In order to stuff the SBF into my Austin-Healey, I ended up using Sunbeam Tiger cast iron manifolds to get the clearance I need. The motor is a Ford 5.0L with Edelbrock RPM Air Gap, Holley SA 570 cfm and a Trick Flow Stage 1 cam. Heads are stock iron GT40P with a nice valve job. It dynoed at the crank at 345 with long tube open headers. The Tiger manifolds were for the Ford 260 and are pretty restrictive. Additionally, I had to make some restrictive bends like this to get everything to work: Obviously, I expected to lose some HP with this set-up, but after installation in the car with a T5 tranny, it dynoed at 199 at the wheels. That just seems way too much parasitic loss and without any further changes to the motor from the engine dyno, the only thing I can think of that would suck up that much HP is the exhaust. The rest of the dual exhaust is 2 1/4" pipe running through Spin Tech Cruiser mufflers. I've found some Summit block huggers that look like they will fit but not without a major amount of work, including engine out, reshaping the footwells and probably moving the engine and tranny back as well. So before going to all that trouble, I need some opinions about whether I'm barking up the right tree. Even if I took parasitic losses at the usual 20% I should be seeing 270 hp at the wheels. Is this exhaust really costing me 70 hp or so?
I thought 30% was a more realistic number. But dynos, especially chassis dynos, are not really very consistent with other dynos...unless you go to some trouble to make sure they're calibrated. The pic is some other type of block hugger headers, eh? not for a Ford, more like a Chrysler? I'd be looking for long tube headers, if you're going to the trouble. And you probably get to make them, if you can't find any for your application.
Thanks, Jim. Good looking out on the headers, I changed the post to show the Ford ones. Long tubes just aren't going to work for me for a lot of reasons, including space and the inability to build my own and not wanting to spend the money to have someone do the fab. So for me to tackle this project, I guess I'm looking for some assurance that I'd get at least another 50 hp at the wheels by switching to the block huggers which would also allow me to take that 90 degree bend out of the down pipe. I know trying to guesstimate hp is tough, and if I was getting about 250 hp at the wheels I'd probably think that was somewhere in the margin of error.
I don't see how the block huggers will eliminate the sharp bend in the pipes. I also don't see a 50 HP increase from them. Maybe there are better exhaust manifolds the will be an improvement without all the work of installing headers? Gene
Go to YouTube and check out the Engine Masters videos (on the motor trend channel). They have done a few different tests with different sized headers, headers vs manifolds, and different sized exhaust systems. Really interesting and will definitely help you make a decision. Sent from my Nexus 7 using The H.A.M.B. mobile app
Not much advantage with Block huggers over the cast iron on your setup. A well tuned free flow 4 into a merge collector or a set of try-Y wound be a great improvement but you will need a good aluminum 180 high rise and Holley to get maybe 50 HP. With a proper cam swap 75 HP at the flywheel is possible But now that takes $$. I would not trust the dyno as they all differ according to who is running it. My guess is it will probably run great with no changes. Healy's are light weight And 200 HP is enough at the wheels to move along pretty good. Sent from my iPhone using The H.A.M.B. mobile app
Those were the optional Tiger cast iron Tri-Y headers. The ones I have were stock on the Tiger. One side was a special manifold just for the Tiger, the other was a standard Fairlane manifold. The block huggers exit at a different point on the chassis than the manifold which necessitated the 90 degree bend in the downpipe to avoid an engine tower mount I looked at every kind of manifold/header I could find when I did the swap and these were the only ones that would work. There is barely any clearance between the manifold and steering column as is. I only saw these blockhuggers recently and I probably would have given them a shot during the install. Here's an idea of how tight it is (I ground the portion of the manifold hitting the steering column to get the clearance I needed) If I try to use the block huggers, I'm going to have to move the engine and tranny back an inch and drop the motor down in order to get the front tube of the header under the steering column (I don't want to put a universl in the column) I just don't want to do all that work without a relatively big payoff.
Yeah, dollars per HP is a battle. Have you looked into the factory headers for say, an '86 'stang? They were tight, designed by Ford engineers, and were heavy wall pipe. Used on the first roller cammed 5.0 in the fox body IIRC. .
I did look at those, thanks, but the outlet is in the wrong place. I need a straight down center dump.
I don't think that I would brother. The heat that a set of headers would heat up the floor boards under your feet. If you really need the extra HP, go out through the fender wells, over the tire and down the outside of the frame or get side pipes. These cars sit pretty low all ready, I am not sure that you would have the clearance to run 4 to 1 long tube headers. Nice job so far.
Have you driven the car? I thought I wanted big H.P. with my last build (slightly warmed up 327) it is more than enough. I would think any v8 in a Healy is going to set you in your seat. Go out and drive it you might be surprised at the performance it already has.
Agree with chevy57dude, pick up a set of stock 5.0 tubular manifolds or used 5.0 shorty headers. You should be able to find them locally cheap. Test fit those, at least they are rearward pointing and dont dump straight down causing the need for a tight 90 degree pipe. If you can weld, you may be able to pie cut the 4 into 1 area and adjust the angle on the flange (aftermarket headers, depends on what you get) Not sure where all the steering, etc is on those cars, what you need to work around. The manifolds you have now are rear dump, the ones you're looking at are center dump. As far as power, 5.0's have been making pretty good power with shorty headers for 30 years. Yours should be on par if its tuned well.
