bored my 327 to a 355?

i had a large journal 327 from a 68 corrvette with 350 hp. i gave my motor to a shop and said i had 3000 to spend on a rebuild, they told me they bored it out to a 355 and are putting in larger rods to increase compression. Anybody have a good guess how much horsepower i will be pushing now? i have a 600cfm edelbrock carb and a edelbrock performer intake manifold. i believe a comp cam is going into it during the rebuild


well aparently he bored it 40 over. so im so ******* lost

Update 2:

they are rebuilding the heads too because my motor was all ******

7 Answers

  • 1 decade ago
    Favorite Answer

    there were 2 - 327 cubic inch engine,s installed in 68 corvette,s. one was 10.5 to 1 compression rated @ 300 H.P....the other was 11.0 to 1 rated @ 350 you must have the 2nd. one...increasing the compression will require higher octane fuel...over 100 octane. so you will need to buy racing fuel with at least that octane to avoid gas ping or clatter from the uneven burn of lower octane fuel which will lower your power rating...impossible to estimate your final horse power rating with out knowing cam lift & duration , hydraulic,solid,or roller cam & lifter,s...valve train specific,s , cylinder head & valve specific,s , ignition type , & type of fuel you intend to use , etc....when it,s done have it tuned & dyno tested...that,s the only way you'll know your true horse power...good luck!..edit....while it,s true that you can't bore a 327 to a 355 on boring alone other thing,s can get you close...but in my opinion boring 40 over is a bad move...that will reduce the integrity of your engine & larger rod,s will do nothing to increase displacement...a custom ground crank might help but something like that will cost more than it,s worth...a 600 edelbrock is only a chromed out weber or carter. edelbrock is known for their intake manifold,s & have expanded to include head,s , block,s , etc. for your engine you will need a holley 750 C.F.M. dual feed- double pumper or a dominator,demon , etc...other thing,s like port matching , porting & polishing , etc. will add to your power...but at .040 over bore your pushing the limit of performance & reliability...if it,s just racing your looking to do...I could think of other block,s that will accomidate your need,s without loosing I said...more info. is needed to estimate your final power rating like type of exhaust,etc....hope you didn't ruin a good of luck!

    Source(s): 45+ year,s wrenching.
  • 1 decade ago

    You got or are getting screwed! $3000 bucks for a bore job and a set of pistons, rings and bearings? even with the "comp" cam and a set of "good" rods, this does not add up!


    You cannot "bore" a 327 to a 355 impossible! A .030 over 350 is about a 355.


    Installed "larger rods" to increase compression? ? ? Can you say pass the "crack pipe"? "Size" of the rods has nothing to do with compression.


    A 350 Horsepower 327 would have come with a 750 CFM Holley carburetor and a GM High Rise intake if I am not mistaken! Those were both pretty good units, so a 600 Edelbrock will cost you power as will the performer intake. Nothing "Wrong" with the Edelbrock parts, just less effective then those "stock" GM parts that the engine came from the factory with.

    Source(s): Been doing this for 45 + years. Master Mechanic, Automotive machinist and HONDA Certified Motorcycle Tech.
  • 1 decade ago

    Right, a 327 cannot be bored to make it a 355. A 350 crankshaft would also be needed. The rods are the same and have nothing to do with compression unless they are of the improper length for the deck height of the pistons. That would be a piston problem, not a rod deal. Either you misunderstood most of what you were told or the guy in the shop is having fun with you. Either way $3000 is way too much to pay for a rebuild. You can buy a brand new GMPP engine for less than that, way less actually.

  • Anonymous
    4 years ago

    331 cubic inches 327 is 4.00 bore and 3.250 stroke undemanding---.030 over may be 4.030 x 3.250 Calculating your Engine's Displacement Calculating your engine displacement is the comparable as looking the quantity of a cylinder. sure, the comparable ingredient you discovered in uncomplicated technology and math type! a million. you detect the area of the circle interior your cylinder. 2. You multiply that area via the top of the cylinder. bear in mind that the area of a circle is pi circumstances the radius squared. (Pi is the comparable as 3.14). quantity = pi x radius² x top A circle's radius is 0.5 its diameter, so the formulation will become: quantity = pi ÷ 4 x diameter² x top permit's say we've a vehicle with those engine specs: The diameter (bore) of one (a million) cylinder is 4.0 inches. Its piston travels (stroke or top) 3.sixty two inches for the period of one cycle. It has 8 cylinders. Now, permit's calculate this vehicle's engine displacement! displacement = pi ÷ 4 x bore² x stroke x cylinders a million. to maintain issues straight forward, circulate forward and divide pi (3.14) via 4. 2. destroy down the squaring of the bore. in case you do this, you will get this formulation: displacement = 0.785 x bore x bore x stroke x cylinders Now only plug in what you be attentive to. displacement = 0.785 x 4.030 inches x 4.030 inches x 3.250 inches x 8 =331

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  • 1 decade ago

    You can't bore a 327 far enough to make it a 355...

  • 1 decade ago

    ** EDIT**

    Sorry to say but it sounds like you walked in iun armed and they seen a 'sucker' coming through the doors so they are just spouting crap out and over charging you like crazy..

    The mild 355's I build for customers for around $3,000 to $3,500 gets you a new scat crank, GM X rods thats weight matched, ARP rod bolts, ARP main and head bolts, hyper flat top pistons, 9.75 to 10.10:1 compression, vortec heads, matched to combo hyd flat tappet cam, air gap style dual plane intake, the right valve springs for combo, etc and makes around 400-425 HP

    A .040" over 327 is 333.2 cid, a .040" over 350 is a 356.8 cid size.

    **EDIT OFF**

    You need to find a new shop ASAP.

    1st, you cant bore a 327 out to a 355 lol

    The 327 has a 4.000" bore and 3.25" stroke crank

    The 350 has a 4.000" bore and a 3.48" stroke crank.

    Max over bore is .060" which gives about 10 cube. inch larger displacement.

    The only way to make a 327 into a 355 is to bore it .030" over and install a 3.48" (350) crankshaft in it

    Next longer rods can not and does not change the compression, engine size or anything like that. If installing longer rods you need pistons made for the longer rods

    With no real engine specs like compression, heads used, cam size, etc can't really tell you HP it will have

    But with clowns like that building it, I would be VERY SHOCKED if it made anything over 275 HP at the crank . It sounds like a bunch of people that don't know crap about building performance engine

  • Tony
    Lv 7
    1 decade ago

    Yeah, can't "bore" a 327 out to a 355.

    Without knowing the cam it's tough to really give you a guess on power. What compression is the motor since you had to replace the pistons? Without knowing cam specs and compression it's a complete guess.

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