Information Exchange for Building Street Supercharged 455

I would like to exchange information and tips from knowledgeable people related to my current project of building a supercharged 455 for street/cruise (not racing). The 1970 Stage 1 block is now starting to be assembled. About $7800 in parts have been obtained to date, mostly from TA, Summit and Hampton Blowers. It has been bored to 470 cubic inches and will be an 8:71 blower application with 8.1/1 TA forged pistons and a TA supercharger cam. Ignition will be full MSD (programmable). Fuel will be two Edelbrock 750s. Two photos of the current assembly status are attached. It will replace the tired old stock 5-liter engine in my fully restored 84 Park Avenue. I will have a number of practical questions in this thread on engine assembly, installation in an 84 Park avenue, transmission mating and on engine tuning. Any info and suggestions in any of these areas would be appreciated. This is my first supercharged engine, so I am learning.
Dave Harrington
Troy, Michigan


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Hello Bob: I'm building it jointly with Tim Parkham of Marine City, MI. He is a fellow retiree of GM Engineering and rebuilt dyno engines for 35 years before he retired. He has some nice machinery in his engine shop, and it's being assembled out there. Yes, I have Steven Dove's book, and we put in some of his suggestions (and are still putting some of them in).

I have a T400 trans, but the target car already has a freshly rebuilt 200-4R trans. I could switch to the T400, but it would be more work. I'm thinking that the 200 trans is a "throwaway", and that it would make the engine installation project MUCH easier, with no modifications required to crossmember, spline, driveshaft or shift linkage. If the engine trashes it at some point it would be no big deal. I see conflicting info on the internet about whether the T400 (3-speed) is really stronger than the 200. There are even some people upgrading from the T400 to the 200! I also read conflicting info about whether the 455 engine will "bolt right in" to the 1984 Buick Park Avenue, which comes stock with a 307 V-8. Some imply "yes" and some say "no". I guess I'll find out later this summer.
Dave Harrington
I also read conflicting info about whether the 455 engine will "bolt right in" to the 1984 Buick Park Avenue, which comes stock with a 307 V-8.

the 307 is ( as i'm sure you know ) an Oldsmobile design. so most of your engine wiring harness is going to be backwards from what the Buick wants.

i would also expect new frame pads, engine mounts and fan shroud.

it should bolt up to the 200r4, though.

There are even some people upgrading from the T400 to the 200!

i think most of those "upgrades" are to get the OD gear and extra short 1st. and, of course, the lesser rotating mass doesn't hurt performance at all.

it is certainly true that the 200s got a lot more durable after hot rodders started looking at ways to make them stand up to more power.

Yes, I have Steven Dove's book

there's nothing wrong with Dove's book, but it's a little outdated. there are several good on line articles and Tri-Shield has an excellent photo FAQ on it.

since you're already dealing with TA, they should also be able to answer any specific questions you might have.
The 200 trans would be great if you have it beefed up a little. It also depends on your rear gear ratio (the rear will also need to be stronger then stock).

TA should have the frame pads and headers to drop the 455 in your car.

You may want to increase the compression depending on the cam. You will have poor performance when not in boost if your DCR falls below 7.5:1. There is a good article on it and a calculator here: The build for my supercharged Cobra uses a 9.75:1 static compression to give me a 7.75:1 DCR with the lagrer cams. Stock it used a 8.5:1 static compression that produced a 7.75:1 DCR with smaller cams.

The same goes for my turbocharged WRX. It will use 9.3:1 static compression in the new build with larger cams. It had 8.2:1 in stock form, but the DCR will remain the same with the new cams and higher static compression ratio.
To Bob and Frankenbuick: June 2, 2010

Thanks for the input and tips. This is exactly what I had in mine when I made the Post. I'll have lots of small questions as I proceed with assembly and installation over the summer of 2010. Such input will save me time in tracking down answers.

Bob; I read in one place on the internet that you need new 455 engine mounts to put the 455 in my car, and in another that the stock 307 mounts will work directly. I bought new mounts for both from Rock Auto because they were so cheap ($6 each) compared to the other costs of the project, so I am ready for that I believe. I don't plan to do anything to my newly rebuilt 200 trans, just bolt the 455 to it and see where the engine sets. The 455 doesn't appear to be much larger physically than the 307 V-8, plus the 84 Park Avenue is the last of the big old rear-wheel-drive boats, with a huge engine compartment. I won't have the 8:71 blower kit for another three weeks, but I'll likely have to cut the hood. I'd like to avoid it, but probably can't. That comes later immediate concern is the engine assembly.

