I am rereading my Y block magazines and in issue 84 (Jan-Feb 2008) Ted Eaton mentions there are two designs of the Blue Thunder manifold versions 1 and 2. Version 2 may flow better than version 1 per Gary Burnette. Are there some visual ways to determine which one I have?? Bet I have version 1, I ordered it from John soon after they became available. Any indication of difference in percentages or more equal flow?

Don Woodruff

This is all from memory as I currently don’t have a version one intake to take a look at.  The external difference in the two versions can be seen in the height of the carburetor pad in relation to how it sits above the #3 cylinder runner at the back of the intake.  On the version two intake, the pad sits about ¼” higher than the #3 runner whereas the pad on the version one intake is almost flush at the same point.  The way it was originally explained to me is that the improved flow on a stock version two intake essentially matches the flow on a version one intake that’s had the individual runners extrude honed.  I was originally quoted the flow numbers but it’s been too long ago now.

Lorena, Texas (South of Waco)

Thanks Ted, I would look at mine except for the foot of blowing snow and below 0 temps. I'll put the info in my files 

Don W.

The first version flowed approx 264 cfms per runner, the number two version after John worked a little magic had them flowing around 300 cfms per runner without extrude honing. The first version after extruding flowed approx 300 cfms as well. That means even the first version stock flowing 264 cfms per runner out flows a stock 57 and later manifold which flows approx 174 cfms by a LOT!!!!!   Hope this helps.

-Gary Burnette-

Thanks Gary. Any Idea what the "Magic" is? Can A guy who has a bit of experience with porting modify a 1st gen to second gen flow rates.

When I spoke to John about his upcoming manifold some months ago he indicated some areas of the BT were too large. I really do not want to bother him as I want a set of heads.

I had no idea the Blue Thunder flowed that much.

I would bet that 99% or more of the engines on this forum can't use the 264cfm capability of the 1st gen manifold. I would not bother to pull and port the 1st gen manifold unless other mods are made to the engine.


Lawrenceville, GA

All restrictions are additive, so adding flow capability to any area on the intake side without comprimizing airflow quality is a plus for peak horsepower. This is more challenging on a mild engine (maintaining air flow quality at part throttle) than an all out race engine, perhaps this is why John M. indicated he felt there were some areas the BT intake were too large.

John would rework the ports for even better flow and scuff the inside in a way to keep the gas and fuel mixture broke up for a more even distribution. And yes Charlie the 264 cfms should be all you need when it's all said and done unless you just really want to go FASTER !!!!!!!

-Gary Burnette-

Is there a simple yet more technical explanation why? It doesn't make sense to me if the heads will only flow so much. In that case, it seems like we would see 1000+ cfm carbs on the race motors.


Lawrenceville, GA

You always want more flow from the intake manifold than the heads. If they flowed the same then the end result would be deluted flow coming from the heads. Say your heads are flowing 235 to 245 cfms at say .500 lift, then it would be easier to achieve the full cfms from the heads with the 300 cfms manifold than with the 264 cfms manifold. Ford almost achieved this by having their manifolds from 1957 flowing about 175 cfms and their heads about 157 cfms. If they had made their intakes flow say 195 cfms then their stock heads would have probably performed even better,REALLY killing the scrubs!!!

-Gary Burnette-