out for hours on end and bigger mains have more surface area to take this kind of load. Also, crank twist and torsional vibration (ultimately breakage) is better resisted with main and big end journals overlapping on the crank throw, relying less on the thickness of the metal in the crank cheek itself. This is made more critical by all the accessory drive stuff hanging off the front of the crank in a truck installation (like compressors, hydraulic pumps, big AC systems, etc). If they didn't have such big journals, the crank would have to be made from a more exotic material than good old nodular iron. While modern stroker cranks are often not forged, they're at least a little bit fancy a grade of steel. Sent from my CPH1920 using Tapatalk

Those are different again. While I haven't seen inside one (we never blew any up in the time we had them) I can only assume that they work pretty much like any 4x4 locker diff, either electric, vacuum or air actuated. They have a hexagon-shaped actuator on the diff hat which tells you for sure. They're just an open diff when not locked, but when you flick the switch, a vacuum solenoid (on the RTV) opens an actuator which locks a dog clutch (splined to one of the axles) to the housing. Locking one axle to the housing in turn locks the spiders, thus locking the other axle as well. So while you have the locker engaged, it's pretty much a mini-spool, and eventually you'll break an axle or some other internal bit if you drive around with it on all the time. Sent from my CPH1920 using Tapatalk

To be fair, he did mention in one video that he had surgery a few years back, sounds like they removed a brain tumour or something and he lost a lot of his ability to recall memory, which explains why they stop and start his videos all the time. Maybe he needs to go over notes constantly? Sent from my CPH1920 using Tapatalk

Yeah that's the challenge... Finding a good presenter that both gets to the point and shows stuff that is useful, not take 40 min to tell you 90% of what you already know. Uncle Tony is pretty good, he gets to it pretty quickly. I saw a vid of his just this morning about resurrecting a stuffed car battery using a stick welder (looked sketchy but that's how he rolls). Above that level of skills, people start getting very cagey about their craft, as they likely are specialists in the field and only give away snippets of info that keep it mysterious and therefore doesn't kill any business for them. Vizard is good but I feel that his tech videos are an annoyingly slow drip feed of info. Sent from my CPH1920 using Tapatalk

I'm a bit of a meat-axe at this but I'll gladly share what I know, it's rare to find anyone who knows them and the ones that do don't like to share. With any luck the interballz will be better for having some knowledge on it preserved. Sent from my CPH1920 using Tapatalk

The Hydratrak isn't the same as the Borgwarner cone type LSD. The Hydratrak came about in the mid-90s in HSVs and the like, whereas the BW cone clutch LSD has been around since probably the 70s. The BW LSD is of similar design to the non-LSD diff in that the centre and spider gears run in the diff oil, it relies on side-thrust in the spider gears under load forcing the cones to bite into the sides of the diff centre. This locks both axles to the housing and drives them together. The Hydratrak relies on the viscokinetic action of a type of silicone fluid in a sealed centre, being squeezed between chambers within the housing, whenever a speed difference occurs between the axles (ie loss if traction from one wheel). As this speed difference increases, the fluid thickens and the resistance increases accordingly, making the slipping wheel hydraulically lock itself to the one with traction. It's kind of like a hydraulic version of a Detroit locker. Subarus used a viscous LSD of a different design in their manual boxes for the centre diff. You may be able to retrofit a hydra to a normal BW housing but not 100% sure, in any case a hydra in good condition is pretty hard to find these days. Brand new I think they are dear as poison. Sent from my CPH1920 using Tapatalk

First drive impressions: pretty good for an old dunga. My dad brain made the mistake of buying 57s jets... The ones that came in it were 57s too. In any case, it surged on light throttle so that told me that 57s are lean. So, I swapped in some 59s I had. The secondaries were also way lean at 67 (wrong on a non-power valve block) so went right up to an 89 drill on some jets I didn't want. Apparently 87 is the correct secondary jet for this carby, so not far off. If it had a power valve in the secondary, you would subtract 8-10 jet sizes to get the right mixture under load. I don't see the point in running a power valve in the secondary, you're always under power whenever they're open, so the power valve will always be open under load or closed when the secondaries are shut. Blanking it off and jetting up to compensate is the go I reckon. Less failure points to worry about. Just got back from a test n tune, it has woken her up a bit, feels more lively than the street demon, but has sacrificed a little bit of bottom end torque and smoothness (probably from having older design boosters). You can still feel a little bit of leanness when accelerating moderately, in that once the pump shot is done, the power drops off a tad. Still might need more jet but I'm happy with the WOT performance. Now to see if it guzzles the juice or is somehow actually better than the street demon. Sent from my CPH1920 using Tapatalk

So it's now on the car and running, haven't taken it out yet but had a few hurdles when reassembling. Secondary pump housing had these weird channels cast into it that were bypassing the umbrella check valve and back to the bowl, could hear air hissing past it when testing. It would have had pissy flow once all together. So I epoxied up the channels to make the housing flat just like on the front bowl. It's hard to see here with the clear epoxy, but it's there. And I marked where the edge of the umbrella check valve would seal on the housing, you can see why it would bypass. I can't find any pics or forums about this kind of accelerator pump, but it's irrelevant now... Test run on bench with pump fixed: Sent from my CPH1920 using Tapatalk

Good find, at least it was a simple (maybe not so easy) fix [emoji41][emoji106] Sent from my CPH1920 using Tapatalk

Probably cost... They're about 5 times the price of your regular power valve but also people have just broadly accepted that you can't get economy out of a Holley, so don't bother chasing it. They aren't recommended on performance carbys, so I wouldn't use one on anything bigger than say a 600 square. Sent from my CPH1920 using Tapatalk

