I'd like to make more horsepower

[pkm123]

Who wouldn't!!  Please look at my setup in "Dyno results"  under 452 cu.in. IR   The engine makes peak hp at 5600 rpm.   My best guess is the heads are holding it back, but it could be the intake tuning.   The torque is about 600 ft.lbs. That's 1.32 ft.lbs/cu.in.  Am I trading high end hp for low end torque or have my heads run out of flow?  Any suggestions would be appreciated.

http://fepower.net/simplemachinesforum/index.php?topic=3154.0

[jayb]

I'm surprised by a couple of things on your build.  First, those are really big valves on the intake to only flow 292 at .600 lift.  Second, if you are really making 550 HP that is pretty good with those heads, and that cam, and only 450 cubes.

I think a porting job on the heads is in order so that they flow more like the valves will allow, but I would point out that at some point the 50mm throttle bodies will become the big restriction.  So, I'm not sure how much power you will pick up if you leave those throttle bodies in place.  Are there larger ones available?  My testing on 48mm Webers showed that they do great in the midrange but fall off on the top end on the higher horsepower engines.  I think you might see the same issue with your throttle bodies.

You probably don't want to dig into the short block, but I'm scratching my head on why you didn't go up to the 4.25" stroke crank.  It would probably be better in terms of durablility than the short block setup you have (assuming stock type FE rod bearings), and the 30 extra cubic inches would pick you up at least another 30 horsepower, probably more.

I guess my recommendation would be to port the heads, but don't go too crazy on it unless you can make the throttle bodies bigger too.  And if you feel like doing the short block, a 4.25" or even 4.375" stroke would be a great addition.

[pkm123]

Thanks for the input Jay.  The engine was originally built when only Ford crankshafts and Edelbrock heads were available.  I think there is another 20 hp if I port the intake and shorten the ram pipes.  I have been thinking of buying a good set of heads.  There are many more options today, but they are somewhat confusing.    I think a set of Blue Thunder MR would be great, but should I get the small bore or the large bore?  I seem to remember Mr. Frances telling me the small bore flow as good as the large bore.  Which one is better for a 4.25" bore?  Barry's heads are also good, as are the BBM heads.  They both would require cnc porting to be significantly better than what I have.  This puts the price point much higher than the BT heads (as cast).  Without stepping on toes, would you have a recommendation?  The IR setup allows great throttle response and a smooth idle at 700 rpm.  If I increase the bore of the throttle bodies I will loose part throttle control.  They presently go static (90 kpa) at 8 percent throttle.   Your opinion is greatly appreciated.  Thanks.

[Barry_R]

Head numbers look about normal to me for an older hand work effort - we did not get over 300 for a while.  But that set of springs look a little light at 550 open on a .640 lift solid roller - you might simply be floating the valves at that RPM.  Does it rev cleanly past the peak RPM or can you hear it falling off?  On the dyno I can often hear float as a raspy sound in the inlet noise even before I print out the data.

All of this is also being referenced to a chassis dyno printout.  Chassis dyno numbers are so inaccurate and inconsistent that I view them as a directional tuning tool rather than any really useful data.

[jayb]

The big issue with Blue Thunder heads is availability; they are hard to find, and are not currently being manufactured as far as I know.  Do you have a source for them?

The earlier, small port BT medium riser heads would probably be what you want, ported to your specs; they will not flow much better than what you have in unported condition.  The later heads have huge ports where the roof of the port is raised so high that most intake manifolds will not fit; there is no sealing surface left on the intake because the port is so tall.  You could run a Victor (which will usually fit) or one of my special intake adapters for the BT MR port (which will fit), or else weld an existing intake to raise the sealing surface, but you need a LOT of cubes and RPM to take advantage of those big ports. 

I think you would be best off either porting your existing heads, or going with a Survival or BBM head.  Those are all good options.

As far as losing part throttle control with bigger throttle bodies, I'd have to disagree.  The trick there is in the throttle linkage.  I have run the Hilborn SOHC setup on the street for many thousands of miles, with 2-7/16" (62mm) throttle bores, and have great part throttle drivability.  You have to set up the throttle linkage so that the first 30% or so of pedal only opens the throttle butterflies 10% or so.  That approach makes an IR setup much easier to drive.

