Engine Dyno results questions
 

So my engine is finally done here is the combo……..
70 4 bolt main block, 461 , compression 10.2, 340 Cfm eheads,, port matched northwind intake, camshaft: 248 intake 254 exhaust 620 gross lift 112 lobe separation.

I am also running a Holley terminator x with a 1300 cfm throttle body

The engine was Dynoed with only a 750cfm carb as they didn’t have the setup to run efi on the Dyno and it made 551 hp and 555 torque at 6500 rpm

When I bought my combo from butler the parts combo was put together with the goal of 650hp so I was about 100hp shy of that

My questions is how close will I get to that with my 1300 cfm throttle body compared to the obviously to small 750 carb?

The goal with the Dyno was only to break the engine in properly before I put it in the car which I accomplished and everything ran great! I just wanted to get your thoughts on how much HP and torque I lost with the engine being under carbed compared to what my goal is.

Thanks as always

I do not think a 248 @ 050 cam would make 650 HP even with the best carb. You have plenty of head for more cam too.
Maybe I am wrong, cam just seems kind of small for your goal.
I am shooting for a little past that 650HP number with a 461 but I have a lot more cam.

At 6500? Seems like something is off. That cam, especially with that carb, should have peaked way sooner.

I've built & dynoed a number of builds over the years with similar combos if not the same.
You can expect upper 500"s hp with proper CFM.

Can you post up a dyno sheet please?

The fact that you on,y made 551 hp tells me that your flat out using only using some 275 cfm out of that 340 that the heads can flow.

Your use of the 750 Carb took 25 to 30 hp off of what the motor could have made with something like a 950 cfm Carb.

I also think that your pick of Intake Manifold is a bit of a restriction and needs some Plenum work and at least a 1/2" spacer.

It would have been nice to know how much vacuum you where pulling below the Carb at the rpm of peak hp, I bet it was over 1.5 hg which is a indicator of a good size restriction.

If you where looking for big power above 5800 rpm with the duration of that Cam it's not going to happen, this all being said I bet the motor as is will be a very nice cruiser and highway stormer!

I would be very happy to just slap on your throttle body and enjoy the motor as is because your not hooking up on the street even the 550 hp your making now without sinking a very likely 4K more into the chassis and tires on the car.

"I do not think a 248 @ 050 cam would make 650 HP even with the best carb."

+2

Not enough cam for 650hp, at least based on the 455 builds I've done here in the 600-650hp level.

The last one I remember doing that made right at 650hp used CNC ported 330cfm E-heads, Victor intake, 2" spacer, HP 950 carb and 260/;260 @ .050" cam. Had a tad more compression too.........

Ya dyno sheet. It would be interesting to know what the air/fuel was at 6500 with a 750 carb.

I will agree with the others that cam is not going to make it. Comparison my 500" IA with 330cfm E heads has a 268/272@0.050 on a 112 IC 108 and was about 650 non corrected 695 corrected with a 4150 850 carb.

More compression and valve lift would have helped. Intake work and spacer can be worth good power. Small carb will be hurting it as well.
Dialed in it has to be a 600 hp plus engine all day easy.
I'm curious though was the dyno just used to do the initial break in and check for leaks etc...no real tuning was done?

engine dynos can be all over the place just like wheel dynos. the same engine will show different numbers on different dynos, lots of variables will determine the final numbers.

the numbers do seem low for that cam & heads. just as an example my 467 with stock 72cc round port E heads, 10:7, OF 236/242 cam with a ported HO intake & q-jet made ~520 hp with a fuel pump that was inadequite, & just under 580tq. a known strict dyno with no tuning to the engine, just bolted on the parts & did a few pulls while breaking it in & checking for leaks.

seems like your engine with those specs should be making a lot more hp/tq, even with a 750 carb. im sure the EFI will help, but testing the car on the track will be the best way to show the ability of the car/engine.

Really cool build and I'm surprised they spun it that high with a 750.

Isn't this comment an entire waste of time not knowing the details of the 750?

Thank you so much for all the feedback guys!

Yes, the purpose of the Dyno session was just to check for leaks and get the rings seated no tuning was done at all because of the carb.

But good to hear when dialed in correctly I can hope to get over that 600 mark at least haha

Well it could be a waste of time I guess, but I was assuming that since the Op had a 1300 throttle body that was not used in that test that he would have also posted up if the 750 had seen rework to increase its cfm.

