Hot Rod Forum banner
1 - 7 of 7 Posts

·
Registered
Joined
·
6 Posts
Discussion Starter · #1 ·
I have an 83 monte carlo and i have just done all the body work on it but i am now unsatisfied with the 305 with a turbo350 (with no overdrive) and would like to switch to a 350 with as little head ache as possible. between what years are other 350 small blocks compatible with my current transmission and can i use a 350 motor out of a truck.

Thanks alot
Dallas
 

·
Not Considered a Senior Member
Joined
·
10,722 Posts
Generation 1 small block chevy`s all shared the same bell housing bolt pattern so dropping in a 350 is a snap. Just about everything on small chevy`s interchanges, this is what makes them the most popular engine, it also makes it the cheapest to hot rod.
 

·
Registered
Joined
·
15,314 Posts
D-FUNK23 said:
Thanks guys that is a huge help. now to track down a decent 350 to rebuild. shouldnt be hard :mwink:
You can use either the older two piece or newer (1986-up) 1 piece seal engine. The difference to your TH350 would be having the matching flexplate for the smaller diameter bolt pattern with the 1 piece seal crank, other than that and a counter weight on the new flexplate to make up for a chunk of crank the new seal configuration removes, the flexplates and flywheels are dimensionally and bolt patternally the same across this divide. The one piece seal is a lot better at keeping oil in the engine. 1987 saw a change to the heads which raised the rocker cover rail, machined the gasket surface, and went to center hold down bolts, again much better at keeping oil in the engine than older models. The newer engines also have a factory serpentine belt system, everything interchanges with your 83 with pulley changes or the front of the engine can be back dated to V-belts, this requires a v-belt year water pump which is a bolt on replacement.

With unleaded fuels, you don't want heads older than 76 to insure they have hardened exhaust seats. But early SMOG era heads have poor combustion characteristics so in-spite of hardened valve seats you don't want these either. Both the aftermarket and GM provide more modern heads which you see hitting production in the latter 1980s and of course the Vortec arriving in 1996 is quantum improvement, good for 40 hp or so by just bolting them in place of SMOG era heads. They do require an intake change for a new bolt pattern and higher positioned ports, but they really make an engine come alive.

In rebuilding one needs to pay attention to the pistons.

1) Many after market pistons lower the pin to crown distance by .020 inch under the assumption that rebuilt blocks will be zero decked. Shortening the crown distance keeps the same clearance between the piston crown and block deck after the deck is machined. If these pistons are used in a block that has not been decked they will be quite a distance from the deck .040 to .050 inch and will significantly lower compression and reduce squish/quench. So watch this carefully.

2) The most effective squish/quench occurs when the piston closes to the squish/quench side of the combustion chamber (side opposite the spark plug) at about .040 to .050 inch. This builds a lot of detonation resistance (often referred to as mechanical octane), speeds the burn, and improves mileage and power by combusting all the fuel your putting in and paying for. Factory engines, especially the pre-Vortecs of the early SMOG era have large combustion chambers and circular dishes in the piston crowns. This greatly lowers compression and makes the engine detonation prone. Detonation aside, these were good for lowering NOx emissions and little else. Modern thinking with modern chambers is to increase the squish/quench function, to do this the close closing together of the piston and the head's squish/quench step is necessary. To this end, flat top pistons provide the best solution but with modern tight fast burn chambers, they will run the compression too high for available premium fuels. The solution is found in pistons with a D shaped dish, these keep a flat area to close with the head's squish/quench step which pushes the mixture into the spark plug side of the chamber for good ignition and a fast burn. The D dish under the valve pocket is used to maintain an over all compression ratio that is compatible with the available fuels. Selecting Vortec/Fastburn chambered heads and D dish pistons allows compression ratios from 9 to 9.5 to be used with iron heads and 10 to 10.5 with aluminum heads. This is turn allows a more aggressive cam without the surrender of bottom end torque or keep a mild cam and trade up on gas mileage.

The opportunities in paragraphs 1 and 2 easily allow a 350-400 horse 350/355 engine to be built that will run on 89-92 octane fuel, in cold weather maybe even 87 unleaded, using a cam as mild as Comps 262 XE hydraulic. This means you don't even need to change the converter stall.

Bogie
 

·
Banned
Joined
·
9,993 Posts
or 87 octane, for 350 hp.

If you can't get 350hp out of a vortec engine on 87 octane- well you should put down the torque wrench and pick up some knitting needles.

When possible I like to be cheap. at 350hp you can be pretty cheap.
 

·
Registered
Joined
·
29 Posts
400sbc

just a thought for ya... look for a nice running small block 400, slap a rv cam in it,,and some vortec heads or whtever,,, and you will probably have a nice small block,,,or a 383... therts a million ideas to go for,,, first things first... --------$ -------?
 
1 - 7 of 7 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top