Nicks Garage 383 build

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I had a friend with a 78 Corvette. He had the shop rebuild his engine with a good bottom end, and I helped spec the cam. It all looked good on paper, but it was a dog, the stock heads were the bottleneck. He bought some aftermarket iron heads, and I helped install them. After it was done it was a night and day difference, everything worked as it should have in the first place.
 
The ones that make me scratch my head are when there are two very similar builds, but not exactly the same……….and one just ends up being noticeably better than the other.

I guess what I’m saying is, it can be surprising how different the results can be between parts that directly compete with each other.
Like heads, intakes, cams etc.
 
The ones that make me scratch my head are when there are two very similar builds, but not exactly the same……….and one just ends up being noticeably better than the other.

I guess what I’m saying is, it can be surprising how different the results can be between parts that directly compete with each other.
Like heads, intakes, cams etc.
Or when you stumble on to a combination that seems to run better than it should for it’s given combo of parts.
 
While we’re all waiting for “episode 3” of Nicks old weaky escapade to air………here’s more underachiever “filla”.

Maybe not so much of an”underachiever” as much as the builder really under-delivering the goods on what the customer asked for.
This one’s a 455 Pontiac.

A shop in town has a business that works on muscle cars.
All types of mechanical work, and disassembly/reassembly of whole cars.

Customer brings in a 74 T/A that’s has a 455 in it.
Supposedly a real SD car, but the SD engine is long gone.
He’s going to have the body done and wants a hot rod type motor done for it.
Owner makes arrangements with the engine shop for the build and is very clear about wanting “500hp”.
Everyone is theoretically on the same page, 500hp.

Some time goes by, the builder contacts the muscle car shop about the heads being cracked.
The shop says, just get new heads, he wants 500hp.

The builder says, no no, I have some cores here we can use.

More time goes by, one of the owners of the shop is up at the builders place to buy some race gas, and the 455 happens to be on the dyno.
They have already made some pulls, and there is a sheet sitting on the desk.
The shop owner says something like, “I hope you’re not anywhere near done yet…..cuz the car owner wants way more that that”.
He is assured all is good, and after they get done with it, it’ll be great.

A little more time goes by, and the engine is delivered to the shop…….with one dyno sheet.
I don’t recall the TQ, but the hp was in the 340’s.

At this point I get a call.
“Hey, we got that motor back and it’s nowhere near 500hp”.
I told them to bring over the build specs, parts list, and dyno sheet.
Basically………what they got is what was built.
A rather stock, low CR 455, with unported late model heads(the number on them were noted in a Pontiac engine build book as “don’t use these”), a small cam, a std Performer, and a 670 Street avenger carb.

They wanted an estimate to upgrade it to 500hp.
My response was…..it needs everything changed.

The rework estimate was about what the original build cost…..maybe it was even a bit more.

One stipulation on me taking it on was that I would dyno it as-is before I did anything else.
The paperwork that came with the engine only included one sheet.
Part of why I ran it first was so that there couldn’t be some mystery sheet produced down the road that happened to be better than the sheet that came with the motor.
I’ll test it, then I’ll know.

On the dyno I used it was like 315hp.
But not only that……..it didn’t run well.
The thing surged during the pulls and had the A/F ratio at wot in the 15’s-16’s.
I put my dyno mule 850dp on it, which ran 100% better but only picked up like 8hp.

That was my starting point.
 
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The ones that make me scratch my head are when there are two very similar builds, but not exactly the same……….and one just ends up being noticeably better than the other.

I guess what I’m saying is, it can be surprising how different the results can be between parts that directly compete with each other.
Like heads, intakes, cams etc.
That's why I find it kind of funny when people ask people on here what's the best "whatever" be it an intake or a carb or cam etc... for their combo and figure they should be able to put together the ultimate combo on 1st try with no experimenting required.
 
While we’re all waiting for “episode 3” of Nicks old weaky escapade to air………here’s more underachiever “filla”.

Maybe not so much of an”underachiever” as much as the builder really under-delivering the goods on what the customer asked for.
This one’s a 455 Pontiac.

A shop in town has a business that works on muscle cars.
All types of mechanical work, and disassembly/reassembly of whole cars.

Customer brings in a 74 T/A that’s has a 455 in it.
Supposedly a real SD car, but the SD engine is long gone.
He’s going to have the body done and wants a hot rod type motor done for it.
Owner makes arrangements with the engine shop for the build and is very clear about wanting “500hp”.
Everyone is theoretically on the same page, 500hp.

