67 Cuda: disappointing dyno numbers, need some advice!

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Brandt Fonda

Brandt Fonda

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Guess its a story that is as old as cars are: "this is a big hp engine" I was told and I bit lol.

So what I "know" (what I've been told) about the engine:
74 360la, Bored 30, Steel crank, TRW flat top pistons, "swirl port" heads (supposedly ported) 1.88 valves, 4.55 purple cam, stamped rockers, M1 dual plane manifold. I don't know the compression but was told 11:1 I've been running 93 octane. Balanced, blueprinted, blah blah

What I've added: Holley sniper EFI 4150, Holley dual sync distributer, (36 degrees timing WOT), Holley sniper fuel tank, MSD 6AL, TTI 1-3/4 step headers, 3" TTI X pipe, dual 3" exhaust all the way out, flow master super 44's mufflers.

So the numbers are rear wheel and I guess not terrible? Just not what I was expecting. What I am planning: roller rockers: already got the hughes ones, and their cam Hughes Engines Also am thinking manifold. So any opinion on that cam and which intake so I can get that HP number up into the mid high 300's?
Barracuda dyno.jpg
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It's not 11:1. The cam is sub-par for my taste, and the head work may be hindering things depending on what he did. It's a mild 360. If it runs good, stick a better camshaft in it and make sure the heads are indeed good.
 
moper said:
It's not 11:1. The cam is sub-par for my taste, and the head work may be hindering things depending on what he did. It's a mild 360. If it runs good, stick a better camshaft in it and make sure the heads are indeed good.
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Yep. It's probably not 10:1 so I hope you didn't tell Hughes you had that much compression of you'll still have the wrong cam.
 
BTW, that's 330ish HP at the crank and that's not hideous for what you have. That's through the exhaust, gear box, drive line and tires.
 
moper said:
It's not 11:1. The cam is sub-par for my taste, and the head work may be hindering things depending on what he did. It's a mild 360. If it runs good, stick a better camshaft in it and make sure the heads are indeed good.[/QUOYou don't like that Hughes cam?
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So you don't like that hughes cam?
 
yellow rose said:
Yep. It's probably not 10:1 so I hope you didn't tell Hughes you had that much compression of you'll still have the wrong cam.
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Don't think he asked compression? But I did say heads had been worked and had headers/free flowing exhaust
 
any opinions on a good manifold? I think the torque is pretty good, but the intake is hurting HP?
 
A good 3500 converter and a minimum of 3.73 gears (3.91's would be better) and I don't mind that cam. I like the lift. Not sure, but if I had enough intake valve to piston clearance I'd think about a 100-102 intake centerline, mostly because I doubt your compression ratio.
 
Tim is the guy you want to talk to at Hughes. Dave, well...……………………………. lol
 
yellow rose said:
A good 3500 converter and a minimum of 3.73 gears (3.91's would be better) and I don't mind that cam. I like the lift. Not sure, but if I had enough intake valve to piston clearance I'd think about a 100-102 intake centerline, mostly because I doubt your compression ratio.
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I have A 833 OD transmission with 3.91 gears. A buddy said we could check clearances with a checker spring and dial indicator?
 
Run a compression check on the thing. I bet those smog heads have big old chambers and the compression isn’t anywhere near what they told you. A home port job could have made that worse too. Cranking pressure won’t tell you everything but at least you’ll have some kind of ballpark.

And what “swirl port” heads are we talking about? 308’s?
 
Lets get this "swirl port" thing laid to rest. According to Larry Shepard hisself (who helped write the MP engine book and lots of other stuff) they found that the "standard" open chamber small block heads were in fact swirl port. That's nothing more than marketing, really. Most if not all heads exhibit "some" swirl anyway since the cylinders are.....oh....I don't know........ROUND. So lets just sweep that little piece of info under the rug. Now, there were some later heads (the 308 castings) that were actually marketed as swirl port, but, they really are "not much different" than any of the rest.

Now onto your engine. How does it RUN? Do you like it? Are you happy with the power output? IGNORE what you found on the dyno when you answer. I agree with the rest. No way you have 11:1 compression. I'll tell you how you can "guesstimate" compression. RUn a compression test. Since you know what camshaft you have you can report back with the compression test numbers and we can give you a REAL GOOD" idea of about what your compression ratio is. I'm guessing under 9:1. You don't have to have an 11:1 motor to run strong. Plenty of stock eliminator engines have broken records at 8.5:1 compression. Low compression engines can haul *** when properly matched.

As mentioned, your combo "ain't bad" for what it is. "I" would not be disappointed. Can it be improved upon? Sure. But that's up to you. If you're happy with it, leave it alone. The ultimate judge is you and no one else.
 
I don't know, maybe it's just me. I would pop the heads and measure chamber and cylinder cc's so I knew what I have before selecting a cam.
 
72bluNblu said:
Run a compression check on the thing. I bet those smog heads have big old chambers and the compression isn’t anywhere near what they told you. A home port job could have made that worse too. Cranking pressure won’t tell you everything but at least you’ll have some kind of ballpark.

