Well ...to late for that! Lol I just figured was a regular freeze plug...does it have to do with setting cam position as well?..engine has been at machine shop for a few days
The cam lobes are slightly tapered so the lifters "spin" ,this causes the cam to thrust rearwards and not walk. The rear face of the timing gear controls the distance of the cam on Chevys. When an engine is converted to roller cam [with parallel lobes] a cam button and/or thrust plate is needed to prevent "cam walk" Also when you buy an aftermarket timing set [eg: Romac] they come with a bronze thrust bearing or Torrington thrust bearing . If the front face of the block is damaged, a Torrington is a bolt in repair. [on race engines we cut a small groove in the front cam bearing bore [to allow a Torrington to be lubed at high rpm] Get the machine shop to install the cam bearings and freeze plugs [and gallery plugs] They can do this cheaper than hiring a cam bearing install tool. Ask him about the rear cam bore plug. [there is a change over year in 283's] The best DIY method is to install the old camshaft and timing gear [which runs against the front of the block] then you know how deep the rear of the cam journal is.
The chamfer on the bottom allows for a longer stroke [327 crank and 307 pistons] The 3789817 casting can be BORED to 4" so it can take longer stroke AND larger bore' Chevy used the 3789817 casting for both 283 and 327 bores [3.875" and 4.000"] Most early 283 [and some 265] blocks without the chamfer at the bottom can go out to 4.000" BUT they cannot take a longer stroke because there is water jacket issues. [unless the crank counterweights are cut down] Some of the later 283's [67-68] can also be bored to 4.000" but not your mid-year block. Personally , I would use a 327 crank [while the engine is apart] and cheap assed 0.030 over 307 pistons and stroke it. [It helps the engine to be lazier and not work hard] and dirt cheap. They are both internally balanced 307's only got the bad name because they were the little brother to the 350 [from 1969] whereas when the 283 was released in 1957 it was King Shit until the 327 came out. [305's suffer the same fate]
That all depends on whether you want to keep the original car's DNA! power packs keep that vintage look to the engine [and power packs were used on 327's in Impalas] A 307 stoker is totally invisible, even an expert couldn't tell when the engine is installed And every thing appears to be period correct! But crack test your heads first, you may have no choice. If I was considering 305 heads, I'd hunt down some L98 C4 Corvette aluminium heads. But "Less is MORE" keep the power packs if possible. They have withstood 60 years of use [and suit the character of the car] Maybe give them a good valve job [1.84 intakes]
The Jalopy Journal
