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Question for the BBF guys......

General engine tech -- Drag Racing to Circle Track

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PRH
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Question for the BBF guys......

Post by PRH »

I’m working on a set of Eliminator products iron 460 CJ Heads.
These are iron heads with unfinished guides and seats.

I’ve got the guides finished, and have started cutting the seats.
With seats cut deep enough to get 1.950”+ installed height(with a spring cup in place), the valve-to-valve clearance is only about .035” with the valves closed and you can’t lift them all that far off the seats before they touch each other.

The valves are 2.25/1.76, and their recommendation is 2.25/1.72, which would put the seated valve to valve clearance at .055”.

Is that .055” seated clearance enough to run a fairly big solid roller without having the valves clipping each other?

Supposedly these heads use the factory valve angles and spacing.

If you had a set of factory heads with 2.25/1.76 valves in them(which are readily available) would they only be .035” apart?
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Re: Question for the BBF guys......

Post by Walter R. Malik »

PRH wrote: Sun Mar 20, 2022 7:53 pm I’m working on a set of Eliminator products iron 460 CJ Heads.
These are iron heads with unfinished guides and seats.

I’ve got the guides finished, and have started cutting the seats.
With seats cut deep enough to get 1.950”+ installed height(with a spring cup in place), the valve-to-valve clearance is only about .035” with the valves closed and you can’t lift them all that far off the seats before they touch each other.

The valves are 2.25/1.76, and their recommendation is 2.25/1.72, which would put the seated valve to valve clearance at .055”.

Is that .055” seated clearance enough to run a fairly big solid roller without having the valves clipping each other?

Supposedly these heads use the factory valve angles and spacing.

If you had a set of factory heads with 2.25/1.76 valves in them(which are readily available) would they only be .035” apart?
Yes .055" is enough.
With using 2.25" intake and 1.76" exhausts it should be about .030" to .040". Usually enough for a smallish cam.
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Re: Question for the BBF guys......

Post by PRH »

Thanks.

I ended up cutting the valves down to get the full .055”.
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Re: Question for the BBF guys......

Post by rebelrouser »

I put some larger valves in a set of 460 heads for a pulling truck, and it was as you describe about .035 clearance between the valves. It worked good made power, but the issue was if they floated the valves they would touch, and sometimes it would bend a valve. Of course, how do you explain to a truck puller not to over rev the engine? A big block chevy has a similar looking head but the Ford has a shallow angle, a BBC does not have the same problem.
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Re: Question for the BBF guys......

Post by PRH »

I can’t remember if these are for a puller or a mud truck, but either way I expect them to not get babied.

I had a set of Blue Thunder heads in the shop several years ago.
They were off a 557 bracket race engine that I had sold a cam to the owner for.

I thought it was a pretty “normal” cam for a combo like he was running.
280/288-112 roller.

I don’t remember why the heads were off, but what I discovered was all the valves were clipping each other.
Those heads had 1.88/2.25 valves. I don’t recall exactly how far apart they were, but I seem to think it was in that .030-ish range.
I cut the valves down, sunk the valves a little, and had him check the valve to valve clearance during overlap. They were very close.
I was looking for over .030 during overlap and it wasn’t there.
I ended up having the cam reground about 8deg shorter to get the clearance.

I’m trying to avoid that situation with these.
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Re: Question for the BBF guys......

Post by 1972ho »

https://youtu.be/p1P6vwDwW2g A little info on this build might help?
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Re: Question for the BBF guys......

Post by panic »

What clears in a static test may have insufficient "ringing" clearance, where the head oscillates radially enough to make contact.
Radial clearance varies with length of stem to guide, stem-to-head radius, stem diameter; worst is 6mm stem lifting .700" with 3/8" radius, etc.
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Re: Question for the BBF guys......

Post by PRH »

Just some info as a comparison.......
I’m sure this is pretty common knowledge, but I thought I’d include it in this thread for a quick reference compared to the BBF.

I just finished assembling a set of new GM iron rect port castings.......
Intake seats were cut to accept a 2.25” valve, exhaust are fitted with 1.88’s.
With the valves seated there is just about .100” between them.
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Re: Question for the BBF guys......

Post by Walter R. Malik »

PRH wrote: Mon Mar 21, 2022 6:10 pm I can’t remember if these are for a puller or a mud truck, but either way I expect them to not get babied.

I had a set of Blue Thunder heads in the shop several years ago.
They were off a 557 bracket race engine that I had sold a cam to the owner for.

I thought it was a pretty “normal” cam for a combo like he was running.
280/288-112 roller.

