Blue Thunder 427MR intake - power increase over stock 390 2V?

[cheeser]

I purchased a Blue Thunder 427 MR 4V intake shortly after purchasing a 68 Cougar with stock 390 2V motor…X code @ 10.5CR.  I haven’t installed it yet as I’m a bit paranoid installing it correctly with out vacuum/oil leaks.  Every project seems to take longer than expected, although it appears to be fairly simple when taking time and checking fit…bit harder looking at rear while in car.  I already have an old Holley #80457 600 CFM carb I was planning on using after I rebuild it, but open to purchasing a new carb.

I’m curious in what I could expect from a power bump in this configuration…30-35?

Update: this was an original family owner California 68 Cougar XR-7 car for 52 years with approx 114k miles.  I purchased it last year, and want to keep it stock appearing where possible.

[Stangman]

Not sure how a 2 bbl motor (low compression , small cam ) would run with dual quad setup. Tuned properly it would make more power dont know how much.

[cheeser]

Not sure how a 2 bbl motor (low compression , small cam ) would run with dual quad setup. Tuned properly it would make more power dont know how much.

I updated my note… have the X code engine with 10.5CR.  BT intake is a single 4V.

[427LX]

Well since you have the intake put it on and give it a run. Folks have been doing those kind of swaps on engines  for years.  Yes might work even better with a bit more cam like the old
390 GT cam. I assume you have dual exhaust with a performance type muffler?  That is a good intake you can always use for further power increases.
Check port alignment making sure it seals okay.

[Stangman]

Ok thats better cheeser now I will guess at 25 horsepower. Wheres Werby!!

[My427stang]

Long before JJ was a 500+ hero, Brent and I played on the dyno with it as a stock, slimy, truck 352

My numbers are rounded and from memory, and we had a good ignition and headers, but otherwise bone stock worn out 352

We saw 20 or so HP from a 2 barrel Holley in place of the Ford 2 barrel, and another 20 going to a Blue Thunder and a dyno carb (certainly bigger than a 600)

Iron manifolds will drop those gains significantly, but I would say 20-25 would be realistic at some points of the curve with a 390

[cheeser]

Thanks for the info. 

Car currently has a 2.25” dual exhaust and 428CJ exhaust manifolds from the original owner during an engine refresh back in 2008.

@My427stang…now considering the header change based on what you’ve mentioned before.  I have to checkout the existing manifolds to see if the heads were modified to accept all of the CJ exhausts bolts, or if they simply left a few bolts out.  I need to double check the existing head casting numbers to see if the are the C8AE-H heads (which I believe would be stock) or if they were swapped as well with true CJ heads.  If I’m able go big down the road with a nice build, I only want to buy headers once…assume ones with the CJ pattern.

[blykins]

Long before JJ was a 500+ hero, Brent and I played on the dyno with it as a stock, slimy, truck 352

My numbers are rounded and from memory, and we had a good ignition and headers, but otherwise bone stock worn out 352

We saw 20 or so HP from a 2 barrel Holley in place of the Ford 2 barrel, and another 20 going to a Blue Thunder and a dyno carb (certainly bigger than a 600)

Iron manifolds will drop those gains significantly, but I would say 20-25 would be realistic at some points of the curve with a 390

That clapped out, goofy 352 went from 208 hp to 264, going from a factory 2bbl setup to a BT 1x4 MR and a Holley 650DP?  Picked up 56 hp.  Was done by 4400 thanks to the 186° .050" factory camshaft, but sure gained a lot of power.

[67xr7cat]

X code 390-4V was rated at 280 hp, S code 390-4V was 320hp.  Are same engine other than intake and carb. I'd think 2V has a milder cam, but seem to recall was the GT cam.  Would have to look that one up as been a long time since looked at any X codes.   Given the BT intake is better then the S code piece can expect a bit better top end HP, certainly lighter!  The 600cfm carb is fine for street, but if you are after performance a 735 CJ carb or if a new buy if off the shelf carb. a 750 VS like the Brawler would be a good choices.

Of course your engine has been rebuild so hard to say what all has been changed.  The CJ exhaust manifolds are a good compromise between headers and the stock GT manifolds.  If you go with headers and your have the C8AE-H heads check for proper port alignment since most are intended for the higher CJ port.  Just have to make sure they will seal properly.