Frankenbuick: I reviewed the DCR info that you flagged. Very interesting, but for a supercharged engine it would seem that the boost level and the detonation tendency are the main factors. I only chose 8.1: 1 (for the static CR) when I got the pistons because that is what Don Hampton of Hampton Blowers recommended for a street machine running gasoline. I got steel multilayer head gaskets of 0.051 thickness specifically to yield 8.1 to 1.

Here are two simple questions for starters that you can waste hours chasing down ... I have the firing order, but which side (drivers front or passenger front) is the number #1 cylinder on a 455? I see different indications on the internet. It looks like the Nailhead convention is different from the 350, etc. I have the MSD ignition components, and am starting to wire them, but I want to make sure I'm using the correct cylinder number convention for the 455. Also, my 84 Buick has a fuel return line to the tank. For the new TA performance pump should I hook up this return line or block it off?

Dave Harrington; Troy, MI
driver side front is number 1 cylinder.

Turbo 400 built good will be more bullet proof for the power you might put out. We have broke 2 200 4R's in the grand national with the turbo 6. One broke the front pump. New one built is on the way to us now and hopefully it will hold together. They are very expensive. 400's are cheap in comparison.

Good luck.
It looks like the Nailhead convention is different from the 350, etc.

it is. and for the same reason that the Pontiac convention is different than Buick, Chevy, Olds, etc.

in a V engine in which crank throws are shared between more than one cylinder, one cylinder head MUST be further forward ( towards the harmonic balancer ) than the other. you can't position them directly across from each other because there physically wouldn't be space for the rods to fit on the crank throw.

in Pontiacs and Nails, the passenger side cylinder bank is the one shifted forward. in pretty much all the rest of GM's engine designs, it's the driver's side bank which is forward.

the #1 cylinder is numbered such because it is the cylinder furthest towards the front of the car.

the block diagrams in the firing order reference sheet don't reflect this, but it's easy enough to see when you're looking at the physical engine ... once you know to look for it.

The 455 doesn't appear to be much larger physically than the 307 V-8

the Olds 307 shares deck height with the Olds 350. and it shares length, front to back, with the Olds 455. so it's not a very "small", small block.

the Buick 455 is the shortest stroke, biggest bore of the GM 7.5L engines. in fact, the stroke on the Buick 455 is only .050" longer than the stroke on the Buick 350. needless to say, the uninformed often confuse a Buick tall deck small block ( 350, 340 ) for a Buick 455.

and in another that the stock 307 mounts will work directly.

doubt it. if you had a Buick 231v6 and you wanted to swap in a Buick 350, yeah, that's a direct swap. because those engines are from the same design family.

the Buick 231 is a Buick 300v8 ( 1964-67 ) with two cylinders knocked off and bored out to the cylinder dimensions of the Buick 350.

and yes, long, long ago, there WAS a Buick 225v6. 300 * .75 == 225
Thanks to Bob, Frankenbuick and Carmantx for good input. Here is the engine build status as of June 4 ... Two photos are attached below ...455 block bored to 470, 8.1 to 1 TA pistons and moly rings filed and installed, block & heads milled 0.005 inch, crank, rods & bearings installed. grooved cam bearings installed, new SS Stage 1 valves and springs installed, new freeze plug set installed. Ready to install TA-288-HH-14 cam and heads using multi-layer steel gaskets. Don Hampton of Hampton Blowers said yesterday that the 455 Buick blower intake is ready to be shipped. The 8:71 blower itself is a new one, and is being assembled (another 15-18 days).

ANOTHER ROUND OF QUESTIONS FOR THE EXPERTS: After some discussion, we did not put seals on the exhaust valves. It didn't come with any originally, and we could see no great reason to add them. Do you guys concur? We have the new TA performance fuel pump in hand (with return line machined). Should we use this tank return port or block it off? I have the MSD #8217 billet distributor in hand, along with the MSD low-impedance spark plug wires and E3-45 plugs. We are planning to get the MSD-6AL-2 Programmable ignition module. Any comments on this choice before we do it?

Intent of this engine: to be a cruise/show car application (no racing). Therefore it will have all of the accessories (power steering, alternator, heater, AC, fan) and will need all of the pulleys and brackets. My 1970 455 block did not come with any of that. I don't want to spend more big bucks on a full serpentine belt system, but will likely go with just chromed stock pulleys and belts. Anyone know a good source for such pulleys and brackets, or for a rebuilt or chromed A6 AC compressor? Final question in this set ... We have a flex plate from the engine for a T400 trans, but also will have the flex plate from the intended 200-4R trans. Which should I use? Are they identical? One is 1970 vintage and the other is 1984 vintage.
Dave Harrington
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I see several issues with your build. I calculated your DCR at 6.0:1 with 8.1:1 static compression and the intake L/C at 110* (4* advanced). I think this will make for poor cruising and drivability (in contrast to your goals).

