i just bought a pontica motor which was suposed to be a 400. but as i took it apart to rebuild i relized it was a 350 . can i bore the 350 over enough to make it a 400 or is the 400 block diffrent?

thanks for any help  

HA! I know how you feel man, same thing happened to me. Unfortunately though, a 350 Poncho block cannot be bored and stroked to a 400 as the two motors are different, only sharing the external size and shape. What you can do is put 400 components into a 350 like a cam, certain heads, intake, etc... hope this helps  

The 350 Pontiac shares the same basic design as the 400 and the crankshaft has the same stroke at 3.75", however the balance is different in the crank due to the different weight pistons. The rods are the same and depending on the year of the engine the heads may actually be desireable (ie:5C-4 or 6X-4 with 2.11" int and 1.66" exh valves and smaller chambers). The intake and exhaust manifolds interchange as well as all external parts and cam/valvetrain parts.
Don't throw it away, depending on the intended use the 350 is a very capable engine. My 79 Formula has a 75 350 with 5C-4 heads, stock intake and exhaust manifolds, duals and Crane cam. With a th400 trans and stock converter and 3.42 gears, it runs 14.45 in the 1/4mile, with 33 year old rings, pistons and bearings! In fact the engine has had nothing but new gaskets and the cam/lifters/timing set and tuneup!
Get some #'s from the block and heads and we'll see what you have. The block casting # and casting date code is on the back next to the distributor and the suffix code is stamped on the front passenger side next to the timing case. The head casting is on the centre exhaust port and there may be a stamping on the end port near the valve cover. Let us know and we can decode it for you and give you some advice.
Steve  

I should be firing up my newly rebuilt 350 here next week and ill see what she's capable of doing. I got all bolt ons, cam, #62 heads, HEI Distributor, Taylor wires and i'm expecting a high 13 to low 14, I would be astonished if I hit 13's but I do plan on adding roller rockers, 3.42's and a shift kit but yes these motors do have potential  

What kind of cam? Specs? The 350's are always overshadowed by it's bigger brothers, but if you want to be as fast as a 400 get PPR's 383 stroker kit- Probe lightweight racing pistons and moly rings, 4340 I-beam rods, a cast 4" stroke crank, main and rod bearings, balanced and ready to install.

The 350/383 stroker kit costs the same as a 400/462 kit, so I'd buy the bigger one since I have 400's waiting for rebuilds. But if I only wanted to deal with the 350 I would go the stroker route and surprise all the big bore Ponchos.

Geno  

My cam is a Crane 272 H10, single pattern hydraulic flat tappet cam, 454" lift, 216 degrees@.050", 272 degrees advertised duration. Here's the link to the spec page
http://www.cranecams.com/?show=browseParts&lvl=2&prt=5&Vehicle_Type=Auto&Cylinders=8&Engine_Make=PONTIAC&Year=1969&Engine_Size=265-455%20C.I.&partNumber=105072&partType=camshaft

Steve  

Yep, I picked the same cam for my 350 overhaul (no. 48's, new cam, timing chain, seals, oil pump)- should run very nice.

Geno  

I'm using a Melling WG-1169, .467 lift, 224 degrees@.050, 298 Duration, I think I chose too big of a cam lol

yo 72blackbird, are you on the firebirdnation forums?  

Yep- I go by 72blackbird on all the Pontiac forums (PY, PZ, FN, Hitmans TA forum, TA country). And as far as I know there's only one guy named Geno in SoCal who drives a primered black 72 Firebird.

Geno  

"I'm using a Melling WG-1169, .467 lift, 224 degrees@.050, 298 Duration, I think I chose too big of a cam lol"

Yup, too big.  The Crane H270 is fine for a 350 with these parts.  Also Summit K2800 will work well.  Been there, done that.  

More cam in a Pontiac 350 does NOT mean more power since it is designed for TORQUE.

Craig  

thanks for all the input guys but i sold the 350 and got a 400. i already got a 400 in my bird and she runs low 13s with a mild cam, #62 heads and a edelbrock intake. but i wanted the 400 because im goin big with this motor. 462 cu in stroker motor, set of kre d-port heads, a edelbrock torquer intake and 150 shot of nitrous and on and on. im lookin to go at least 11.00 in the quarter if not 10.50.  

hey i'm in almost the same boat woundering i got a 69 firebird with the 350 i'm intrested in replacing the heads it can't even spin the tires now i oput hei on it whats the best heads at a reasonable price and where to buy them  

What kind of condition is the motor in? How many miles on it? Have you done a compression test on it? If you still have the original motor in it and it needs a rebuild you should do it- even the '69 350-2 bbls. had 9.2:1 compression  and were rated at 265 hp. Common heads on '69 350s were no.17, 18, 47 and 48s- all are good performers, with the no.48 s being the most desirable.

This motor rebuilt will respond well to upgrades like a 4 bbl. carb, aftermarket cam w/ more duration and lift, and headers with 2 1/2" dual exhaust. And it's very possible to make 325-350 hp from this motor with all of the upgrades mentioned and a proper tuning.

HEI ignition is also a good upgrade but won't wake your engine up if it needs a rebuild, or even a tune up.

Geno  

the compression is good my friends think the valve guides are shot the cam was replaced about 3,000 miles ago H.E.I. was installed then so guess i could take it apart myself so thanks alot guys i will have a rebuild done  

How many miles does the engine have on it.