How much HP am I leaving on the table?

[Bad Byrd]

Hello everyone

I am building a Resto Mod/ Pro Touring 1961 Thunderbird, I had a guy out of Florida build my engine. We discussed this build over the phone many times and after all my waffling and direction changing he finally finished the engine to my exact specifications. He did a great job and the engine looks GREAT. My question to you FE experts which I am not is this. How much HP did I leave on the table by not running a set of Aluminum heads? I realize this is a broad question being all the different heads out there, but a general # is all I am asking for here no exact numbers of coarse. Here are the engine specs.

406 Cross Bolt Main block 
Probe 4.160 Pistons
4.125 stroked Crank
Callies 6.700 BBC rods
Cam is a Comp Cam Specs 282/288 .530/.540 108 LSA (hydraulic roller)
Intake is a Shelby Side Winder
Heads are a worked over set of C4's 2.09 Intake 1.65 Exhaust
Comp Ratio 10.41 (static) 7.96 (dynamic)
Harland Sharp Roller Rockers
Carb is a Quick Fuel 780 I had built to the specs of the motor
Headers are FPA

Any input would be great, the engine isnt going in the car for its final resting place for a few months, so before I send it home for good, I am questioning my decision of not running Ported Aluminum heads. To invest another 3K I kind of wanting your expert opinions of what gains I would get to see if it is worth the $3K.

Thanx for your time and I appreciate all opinions.

[My427stang]

Maybe none, depends on what you have now and what you bought to replace the iron heads

A good rule of thumb is 2 x intake flow in cfm fto calculate max power with a healthy street FE like your combo.   Not precise, but a good WAG.

If your worked iron heads flow 280 cfm, you'd need to beat that with a ported set of alum heads before you got anywhere, and that takes a healthy set of heads

I do think the Sidewinder intake is costing you about 10 hp over some of the better intakes, (ported RPM, Streetmaster, Street Dominator) but not sure that is worth enough to chase it in your use.

Too late I think the best gain, going with a 4.25 stroke instead of the 4.125, but it is what it is, it should run strong regardless.

If your heads are unported, I'd probably consider a set of ported alum heads and a better intake, if budget allows, but I am not sure I'd take apart a good engine based on the street use of your car, at least not until I needed to

[Bad Byrd]

Hey Ross

Here are the flow numbers of the Iron heads, I should have posted these.

Valve lift  int/exh cfm
     .100         70/55
     .200        156/109
     .300        221/151
     .400        257/180
     .500        272/195
     .600        276/197

[My427stang]

Certainly not a bad set of heads

The question is, how much time do you expect to spend at the  middle and upper end of the RPM range?

A set of Barry's CnC heads, combined with a better intake may give you 30 hp, but it will likely be at the top of the curve and if the car doesn't run that way often, it may not be worth the money.

Of course if you sell the Sidewinder and the worked heads, which should have decent value, the cost goes down, so it may be attractive enough.

I'll defer to Jay and Barry to what they think they'd see on a dyno, but there's my WAG

[Bad Byrd]

Thank you Sir!

I am a very spirited driver too say the least LOL!!! The car will be a cruiser though as a whole, probably an occasion 1/4 miler. I have spent a lot of time lightening the load of this 2 1/4 ton land barge down to 3900 lbs, to make it a little more 1/4 mile friendly...............but make no mistake about it its not a drag racer. More of a fun street toy with 15" wide tires and an obnoxious sounding exhaust system.

[My427stang]

One thing I can't seem to duplicate is your SCR/DCR relationship

In order to make the numbers work I have to retard your cam to 109 centerline.  Is that correct?

Also, FYI you have a typo in your rod length (4.7 vs 6.7)

Just technique, but if that is true, if you do go with a good performing set of heads, I'd run it at 104 ICL.  Assuming no change in compression that would get you to the low 8's and get you additional part throttle response and the big heads would keep the numbers up on top.

[Bad Byrd]

Thanx for the Typo correction!

You know I dont know about the SCR/DCR that is the specs he sent me in the very beginning, he might have made a typo! The intake change isnt an option either and the reason for this is my father left me some parts when he died.............I am not a big FE guy but he was, so this car is kind of a tribute to him and so the Shelby Sidewinder, the CS valve covers and air cleaner where all his stuff it is the backbone of this build.

I knew going into it that the intake had some short comings, but at the end of the day it was the only reason I am building this car.

[My427stang]

Brad, every DCR calculator is a bit different, so no big deal. 

