my 87'-88' 305 TPI was bored over .30 from the stock application so whats the overall bore on the motor is it 3.75 i doubt its a 4.00 bore so what could it be????, how much boring is necessary to get a 4 inch bore from a 305 TPI. Is it possible??

 

No, the water jackets are different on a 305 and you'll hit those before you ever get to the 4" bore.

 

30 thousandth's is .030, not .30. Glenn is right about the water jackets. A 305 can't be a 350, and a 350 can't be a 400. There's just not enough material in the cylinder walls.

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89 Transam GTA, 350TPI, auto, 3.27 rear, dual cats, gray.
Magnaflow cat-back,
K&N open element,
Best E.T. 14.63@95mph

 

The stock bore is 3.736". With .030-over, you're at 3.766". That's a long way from 4", and like said above, you can't get there from a 305 block.

I suppose you could have wet sleeves installed, but I've never heard of that being done.

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82 Berlinetta, orig V-6 car, now w/86 LG4/TH700R4. 2.93 limited slip. 2-1/2" cat-back, ZZ3 intake, Accel HEI SuperCoil. AMSOIL syn lubes bumper-to-bumper. Daily driver, work-in-progress (LG4 CC system w/'87 LB9 block, ZZ3 cam, ported World 305 heads, Hooker 2055 headers, 3" Catco cat & 3" catback, restalled TC, Spohn SFCs).
57 Bel Air, my 1st car. '66 396, 9.7 CR forged TRWs, Weiand Action+, Holley 750VS w/4150 conversion, GK 270 cam, Magnum rockers, Jacobs Omnipack, 1-3/4" Hedders & 3" Warlocks, TH400 w/TCI Sat Night Special conv & Trans-Scat shift kit, MegaShifter, 3.08 8.2" 10-bolt w/Powertrax, AMSOIL syn lubes bumper-to-bumper. Idles smooth @ 600 RPM in D. Best 15.02/95.06 @ 5800' Bandimere (corrected 13.93/102.4 @ sea level).

 

vortech305

I'm doing simmilar mods to you. e-mail me as I'd be interested to know how your car turns out performance wise.

Robert