And what “swirl port” heads are we talking about? 308’s?
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yes 308's I believe tho I haven't seen the casting number. I do have some pics of them without valve covers on if that can help identify them. What cylinder compression would indicate anywhere near 11:1?
 
fishmens67 said:
Tim is the guy you want to talk to at Hughes. Dave, well...……………………………. lol
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I have grown tired of them both. THey are so full of themselves, all they want to do is push their products. I'm not impressed.
 
Brandt Fonda said:
yes 308's I believe tho I haven't seen the casting number. I do have some pics of them without valve covers on if that can help identify them. What cylinder compression would indicate anywhere near 11:1?
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With "that" camshaft, I would say anything "above" 180 PSI.
 
RustyRatRod said:
Lets get this "swirl port" thing laid to rest. According to Larry Shepard hisself (who helped write the MP engine book and lots of other stuff) they found that the "standard" open chamber small block heads were in fact swirl port. That's nothing more than marketing, really. Most if not all heads exhibit "some" swirl anyway since the cylinders are.....oh....I don't know........ROUND. So lets just sweep that little piece of info under the rug. Now, there were some later heads (the 308 castings) that were actually marketed as swirl port, but, they really are "not much different" than any of the rest.

Now onto your engine. How does it RUN? Do you like it? Are you happy with the power output? IGNORE what you found on the dyno when you answer. I agree with the rest. No way you have 11:1 compression. I'll tell you how you can "guesstimate" compression. RUn a compression test. Since you know what camshaft you have you can report back with the compression test numbers and we can give you a REAL GOOD" idea of about what your compression ratio is. I'm guessing under 9:1. You don't have to have an 11:1 motor to run strong. Plenty of stock eliminator engines have broken records at 8.5:1 compression. Low compression engines can haul *** when properly matched.

As mentioned, your combo "ain't bad" for what it is. "I" would not be disappointed. Can it be improved upon? Sure. But that's up to you. If you're happy with it, leave it alone. The ultimate judge is you and no one else.
Click to expand...

The car runs really good, snappy throttle response, great set you back in the seat torque but its underpowered for what I want. It feels like it jumps up and goes but then just kinda meanders lazily to redline. I have a video of the dyno pull I'll load it to YouTube and link. I had in mind a street/strip car and it seems like it is just street atm.
 
Brandt Fonda said:
The car runs really good, snappy throttle response, great set you back in the seat torque but its underpowered for what I want. It feels like it jumps up and goes but then just kinda meanders lazily to redline. I have a video of the dyno pull I'll load it to YouTube and link. I had in mind a street/strip car and it seems like it is just street atm.
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Sounds like it's runnin outta camshaft and or valve springs. It probably is. But before you make changes, run the compression test and tell us what you come up with. We can then come up with some parts to optimize your combo if that's what you want to do. As usual, we won't all agree on what camshaft, BUT you will see a good enough pattern with our recommendations that you will be able to make a decision.
 
RustyRatRod said:
Lets get this "swirl port" thing laid to rest. According to Larry Shepard hisself (who helped write the MP engine book and lots of other stuff) they found that the "standard" open chamber small block heads were in fact swirl port. That's nothing more than marketing, really. Most if not all heads exhibit "some" swirl anyway since the cylinders are.....oh....I don't know........ROUND. So lets just sweep that little piece of info under the rug. Now, there were some later heads (the 308 castings) that were actually marketed as swirl port, but, they really are "not much different" than any of the rest.

Now onto your engine. How does it RUN? Do you like it? Are you happy with the power output? IGNORE what you found on the dyno when you answer. I agree with the rest. No way you have 11:1 compression. I'll tell you how you can "guesstimate" compression. RUn a compression test. Since you know what camshaft you have you can report back with the compression test numbers and we can give you a REAL GOOD" idea of about what your compression ratio is. I'm guessing under 9:1. You don't have to have an 11:1 motor to run strong. Plenty of stock eliminator engines have broken records at 8.5:1 compression. Low compression engines can haul *** when properly matched.

As mentioned, your combo "ain't bad" for what it is. "I" would not be disappointed. Can it be improved upon? Sure. But that's up to you. If you're happy with it, leave it alone. The ultimate judge is you and no one else.
Click to expand...

Yeah, I mostly agree. The biggest thing with the “swirl port” deal is that all kinds of people misapply that label anyway.

The guy that ported the 308’s for my 340 said the exhaust port floor looked better than some of the earlier heads. It wasn’t a huge difference but the 308’s did flow better on the exhaust side than the J’s.

fishmens67 said:
I don't know, maybe it's just me. I would pop the heads and measure chamber and cylinder cc's so I knew what I have before selecting a cam.
Click to expand...

It may come to that, but a simple cranking compression check will tell you some things without tearing all the stuff down first. Like Rusty said, we know the cam, we can ballpark the cranking compression to the static.

Brandt Fonda said:
yes 308's I believe tho I haven't seen the casting number. I do have some pics of them without valve covers on if that can help identify them. What cylinder compression would indicate anywhere near 11:1?
Click to expand...

RustyRatRod said:
With "that" camshaft, I would say anything "above" 180 PSI.
Click to expand...

My 340 has a static compression at 9.8:1 and cranks between 175-180 on all cylinders
 
awesome thanks for the responses guys, I'll get a compression gauge and see what it looks like. Based on that hughes cam is there any intake manifolds that would work well with it?
 
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