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If you click on my link in my avatar, you can see 230bhp with a 197 head and inlet fitted to a 172 block. It may have also had some quite lairy items inside the engine as well 😂
I haven’t used this setup personally, but I just use the Karcher patio cleaner attachment turned upside down. I mix up BH autofoam in the bottle for the patio cleaner (karcher pw), as it has rust inhibitors in BH AF and send it under. I find it works really well tbh.
I have no data on oil flow from the pumps, so difficult to comment tbh. But just closing up the tolerances on the original oil pump works very well, but it’s an ‘in combination with’ kinda thing.
It’s got the potential to be the same story as the diesel boxes having ‘bigger bearings’ in them...
The reason they let go is because the oil pressure on the f4r is absolutely dire.
The cranks flex, centre main spins and goodnight vienna.
There are many reasons for them to fail, which I’ve listed many times before. But as far as being a ticking time bomb, I’m afraid I disagree.
That’s what was measured from a genuine Grp n cam timing tool.
The issue you’ll have with 421’s is that they’re going to be done to maximise lift and duration for the intended use.
But only one way to find out, and that’s to try it.
Knowing the f4r like I do, I don’t think any double valve springs are suitable for the standard hydraulic lifter setup mate, as the oil pressure up the top end is piss poor.
However, if you are suffering from valve float, that’s not an oil pressure related issue, it’s a fitted length issue...