How difficult is it to put a pontiac 400 into a 3rd gen? And why does everyone say it is pretty tough? I am considering buying a 400 but I am still trying to find its origin. I am told it looks to be a poncho.

HELP!!! Please!!

 

do a search on this. at least 4-5 other post on this swap, & @ least 1 person has done it.

looks to be a poncho? sniff it..if it smells of torque, it is one
year of block will be backby the distributor hold down on block, size of block cast on block by front freeze plugs. head# on middle exhaust humps. mid-late 70s will be 4X or 6X.

these motors are great! More powerful than chevy 350 &weigh less than 454.

 

The Firebird was originally engineered to take the Pontiac V8 ... the low-deck 301 not the big injun. When the gas crisis came, the Firebird was delayed, and when it was all over, Pontiac was out of the V8 engine business for good, sorry to say.

The BB Pontiac can, does and will fit, but you need to do a few things. One of the Pontiac tuners (Rock & Roll? Butler?) makes a swap kit that pulls it all together.

But, if you can't tell it's a Pontiac, you should put the wrenches down and do some more homework before you start spending money or yanking anything out,

BOB

 

i may be wrong and there could be more to it...but arent all pontiac blocks the same size?just different bores?if so then you shouldnt have to worry about the size of it being too big.My 2 cents.

 

326-455 can interchange : heads, water pumps, cams, intakes, exhaust manifolds, distributors, push & connecting rods. different years will have some variation. the main difference between the 421/428/455 & the 326/350/389/400 is the diameter of the main bearings 3.25 vs 3" (bore ot withstanding).

 

you're right. no big/small block, same block size just different bore and stroke. 400 has a 4.121 bore. Building Poncho 400 for my 87 Camaro. As I probably stated before, The exhaust is the main issue. For headers... Indian Adventures is currently building them just for this swap. Waiting on donor car to test fit. Dick Duclow at www.chiefmanyhorses.com. The Poncho costs a lot more for parts the Chevy but worth its weight in Torque.
Bob

 

if you want to realy build up the 400, save some $$$$ & get the NEW 4.25 stroke cranks for the 3" mains. Jim Butler & a few others offer these. price dropped to $399. the rod journals are sized to use bbc rods, but the counterweights should be made to clear block w/out grinding for clearance. If you go cast iron heads (lot cheaper than edelbrock) go w/smog era heads so you allready have the hardened exhaust seats. Factory spec RA-I cam should be good, better w/1.6 full roller rockers. performer rpm is a good intake. I'm using an intake from 69-70 400 on my bonnie because of better layout & got it a lot cheaper than edelbrock intake. I have had no probs w/quadrajet intake, but holley makes spreadbore replacements, or if you go edelbrock carb, get the jegs reman for less than $190 w/electric choke. don't forget the 200-4r tranny. overdrive, so you can run bigger # gears in back & cruise @ decent highway rpms, and it will bolt right up!

 

HUH? 200R4 will bolt right up to a Pontiac block? I thought the 700R4 had the overdrive?
Bob

 

THe th-200r4 is an overdrive tranny that has a BOP bolt pattern, some if not all also have the Chevy bolt pattern. THe th-700r4 has a final ratio of .70 while the th-200r4 has a .67 final ratio. In my opinion the 200r4 is superior to the 700r4 in most aspects mostly because the 1st to 2nd gear drop is not as great.

 

Yep, but be careful about your choice of parts.

Building monster torque in a light car like a thirdgen, and then running a steep gear (which you can use to keep the o.d. from bogging down on the eway) will make it close to un-driveable on the street. A built 455 will light the tires on a 4000 lb Grand Prix pretty much at will... but that might be your idea of a good time.

A good rebuild of a 400, with some ported 6X heads, or better yet, the Edelbrocks will give you all the power you can use without back-halfing the chassis. Their website has the dyno chart for a boneyard smogger 400, built with the heads, performer plus intake and cam, and about 10:1 compression. They got 420+ hp, smooth as butta.

The 200 R4 has to be built pretty carefully to hold up for any length of time to a real good running 400-455. The saving grace for this trans is its popularity with the Buick Turbo GN/GNX guys, who have done some pretty incredible times with the basic guts.

Good luck.

 

the th400 auto trannys were used in a lot of pontaics,so you shouldnt have much problem bolting that up,and they can take a lot of abuse.I dont remember if they have overdrive tho or not.

 

The Th400 is not a overdrive transmission, but it is nearly bullet proof from the factory.

 

yup, my 76 bonnie has the 400/400 setup. bullit proof setup. my old 77T/A had the 400/T-10. Icouldn't afford a centerforce clutch setup @ the time & just kept eating clutch discs

 

My brother has a 400 block and 6x (the better ones, with the hardened exhaust seats and more port to work with) for sale. He wants about $400 for both. He has all the parts for the engine, except the crank and new bearings. Its all in good shape. Email him at calereeves@hotmail.com if you're interested.

Tristan

 

I am doing the 455 swap currently one of the local mechanics races Pontiacs only and his kid that works for him is the same they told me that a friend has done the swap and the hardest part is the headers and on one side (I dont recall) you have to run it on the outside of the frame rail for clearance issues. Before you do this I sudjest doing all the susspension mods and building of engine then go to droping the engine in (that is what I am doing). Another thing is you need a different starter, bellhousing (if standard) or transmision, springs, all assecories and stuff like that just so you know.