I don’t remember why the heads were off, but what I discovered was all the valves were clipping each other.
Those heads had 1.88/2.25 valves. I don’t recall exactly how far apart they were, but I seem to think it was in that .030-ish range.
I cut the valves down, sunk the valves a little, and had him check the valve to valve clearance during overlap. They were very close.
I was looking for over .030 during overlap and it wasn’t there.
I ended up having the cam reground about 8deg shorter to get the clearance.

I’m trying to avoid that situation with these.
Blue Thunder heads do have a slightly wider valve guide spacing; O.E.M. angles though.
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Re: Question for the BBF guys......

Post by mag2555 »

It’s the exh side on these factory iron heads that suck badly!

As you might know these heads in stock form only have a peak flow of 129 or so cfm, pretty much the same peak flow of a stock 351W casting.

The last set of 460 marine castings I did ( yes these where not cracked due to some miracle! )
I used a smaller intake valve and went up the stock 1.72” to a custom 1.77” exh valve.

Even then I had a hard time reaching 185 cfm@ .550” lift.

I guess I might have gone a little further reaching for bigger high lift flow numbers, but I did not want to give up any of the low lift flow gains I had produced by means of the valve job and throat size used, plus the flow bench output sounded very smooth, so I left it as is.

At only .100” lift I picked up 22 cfm, then over 35 cfm at .200” and 49 cfm at .300” lift.

From there on up there was over a 50 cfm flow gain and I started to ask myself if I should really care about cracking the 200 cfm level.
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Re: Question for the BBF guys......

Post by PRH »

Blue Thunder heads do have a slightly wider valve guide spacing; O.E.M. angles though.
They’d have to.

These Eliminator heads would have the valves touching each other while seated with a 2.25/1.81 combo.

After I saw the valves had been clipping each other on the BT heads I did a little on line searching........ and discovered I wasn’t the only one who’d experienced it.
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Re: Question for the BBF guys......

Post by NXBOY »

Mag if you got the port smooth sounding thats a big deal for a Ford BBF head!
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Re: Question for the BBF guys......

Post by PRH »

Just a little follow up with these......

I ended up cutting the valves down to 2.23/1.73.
The seats had already been machined for the 2.25/1.76, so a little sinking was required to accommodate the smaller valves.
In the end the seated valve to valve clearance ended up at .060”-.065” with the heads assembled with 300lbs on the seat.

The builder is going to check the valve to valve clearance during the overlap and see how close they get.

All I did was blend the seats into the bowls and roll the exhaust SSR a little.

The intake low lift numbers are way higher than what I’m used to seeing for this size valve.
It was strangely high enough that I double checked to verify I had no leaks.

These are the B3V BD version heads.

Tested on a 4.500 bore, 28”, clay radius, no tube on exhaust:

Lift———I/E
.100—— 78/51
.200——164/98
.300——239/133
.400——307/165
.500——333/192
.600——354/210
.700——368/223
.800——374/231
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Re: Question for the BBF guys......

Post by Bos's5.0 »

Is there any side benefit to Ford having put the valves that close together?

The Ford has a much larger bore than a Chevy, so why did they put them that close?

The canted valve thing was always about de-shrouding the valves, but it seems Ford went overboard.

Are the Fords getting any benefit from how close the valves are to each other?
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Re: Question for the BBF guys......

Post by Walter R. Malik »

PRH wrote: Fri May 13, 2022 4:06 pm Just a little follow up with these......

I ended up cutting the valves down to 2.23/1.73.
The seats had already been machined for the 2.25/1.76, so a little sinking was required to accommodate the smaller valves.
In the end the seated valve to valve clearance ended up at .060”-.065” with the heads assembled with 300lbs on the seat.

The builder is going to check the valve to valve clearance during the overlap and see how close they get.

All I did was blend the seats into the bowls and roll the exhaust SSR a little.

The intake low lift numbers are way higher than what I’m used to seeing for this size valve.
It was strangely high enough that I double checked to verify I had no leaks.

These are the B3V BD version heads.

Tested on a 4.500 bore, 28”, clay radius, no tube on exhaust:

Lift———I/E
.100—— 78/51
.200——164/98
.300——239/133
.400——307/165
.500——333/192
.600——354/210
.700——368/223
.800——374/231
If I remember correctly, those Eliminator heads have raised "A460 head" intake port locations and regular location Ford exhaust ports,
A larger intake valve will help the intake side a whole lot more than a big exhaust valve will help the exhaust side.
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