Valve guides.

[Big Bob]

I have a 440 Duromax that I’m doing a little engine work on. Billet, cam, rocker arms. When I took the head apart to put stiffer valve springs in I was surprised by a couple things.

1. No valve seals. I doubt that’s a big deal.

2. The valve stems on this big block are 5.5 mm where all other big blocks use 6.5 mm.
The big block likes valve springs in the 50-65 lb range. I need to go with stainless 6.5 mm valves.

So I need to pull the old 5.5 mm valve guides and put in new Bronze 6.5 mm guides.

I’ve done this on automotive stuff with special tools.
Has anyone done this on the small and big block clone type engines? What do I need?

Thanks, Bob

 

[Denny]

I can’t help but think it would be any different than doing a car cylinder head. Just smaller. And the proper sized reamer.

 

[Big Bob]

Yeah. It looks like if I want to go with bigger valve stems I’ll need to do a lot of research. I’m not sure my guides are the same outside diameter as other big block guides.

 

[karl]

$70 for a superior quality honda head , ill give you more compression too

https://www.nrracing.com/product-p/12200-z1c-406.htm

 

[Big Bob]

$70 for a superior quality honda head , ill give you more compression too

https://www.nrracing.com/product-p/12200-z1c-406.htm

I am looking into that. Of course that does not include valves. They do have a couple heads with valve job done with stainless valves etc.

 

[panchothedog]

I have heard from a reliable source that their built heads run real good.

 

[Big Bob]

I wonder if I can just ream out my 5.5 guides to 6.5?

 

[panchothedog]

If there is enough meat there and you have the right tool to do it. Yes.

 

[Big Bob]

Well, I think I got it fixed. The machine work to install valve guides and do a valve job was going to cost a lot. So I got a Honda GX 90 head from NRraceing. 40 mm intake, 32 mm exhaust. Small port head milled .025 for lower RPM torque and power. It is ported and polished. SS Valves, springs, all the retainers etc. Also got some steel roller rockers. This cost more than keeping the stock head and doing all the machine work. But the Honda head is stronger and I'm pretty confident NRraceing built it right.

Thanks to all for the suggestions.

 

[panchothedog]

Stainless steel valves, milled, ported and polished. You might have spent more,
but you ended up with more. Bet you're going to like it.

 

[Big Bob]

Stainless steel valves, milled, ported and polished. You might have spent more,
but you ended up with more. Bet you're going to like it.

I think so. Can’t wait to get it together and fire it up.