Big valves / small bore

[fekbmax]

So the 1.75 Ex and 2.25 In in edelbrock heads work fine in a 4.130 bore. Anyone use the big valves in a 4.110 bore ?

[scott foxwell]

Bore, stroke and rpm where you want to make power determin ideal valve size.

[plovett]

Do you mean the 2.25/1.75 valves FIT in a 4.13" bore?    That's not the same as working fine.

JMO,

paulie

[fekbmax]

Yes, FIT. Cylinder wall clearance.
Im aware of the factors that help determine proper valve size.
Pardon me for saying 'work fine' .

[plovett]

No problem, senor.   

I know 2.20/1.71" valves are used in 0.040" over 390's with no problems.  So a 4.11" bore would make a little more room, but maybe not enough for 2.25/1.75" valves. 

I would guess it would be too close on the 4.110" bore.  Even if they did fit, that doesn't mean it would be a good idea, though.  If you want to put things together just because they FIT, that's on you.

JMO,

paulie

[cjshaker]

  If you want to put things together just because they FIT, that's on you.

JMO,

paulie

I'm pretty sure Keith has some knowledge of what he's doing.

[plovett]

  If you want to put things together just because they FIT, that's on you.

JMO,

paulie

I'm pretty sure Keith has some knowledge of what he's doing.

I don't doubt it, Doug.  And his stuff is faster than mine.   I'll stand by my statement, though.  Anybody who puts 2.25"/1.75" valves in a 4.11" FE bore is making a mistake, even if it FITS.

My guess is that it won't fit anyway.   It has to be super close even in a 4.13 bore?

edit:  also influenced by cam events, no?  It's not like the valves are at 0 degrees relative to the bore.

[Falcon67]

Sounds like the FE needs a canted valve head LOL

[plovett]

Yeah, In a 396 BBC with the same bore, it would be a different story.  You might be able to make that work well.  Inline valves have their own advantages too, though.  A simpler lighter valvetrain is nice.   The LS motors have taken that idea to the limit.

[Joe-JDC]

I am going to go against the flow here, and say that a 1.750" exhaust valve is going to hit the cylinder wall with a 4.110" bore and over .500" lift.  Many of the builders here have said that 1.685" is about the maximum on the 390 block without hitting at high lift.  Ford actually chamfered the cylinders in the 427 for the exhaust valve on the 4.233" bores with a 1.725/1.750" exhaust valve.  Just because something can be done does not mean it will work well, or be optimum.  Joe-JDC

[KMcCullah]

When you start down the road of valve to bore clearance concerns, you gotta try it. I've done 2.15/1.65 valves in a 4.05 bore. The exhaust valve gets damn close at .750+ lift. But this was with C4-G iron castings. Aluminum Ed castings might be a different story.

I'd mock it up, Keith. Lot's of variables here.

[fekbmax]

  If you want to put things together just because they FIT, that's on you.

JMO,

paulie

I'm pretty sure Keith has some knowledge of what he's doing.

I dont know there Doug,
Apparently i had no idea that bore, stroke, compression, RPM, intake runner and head volume, along with many more variables help determine ideal valve sizing. 
Hell i guess i just did it cause it fit.
After all it must always be a mistake for anybody who does something like that .
I had thought it worked very very well my race FE's.   I go for max bore depending on block, good bit of stroke, lots of compression, custom cam, and lots and lots of RPM.
The 2.25" and the 1.75"  FIT, work and perform very well in my 4.140 bore with my engine combination .  So i had thought anyway.    Oh well.
I guess there's not more than one way to skin a cat.

[plovett]

Sorry Keith.  I obviously tweaked you.   I will try to use softer language next time.  The word "mistake" sounds harsh.   It doesn't bother me, but I must be from a different generation.  I have made lots of mistakes in picking parts and putting together engines, if that makes you feel better.   When my machinist or head porter tells me I'm making a mistake I just look at what he's saying and try to understand.  I don't feel personally offended.  Still, I am sorry.

I have 2.09/1.655" valves in my 4.155" bore FE.  I think it was a mistake for me to go with the 2.09" intake.   A 2.15" or maybe even a 2.19" valve would have been better and made more power.  I'll rectify that on my next build. Having my C6 tranny built with a wide ratio gearset was a mistake.  Too much 1st gear ratio in a street car making good power doesn't work very well. I've since replaced it with another C6 with a standard gearset.    Me getting a cone type limited slip was a mistake.  I've since replaced it with a Detroit Locker.........

So if you test fit your 2.25/1.75" Edelbrock combo in a 4.11"  bore then you'll know if it fits. I've never heard of anybody trying that, specifically. I don't think they are the best sizes for flow in that bore even if they fit without clearance issues.  That doesn't mean you can't go fast with non-optimal valves sizes.  I'm sure you can.   

JMO,

paulie