I would also worry that the thickness of the head gasket could cause far more detonation then any possible by higher compression. Your quench distance should be .060" at most (best at .035"). I think your pistons may still be .050 down the hole with gasket of .050. This makes for a .100" quench distance. This will increase detonation tremdously.

I would also be concerned over moly rings in a SC application. They are prone to detonation damage and the molly can melt out of the ring under the extreme pressure and heat caused by supercharging. Most of the Turbo and SC guys are going with a chrome top ring and cast second ring. I know it would mean a different hone and new rings, but ..........................

Also, you need a 455 flexplate. These are extermally balanced engines, and the flexplate needs to be balanced to the rest of the rotating assembly. Did you balance your rotating assembly? Your new pistons are not the same weight as stock. You will need to have the flexplate balanced to your pistons, rings, rods and front balancer. There are some better aftermarket flexplates that are availible and SFI rated. I would use an aftermarket front balancer that can take the stress of a SC if you do not already have one. The stock one was not built for a SC requiring up to 100 HP to drive. They were thinking alternator, PS pump and AC using 15-20 HP combined.

I am trying to help here! It may not seem like it, but my 30 years of experience with the 455, 7 years of modifying and tuning my factory SC Cobra and the last two years modifying my hybrid turbo Subaru tell me you have some issues with your engine. It could use a little attention now rater then a lot later!
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To Frankenbuick: June 12, 2010

Sorry to take a week off before replying ... family activities in June (two high school graduations) took some time. Your comments are good, of course, but I perhaps waited a little too long to post my original request for info. I've attached a photo showing that the short block and heads have been fully assembled. What you suggest would require a full tear down and rebuild, with new parts purchased. My fault, not yours! I should have posted my original request for info at least a month earlier. Some of your guidelines look difficult to achieve. I measured the piston as sitting down 0.054 inch below the deck. I don't see how it is would be possible to obtain a 0.060 quench height and still keep the CR near 8:1 (which all of the blower guys tell me is a good target). I needed a 0.051 head gasket thickness to keep the CR down. Your guidelines for the DCR are no doubt good ones, but I relied on discussions with the TA cam guys to come up with a cam and an 8:1 CR combination that would be compatible with a roots blower. I apologize for locking in some of the hardware such as the pistons, cam, etc, before asking for advice! I do appreciate the advice from everyone however. My needs at this stage are expert thoughts on assembly of the blower components, assembly and installation of the full complement of peripherals (such as power steering, AC, alternator, fan), and for installation of this 455 engine in my 84 Park Avenue. For example, are there any problems to be anticipated in bolting to the existing 200-4R trans using the 200-4R converter and the 455 flex plate, can I run a normal fan and shroud or will I need to convert to electric fans? Do you have to retighten the multi-layer steel head gaskets after initial engine warm up? Should I put a zinc additive in the oil? Will the headers clear the steering column? There are probably some experts out there who have done all of this, and I could benefit from your experience. Thanks. Dave Harrington
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To: Carmantx Thanks for the input on the oil. Yes, I have a lot of practical questions. Every day seems to have a new question. In some ways a street cruise engine requires more parts and aggravation than a race engine. If you want an alternator, PS, AC and fan on a supercharged engine there will be lots of pulleys on the crank, lots of interference and lots of problems to solve. I'm trying not to pour another $2k into it by avoiding a serpentine belt system and by using my perfectly good R4 AC compressor instead of buying a new A6 that went with the original 455 engine. That means a lot of bracket fabrication. I have a higher cowl scoop on my 84 Buick, but even that may not clear the carbs on top of the 8.71 blower. I'd like to make the motor set down as low as possible. Any tricks out there for that? I'm attaching a few photos of interest, showing the two cars I've restored so far ... a 1966 Chrysler New Yorker and an 84 Buick Park Avenue. Also one of my workshop and the shorty headers for the 455 engine.
Dave Harrington
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Status Update on Supercharged 455 Project

