[Gach]

Originally Posted by Verdoro 68

It was very intentional to have a factory-looking setup and I knew that using those parts was going to create some limitations. I was honestly expecting anywhere from to 425-450hp with 500tq at the crank and I got that. You all know how it goes though, you get a taste and want a little more. I'd love 500hp, but that breaks the spirit of the build. Maybe I'll drop a set of aluminum heads or headers on it one day when I get bored with it as is.

Funny that cam is considered smallish - I was originally going to put a 232/236 in it.

Going to back to the point about the power band and converter, how can I tell if I should have the converter restalled to better fit the curve?

Sooner or later we all get bored with what we have. But you nailed it. It’s a damn good combo. As far as converter goes a stock converter maybe ok I don’t know what you have for converter now. Pontiacs like tight converters Rich combo ended up liking 3500 stall. The way it works is you want it to lock up about 300 rpms above where it makes peak torque, so question is where is it actually making big torque, you will kind of know once you made the 1-2 shift. If the rpms drop more then say 300-500 rpms then the motor is going to take time to recover meaning getting back up to the peak RPMs. In other words it’ll feel like a dog once you make first to second gear shift. Because it’ll take longer to recover. You’ll know.

[Verdoro 68]

Originally Posted by PAUL K

How do they seem to compare?

The '04 felt faster and more responsive. Fuel injection, computer tuned, less cubes, lighter car - to be expected.

The '68 gets up and goes, it just feels like the lumbering giant it is. If I had to guess, I'd say the '68 is a low to mid 13s car but maybe I'd be surprised if I took it to the track.

[steve25]

On taking a second look your probably ok with that converter.
You torque is likely close to 400 a little above 1900 and does not really start to nose over fast below that number until 4300.

[steve25]

What odd to me about that dyno test is that a motor of that cid with what amounts to near stock D port iron heads would have the HP not nose dive well before 5700 like the pull showed.

[Formulajones]

Neat setup, I didn't know you had the car done. Glad to see you're enjoying it.

Numbers look fine to me for what ya got. It's a mustang dyno anyway and they tend to be a little stingier than a dyno jet for example. Peaking at 5000 isn't a huge surprise. I've mentioned a few times how 455's soak up these camshafts, even a 236 @ .050 won't act all that big, and it showed that on the dyno. Glad you at least went with that instead of that 232. I don't think those heads would flow enough to support much more than that anyway. I would have liked to see you experiment with timing though. From the factory head stuff I've done I've never had one that liked less than 34, and usually a pinch more than that on pump gas.

Take it to the track and have some fun with it, see if it runs a number you're happy with.

Congrats

[Verdoro 68]

I bumped it up to 36 total timing recently and it likes it. It kind of feels like it may take a little more.

I've stayed away from the track since I had so much trouble getting the rear main sealed up. I think it's good now, knock on wood. Not sure how many passes that old 8.2 would be able to take though.

[ponjohn]

I think the 9.5" convertor is part of the problem. I'd bet that is stalling way higher than 3k rpm or it is not very efficient.

Get a dragy and make some street hits to see if the numbers align.

[Formulajones]

That's always a battle. We just had a long thread about how different converters can be and how difficult it is to find a manufacture that can nail one down. They for sure don't really shine on a chassis dyno much, the real test is how it does at the track.

That 9.5" converter I'm going to guess is a TSP. I run one of those myself in one of the cars here (600hp and 4120 lbs.) and it does a pretty decent job of coupling under normal driving but does flash pretty good when you get aggressive with it with good traction. However it's also a lockup so in 4th gear I'm cruising like a stocker, and have the ability to lock it under power if need be. So even though it could be a pinch better at part throttle, I don't concern myself with it being maybe a little on the loose side during stop and go light throttle cruising, since it locks anyway at a mph I pick. In a non lockup deal, it's a little more critical.

[Gach]

Chasing et, mph and weight, tells story on what its really making for hp. But unless it’s geared and tire diameter so it goes through traps above peak hp. Just an example on how it relates to convertor stall. If my motor makes peak hp at say 6500 rpms, I want to go through the traps at 7000 rpms, so if it not geared ( along with correct tire diameter. Its not going to happen. So how dose that effect convertor stall. Well it could make you think convertor wrong or off. But of course if its making peak torque at say 3700 and convertor flashing at 4000-4200 when it really should be locking up at around 3500-3800, you are going to know. What a lot of these converter companies don’t know is Pontiacs like tight convertor. Whereas BBC like it locking up around 600 rpms above where it makes peak torque. So they usually get it wrong. To lose of a convertor usually shows up in frist to second shift, of course the air speed in the head effects motor recovery. Which will also make you think convertor is off, a head that only has say 252 fps is going to be a dog on **** recovery where as a head that has say 300-325 air speed is going to be right on the money. I’ve seen head porters brag about how they got that head to flow 380-400 cfm when no one else has. But air speed on that 380-400 cfm head was only 252. Not saying thats the case with you. Just trying to make everyone think. So critical things to think about is right gear tire diameter and air speed in the port, if those are all correct, convertor diagnose is going to be easy.

