Hi All,Bought a 68 Firebird 400 that came with a 455 out of a 72 about 5 years back. The 455 has had recent mechanical problems and it's time for a rebuild. I had previous work done on it and it looks pretty sharp (just not running very well). However, having the 455 puts me into the "modified" class at most car shows and being a 98% stock vehicle, no way I can compete with those off the charts mods. So I'm considering replacing the 455 with a 400. Any thoughts suggestions or words of wisdom would be most appreciated.Thanks in advance,DJ
I personally could care less about trophies and am much more concerned about exceeding the coefficient of friction, therefore I would build the 455 to around 455 hp.I could then simply drive my car to the show, pop the hood, let the other Concours guys look, drool and dream about having an engine with a ton of hp that is actually fun to drive instead of driving a slow car that any old beat up Toyota Camry with 200,000 miles on it could beat just to "try" and win a trophy that you can't eat or drink and will just end up in the trash or yard sale someday when the wife gets tired of having to look at it and dust it every week.There's no replacement for displacement.
I can see the logic if the 455 is having troubles. If show points are an issue, you might want to check around and see how tough its going to be finding a '68 400 that won't also need work. An incorrect 400 engine may weigh just as heavily against the car in that next class.
if you restamp the code on the front of the block and use a set of 68 400 heads nobody will know it is a 455. you can also grind the 455 off the side of the block.you can also stroke a 400 if you like the torqe of the 455!
76 455/4spd TRANS AM69 GRAND PRIX 455/5SPD
The 455 currently has a Edelbrock Performer intake and a Holly 750 carb. If I have the 455 rebuild, what else might I consider changing / adding to bump up the horsepower? Have to admit, when putting the pedal to the metal, it's an awesome feeling!
"Have to admit, when putting the pedal to the metal, it's an awesome feeling!"Lol, Ok now you’re talkin, 1 455 engine, sold American.How much money do you have?Do you want a mild moderate or rough idle?Street only, fwy only or both types of driving?Here’s a few typical upgrades.STROKER - There might be a stroker kit.to around 490 ci.AFTERMARKET HEADS – Alum Eddy D port or RPM’s.STOCK HEADSTell us the numbers on top of the ex and on the little square just below the valve cover on the exhaust side and under the cover.Pocket port heads and back cut intake valves.Do additional porting for big hp.Get heads with 2.11 intake valves for big hp if yours don’t have them already.Install ARP screw in rocker studs."if you restamp the code on the front of the block and use a set of 68 400 heads nobody will know it is a 455. you can also grind the 455 off the side of the block."Some of these heads have high compression, screw in studs and big valves. COMPRESSIONYou want around 9.2 - 9.6 static compression for optimum performance if you use iron heads and 91 – 93 octane or E85 corn gas and up to around 9.8 if you use alum heads.You can mill stock heads to increase compression however most stock 455 heads have huge chambers and a set of good used heads needs to be purchased for around $400.00, not very expensive.DETONATION REDUCTION/COMPRESSION INCREASEYour pistons are currently around .020” below the block surface. If you mill the top of the block [$140.00] to .005” or less, it will not only increase your comp but will also reduce the potential for detonation at the same time, pretty cool.PISTONSYou can run stock TRW or Badgers if you are on a budget but KB Hyper pistons are better and forged pistons are best but a bit of overkill on a medium hp build. They should be basic flat tops.CRANK - Get your stock one ground to HP specs by a GOOD shop. They will put a large radius on the journals.CAM - Most people opt for around a Lunati 60902 or 60903 or comp XE274H for middle of the road perf.ENG BALANCE - Must be done by a good shop.CRANK DAMPER - A high perf one is recommended. I use the dual inertia ring ATI ones. They are pricey but a very critical part of a build that many people po pah.RODS - Stock with ARP bolts and maybe have them shot peened. Eagle forged rods are a nice upgrade.INTAKE - For any reasonable increase in hp you should run an eddy rpm intake.CARB - I would run an annular type. Quick fuel makes them several. Summit makes two in a 750 cfm.EXHAUST – In your case if you do not have or want headers I would run the factory RA II cast iron ones. They flow good, fit good, look cool and stock.GEARS - Common middle of the road perf gears are 3.31. You will need a posi.DISTRIBUTOR - Get a rebuilt orig HEIunit from an auto parts store then get it re-curved or buy an aftermarket one from summit.IGNITION - Buy an analog MSD box from summit. They are on sale for STUPIFYING price of only $109.00. Hide it inside the cab or trunk.STALL CONVERTER - Will likely need a 2000 - 2200.
4real what heads do you have on the 455 now? what does the cam sound like?exhaust manifolds or headers. what type of mufflers and pipe size?
76 455/4spd TRANS AM69 GRAND PRIX 455/5SPD
im4real950:The 455 currently has a Edelbrock Performer intake and a Holly 750 carb. If I have the 455 rebuild, what else might I consider changing / adding to bump up the horsepower? Have to admit, when putting the pedal to the metal, it's an awesome feeling! high compression makes torque AND a more fuel efficient engine. water/methanol injection allows 87 octane fuel to be used [you can get 87 octane gas and windshield washer fluid ANYWHERE]. as pontiac man says [with out the need to be taught james watts 5252 math equation again] horse power sells engines... torque wins races.
i did a comp cams dyno-sim for you [its the only one i have and is probably 10%-15% optimistic] using a 40 over bored 455, for 464 cubes. ported 6x heads with 2.11 x 1.77 valves. kb #347 domed cast pistons [use the light wrist pin option], rated at 12.8 to 1 compression with 71cc chamber heads, with total seal gapless top ring. i spec'd a std. flow dual plane manifold [use a hi-riser like the stealth or performer rpm] 1,000 cfm carb [or throttle body fuel injection] large tube headers with mufflers [like 2" tubes/flowmasters], gasoline fuel. using 1.5 ratio roller rockers, and solid roller cam #51-751-9 with specs of.... 244 degrees duration at 50, 110 degrees LSA, 0.550" gross valve lift, the cam picker spit out 518 horse power @5,000 rpm, 593 LBS. FT. @4,000 rpms. torque baby-kool !!!! use water/methanol injection AND one step colder spark plugs in the four center cylinders.... one mans opinion, have a great day!!
"if you restamp the code on the front of the block and use a set of 68 400 heads nobody will know it is a 455. you can also grind the 455 off the side of the block" Wonder how that would work on my 69 OHC-6 Firebird...
Restamping would be a sinch, bolting the heads on could get tricky.
Poncho huggen gear snatchen posi piro.
It's got a 326, all I had laying around at the time. I tell everyone 326 stands for tri-power with dual exhuast 6 Cyl.
Nothing tricky about it. Could have the head volume adjusted (cnc machined) or buy dish pistons. Bolt right on.
the doctor says its BAD [for me] to be an alcoholic, i told my engine ITS OK!!
A Crane Ram Air 3 cam.