This weirdo thing is a dual stage power valve. First stage opens at 10.5, second at 5.5. first gives around 0.030 of equivalent total PVCR while the second gives whatever your metering block PVCRs are drilled to, up to a maximum amount which I can't remember right now but I seem to recall 0.045 each side being the maximum that the valve can suport. I measured mine and they are sitting at around 0.035". Above that amount of enrichment, the valve can't flow enough so you'll have a lean-out at a certain power level. I would guess that this valve would flow enough on the primary side to support an engine making 300-350hp. The reason why they made these is to try and get maximum economy and lowest emissions out of the factory-style Holleys of the 70s and 80s. One model that comes to mind is the first of the Fox body 5.0 HOs with the special Holley 4180C (600 cfm) square bore, which was considered a very good carby considering the tough emissions requirements of the time. They came with dual-stage power valves like the one pictured. The premise behind them is that while jetting for cruise AFR, there needs to be some richness dialled in to cover the part-load conditions seen somewhere between cruise and the usual opening point of a standard power valve. With a dual-stage, you can jet leaner without the need to fudge it to cover any holes in the fuel curve. At light load the first stage covers this slightly richer requirement, then the second stage kicks in when the load comes on fully. So instead of the enrichment coming on and off like a switch, it's staged like a multi-step needle on a Carter/Edelbrock or even a bit like a bike carby. Dummy assembled Sent from my CPH1920 using Tapatalk

I thought of that too, but gripping such an irregular shaped body in the vice isn't easy, it would be best to make up some kind of jig for it in that case. Knowing my luck, the body would jump out and Chernobyl itself in the cutter head or something dumb like that Sent from my CPH1920 using Tapatalk

I was thinking the same thing Bear, the surfaces aren't machined so maybe they rely on thick gaskets to take up any wonkiness in the as-cast finish. Holleys in particular have lots of circuits going through tiny passages in the gasket surfaces, so any small gaps between these circuits might have cross-feeding and affect the tune. For a carby that's made in Japan, I can't say the casting quality is terribly good. Maybe Holley farmed it out to a Japanese factory very early on when Japanese quality wasn't quite what it had become by the 80s. These were a 70s replacement for a Quadrajet so I guess they may have cut corners to get it to market quickly. I don't really know if making everything dead-flat has an effect on how well it works but I figured it wouldn't hurt do do it right while it's in bits Those blank holes@gregaust mentioned are the ones that go under the power valve cavities? I drilled and tapped those too so I now have 8 x 6mm screws holding it all together. Next is assembling the bowls and internals... And buy a wideband kit to tune it Sent from my CPH1920 using Tapatalk

Ok into it today... After inspecting the threads in the body, I found another one mostly stripped. So I made the leap and punched all of the base screw holes out to take M6 Phillips head screws. Firstly, I made sure all gasket surfaces are flat by hand-filing them down to an even finish, progress shots show how important this is due to casting warpage over time (possibly even during manufacture). Sent from my CPH1920 using Tapatalk

They are a Holley-specific thread I have since found out, 12-24 (12-gauge?), which need special taps and dies. This size is something between 1/8” and 3/16”. One of the "missing" screws is in fact snapped off in the body so I'll be carefully digging that out. Luckily, both of the dud threads go into the power valve cavities, so I can nut-and-bolt them if needed. Sent from my CPH1920 using Tapatalk

Maybe try and look up what thread they are and get some generic ones? Could they be 5/32" or 3/16” something? I'll keep you posted.... Sent from my CPH1920 using Tapatalk

Are you sure you're not me in a parallel dimension Bear? Sorry I can't remember if I have spare screws and I went to Hume performance today and bloody forgot to get some screws off them when getting a rebuild kit. I will look at my power valve tomorrow in the area you pointed out, but my guess is it's a 7.5 and the "2" might refer to 2-window or maybe manufacturing tolerance (some jets are stamped with an extra "2" to denote being flow tested). My kit came with 6.5 and 8.5 power valves, but I won't be using either as I specially ordered a 2-stage power valve from the States. Sent from my CPH1920 using Tapatalk

Well mum finally arrived with my Holley... imagine a woman in her 60s going through airport security with a big lump of 4 barrel carby in her bag [emoji23] Carby looks good on the outside, throttles are a bit stiff, the lever that's peened onto the throttle shaft is flopping around like a cock in a sock, filled the bowls with wash solvent and worked the throttles, no acc pump working either end, but no obvious fuel leaks there generally. Choke port hadn't been blocked after choke delete, so would have had a vac leak there. Gaskets all came off intact, but there were signs of moisture and dried fuel in everything. Acc pump diaphragms both solid, crunchy and falling to bits. Bowls are a bit corroded but floats and needles seem fine. Someone's been in this carby before, as the jets don't seem anywhere near right for the application.... 57 front, 68 rear. They should be more like 60 front and somewhere in the 70s or 80s rear.l, especially since this one doesn't have a rear power valve so needs extra jetting to compensate. Some missing/bodgy screws in the base plate, missing circlip on the primary pump arm, all choke hardware has been deleted. Also they'd pinched an o-ring on the fuel transfer tube, so it would have pissed fuel everywhere. Primary power valve seized open, and unmarked (likely to be standard 6.5) Throttle shafts seem tight without slop, now freed up with a bit of solvent and working. Overall, it looks like it had done a lot of work then sat around for years in storage, but the biggest issues with it are bad assembly and missing parts, all fixable with a rebuild. Here's what I can see so far: 57 primary jets 68 secondary 25 primary squirter 37 secondary White primary pump cam Brown secondary Unmarked power valve Secondary blanked off Pinched o-ring Buggered diaphragms Made in Japan! Lots of carbon buildup in the power valve cavity Blanked off power valve Sent from my CPH1920 using Tapatalk