[Verdoro 68]

New TSP 9.5" Cliff specced for me behind a TH400. I like the way it drives, just wondered if it should be tweaked further now that I've seen how the engine operates. I haven't really done any honest full throttle runs yet so maybe I'm jumping the gun. Honestly, I have trouble keeping the car straight when I put my foot into it even a little bit.

I was thinking back to the last time I had the car dynoed about 15 years ago. Same place, same dyno with a 400, #16 heads, RA manifolds, 744 cam, a 13" Continental converter and probably poorly tuned carb and distributor. IIRC, it put out a embarrassingly measly 220 hp.

[Gach]

I think you’re going to find there’s not much tweaking, until you’ve played some more. Timing sounds like it on the money. Its making ton of torque probably why you can’t keep straight…LOL

[Gach]

By sounds of it that convertor it’s s on the money. Personally I think your making more hp then what that chassis dyno says. That RA69 head is a good head.

[Cliff R]

"The converter flashes to 3k when you stomp on it, but stalls much lower (2k-ish?) in regular driving."

That's what it should be doing and since you're having trouble keeping the car straight even putting your foot in it a little bit I'd leave the converter as-is.

The factory RA manifolds and 2.5" exhaust knocks a LOT of power out of an engine like that. Even with an "H" or "X" pipe you'll be WAY down on power compared to a good set of headers, 3" exhaust (with X or H pipe) and straight thru performance mufflers.

Below is a dyno sheet from one of my customers (did the carb for it and helped with cam selection) with a similar build. Factory "D" port heads, dished pistons, 236/242 custom ground HR cam. You'd think 69 round port heads would do even better.........

[steve25]

Cliff, just so we are all on the same page here, the OP combo uses 1968 1/2 RA2 heads, so D port intakes , round port Exh.
Only a bowl blend was done on them.

If I had to take a educated guess I would say that in terms of peak Intake flow he might have 215 to 220 cfm @ 550" lift.
Don't know what might of happened to his flow numbers below 300" lift because there easy to screw up and end up with less then stock.

Exh wise if a bowl blend was done he likely picked up a lot at peak lift and if he was to slap headers on would be over scavenging due to the high flow ratio and the duel pattern Cam used.

[Cliff R]

RAII headed 400's rule Pure Stock and FAST for Pontiac powered cars, so you'd think using them on a 455 build would do at least as good as a set of big valve small chamber "D" port heads.

The chassis dyno thing also throws some variables into the equation and it didn't appear that they did any tuning while it was there to see if there was some more power lurking in the tune.

As far as exhaust goes I haven't seen a single 455 based set-up that didn't respond quite well to adding 3" head pipes with an "H" or "X" pipe, free flowing mufflers and 2.5 or 3" mandrel bent tail pipes.

Headers also make more power with any set-up I've worked with vs the cast iron Ram Air manifolds.

So at the end of the day the numbers aren't really all that bad and there may be some more power hiding in there with something as easy as adding a few degrees of timing. I didn't see the engine details but most likely it's got dished pistons in it. I did one dished piston 455 build here using a known combination of parts and it was well down on both HP and Torque from doing a very similar flat top piston build at the same compression ratio. So that may not be helping either.........FWIW.......

[OCMDGTO]

Sounds like you're having fun with it on the street so I would consider it a success. Dyno #s on both your engines sound low. I'd experiment with timing and take it to the track, you might be pleasantly surprised. Many years go I had an iron headed 400 that wasn't living up to expectations. I advanced timing and it was a completely different car. 2 degrees at a time until it pings. The engine I have now I started off with a horrible converter that wouldn't burn the tires as good as my old 13.0 second 400. Converter swap was like night and day. Sounds like your converter is good to me if you're frying the tires easily.

[PAUL K]

Originally Posted by steve25

What odd to me about that dyno test is that a motor of that cid with what amounts to near stock D port iron heads would have the HP not nose dive well before 5700 like the pull showed.

The better exhaust ports are most likely the reason the power hangs on for longer.

[PAUL K]

Originally Posted by Verdoro 68

I was thinking back to the last time I had the car dynoed about 15 years ago. Same place, same dyno with a 400, #16 heads, RA manifolds, 744 cam, a 13" Continental converter and probably poorly tuned carb and distributor. IIRC, it put out a embarrassingly measly 220 hp.

That's a huge difference..... You did good!

[AG]

You might want to upgrade the rear end and tires so you can take it to the track and get a good idea of how everything is working together.

[Formulajones]

Yeah I just read that, still the 8.2 rear............Yikes

There is no way I could resist having some fun at the track with that car so a rear and driveshaft upgrade would be the first thing on my list because I'd for sure have sticky tires on it.

You might get by with a trip to the track using sticky tires on what ya got if you just wanted to make a couple passes if that's all you're interested in. I just tend to make it a habit