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Old 06-23-2013, 08:54 PM
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Pontiac 455 build (on a budget)

Figured I'd start a build thread and throw in some pictures..

Picked up a 455 short block this morning for 75 bucks. Casting 9799140 drilled for 4 bolt mains, but currently two. Has been sitting for about 10 years in the yard so it needs some love, but I think it will be usable.

Plan is to swap it into my '76 Grand Prix. It currently has the crappy year 400, with 6x-8 heads, and about 107k miles. Performance is pretty poor for a car with that sized engine, and the rear end gearing seems pretty tall too.

I've done a few weeks of reading and learned a few things... don't use '76 400, 6x-8 are ok heads but compression is in the 7s. However putting them on a 455 gives me ~9:1, which is perfect. Stock intake is probably fine. Headers are a pain as far as fit, but ram air manifolds are pretty good.

I am on a budget. And I mean a small budget. I don't *need* a rebuild as the current engine appears to be in excellent condition, but I am interested in the project and would love to have more power on the freeway.

I am tearing the engine apart, taking it to the local machine shop for cleaning and checking, and go from there. I would like to reuse crank, mains, possibly rods. I will take the 6x-8 heads off my 400, a roller cam, and better springs (xe262 is the cam I believe I will use?), my stock intake, quadrajet, and a set of ram air manifolds.

Guesstimating 340hp/450tq, hopefully that provides the power I am looking for. I've seen some people run the combo and they seem very pleased. I will not be drag racing (lets be real - this is a boat not a race car) and am looking for low end grunt / cruising power.

Estimating couple months to completion, depending on time + finances

Some pictures..






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Old 06-24-2013, 02:22 AM
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balance and blue print the engine to the best of your ability.9:1 CR is great. A good carb and free flow exhaust. Then drive the wheels off it.You might be surprised how well it can perform,
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Old 06-24-2013, 06:54 AM
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I did a budget 455 using 6X-4 heads, it ran very good in my all-steel '81 Camaro. I used a Performer intake w/a 4777 Holley (the RPM intakes for Pontiac weren't out yet) w/a divided wooden spacer about 1-1/2" tall, inexpensive Hedman headers, 3" 40 series Flowmasters w/an H pipe. Nothing fancy- stock valve size but the heads were ported to about 175cc on the intake side. Sounds small, but the comparison to a Chevy head cannot be made by volume alone.

Stock crank and rods. Used a set of TRW forged flattop pistons I got in a trade. I didn't opt to balance it dynamically; I did static balance the rods after having them resized. Used ARP bolts, Clevite 77 bearings, Fel pro gaskets. Didn't use a windage tray- but it's a good thing to use and you have one already. Used a modified Cadillac rear main seal to replace the rope OEM rear seal, there are rubber 2-piece seals now that are made for the 455.

For the cam, I couldn't find a dual pattern that suited my budget so I went w/a hydraulic flat tappet cam that had 236 degrees @ 0.050" lift and 0.490" lift on a 108 LSA, installed straight up (cam was ground w/4 degrees of advance already). I used Rhodes lifters on the intakes only. 1.5:1 stamped steel rockers.

This deal ran mid 12's w/3.31 rear gears, TH400 shifted at 4900-5000 rpm. I ran it w/a 3.08 10-bolt that I had before the 12-bolt and it went 13 flat- w/the shifter in Drive! Now this wasn't gonna throw fear into many BBCs, but for what it was- and what I had in it- it was a fun, reliable, daily driver that I put a ton of HARD miles on w/o a whimper.

Don't worry about the 4-bolt caps unless you plan on using aftermarket heads and rods. If you use the stock rods, they need ARP bolts, resized and magged. Nowadays aftermarket rods are cheap so you might go that route just for peace of mind.
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Old 06-24-2013, 08:42 AM
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Wasn't 6x-4 too small of cc on 455? My understanding was its great for 400 and below, unless you ran high octane?

Thanks for the blueprint suggestion, I didn't think it would be needed in this low rpm motor
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Old 06-24-2013, 09:02 AM
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spawn-x,

There's a TON of "information" on "the net" about Pontiacs, no less than 1/2 of which is "myth and superstition".

From looking at the pics, that block will NEED boring (the rust in the cylinders). DO NOT waste a single dime on the original cast rods. Discard them immediately. The RPM 5140 forging is a good "replacement" rod at a reasonable price, about the same as paying the labor to have the cast rods resized and new bolts. NOTHING you can do will make the cast rod "good".

6X heads are popular because the chambers are about right for various applications. In this case, the -8 (about 98 CCs) is called for. Be sure to have the 1.77" exhaust valves installed. For this application, I see no need for port work.