Did they give you any AFR data? It had to be super lean pulling it that high.

If the dyno had the type of Carb air hat that could measure cfm, then it would have been known in the blink of a eye if at any rpm point the Carb was trimming off needed cfm.

Just fwiw, I made 620+hp with 243 duration. I'm sure 650hp can be made with 248 duration but things need to be right

Posting a dyno sheet would really help.

That said here is a WAG. Note even at a dyno correct = 1.0 it is not using 750 CFM.

Stan

Engine_Size_=_462.18350__-__Volumetric_Efficiency_=_0.83000
BSFC_=_0.46000__-__Air_/_Fuel_Ratio_=_13.0000__-__Blower_Pressure_=_.00
BSAC_=_5.9800__-__Barometric_Pressure_=_29.9200__-__Temperature_=_60.00

__________UnCorrected______Fuel
_RPM______HP_____Torque___lbs/hr___SCFM
_6500___552.62___446.51__254.203__721.54

Maybe 30-35 more hp. The cam just isn’t enough. Need something in 260 range duration.

Still you’ll be very happy with 585 hp, but yeah 650 be nice. Nice combo tho. Enjoy

My similar combo: less head flow(295 dport), rpm, quadrajet…made 555/577 on the engine dyno. Pulls to 6k. Peak hp was 5800 I believe. Didn’t do a thing to it. Pure tractor motor. Didn’t care if timing was 30-36….You could certainly achieve higher peak dyno #s with carbs/intakes/spacers …cam would certainly help

I swear I just watched a hp tv episode where they installed a butler crate 455….supposed to see well north of 500hp….don’t recall that they were close

Dyno’s……..

No way is it worth 30-35hp. A 455 isn't remotely in need of that much cfm! And 260° duration is enough for 700+hp

The bottom line is he’s asking if it’ll make 650 hp. No it won’t. I said MAYBE 30-35 more if any. With 1300 cfm deal.

He has the basic parts to make 650hp on paper anyway. I agree just swapping over to his throttle body isn't getting him to his goal.
Like others said 550+ is loads of fun on street and plenty for most.

Tony angelos firebird was on hagerty and made like 340 rwp. He seemed disappointed.

Yeah, he was way disappointed but it is a low comp blower motor set up.

Murf

Thanks for the info boys! I’ll get you the dyno sheet……even if I get over 600 with my throttle body and a tune I’ll be happy….the shop that had the dyno wasn’t very technical so I wonder about everything …..it’s ok though the point was just to check everything and get her broken in right before I messed with the efi

Plus I was planning on giving it alittle spray anyway :cool::cool::cool:

Maybe I can shed more light on to what may also having a effect on the level of power being made here by the OPs combo .

Way back in 2014 I had the very good fortune to spend about 10 minutes talking to David Vizard about the need for a certain cfm carb to produce a given level of power.

He cited to me a example of 2 BBC motors that both made 1100 hp, give it take 4 to 5 hp.

These 2 motors where both the same cid and used the same cam and the same pistons producing the same compression.

The only difference was the heads and intake manifold used.

So they both where extremely close to being the exact same build.

The main difference was how much fuel per hour each motor needed to make that 1100 hp which ties right in with the needed cfm rating of the carb used.

One BBC needed only 1260 cfm or like 5.2 pounds of fuel per hour, and the other needed 1450 cfm , or 6 pounds of fuel per hour.

These two differences where basically related to the how equal the fuel distribution was per cylinder that the intake manifold used produced, and how good the cylinder heads where in shredding up streams of wet flow ( wet flow management ) back into a burnable useful state.

As happy as I am that we have very useful formulas to get us to base line numbers, many of them assume ideal conditions and not the variations that take place in the real world!

Theory is fine, real world experience (dyno and track) are what really matters

Facts.

Kinda like folks who think they can work as a mechanic, for a living, by watching youtube videos.

Steve,
This does not make any sense to me. The only thing that I can think of that those number would be close to is BSAC.

This a screen from a program I wrote with David Vizard.

Stan

Yes. The BSAC factor.

I can't see it making less than 600 fully tuned.

Fwiw.... Just because a head is CNC ported and flows X amount doesn't guarentee it's a good port or even flows that CFM. We have seen some real crap CNC ported heads as of over the years. We've also seen some builds using these heads fall way short of their power goals.

Another thing, just because the guy selling the parts says it'll make X amount of power, it isn't a guarantee it will. In forty years I have NEVER gotten any power number from a knowledgeable cam guy and it took me several years to realize why.