Hello to all interested forum members. Sorry to take 6 weeks off without a post, but as you will see in the status photos I have been working hard every day to complete this project. July was the main effort. The status is that the supercharged 1970 Stage 1 455 engine has been completed. I have a tight deadline which is the big "Woodward Dream Cruise" that is held in August each year in Detroit. I want to get the car running and have it in the cruise. I'll outline some of the minor difficulties (no major ones thank goodness). Two photos showing the completed engine are attached. The 8.71 blower kit was received and two Edelbrock 750 carbs and the complex throttle linkage were installed. Those difficulties will also be noted. A photo of the final setup is attached. The tired old 307 engine was removed at the PFE Racing shop near my home, and 4 weeks solid of 10-hour days were spent on cleaning and beautifying the engine compartment. Also, much time was spent on the complex 84 Buick wiring harness with a shop manual, sorting through the myriad of connectors to determine which were needed and which were not. Remember, the 84 Buick was an emission connector nightmare. The programmable MSD 6AL-2 ignition system with billet distributor was installed, and that wiring was blended with the 84 Park Avenue harness wiring. This system monitors the supercharger boost through a 2-bar map sensor and controls the spark timing to whatever curve you program. A photo of the finished engine compartment, frame, a-frames, MSD ignition system and steering linkage is attached. Two days ago the new 455 engine was dropped into the 84 Buick engine compartment for the first time. Guess what ... it fits! There were no major problems. The shorty headers clear on both sides (not by much but they clear). The engine bolts to the 200-R4 trans, thus avoiding the need for a new trans, spline, cross member and driveshaft. It looks like even the fan will just barely fit it with its 3-inch extension to clear the blower belt. The engine is not in yet ... it was taken back out to drill the marked motor mount holes in the frame. Also, the 8.71 supercharger assembly has not yet been placed on the intake manifold. That will come after the engine has been installed.

To me the main value of these forums (in addition to getting good advice) is to read about problems, potential problems and how they were solved or avoided. In the next couple of posts I will list the things that I encountered. It may save someone else some time and aggravation.
Dave Harrington
Troy, Michigan


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Supercharged 455 Installation Completed

To All Interested Members 9-30-10

The status as of the end of September is that the supercharged 1970 Stage 1 Buick 455 engine was successfully installed in the 84 Buick Park Avenue. For those members who did not see the earlier threads from 6-7 months ago, it has an 8:71 roots blower and TA cam, pistons and valves. Some photos are attached to the end of this posting. I have been driving it for a few weeks at the end of summer here in Michigan. In about 6 weeks the first snow will hit and it will be retired into the garage until next April. I had it in three car shows and it draws a lot of interest and questions. There are not too many cars running 8:71 blowers (most are 6:71s), and even fewer of those are Buick engines. Therefore it attracts a lot of interest at car shows, or anywhere for that matter, even gas stations, especially from Buick fans.
I have about 600 miles on it, so it is just about broken in. It drives fairly well, although the stock 200-4R transmission is deteriorating rapidly. This is not unexpected, as I mentioned in a much earlier post that I considered it a throwaway trans that made the original installation much easier and quicker, with a direct bolt-up being possible. It started slipping in 2nd on full throttle bursts, and is now slipping in both 2nd and 3rd. I just got off the phone with Art Carr in California and over the winter I will probably go for his top-of-the-line 22 trans (for 700 HP) with his 2800 stall converter. This will be a necessary winter project. As of right now you cannot really go to high rpm and high boost because of associted trans slippage. I could a few weeks ago however, and it was impressive for a big, heavy car. I haven't gone over 6-7 pounds of boost yet because of the trans and the fact that the engine isn't quite broken in yet. This is a preliminary report.

As for the installation, it went fairly well, and I will report some problems that had to be solved. This may help some other members out there who may be installing 455 engines, blowers or both. First, even with compact shorty headers from TA, the headers almost touch the frame on both sides. In fact, they did touch on the passenger side and had to be flattened a little to clear. Second, the passenger-side brake line touched the header and had to be run through the frame instead of over the frame. Fortunately there was a frame hole already there that was used. Third, the stock radiator and clutch fan was used at first, with a 3-inch fan extension to clear the blower belt. My advice ... don't even plan on doing this. It fit (barely) but it would not cool the engine. The engine ran at 230 degrees and would overheat at idle. Then the entire cantilevered clutch-fan mass broke off during an accel and went through the radiator. The entire system was scrapped for a double core aluminum radiator and Flex-a-Lite Extreme electric fan (3300 CFM). This works like a champ and keeps the engine at 185 degrees. The cost of the engine project so far is about $13.4 K, including the cost of the 1970 buick 455 starting engine and $1.2 K for the custom radiator and fan. I am looking at another $3k this winter to upgrade the transmission and converter. I got some good deals on services like engine and exhaust installation, and did a lot of the work myself such as cleaning, rewiring and painting the frame and engine compartment, so I doubt that this type of project could be done much cheaper.
There is a lot of performance optimization to be done over the winter and next spring. I am still running on the MSD centrifugal advance of the distributor, and have not yet programmed the MSD 6AL-2 ignition module for custom advance curves. This will also be a winter project, as the mechanical advance has to be locked out and the ignition module hooked to my computer for installing the custom advance curves. Actually they are "retard" curves from some advance position of the distributor. The Edelbrock 750 carbs have to be tuned also, in conjunction with a chassis dyno once the trans is upgraded.
If any interested member has questions, suggestions or comments, please post them.
My best regards to fellow Buick fans,
Dave Harrington
Troy, Michigan
Congratulations on getting it all together. That's a bunch of work.

