[RossGN]

I may have an opportunity to do a build I've had in the back of my head for several years. The goal would be to build a standard 455 to stock SD455 performance and appearance. Without the expensive SD455 heads, manifolds and intake, what would be a formula for the build. The project goal would be to create a 1974 GTO that would appear and perform as if GM had offered the car.

Would appreciate any input on the engine build. Once again, it's a budget build, but I can take care of the machining and assembly at no cost. Would like to keep the out of pocket less than $5k including the donor engine. Any tips would be appreciated engine-wise or anything about the build.

[steve25]

Well to at least match the performance of the SD455 heads ( and the looks of the round exh ports ) your going to have to go with a aftermarket round port head.

You will then need reproduction round port exh manifolds.

Then you will need a standard iron Qjet intake that has been ported to at least match the 240 intake cfm of the stock cast # 16 SD455 heads.

[Dragncar]

Its not hard to get 400 HP out of a 455. But doing it for 5K if you don't already have the engine will be tough.
The cam required to get SD 455 power out of D ports will be more lumpy than if you had real SD heads. Especially if you kept the CR stock.
Best way to get it would be a pair of those stealth E heads. You could do it with far less cam. Then your 5K goes out the window.
And doing it with manifolds makes it harder.

[John Milner]

Just a mild 455 will make a 74 GTO a lot of fun to drive. Something like a stock rebuild on a 455 with 6X4 heads and a Summit 2802 style cam will make it run good and probably run nearly as good as an SD engine. Run a cast iron intake, quadrajet and some long branch manifolds and it will look like it grew up in there.

I went with a 428, 614 round ports, stock aluminum intake and a q-jet on my 74 GTO and it looks like it grew up in there. Pontiac really should have put a round port engine in the 74 GTO.

[JLMounce]

I'm with the others on this. The problem that I see is not being able to create similar performance, but the need to look like an SD455. That means you need actual SD heads, or aftermarket round ports, and you don't have the engine yet.

I'm not sure what pricing for blocks look like in TX, but here in Colorado a rebuildable true 455 asks around $1200.00. Mind you that's just the block, often not including a rotating assembly.

Real #16 SD455 heads are going to be $5000-$7000. Your budget is already gone right there. A set of Edelbrock performer rpm heads are going to land around $3000.00. If you go in that direction, that gives you somewhere around $1000.00 to handle the rest of the engine. The budget unfortunately isn't sufficient for the goal.

If it doesn't have to look like an SD455 and it just needs to be fun, John's recipe above would be great. Do some minor hand porting on the 6x4's, make sure the qjet is tuned well and you're going to have a lot of fun with that combination, while looking like it was meant to be there.

[Maxthe222]

Originally Posted by RossGN

The goal would be to build a standard 455 to stock SD455 performance and appearance. Without the expensive SD455 heads, manifolds and intake, what would be a formula for the build.

So... just a regular Pontiac 455 with a valve cover sticker?

At that point, you can just source any Pontiac 455, complete a mild or reasonable build to achieve ~310hp, and all you really need is the sticker? It won't look any closer to a SD engine if you don't have the heads or quadrajet etc, there's nothing that will look any different externally aside from the casting numbers specific to the SD.

[67Lemons]

I think if you used RA manifolds you can’t see the difference between round port and D port heads correct? It’s just casting numbers at that point and most car show folks won’t know the difference.

[nas t eh]

Aren’t the Speedmaster heads round port? Then some Ram Air repo manifolds, Edlebrock performer rpm intake. Grind off all the aftermarket names and paint it late Pontiac blue. Add the sticker on the valve covers and be happy. But it will not be <$5000 unless you already had a rebuilt 455 short block.

[steve25]

If you already have a block and a crank and like you posted do not have to pay for machining or assy then 5K should get you done as long as you use aftermarket round port heads like I posted back in reply # 2.

If you pick up a used set of heads and a rebuildable 400 block that cost saving might allow you to get a new 4.210” crank which will then allow your needed end result.

[RossGN]

Possibly another option....scrap the budget, are there any complete SD455 engines out there for sale? I know I have seen a few over the years since I had mine, but assumed they've all been utilized in some form or fashion?

[JLMounce]

If you're scrapping the budget, you might consider waiting on a set of DCI's new heads. They aren't available for sale yet, but I think the project is starting to get close.

You'll make all the power you want with those things on either a true 455 or a stroked 400 and the round port versions are designed to look as close to original as they could get an aluminum casting.