In addition, DCR is really only useful if you have a few under your belt using the same calculator and compare differences, it's not a critical number and just an additional forecasting tool, your number is in the ballpark but using my calculator (because I have a lot of experience with the results of that calculator) I couldn't back into your numbers with something that made sense to me

What would be interesting is if you know the intake centerline he installed the cam on.  My guess would be 104 (4 advanced) or 108 (straight up).  Not a huge deal for your original question, but now I am nosy LOL

[Bad Byrd]

I remember him stating during the build it was strait up!

[jayb]

For the purposes of these estimates I'm assuming that you are running right around 475 horsepower.  I think that if you got yourself set up with a good set of aluminum heads that flowed 10% more than the heads you have, you would only be picking up 20-25 horsepower.  That intake will definitely be holding you back as you get to the higher power levels.  For example, on my 446" 390 stroker engine, the port matched Performer RPM intake made about 10 more peak HP than the Sidewinder (505 vs. 495), but on the 427 engine, which was quite a bit stronger, the Performer RPM made 565 HP vs. 528 HP for the Sidewinder.

If you decide to go through the engine again at some point in the future, you might consider having the intake ported.  Joe Craine posts on this board a lot, and he may have some experience porting the Sidewinder, and could let you know what kind of gains could be had.  Ported Sidewinder + aluminum heads with 10% more flow ought to pick you up at least 50 horsepower.

[Bad Byrd]

The Intake has been gasket port matched, and hand blended in the runners. I am no expert on porting the Side Winder intake but I did gasket match it and smoothed out the runners. So with that being said and knowing I am running that intake no matter what it sounds like a 20 to 30 Hp is really what I could expect. I kind of thought thats what I was leaving when I made the decision to stand pat with the Iron heads.

Thanx Guys

I appreciate the input.

[Joe-jdc]

Honestly, I don't think you would see much improvement unless you changed camshafts to get more lift.  The sidewinder is probably already larger than the heads really needed to make best torque and hp, so unless you get a set of heads that bring the average airflow cfm up considerably, then you are just throwing away money for your purposes.  I would just drive it until you decide you want more from the combination.  JMO, but to get a real improvement would mean a complete rethink of the package, and keeping your dad's parts trump the "what ifs".  Joe-JDC.

[cjshaker]

I have to agree with Joe. You would be spending a lot of money for something you would most likely never even notice, by just changing the heads and intake.....let alone just the heads. The cam should have all the airflow it can use with those heads and intake anyway. C4s are good heads, and the sidewinder is not a bad intake, just not as good for big HP numbers as some of the newer designs. But honestly, you want torque in that bird. To say you picked up another 30hp would just be for bragging purposes in my opinion.

Just as a reference, Rory used a sidewinder on his 10 flat Fairmont if I recall correctly. He switched a few intakes, trying the Edelbrock Victor, and didn't change his ET at all. That was on a fairly healthy 454 FE. The engine may have made more power, I don't know, but somebody forgot to tell the car that

[Barry_R]

Interesting cam selection.
A pretty large duration and narrow lobe sep for a big car stick.
Certainly will have "the sound"...

Heads are pretty similar in flow to off the shelf Edelbrocks.

I generally concur that its a middle to high 400s type of package in terms of power.  We've had fairly similar stuff on the dyno with those results - but not with a sidewinder.  Should be close.

I would expect a solid 30-40 HP potential gain with either my castings or a set of worked over Edelbrocks.  I think the gains would show up all over the curve though as long as port cross section was kept modest.  CNC ported stuff is in another zip code and probably not appropriate for this build.  Nothing wrong with iron heads in this type of car though - vintage vibe and enough power to do the job.

I'd have gone bigger on the cubes - but I always "go bigger" - that's just me 

[Bad Byrd]

Thanks for the input Barry!

The cam was designed for the very reason you mentioned SOUND.............I could have went down the bigger CI, bigger HP path without a problem, However and I dont mean this disrespectful the FE motor as a whole and the car I am putting it in really isnt going to be a rocket ship on pump gas anyways.

You builders are doing very well with what you have to work with, but at the end of the day where dealing with a 600 HP at best crank HP in a 4000 lb car. I want it strong..........no doubt and at the end of the day if I was potentially leaving 65-100 HP then one would notice a big difference.............but with the power loss through the drive train and the weight of the car itself 40 HP really isnt enough.

I remember back in 2005 doing some dyno tuning on my 01 Ford lightning and gained 40 hp, this was tuning only.........this cost me $750.00 for the dyno time and the tuning. $3K for 40 hp I guess isnt enough for me to bite.

Keep up the good work, you and Blair are doing some great things and I love what you guys do for the diehard FE guys!