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will a chevy 350 parts fit a 305?


mike5721947
01-27-2005, 10:54 PM
well looking at building a 305 or 350 and am wondering the main differences between them (350 has longer stroke or bore?) will 350c.i.d heads,exhaust,intakes and whatnot fit the 305? what trans would you throw behind a 305, maybe a THM350 or is that overkill?


also what motor mounts will work for swappinga 305 into a chevette will stock mounts from another chevy work or will they have to be a kit or custom?

RandomTask
01-27-2005, 11:35 PM
I believe the bore to be essentially the same, but the stroke to be longer. However, the heads are slightly different. 305 Heads are generally smaller CC wise and putting a 305 head on a 350 will boost compression. HOWEVER, 305 heads were not meant to flow for a 350 so extensive porting and polishing have to be done. (And in most cases, the valve sizes are smaller, and not much can be done to compensate)

As far as transmission, how much power do you plan to put out? I believe a TH-350 to be fine, you break away from the computer controls as well as adjustable bands that weaken the TH-250. You could also go with the 700R4 (POST 1989!) And you would be set for a good 450 ft/lbs with no significant mods. (But I would always reccommend and inexpensive $30-$70 shift kit from B&M.

As far as your chevette is concerned, what motor is in it now? Is it RWD? Pretty much, if it has a 229ci (3.8L) a small block is pretty easy to install, provided its RWD, also if its mated to a TH-250, that is almost an econ crap version of the TH-350.

This knowledge that I'm spitting off is fairly dusty in this cavernous brain of mine, so any corrections would be beneficial to mike as well as me...

mike5721947
01-28-2005, 12:56 AM
well the chevette is rwd and has a 4 banger 2.8L ? well im looking at doing an automatic trans but i want to know about mounting this all up

curtis73
01-28-2005, 04:05 AM
The external parts bolt up the same; exhaust, intakes, etc. Inside, the difference is entirely bore size. Both engines share the same stroke at 3.48" but the 305's bore is 3.735" while the 350's is 4.00".

There is nothing wrong with a 305, but its bore is severly limiting to flow. If you look at the difference between the two, its basically a 15% difference in displacement. But, since the entire difference is in the bore, the power difference is much greater than 15%. Go with a 350. Completely identical externally, and much more potential inside.

The parts physically interchange, but a 305's heads have two limiting qualities; 1) small ports for the smaller engine will make the heads perform terribly on a 350. 2) If you use 305 heads on a 350, the small combustion chambers will make it about 12:1 compression. Not pretty on pump gas.

In general, dont' mix and match parts between the two. Although they fit and work, there is very little between the two that truly interchange as effective parts.

I don't know of many V8 chevette swaps, but I'm sure its been done. The 2.8L you have should be a V6... unless there is a bastard I4 I don't recall. Look to the S-10 trucks. Thousands of 2.8L S-10s have been converted to V8 and the motor mounts should help you.

RandomTask
01-28-2005, 10:35 AM
K, yeah, I knew one of the bore and stroke were different but not both. TY for the info curtis...

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