Good accurate chassis dynos are hard to come by and even an engine dyno as far as real world numbers are concerned are at the mercy of the operator. That said, I have been swapping headers in for a very long time. I don't care for block huggers as they are sometimes not very well engineered and nothing more that a sheet metal manifold. I am not building a healy so I don't have an off the shelf solution that will work, but maybe a set of custom built headers is in order.
Steinauge may be on to something if you can't build your own headers and don't want to pay someone to do them. There used to be (is) a company called "ExtrudeHone" that could clean up the inside of intake and exhaust manifolds and help them flow as well as the design will allow. Google them. My guess is it is somewhat expensive. I would just save up and have a fabricator in your area build you a clean set of Tri-Y headers to fit your Healey. It can be done, I built headers for my Chevy powered 100-4 Healey years ago so I know what you're up against. Standard Ford exhaust manifolds have always been a bad choice for making power, headers should give you back a significant amount of it.
F.A.D. (Factory Appearing Drag) guys have been using the extrude hone trick for years. It aint cheap and it's used to get the last bit of power out of manifolds. Like forcing gritty play doh thru it.
Speedway sells a u weld it kit for small block fords. It is what I used for my V-8 Morris minor. Basically turned it upside down and bought a couple of bends and made fenderwells from that kit. You want power,but don't want to pay for it. Sounds like about 98% of the customers I deal with. They ask me how fast can you make it and I answer, how fat is your wallet ? Horsepower costs money. Most block hugger headers are not much better than manifolds. For what you are trying to do it sounds like a tri y would work.
You're missing my point. I had the power on the engine dyno (345hp) and somehow lost almost 146 hp at the rear wheels. Before spending any more money (and believe me, I've spent plenty) I'd like to get an idea where all that lost power went. That's almost a 43% loss of power and no parasitic losses I've ever heard of explain that. And the only major change made to the motor from the time of the engine dyno was an air cleaner and exhaust system. The car runs great and has plenty of power, but who wants to leave about 50 hp on the table (if you took 30% as parasitic loss)? I guess my first question should have been whether anyone has any good suggestion where my lost hp went to rather that concluding it got lost in the exhaust? Since most of the suggestions say maybe I'll get 20 hp from great headers. where did the rest of the power go?
Dyno numbers are iffy, too....so maybe you lost 50 hp, maybe not. If you want to find out for sure, take the motor out, back to the dyno, test it with different exhaust systems and air cleaners. Also look at the air and coolant temperatures. What did it have for an exhaust system on the dyno?
When they dyno'd the motor you had long tube headers. Now you have manifolds. Do the ports line up on the GT 40 heads to those manifolds? Did you dyno it with the alternator on it and all the rest of your accessories. Do you have a low profile restrictive air filter on it now to clear the hood? Is your clutch slipping ? Is the car spinning on the dyno? Did the timing get moved? Have you tried unhooking the pipes and run right out of the manifolds? Just trying to help.
I appreciate the help. Here it is on the dyno. Long tube headers (don't know if there were mufflers attached) alternator attached and I'm guessing no air cleaner: Clutch is not slipping, ports line up. I'm using a Cobra style hi-po aircleaner which is probably somewhat restrictive. I'll recheck the timing. Thanks for the suggestions.
You will have more than enough power for fun factor ! If it were me I'd leave what is working and enjoy the ride ! Your doing something , I have done many times on a old Harley change this , now I have to modify that to make first change work . That's all well and good but is it worth it when measured in the lost fun you could be having driving about enjoying the hobby . Just some thoughts maybe helpful maybe not ! I think your dyno reads are not so accurate , measure in fun , it may be a bit closer than you think ! Sent from my iPhone using The H.A.M.B. mobile app
Dynos are great but ,as has been mentioned, they don't ll read the same, so if the engine one was reading high and the chassis one low you may not be as short on HP as you think, does the engine builder have a chassis dyno? if yes drive over there and ask WTF (nicely), if no, when you tested on the chassis dyno what were the mixtures looking like ? Id guess the engine guy will point at your exhaust but sounds like a lot of hassle and cost to claw a bit back.
That's the ticket there! It may need a different tune, jets/air fuel ratio or cam with manifolds. Ask any dyno operator about the discrepancies. The Same combo with same operator on different dyno gets you different numbers. Then there are different kinds of dynos too. A dyno is a tool (just like you're favorite ratchet is a tool) to measure the impact of a specific change. If you go to a different dyno, it's not a good comparison. That's exactly why you need to run your exhaust system on the same dyno to see what the difference actually is. There's plenty of dyno evidence that a mechanical fan robs up to 40 HP in a dyno room. I don't get it but it's out there for sure.
This is what was mentioned, have it done and keep changes to a minimum. https://boneheadperformance.com/extrude-honing/
Thanks for all the suggestions guys (including some PMs) and it's helped me make a decision. It seems it's very possible this is a function of different dynos and not something basically wrong with the motor. It doesn't seem like adding the blockhuggers is going to get me a dramatic increase in hp. When I did the swap, I already determined I wasn't going to be worried about a loss of 10-20 hp or so by using the cast iron manifolds, so I'm not going to go to all the hassle of installing them (and it's quite a bit) just to get those 10-20 hp back. Deathrowdave nailed it, I'd rather be driving than chasing some small improvement. I'll check everything else suggested, just to make sure but the car runs very strong now all the way to the redline, so I may not find much. If I do, I'll report back. It's great to have a place to turn where there's so much good info and help fro guys that have been there before.
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