XE262H is a flat-tappet hydraulic cam, not a roller. It's okay, but the larger cubes "like" a little bigger grind. For your application, I would recommend 275DEH (Comp). Avoid hydraulic rollers, as the retro-fit lifters have proven to be problematic. NOT a Chevy... (:-

Headers on Pontiacs are as easy as ANY car I've ever installed them on. Reports of difficulty come from those with a limited experience base. They should try a '69 Mustang with a 428 in it... Or a '70 'Cuda 440 car... But for the GP, I think the HO exhaust manifolds are the way to go. Use the '68-'72 GTO version (it will fit).

A STOCK 455 makes nearly 500 lb. ft. A mildly upgraded one will easily break 500. 375 HP is also easy enough. This should make that GP get some respect...

Jim
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Old 06-24-2013, 09:53 AM
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Mr P Body you are correct there has been a ton of "information", some contradicts others, so I've tried to read it all.

I have seen your name in many threads, and appreciate you posting.

Point taken on the cam and rods. What would be a good piston to use?
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Old 06-24-2013, 10:34 AM
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Quote:
Originally Posted by spawn_x View Post
Wasn't 6x-4 too small of cc on 455? My understanding was its great for 400 and below, unless you ran high octane?
No, not for my combo. My heads measured 95cc, my compression was 9.5:1 on the nose.

You have to measure the chambers to know what you have. I have seen 6X-8 heads that were well over 100cc before milling.

Edit: In case it wasn't obvious, my engine wasn't optimized by any means: Carb was 650 cfm. Header diameter was too small. Intake could have been better. The cam was a single pattern crutched w/Rhodes on the intakes. Not balanced. Stock rods. Get the idea? I mean, you did say budget, right? Not saying do what I did. I simply related what I did and the results.

Last edited by cobalt327; 06-24-2013 at 10:51 AM.
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Old 06-24-2013, 10:41 AM
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Pontiac info/sites
Pontiac engine info
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Old 06-24-2013, 12:50 PM
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Speed Pro L2359F-xxx is the piston of choice here. Icon also has the FHR technology version at a reasonable price. Both are tough forgings. Good stuff. The Speed Pro is a "replacement" piston, so clearance is "tight" (compared to other forgings) and the ring pack is stock.

MANY 455 blocks (and 400s of the same era) were drilled for 4-bolt caps but didn't have them installed. No need at this level.

Jim
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Old 06-24-2013, 03:05 PM
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Quote:
Originally Posted by Mr. P-Body View Post
Avoid hydraulic rollers, as the retro-fit lifters have proven to be problematic. NOT a Chevy... (:-
Really????? Nobody makes a roller that will work?????
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Old 06-25-2013, 11:06 AM
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Define "works"...

The Comp, Crane and Crower hyd roller lifters for the Pontiac are very "tall" and have a riveted link bar. They're very heavy and known to "collapse". We've seen a couple just come apart, too. They just haven't proven to be reliable long-term. We recommend solid rollers when appropriate. In this case, though, hydraulic "flat" is the way to go.

Jim
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Old 06-25-2013, 11:38 AM
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cams

Quote:
Originally Posted by Mr. P-Body View Post
Define "works"...

The Comp, Crane and Crower hyd roller lifters for the Pontiac are very "tall" and have a riveted link bar. They're very heavy and known to "collapse". We've seen a couple just come apart, too. They just haven't proven to be reliable long-term. We recommend solid rollers when appropriate. In this case, though, hydraulic "flat" is the way to go.

Jim
whats wrong with using small solid roller cams?
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Old 06-25-2013, 11:39 AM
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Quote:
Originally Posted by Mr. P-Body View Post
Define "works"...

The Comp, Crane and Crower hyd roller lifters for the Pontiac are very "tall" and have a riveted link bar. They're very heavy and known to "collapse". We've seen a couple just come apart, too. They just haven't proven to be reliable long-term. We recommend solid rollers when appropriate. In this case, though, hydraulic "flat" is the way to go.

Jim
OK then.
Spawn_x, here's a flat tappet tutorial that will help....
http://www.crankshaftcoalition.com/w...ips_and_tricks
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Old 06-26-2013, 12:05 AM
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What a pain.. bolt holding timing cover + water pump snapped because it was stuck inside the cover, still have to finish getting the cover off

Started to remove the crank and put some tiny damage onto the crank from trying to beat the rods/pistons out didn't do a lot of thinking on that one, just started beating with a hammer and a long extension, and realized it was touching the crank

I'll snap a picture in the morning, surely will get mixed feedback. I think if I clean it up right with fine grit and wd40, it'll be fine, or maybe polish at machine shop

Too late for advice I guess, since damage is done. Did not think the rust would be this problematic

Last edited by spawn_x; 06-26-2013 at 12:12 AM.
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Old 06-26-2013, 12:12 AM
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clean bores before removing pistons? use a ridge reamer?Its also possible to remove the pistons out of the bottom on some engines,royal P.I.T.A.
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