Was purchased complete.dont care about mileage.mostly around town driving not to much on highway.will prob go with 3.55 gear what do you recommend for stall
Are you more interested in drivability, the desire to sound like a racer or have that old time ragged idle sound, do you want this to actually be a competitive racer or have that ability over just being a cool and easy car to cruise with?
The answers set the direction for components, machining and assembly/tuning.
The times have changed how we build engines in particular a lot. Similarly this has affected and effected the selection of transmissions, rear axles and wheel and tire sizing.
The long duration ramp intensive cam designs demand high compression ratios which modern 91-93 octane does not support with old time head’s and their combustion chambers. So right off the cam you have and the head’s will not work well together, you will get a rough idle but not near the power or torque you would expect. If you stay with a cam like the one in hand then you need modern Ricardo chambered head’s which for the SBC become apparent with the 1996 L31, 5.7/350, Vortec engine. These are duplicated and improved in the aftermarket which includes the GMPP Fast Burn but also a plethora of equal to vastly superior aftermarket head’s that range from reasonably priced imports to outrageously priced but offer competition level performance out of the box. These set the stage for not only getting 1960’s level performance from the SBC but it’s easy to exceed those old time engines on today’s fuel with a lot less cam which makes these engines easy to live with. Today you actually have to work at cross purposes to build a 350 that won’t deliver 400 ft pounds of torque and 400 some horsepower under 6000 RPM and use a stock stall converter to boot! Big valves come on the aftermarket head’s but with modern port thinking and the Ricardo chamber the factory L31 Vortec head with 1.94/1.55 valves blows these old head’s with 2.02/1.6 valves in the weeds without even breathing hard, pun intended.
Back in the 60’s it was outrageous cam timing and compression ratios with Rochester mechanical fuel injection to squeak 365 horses from a 350 using 100 plus octane fuel to keep from blowing holes in the pistons. Today it’s a much easier cam and lessor compression of highly refined head’s with Ricardo combustion chambers and paying attention to the piston clearance to the head’s step and the piston crown shape. Modern head’s depending on the details below them and the block are a 30 to 80 horsepower bolt on, while some of this is porting which is much improved the vast majority of the power gain is from the chamber shapes that are controlling mixture flow within the chamber to manage burn quality. So figure right off the bat that any engine build needs to have modern chambered head’s. To that end aluminum let’s you go farther because it moves the heat that results in detonation faster so you not only can but for thermal efficiency reasons it is recommended to run a more compression than iron will tolerate. Yes it is possible to get good power numbers out of the old head’s but that takes a lot of shop tricks which includes angle milling which improves compression and tips the chamber more upright which gats into intake milling and angular fitmemt issues with exhaust manifold ink or headers that need to be fixed with more milling or wedge shaped adapters. For the chamber the exhaust valve can be sunk to create a beake between it and tge intake as you would see in a picture of an L31 Vortec or other modern head. This of course gets into shimming the exhaust side valve spring to chase its resulting high sitting stem. You still can’t solve the poor spark plug location of these old heads, to some extent you can use a projected tip plug for that in an attempt to get the plug electrodes deeper toward the bore center but the down side is projected tip plugs are hard to cool enough that they don’t become a source of pre ignition.
But and there always are these “but’s” the best output with aluminum demands a tight squish/quench clearance between piston crown snd the combustion chamber’s step. This is considered to be optimum around .035 to .045 inch which is more critical for an iron head where aluminums faster heat transfer is more forgiving. To get at the optimum clearance with am aluminum head and still use the desired composite head gasket for better wear between aluminum and the gasket than is provided by a thinner steel shim gasket. To get here with aluminum head’s requires the block be zero or nearly so decked or the use of a raised crown (compression height piston, compression height being the distance from the wrist pin center line to the edge of the piston crown.
The long duration old time cam uses a lot of ramp which makes for a lot of overlap but more importantly closes the intake late into what should be the compression cycle. This blows a lot of the mixture just taken in back out into the intake track. Your very high ratio rear end and probably stylishly large diameter tires works against getting to the RPM where there is enough mixture inertia to overcome the reversion pressure that results from the rising piston. Back in the day of these long duration rampy cams the factory put in rear axle rations of 3.75 to 4.11 as standard issue and with a manual gear box specifically to get the engine revs up to where the incoming mixture had enough inertia to force feed the cylinder against the effects of the rising piston. Modern cam design is to greatly reduce the ramp duration while increasing duration between the .050 points and adding lift. Unfortunately this is a hard bargain for flat tappet cams especially in the age of reduced ZDDP oils. This, however, can be managed with a careful breakin using specific flat tappet breakin oil and maintaining a high ZDDP hotrod oil afterwards.
There there is the rockers, ball and socket rockers are so yesterday, they are not good at high lifts especially if mixed with RPMs and stiff valve springs. This just fries the rocker and ball. So you need to organize your parts around RPMs and spring pressures. More lift as in .530 inch engenders stiff springs.
I guess what a points distributor they are a high maintenance item though a 6AL cuts that down some by taking the heavy amp load off the points. But here again the trade is a long duration spark of an induction ignition be that points or HEI that is very suitable for typical street revs gets traded for a capacitive discharge that is very short low amps but very high voltage quite suitable for high RPM racing but only survives on the street by introducing another sprightly speed switching circuit to deliver multiple short strikes under 2500-3000 RPM to emulate the long high amp spark of an induction ignition, there doesn’t seem to be a requirement other than to point and grunt at the big red box.
I really don’t know this whole thing sounds OK for 1969 but is out of step in many ways for 2022. Not that it won’t work but it seems like a very dated approach.
Bogie
