This discussion makes me want one of JM's new aluminum manifolds even more.  Few of us need 300 cfms, and that much flow potential can cause problems on a street motor.

Mike, located in the Siskiyou mountains, Southern, OR 292 powered 1946 Ford 1/2 ton, '62 Mercury Meteor, '55 Country Squire (parting out), '64 Falcon, '54 Ford 600 tractor.

A problem with the Blue Thunder intake, particularly on milder smaller engines, is shown on a couple of Dyno tests that have been published. In one test after some preliminary Dyno tuning, the Blue Thunder was installed & the engine immediately lost about 14 lb. ft. of torque & a couple of H.P. It took 600 rpm more for the torque to draw even with the previous stock B intake. In MHO, in a street driven heavy car, or one with moderate gearing, it's questionable if there's much advantage to using a Blue Thunder, especially when you consider the cost.

Paul

I knew there had to be dyno tests somewhere. Are you able to post more details of the dyno comparisson, Paul.

I have the 2nd generation Blue Thunder intake and it seems to work well for my use. But I am looking forward to the new manifold because I suspect that it will provide a nice boost in torque with little impact on horsepower. Can't wait for that thing to be ready for testing!


Lawrenceville, GA

Ted did a little dyno testing, maybe he'll chime in and share some of the results from the original intakes versus Blue Thunder.

-Gary Burnette-

It has to do with pressure drops, air flow is typically determined at 28 inches of water drop across the port. If you have 28 inches of drop across the intake AND 28 inches of drop through the head you are looking at 56 inches of total drop to maintain the airflow (assuming equal air flow of intake and head). This is a general rule as port/ manifold air entrys will fudge this some what as will using an exaust pipe on the exaust. The key is total restriction like resistors in a series electrical circuit. This is why dominators are used to minimize intake restriction on the Engine Masters entries.

And here’s what Jon Kaase has to say about flowbenches.

Jon Kaase link

 

And I agree in principle with this.  Flow benches are simply one tool in many that are used to define particular engine parameters without actually running it.  As such, flow numbers are not gospel but simply another variable in which to consider.  A personal experience on the Y engines that helps to drive this home for myself comes from running two Blue Thunder intakes that were modified differently internally while still flowing the same but had the engine exhibiting completely different torque curves.

Lorena, Texas (South of Waco)

I haven’t personally dyno tested a Blue Thunder intake against the ‘B’ iron intake but that is planned in the near future.  To date for intake comparisons on the Y, I’ve only tested Blue Thunders against modified Blue Thunders and sheetmetal (fabricated) intakes.  But there’s way too much talk about air flow numbers and not enough about air quality.  Keeping the velocity of the mixture high while at the same time being able to support a larger volume of air throughout the rpm range is the key.  Runner shape and size is critical in getting this to happen.  But regardless, the intake runners must have more flow capability than the heads or the intake tracts themselves will be the choke point and those enhancements performed to the heads will not see their full potential.

For the stock Y heads, the factory ‘B’ intake manifold is suitably sized (slightly larger) but any modifications to the heads requires the ‘B’ intake to also be appropriately modified so it continues to out flow the heads.  This is where the Blue Thunder intake shines as it’s more suited for heads that have been modified and/or engines that have been increased in cubic inch.  As has already been said, the BT intake is obviously oversized for dead stock engine applications but start working on the camming and heads for improved flow, the stock ‘B’ intake is suddenly inadequate for the job.  The new intake manifold being worked on by John Mummert is expected to be an improvement in regards to the lowend torque curve for these engines while still maintaining the higher rpm characteristics that the BT intakes are noted for.

But with a fresh 312 dyno mule engine currently being put together, I’ll be performing some serious testing on intakes in the near future.  Header testing is also being planned.  When that time comes, I’ll put the call out for some of the other single four intakes and headers that I currently don’t have sitting here.

Lorena, Texas (South of Waco)

I agree with what you have said Ted, And as I posted airflow quality is extremely important. Plenum modification in particular can alter dyno results as will port and runner configuration. There general directions to go but each engine and engine combination has its own likes and dislikes. I am following Jay Browns dyno testing in the FE forum, what works well at one horsepower level may not work as well at a different level.

Gary Brunette comments about J Mummert's massaging the interior of the BT were very interesting.

On The FE site there is a fellow J.D. Crain that specializes in equalizing the flow of intake manifolds. Dyno testing by Jay has confirmed benifits of his work.

Ted if your going to do some testing , one thing I would like to see is how Rams Horn exhaust manifolds flow against some others. I was told by two different subscribers, one lived in PA, that their trucks performer better with those, than the Red's Headers they had before. I found that quite ineteresting.

                                                   Michael

Michael

Sandy Valley, NV

Thanks Don.  I do deal quite a bit with Ford FE engines where dismal flow numbers are observed in the heads but the end performance on the engine breaks all the rules with the right parts selection.  With an FE, the intake tracts are the key due to the shortened runner design within the FE heads themselves.  This is not saying that the heads in this instance are not important but instead emphasizes just how important the intake manifold itself is.  But on plenum volumes, my own experience points to the FE plenum sizes not being critical whereas the Y seems to be overly sensitive in this area.  I’ve got my own thoughts on runner design and will be curious to see if Johns’ new Y intake also mirrors my thoughts in this regard.

Although I haven't given much thought to testing the factory exhaust manifolds, what you bring up makes it a valid area to pursue.  When the time comes, I'll put the call out for borrowing a set of rams horn manifolds just to throw on the engine and get some numbers.  There are already the early and late cast iron passenger car exhaust manifolds sitting here so those can be subjectively tested also.  Part of the criteria here will be to determine the size and length of the lead pipes to use with these manifolds to get a real world comparison.  May consider two different diameter lead pipes also as gut feel says there's a difference to be found here also.

Lorena, Texas (South of Waco)