Some time goes by, the builder contacts the muscle car shop about the heads being cracked.
The shop says, just get new heads, he wants 500hp.

The builder says, no no, I have some cores here we can use.

More time goes by, one of the owners of the shop is up at the builders place to buy some race gas, and the 455 happens to be on the dyno.
They have already made some pulls, and there is a sheet sitting on the desk.
The shop owner says something like, “I hope you’re not anywhere near done yet…..cuz the car owner wants way more that that”.
He is assured all is good, and after they get done with it, it’ll be great.

A little more time goes by, and the engine is delivered to the shop…….with one dyno sheet.
I don’t recall the TQ, but the hp was in the 340’s.

At this point I get a call.
“Hey, we got that motor back and it’s nowhere near 500hp”.
I told them to bring over the build specs, parts list, and dyno sheet.
Basically………what they got is what was built.
A rather stock, low CR 455, with unported late model heads(the number on them were noted in a Pontiac engine build book as “don’t use these”), a small cam, a std Performer, and a 670 Street avenger carb.

They wanted an estimate to upgrade it to 500hp.
My response was…..it needs everything changed.

The rework estimate was about what the original build cost…..maybe it was even a bit more.

One stipulation on me taking it on was that I would dyno it as-is before I did anything else.
The paperwork that came with the engine only included one sheet.
Part of why I ran it first was so that there couldn’t be some mystery sheet produced down the road that happened to be better than the sheet that came with the motor.
I’ll test it, then I’ll know.

On the dyno I used it was like 315hp.
But not only that……..it didn’t run well.
The thing surged during the pulls and had the A/F ratio at wot in the 15’s-16’s.
I put my dyno mule 850dp on it, which ran 100% better but only picked up like 8hp.

That was my starting point.
That's crazy to miss the mark by that much, how could that be possible even with a limited knowledge of performance engines.
 
I have to remain silent, although the Chief was running mid 8's in his 383 powered Bantam in the early 2000's. lol
 
Headers used on the dyno?
Any idea what size?

Let’s see a sheet.

I realize for your combo, the cam requirement is going to call for something pretty small.

But I feel cams like that generally don’t produce power curves that look impressive on a dyno sheet.
Here is a copy of the dyno sheet for the best run with the Holley

IMG_20240606_185301971.jpg
 
I could be wrong(or the TV show) that I watched. But I think they said those SD455 didn't even put out 300hp stock??
While we’re all waiting for “episode 3” of Nicks old weaky escapade to air………here’s more underachiever “filla”.

Maybe not so much of an”underachiever” as much as the builder really under-delivering the goods on what the customer asked for.
This one’s a 455 Pontiac.

A shop in town has a business that works on muscle cars.
All types of mechanical work, and disassembly/reassembly of whole cars.

Customer brings in a 74 T/A that’s has a 455 in it.
Supposedly a real SD car, but the SD engine is long gone.
He’s going to have the body done and wants a hot rod type motor done for it.
Owner makes arrangements with the engine shop for the build and is very clear about wanting “500hp”.
Everyone is theoretically on the same page, 500hp.

Some time goes by, the builder contacts the muscle car shop about the heads being cracked.
The shop says, just get new heads, he wants 500hp.

The builder says, no no, I have some cores here we can use.

More time goes by, one of the owners of the shop is up at the builders place to buy some race gas, and the 455 happens to be on the dyno.
They have already made some pulls, and there is a sheet sitting on the desk.
The shop owner says something like, “I hope you’re not anywhere near done yet…..cuz the car owner wants way more that that”.
He is assured all is good, and after they get done with it, it’ll be great.

A little more time goes by, and the engine is delivered to the shop…….with one dyno sheet.
I don’t recall the TQ, but the hp was in the 340’s.

At this point I get a call.
“Hey, we got that motor back and it’s nowhere near 500hp”.
I told them to bring over the build specs, parts list, and dyno sheet.
Basically………what they got is what was built.
A rather stock, low CR 455, with unported late model heads(the number on them were noted in a Pontiac engine build book as “don’t use these”), a small cam, a std Performer, and a 670 Street avenger carb.

They wanted an estimate to upgrade it to 500hp.
My response was…..it needs everything changed.