[HolmanMoodyStroppeGang]

Awesome job and bitchin car and thumbs up and cool cool

Besides all of the great thinking above, here's what we said at Holman Moody Stroppe a lot, well

One thing many would kind of end a power quest with, was

Put a blower on it

Been done since the 50s.   Too many guys fear the boost and they shouldnt

We have friends with 100,000 miles on their blown gas cars, one is a SOHC

2nd thought

Pro Shot Fogger

NOS is fun and if you are smart and careful, you have a nice kick in the back side for many cars

Dual fuel pumps, dual fuel lines, down nozzles and tuning jets

You sneak up on it carefully until you have a safe combo with a bunch more oats

Also, I hope more guys think, injected alcohol

Injected alky is just bitchin'. and easy.....  we never did a build that didnt see an eay 10% power gain plus a lot of mile an hour.    The mile an hour jumping up a lot on a Drag car is something else, if you care to do the work

On your current build, as is, sounds like you want to re pick some parts and step up the power ladder

we had another saying


spin to win

[My427stang]

Do you know how long the intake runners to the end of the air horn are?

I think that your setup could really use some plenum, but if not, at least a longer runner to match the RPM peak.

Along with that, like Barry said, it dropped pretty hard at the top, some spring could help, make sure fuel pressure is hanging in, and IMHO if you aren't going to stroke it, start porting

Also not sure whose Stage 1 heads, but I had a set from KC built in 2006, they barely outflowed a stock Edelbrock head, I think they were at 280 cfm as delivered (even though the flow chart said 334 cfm LOL)

Ironically after he bumped them up to Stage 2 specs, they flowed less by his own documentation (well less than the made believe 334)  and were still under 300 flowed locally.  I will say though that something changed since 2006, because I understand Joe Craine sees good numbers from Keith's Stage 2.

[blykins]

Keith finally had enough of it and sold out....

One of his guys that worked for him (Lance) bought him out.  It's now called "Craft Performance Engines". 

Keith is building houses now....no kidding.  Started a construction company and titling business.

[My427stang]

Keith finally had enough of it and sold out....

One of his guys that worked for him (Lance) bought him out.  It's now called "Craft Performance Engines". 

Keith is building houses now....no kidding.  Started a construction company and titling business.

Wow, can't say I am surprised, he's been telling you he was looking to do something else for a long time.

[pkm123]

Thanks everyone for the support.

Barry:  I'll have to check the exact spring pressures.  The cam is a street roller with 0.02 lash, so it nets 0.620 lift.  I was running lighter springs in the past.  I too was worried about valve float, so I changed the springs to a higher seat and open pressure.  At this time I don't think I am getting valve float.  I used to run the engine with a Edelbrock Victor and 850 Mighty Demon.  The engine chassis dyno had max hp at 5900 with the lighter springs.  The flywheel hp is calculated based on a  18% drivetrain loss.  The T56 and 9" Ford Locker should be close to this number.  The car weights 3400# and ran 7.1 sec and 125 mph in the eight with the four barrel through a C6.  I also ran the exact same time with 4 Weber IDA 48's,  This equates to about 520 to 550 hp at the flywheel.  The intake runners are about 12" to the head, or about 17" total.  This puts 4rd wave tuning about 4200 rpm and 3rd wave about 5400 rpm. 

Jay:  You are exactly correct.  The drive-ability would improve with a progressive throttle.  I may fabricate a better linkage in the future, but presently she is manageable.  My main constraint of larger throttle bodies is the cost.  TVM's cost about $4000.  "Speed costs money, how fast do you want to go?"  I think the intake is restricting the upper end and my first effort will be to port it.  I have a tig welder and can weld aluminum.  If I can't get enough airflow I will switch back to the Victor.  Modifying the Victor intake for BT heads would not be a problem, but I sure like the idle and low end torque of the IR setup.

I previously used to have an Edelbrock Victor on the car, and bracket raced it occasionally.  After a few years,I  plumbed the Victor for a fogger.  The car has dual fuel tanks, dual fuel pumps, dual feed and regulators.  The first time I used the fogger, 100 shot, the engine blew through the 4500 rpm converter.  I replaced the converter with a tighter one, 3000 rpm. Then the 2nd gear band began to slip (C6).  I was working out the kinks; but unfortunately, the local track in Holt, FL stopped paying their taxes, and the county shut them down.  I decided to convert the 68 back to the street.  I removed the shock towers, dropped the engine mount down 2 inches, and replaced the C6 with a t56.  I also converted her from a single carburetor Victor intake to the Megasquirt EFI 8 stack induction.  She is now very street-able.

Although I don't race on the street, I did hear of someone in a 68 Mustang fastback embarrassing a late model Dodge 392 Challenger.

I am a hobbyist,  I have been fabricating and modifying this mustang for over 10 years.  I like to think of these cars as works of art.  Not just for their styling, but as extensions of our mechanical skills and ingenuity.   These cars represent the best of hotrodding.  I have built several turbo setups, and could easily push the horsepower over 1000 with forced induction, but I would like to think we value the classic appearance and aesthetics of this generation Ford.

When I upgrade this engine, it will be with this philosophy in mind.  It will be better heads, better intake, better cam, better execution of the classic design.

I digress, but I think the next step is better heads.

Thanks for the help.