Mostly as a result of seeing Rob's results in issue 128 of Y-Block Magazine, almost 13ftlbs with a 2" 4 hole spacer, I decided to try a few for myself.

I purchased 1/2", 1", and 2" 4-hole, phenolic spacers.  I also got a thinner 14" air cleaner for use with the 2" spacer because my current 11" air cleaner is too tall to fit under the hood with the 2" spacer.  The 14" is a Moroso.  I read a lot of good stuff about those. The 11" is a K&N with a 3.5" tall filter, good for about 725cfm, according to K&N.  Both are raised base.  The Moroso works out to be nearly 1" shorter.  The 11" was also used with a K&N stub stack, which will not fit the 14" out of the box.

The baseline is a 1/2" divided spacer, phenolic or wood.  All but the 2" spacer were used with the 11" filter and stub stack.

With the 1/2" 4 hole, I couldn't tell any difference at the low end and it seemed  to hurt top end.  A rev test, just wack it wide open, and observe the rpm reached, was no better than before.

With the 1" 4 hole, the bottom end felt much stronger.  The following morning I was creeping along in traffic about 150rpm lower than is normally tolerable.  More evidence to confirm that came in the following days, on wet roads.  I had more significant traction problems when leaving from a stop.  Top end felt as good, maybe better than with the 1/2" divided spacer.  I was also able to turn the idle screws in 1/2 turn.  The rev test improved.
I also looked at the carb and intake temperature, which I didn't do with the baseline.  With the 1", the intake was 175 degrees right below the carb and the carb was 99 at the main body, and about 110 on the fuel bowls.

The 2" is not yet complete, but the results so far seem promising.  Low end feels significantly stronger than the 1".  The roads have been wet, when I've had a chance to get out and do some testing, but a 2nd gear rolling start resulted in tire spin, which hasn't happened before and another first, it spun while leaving from a stop heading down hill.  Again, this is on wet roads.  I have yet to see what it does in safer conditions, on dry roads..  I'll update when I've had a chance to find out.  The rev test improved over the 1"
Had dry roads today.  It is much more responsive with the 2".  Top end seems to be about the same.  The temperature difference is about the same with the 2" spacer.  The 2" spacer will stay.



Lawrenceville, GA

After driving it for a few days to get a thorough feel for it, the 2" spacer will stay.  Even if it hurts top end a bit, the low end is much improved and since this is 99% street truck, that is what counts.
I'm going to get another of the same 2" spacer and modify it so that it is similar to a Wilson Manifolds or HVH tapered spacer, but leaving a dividing wall in place to maintain dual plan functionality of the manifold.  So instead of being 4-hole up top and open on the bottom like Wilson or HVH, it will be 4 hole up top and divided on bottom.
That will wait until the next round of changes.  First, I want to get to Atlanta Dragway to evaluate all these other changes I've made over the past year.



Lawrenceville, GA

Interesting testing Charlie!

 Unfortunately I haven't had a chance to run my car yet, but the "seat of the pants gauge" has me VERY impressed!!! As per the torque in this new motor, I am going to have to play a bit with my suspension this winter, or have to break down and buy some drag radials. I am finding it almost impossible NOT to squeal the tires unless I ride the clutch out from a standing start. If I dump the clutch at anything more that 1500 rpm (on dry pavement) I incinerate the tires and ride up to the rev limiter. If I keep my foot in it, second gear has the same affect!   

I seem to be in a bit of a catch 22 as my 5th gear has virtually become useless, unless I am traveling at 60 MPH or more. With the 3:55's I am barely running at 1800 rpm at 60 and the motor seems to almost be sluggish. If I kick it down into 4th and bring the rpm up around 2300, it pulls like a freight train. I could easily go to some 3:70 or 3:90 gears, but this would eliminate 1st gear in my T-5 as I am shifting about 10' into an intersection now and plus there is NO way I would hook it up unless I install ladder bars or something! 

Got to LOVE the torque of a Y-Block!!! 



I love the smell of burning rubber in the morning!

Some sort of drag tire will be needed, ultimately.  Street tires are terrible for traction, even with traction bars.  I think I will try Nitto 555r's.  Not as good as Mickey Thompsons for traction but they last on the street, and people run faster with them than I will any time soon.  There was a GT500 at Columbus running high 11s with those.
I don't plan to leave them on, but from what I read, the MTs last about 500 miles on the street.  That's 3, maybe 4 trips to Atlanta Dragway, figuring in burnouts and runs.  The Nittos last several thousand miles, I've heard up to 10000.  That's quite a few trips to the strip.  And, I know I can always carry the tires with me and change them at the strip, but that is annoying and I'll be wondering if my street tires will still be there after I've made a run.

I have the same issue with overdrive.  You'll probably need to get the ratio up into the 4s to get the engine at an rpm that is acceptable.  The 3.90 will put you just under 2000rpm.  If you have an idea where you want to be, take your current gear ratio x desired rpm / current rpm and that is the gear ratio you need.



Lawrenceville, GA

Here's how it looks with the 2" spacer and new air cleaner.







Lawrenceville, GA

Not to hijack the thread, because I've got room for a spacer on my bird. Just need to lower the air cleaner I built up. CHR, which ratios in your trans?

Great looking motor, Charlie.

miker
55 bird, 32 cabrio F code
Kent, WA
Tucson, AZ

Thanks for the pictures. Your motor has the wow factor. Is there a pvc or just the two breathers? Also, were did you purchase the 4 inch spacer? Thank you very much

For now it is just breathers.  PCV will be installed, though.  The spacer is 2".  I got it from Summit.



Lawrenceville, GA

I got a second 2" spacer and tapered it between the front and rear bores.  I looked at lots of pictures of Wilson and HVH tapered spacers to get an idea of the shape to go for.  I even found a picture of what must be an older Wilson spacer for a dual plane manifold, modified in a similar way but one inch tall.  So hopefully it is in the ballpark and actually will help overall.

After driving with this a few days, there seems to be a slight decrease just off idle but everywhere else feels the same as the unmodified 2".  The off idle decrease isn't a big deal since traction is an issue, anyway.







These are the spacers I have used so far.




Lawrenceville, GA