Well you need to share why Paul, why?

Just looking at the engines I've done here 230 @ .050" will get you 500hp with 260cfm heads.

236 @ .050" will get you 550hp with 290-310cfm head flow.

260 @ .050" was worth 650hp with 330cfm head flow (very well prepared Edelbrock round port heads)..

I don't see 248@.050" ever getting you to 650hp even with 20cfm more head flow. Probably closer to 590-610hp with 10 to 1 compression and ideal intake, carb and exhaust system.......FWIW......

An added note here. I was involved but did not build a 455 that ended up making 612hp. It used early KRE aluminum "D" port heads ported to 310cfm. Can't remmeber the exact cam specs but it was a solid roller grind around 245/255 @ .050".. Two different intake/carb combo's were ran on that engine while it was on the dyno.

The new (at that time) Tomohawk intake topped with a 1" spacer and 850cfm carb. We also ran a Victor/Dominator on it. There much bigger Victor/Dominator set-up was only worth about 10-12hp and we made quite a few pulls with both set-ups to get those numbers.

I've also seen the T-II intake, 1" spacer and 850cfm carb set-up rival the Victor/Dominator at that power level on several other 455 builds.

With all that said I don't see the intake/carb being a huge restriction on what you are doing........

If I can make 620+ with 1 pull (no carb tuning or playing with spacers) and alum d-ports with 243-249 cam then I see no reason real close to 650hp can't be achieved with a little more can and a better exhaust that the round ports offer.

We made 585 with a 455 and Daves 290CFM D ports with 245-252 hyd roller cam.Joe Shermans dyno.Tom

I would still like to see a dyno sheet.

Also a flow sheet for the head might help. It stated they flow 340 cfm but at what lift. As stated the cam has 0.620"

Stan

I'm at 127.5 mph with Dave's 310cfm heads and his 235/245 cam at 3700 lbs what ever that works out to? 590?

If we are going to throw out HP numbers how about MPH and weight to go with them. That kind of helps even out if a stingy or a happy dyno. and numbers can be changed by a different correction factor easily also.

My IA runs closer to the uncorrected numbers(132.5mph 3595 lbs) which is less than the 695 corrected. probably because most track days are warm and humid like the dyno day was! The 455 in my TA at 3750 ran 124 mph and only dynoed 525 corrected! Wallace calculator and Moroso slide 550 hp.Different dynos.

Issue with dyno and track comparison for street cars is there are accessories and full exhaust that kill power at the track. Easier to look at race cars vs dyno numbers.

Watch this video, give you a good idea on what you could pick up with Throttle body. Forget it’s a Chevy tho…LOL

https://youtu.be/iry0QhiuulM

My TA had no accessories on the engine dyno yet track numbers show more HP! PS, PB, full exhaust, transmission and rear end. So kind of opposite there. And it ran the same without any exhaust at all on it as with full X 3".

I understand what you are saying and why maybe the IA is less based on mph running an exhaust. But dynos like flow benches can be all over the place on the same engine, especially when you start using correction factors.


I still think knowing taking some off for accessories and some for a full exhaust would get us closer to comparing using mph. ET yes more traction/60ft bottom end issues(chasing that on the IA Camaro).

No doubt you need to know your exact race weight at the very least when trying to convert et/ mph to hp

Body style and wind conditions will play large factors as well….a low slung car with low frontal area and a tail wind will obviously mph higher …

Not an exact science by any stretch!

That video is great! I’m hoping for some results like that with my efi….especially with the carb that was used being so small

I think you will. Being crab was only 750. How much who knows. But hey down road you can always make a cam change, that will definitely get you there.

Pontiacs take more carb for a horsepower number than a comparable Chevy does. Its always been that way.
Has something to do with our long strokes for a given cid and crappy heads.
Still better than a puke Chevy.

If your going to compare track numbers you're in the same boat with dynos. You still need correction factors. Cars out here at elevation and desert heat won't run as quick as someone in Florida or Maine.
In fact all my stuff ran quicker in Ohio than it does here in Arizona.
Figure in DA and it starts making sense.

Yeah Pontiacs never have been big HP makers anyway when talking about using conventional heads. So they always make great torque curves and that's what carries them down track. BBC has a far superior head much easier to make HP with that doesn't need a monstrous cam to get there, but they don't have the torque curve a Pontiac does.