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Discussion Starter · #1 ·
What is better for my application, A 4 hole tapered spacer or a anti reversion plate?

Engine combo is a 442 cube SBF with CHI C400 clevo heads we will turn to 8000 rpm, single 1250 cfm APD carb with a 2.125 blade
Hoping for 900 ish HP

Thanks
 

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Only way to tell is to see what your intake likes. I had a 4 hole tapered spacer that we knew made 8-10 hp on small block circle track engines. On my 548 the 1" open blended to the intake plenum made 2-4 hp more than the 4 hole.
 
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Chances are they'll be close enough that you won't see the difference on the track.



A couple more were out on loan when I took that picture.
 

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In my opinion, what the right “spacer” does is provide conditions underneath the carburetor that is conducive to proper carburetor function, tuneability and enhances airflow distribution to the cylinders. As always, this is dependent on the engine’s operational RPM band.
 

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Discussion Starter · #5 ·
Thanks for the replies

ill buy both & see what the engine likes
 

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Spacers are fickle things, I've made many different types and the results have always surprised me. As most have already said, test them and see how you go. Does your Dyno shop have spacers you can try? Might save you some $$$
 

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Discussion Starter · #8 ·
I had a few different spacers from my 2” blade carb but we have upgraded to 2.125 & was trying to avoid spending money if I didn’t have to. All good I’ll buy a couple to try
Cheers
 

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I had a few different spacers from my 2” blade carb but we have upgraded to 2.125 & was trying to avoid spending money if I didn’t have to. All good I’ll buy a couple to try
Cheers
The problem with “spacers” is they are not specific to the particular flow dynamics of a given engine. One, two or three sizes doesn’t fit all. If your dyno is equipped with fast O2 sensors for each cylinder look for discontinuities in the power curve that correspond to “choppy” air/fuel ratios. That will give you a clue. Shows up a lot better with engine air flow readings but most dynos these days aren’t equipped for that. A well-designed laminar flow element has a response time of about 16 millionths/sec. and lets you see if there is anything going on under the carb that is hindering air flow.
 
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