[GerryP]

I know this will make me the odd guy out and maybe about as popular as an unvaccinated guy wearing a MAGA hat in a Starbucks, but my experience has been carb and intake swaps are relatively ineffective until you start getting closer to that 1HP/CI arena.  And even then, it gets very situational.  When I was young, I bolted down a Holley 350CFM 2bbl in place of a Rochester 2GC on a 327 Chevy.  I had great expectations.  But boy, was I disappointed that it didn't appear to make one bit of difference.  I also swapped 2bbl intakes for 4BBL intakes on stock engines and saw no improvements.  I'm talking seat of the pants.  Not a dyno.  A long time ago, I did an A-B with a swap of a box stock Holley 1850 to a 3310 on a 390 with a Performer RPM, a Comp cam and stock exhaust manifolds.  The top end was slightly improved.  Throttle transactions were a little crisper with the 600CFM but I didn't do anything to the 750CFM and that might have helped a bit.  The result was underwhelming.  It was at that point many years ago that I began to formulate my understanding of the intake side of the engine based upon many, many observations.  Your mileage may vary. 

It is worthwhile to look at the whole combination when doing intake swaps.  Bigger cam, headers, better cylinder heads, and then the intake becomes relevant.  After all, even FoMoCo put bigger cams in their 4V stuff than they did in the 2V stuff.

But then, there is also the prospect of doing an intake swap because an aluminum 4V intake is a whole lot more sexy than an iron 2V intake even if it doesn't do anything other than drop some weight.

[1968galaxie]

From my personal experience.
390 2V 1968 Galaxie 500.
Biggest bang for the buck as far as performance - headers, dual exhaust and 4 barrel.
Adding 3.56 rear gear also helped performance.

Agree with Brent - 4 barrel intake and carb was worth a bunch of power. Same goes for removing the old log exhaust manifolds.

Back then it was all about stop light racing.

[frnkeore]

My view on FE intakes is this........ If I ever had to work on a FE and had the intake off, a cast iron (even a CJ) would not go back on!

I was a mechanic from '62-'70, the hat day of the FE. I was in SoCal at that time and in the Summer, it would never fail, I would get a rash of  blown head gaskets. People would loose a WP or bypass hose and keep driving, until it quit. So, I got to do many of them.

I was in my 20's then and only 150 lb so, I would pull the hood and straddle the engine, to get the manifold off and on. I do not think you could go wrong with any aluminum manifold, with the exception of the Offy & Weiand 360° types.

I think a good one for stockish, small cam engines, of all sizes, is the Edel 390.

[1968galaxie]

As I was poor back at 16 years old I replaced the 2V intake with a junkyard 4V iron intake (750 Holley)
This along with the headers made a huge difference in power.
I do recall how heavy the iron intakes were when changing from 2v ir 4v iron - lol.
Later when the Edelbrock performer came out early 1980s? (not the performer rpm) I replaced the iron intake.

Fun times.

[JamesonRacing]

The engine should make a good seat-of-the-pants impression from 3,000-5,200 or so revs.  You may notice a loss of torque off idle and when lugging the engine at low revs.  If it were my car, it would have already been swapped.

[shady]

I know this will make me the odd guy out and maybe about as popular as an unvaccinated guy wearing a MAGA hat in a Starbucks, but my experience has been carb and intake swaps are relatively ineffective until you start getting closer to that 1HP/CI arena.  And even then, it gets very situational.  When I was young, I bolted down a Holley 350CFM 2bbl in place of a Rochester 2GC on a 327 Chevy.  I had great expectations.  But boy, was I disappointed that it didn't appear to make one bit of difference.  I also swapped 2bbl intakes for 4BBL intakes on stock engines and saw no improvements.  I'm talking seat of the pants.  Not a dyno.  A long time ago, I did an A-B with a swap of a box stock Holley 1850 to a 3310 on a 390 with a Performer RPM, a Comp cam and stock exhaust manifolds.  The top end was slightly improved.  Throttle transactions were a little crisper with the 600CFM but I didn't do anything to the 750CFM and that might have helped a bit.  The result was underwhelming.  It was at that point many years ago that I began to formulate my understanding of the intake side of the engine based upon many, many observations.  Your mileage may vary. 

It is worthwhile to look at the whole combination when doing intake swaps.  Bigger cam, headers, better cylinder heads, and then the intake becomes relevant.  After all, even FoMoCo put bigger cams in their 4V stuff than they did in the 2V stuff.

But then, there is also the prospect of doing an intake swap because an aluminum 4V intake is a whole lot more sexy than an iron 2V intake even if it doesn't do anything other than drop some weight.

Yeah Jerry, It must be a chevy thing. I had a 350 2bbl stone stock it ran 14.6s, sooo. I had to put an  alum. Weiand with a holley 750 4bbl expecting 14.0s and it ran 14.6. Seat of the pants told me it was no faster and the time slips proved it.