The rework estimate was about what the original build cost…..maybe it was even a bit more.

One stipulation on me taking it on was that I would dyno it as-is before I did anything else.
The paperwork that came with the engine only included one sheet.
Part of why I ran it first was so that there couldn’t be some mystery sheet produced down the road that happened to be better than the sheet that came with the motor.
I’ll test it, then I’ll know.

On the dyno I used it was like 315hp.
But not only that……..it didn’t run well.
The thing surged during the pulls and had the A/F ratio at wot in the 15’s-16’s.
I put my dyno mule 850dp on it, which ran 100% better but only picked up like 8hp.

That was my starting point.
 
I thought it was like 285 or something like that, still quite unimpressive imo.
OK, had to look it up. Hemmings says 290 hp for 73-74 SD 455, Car and Driver says 310 for the 73 version. (They reported a quarter mile time of 13.75 at just under 104.) Without doing more research, I'm thinking 73s had 310 and 74s had 290.

Still decent for 8.4 to one compression. If I remember correctly, a 440 6 pack was rated 305 net hp with 10 to one CR.
 
Dang those are low #'s for bb's lol, but like you said smog era.
OK, had to look it up. Hemmings says 290 hp for 73-74 SD 455, Car and Driver says 310 for the 73 version. (They reported a quarter mile time of 13.75 at just under 104.) Without doing more research, I'm thinking 73s had 310 and 74s had 290.

Still decent for 8.4 to one compression. If I remember correctly, a 440 6 pack was rated 305 net hp with 10 to one CR.
 
1970 455 HO 370 HP and 500 ft lbs torque.
 
I could be wrong(or the TV show) that I watched. But I think they said those SD455 didn't even put out 300hp stock??
That's right. They were a smog era engine. The FIRST year for the SD455 was 1973. What did they expect? LOL
 
(They reported a quarter mile time of 13.75 at just under 104.)
Not disagreeing with you, but I don't believe that any farther than I could throw an SD455 Trans AM. Those cars were big and heavy pigs with crappy tires and not built for drag racing. So they were quicker than a 69 1/2 A12 440 six pack 4 speed car? Yeah. My big old butt they were. lol
 
The SD 455 was hampered by a 8.4:1 CR....& cam. Pontiac wanted to run the Ram Air 4 cam which was pretty stout for a production car, 231/240 @ 050 & had over .500" valve lift....but failed 1973 emissions. A milder cam was installed...& lost power. I believe it did 13s with the RA4 cam, showroom stock, the only production 'muscle' car to do so in 1973-4.
In production testing, the tq/hp went from 477/404 to 524/451 with headers & a tight 105 LSA RA 4 cam. With a Holley carb replacing the QJ it lost 13 ftlbs @ gained 12 hp, 511/463.

When the CR was increased to 11.9:1, the numbers were 574/530.
 
I believe it did 13s with the RA4 cam, showroom stock, the only production 'muscle' car to do so in 1973-4.
Horse feathers. Not without slicks, not without something better than the bullcrappy 3.42 gear, not without headers and even then maybe not. What you been smokin? Those cars weighed 3750 pounds and had 8.5:1 compression AT BEST. No way Jose.
 
Horse feathers. Not without slicks, not without something better than the bullcrappy 3.42 gear, not without headers and even then maybe not. What you been smokin? Those cars weighed 3750 pounds and had 8.5:1 compression AT BEST. No way Jose.
Several road test were in the 13s the trap speed is telling all were 103 104 mph
They had F-60-15 about the best tires of the era
the 69 440 dart time/mph was about the same 13.71@105 mph 310 net is more hp then a 375hp 440
I saw one do it at the strip no headers could not even see the engine chitless air cleaner and all the smog
It is also number 32 on the 50 fastest list@ [email protected] F60s helped it just as it helped the t/a and aar cuda turn the best stock 340 times they weighed more then an A body
Oh and the 69 road runner 440 6pack is number 11 on the 50 fastest list list [email protected]
 
Also remember that the SD455 was rated in net horsepower, not gross. Its 290 rating was probably more like 375 or more with the old ratings.
 
The SD 455 T/A was a fast car relative to any factory performance offerings from the 60s and 70s in spite of its low CR.

The Ronnie Sox 12.91 was a stacked car/engine with a stacked driver. I would consider it more of a Chrysler sponsored promotional event. It did however shed light on its potential without a whole lot of effort.
 
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