I understand the frustration with the 200 4R. Tyler just broke his 3rd one in his GN and is currently building a turbo 400 for it.
Hey! I'm not sure how I missed this post before.

That's a great project - in the 20+ years I've been into the 455's, I only know of two people that run Roots blowers on these cars. And I think that one of them is a 4-71 or 6-71.

With regards to cooling, I used to have lots of cooling issues, but eventually I switched to a custom-made 5-core radiator. I went with aluminum for a while, but that developed some leaks and couldn't be repaired, so I switched back to copper-brass. However I don't have A/C so I can't say whether a 5-core would fit. I also made mine 1" wider to prevent air from going around the radiator, it all goes through the radiator now. With my 160-degree thermostat, the engine now runs too cold IMO (usually around 170).

I actually have a supercharger in my garage, that was destined for my 455. However due to financial issues (got laid off, etc.) that's been on hold for a year now... (sad face)

If/when I do get around to installing the blower, I have no intention of exceeding 6 PSI, and In intend to start around 4 PSI. For my 455, I did some rough calculations and every PSI is worth about 25HP, so 6 PSI would be 150HP over what I run now (which is already pretty darned fast). Although I have a very stout engine (block girdle, crower rods, JE pistons, etc.) boost can drive up your intake temperature quickly and this leads to detonation. If I remember correctly, a 6 PSI boost will drive up intake charge by about 100 degrees, excluding conduction/convection heating.

My problem right now is the brackets & pulley, otherwise I'd have that baby on there already! Glad to see your project is going so well.

-Bob C.
And with regards to transmissions, I love the idea of a 200-4R. However when I re-doing my drivetrain about 10-15 years ago, there was nobody at the time who could build a 200-4R to handle my kind of torque. So I went with a 2.56 12-bolt posi and a 3-speed TH400 with a switch-pitch converter. For a street-driven machine (last year I put 10k miles on my car), I consider that to be the perfect combo.

Don't worry, with a 455 I still have too much torque in 1st gear. (Granted, I don't run slicks or a racing suspension...) And there's something cool about running 1st gear to 65 MPH.

-Bob C.
To: Carmantx, bobc455, bob k. mando and others

Thanks for the comments. Yes, a 455 with an 8:71 blower is fairly uncommon. I found that out when I tried to buy the blower intake manifold. For bobc455, keep the faith on your blower installation. You didn't say if it was a 4:71 or 6:71, but the nose drive assembly, belt adjuster and belt will be about $700. Also plan on about $190 for the complex throttle linkage assembly. Add about $60 if you want a progressive linkage for two four barrels. I would recommend that. As for boost on my system, I am shooting for about 9-10 psig max at 6000 rpm. Right now I am getting about 5-6 psig at 5400. I won't go over 5400 until I get it broken in. I spoke to Don Hampton at Hampton Blowers and he will just supply a new drive pulley to me this winter to tweak up my boost a little. In defense of running 9-10 psig boost, I'm only at 8:1 CR (by careful design), and I have the MSD option of spark retard with boost, with a 2 bar MAP sensor to reduce detonation (when I program it). I inserted a couple of close-ups of the engine and blower installation that the forum members might enjoy.
Regarding the cooling discussions, there is some debate on whether to use a thermostat or take it out. I'm running a 165 degree thermostat with my aluminum radiator and electric fan because the Flex-a-Lite people recommended it. I don't drive my Park Avenue between November and April, so I'm talking about summer cooling only. (I have no heater hoses hooked up). What do you gentlemen think ... thermostat or not?
As for transmissions, it is indeed confusing, anf its my biggest current problem to be addressed in the next few months. There is much discussion on the internet regarding the relative "strengths" of the 200, 400, 700 and 460 transmissions. There seems to be much disagreement. I had a long talk with Art Carr last week and he recommends the 200-4R (he sells them all). He said the 200 can be made just as strong as the others if you build them right. I really hate the multifunction TV cable system and would like to get away from it to be able to independently set shift points, but Art says you have to have the TV cable with the 200 trans (no upgrade kit gets rid of it). I am also not an expert on lockup versus non-lockup, and the ideal stall speed to get. I would appreciate any input from forum members on this.