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Mysterious ‘China-wall’ gap

lf-tp2511lf-tp2511Member
All,

I checked on the assembly of my 404 stroker Cleveland last week, and there is an assembly issue that neither me, my builder or others I have spoken with can explain.

The block is an iron four bolt version bored 10-over. The heads are new, out of the box CHI 4V aluminum and the intake is a new, out of the box blue thunder Pantera version.

Both the front and rear China-wall gaps, between the block and the intake, are approximately 1/4 inch wide, perhaps even a little bit more.

All the intake manifold bolts dropped into their respective threaded holes slick as butter.

Assembly of the manifold used the cork gaskets and additional RTV to completely close the gap.

No one seems to have an explanation as to why this gap is so large.

Has anyone ever come across something similar, or have any input that might explain this?

As always, thanks,

Larry

Sent from me using a magic, handheld electronic gizmo.
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hustlerhustlerMember
I tend to just lay thick beads of rtv on those gaps with no gaskets. Due to the variations using decked blocks, resurfaced heads, milled intakes. 1/4" doesn't seem that bad. The key is the bolts are threading with ease which it sounds like you are good on. The problem I recently ran into was the intake gaskets had to be elongated slightly on the 4 middle holes. The tops of these gaskets were bumping up against the valve cover gaskets. I have a sheetmetal intake that has a larger gap than my cast intakes, so I'm guessing the intake valley depth on the casting will play a part the degree of gap. See video below, I just don't have pictures of the gap variances.

Intake assembly
lf-tp2511lf-tp2511Member
I have been doing some additional research on the valley end wall gaps that have been found on my engine build using the CHI 4V heads.

Today I received the following email direct from CHI in Australia, which fails to support the previous explanation from George.

But this explanation and suggested solution of machining the intake fails to address the fact that all of the intake bolts were perfectly aligned with the cylinder heads.

Mystery continues.

Thought this information should be made available to others.

Larry

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rockyrockyMember
I can't recall exactly, but wouldn't you be able to make a measurement with a big pair of calipers between the machined sides of the heads?

You could compare it to one of the sets of 4V heads I am sure you have laying around in your garage.

It wouldn't tell you FOR SURE that any additional thickness you might measure is on the intake valley side of the head, but it might give you a starting point to continue your investigations....

(Not that it will solve the problem, either!)
George PGeorge PAdmin.
The fact that the manifold bolt holes line-up should be a dead give away.

Lay one of the heads on a table, combustion chamber facing downward. Measure from the table top to the top of the intake port. If it is any amount significantly more than 3 inches, the port is raised. If its 3 inches then I am wrong.

(the head in the picture is a C302 race head)

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V 4vandproudMember
measuring overall width would be something but you'd need a reference point establishing the intake side from center, the dowel holes or somewhere. just because they're the same or different doesn't tell you where they're the same or different, they can be the same overall AND different from center

a quick visual indicator would be the intersection of the intake face to the china wall

not much help but here's a print to give an idea of the reference points

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lf-tp2511lf-tp2511Member
quote:
Originally posted by LF - TP 2511:
Thanks for all of the suggestions.

We have pulled the intake and heads off of the engine due to a dyslexic and asleep at the wheel problem regarding the head gaskets. Turns out the Fel-Pro gasket number for a Windsor is 1031 and the number for a Cleveland is 1013. I’m afraid you all can guess what happened, just glad that I caught the problem when going over the build sheet.

I am returning to my engine builder tomorrow but fear he has already installed the heads this afternoon. I did tell him to delay installing the manifold pending further investigation on this issue.

Whether the ports are raised or the manifold was somehow incorrectly machined are both certainly questions worth answering. However, since everything bolts together just fine I am inclined to just find an acceptable manner to fill the large gap rather than try to diagnose exactly what is happening.

I have learned another owner had his engine builder fabricate spacers when faced with this problem.


Is anyone aware of a source for pre-made end valley spacers?

Larry
George PGeorge PAdmin.
quote:

Originally posted by Rocky:

... Why is it called a “china wall” ...



Esoteric term originating in California's central valley.

quote:

Originally posted by LF - TP 2511:

... Is anyone aware of a source for pre-made end valley spacers ...




CHI used to sell them, honest, no lie.


So its valley spacers now, not china wall spacers? Confused Smiler
lf-tp2511lf-tp2511Member
I did a dry fit of the blue thunder on the very same iron heads and iron block.

It now becomes pretty obvious that the large valley end gaps are a result of something different with the CHI aluminum heads

Tomorrow I will take a iron head to the shop and compare it to the CHI head.

Looks like the CHI representative who replied to my email doesn’t really know what their engineers have done with their design.

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George PGeorge PAdmin.
Larry

The extra width of the CHI head will be immediately obvious. Notice in the picture how the manifold face of the factory cylinder head is right at the corner formed by the valley rail and the cylinder head deck. The manifold face of the CHI heads will stick-out beyond that corner. The spacers CHI once sold had wedge shaped ends that would allow the spacers to fit under the heads, necessary because of the way in which the heads stick-out over the valley rails.

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lf-tp2511lf-tp2511Member
Thank you, George, for that additional bit of information.

That is now added to my list of things to check when I return to my engine builder tomorrow. And that one seems to be a pretty easy visual check.

I have sent an email back to the CHI representative, outlining with photos and text what I have discovered and requesting that he actually contact their engineers for their feedback. I also specifically asked for him to check on the spacers you said they once offered.

Do you think it is possible that there were slight differences between the USA heads and the Australian heads? This might explain why they do not believe there are any changes in their design, if Australian heads were used as their base point?

Larry
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