[mgarblik]

"Budget" and SD-455 just don't go together, unfortunately. I recently put one together and I can attest to the pain of having to buy some specific SD-455 parts. Couple simple examples would be the thousands and thousands for a real SD-455 Q-jet, $600.00 for a correct SD-455 PCV system, the list is endless. Now, achieving around 400 HP from a regular 455 is pretty easy. My real SD-455 made 407 HP at the flywheel which a regular 455 can duplicate with a flat tappet cam, iron intake, Q-jet and D port heads. If you want the round port look, of course aluminum heads are an option. Your 5K budget is pretty restrictive but there are used Edelbrock, and Speedmaster heads out there. The dead giveaway on those heads is the angled spark plugs vs straight on 455-HO and SD-455 heads. If you really, really wanted the looks, Edelbrock or Speedmaster heads could be welded up and re-tapped for straight plugs. Probably give up 5-8 HP with the conversion and lighten your wallet by $1000.00 or so. But it can be done.

[sdbob]

I priced a set of Kauffman round ports early last year very reasonable ready to bolt on. If I remember price then was about $2500.00.

[67Lemons]

Originally Posted by sdbob

I priced a set of Kauffman round ports early last year very reasonable ready to bolt on. If I remember price then was about $2500.00.

They’ve gone up a little but still a great value vs Edelbrock IMO

[b-man]

SD 455 cars off the showroom floor would run mid-13s which was quite respectable at the time for a low-compression smog engine.

My daily driver low-compression D-port 455 with untouched ports and HO exhaust manifolds easily ran high-13s with a TH400 and a 2.56 geared open rear end. SD cars had either 3.42 or 3.08 gears if I’m not mistaken, and a posi differential standard like all Trans Ams.

https://forums.maxperformanceinc.com...22&postcount=4

Getting SD-like performance out of a D-port 455 is like falling off a log.

[sdbob]

My 74 new in 74 ran 14.17 at 99mph spinning. Still stock as delivered. Non air cars got 3.42 St. either 4spd or auto.. Air cars got 3.08. Air from order form was not available with 4spd. Now there may be cars that are different. I still have all the original order forms.

[P@blo]

Originally Posted by JLMounce

If you're scrapping the budget, you might consider waiting on a set of DCI's new heads. They aren't available for sale yet, but I think the project is starting to get close.

You'll make all the power you want with those things on either a true 455 or a stroked 400 and the round port versions are designed to look as close to original as they could get an aluminum casting.

JL, any detals on the new DCI head offerings? There has been talk of cast steel heads for some time but they never came to be.

[Skip Fix]

I thought I posted this before. I have seen E heads name ground off and 6X welded on. And awhile back someone had milled the ends of E heads to look stock. Angle plugs only a hard core Pontiac guy would know that and I've even seen a set of iron heads welded and redrilled for angle plugs.
I sold an SD intake a few years back so those heavy ass iron things are around.
I sold an extra SR 73 SD replacement Qjet NIB to Lloyd Couilson a few years before he passed away. Best out of the box Q jet I have found!

[poncho-mike]

I've run a number of round port engines over the years in varying levels of compression ratio and camshaft specs. Here is some info you might find useful.

I think the best combo was a 455 +.030 with a 428 crank and pistons. It was stock compression ratio, and the cam was an old HO Specialties HC02 (if my memory is correct). The cam was pretty similar to the ram IV cam. I was running headers, a 455HO intake, and I believe the carb was off a 1971 455HO. It was in a 1970 Trans Am w/ 4-spd no a/c and 3.73 gears.

When I rebuilt my 1974 SD455 4-spd T/A engine, I used the HC62 cam, which was the same grind as the SD455 cam, but with the SD distributor gear. I kept it stock compression, stock intake, exhaust manifolds, and 3.42 rear end. I bought one of the carb kits from HO Specialties. The car was fast, but not as fast as the 428 with Ram IV top end. I think that mainly had to do with the huge difference in compression ratio and the headers.

If you want to stick with stock CR, I would consider getting a set of 455HO heads (probably 191s) and grinding the numbers off. If you want power, you need to go with smaller chamber heads.

I have a really solid 1970 Firebird body I squirreled away about 40 years ago. I was thinking about doing a mild street build on it. I would probably go with the 428 +.060 and Ram IV heads, but try to cut the compression down to low to mid 9's. I have all the parts to do a SD built, but I'm not sure it's worth putting real SD stuff into a base Firebird.

[android 211]

Several years ago High Performance Pontiac ran an article about a guy who had two Firebirds. He had a mint Super Duty Trans Am and he then acquired his mother in laws 76 Firebird which had a 350 2 bbl. He couldn't regularly drive the SD TA so he built a 455 for the 76 'bird. Rochester carb, iron intake, 6X heads on a 455 with the Summit 2802 cam. I don't recall the exhaust. Maybe RA manifolds. He said it was more powerful than the SD. Some forged flattop pistons and forged rods. Baffled oil pan. I would go with the newly re available RA manifolds with the 2.5" outlet. I had a TA with headers and they contacted the ground too many times.