i know this is going to be a stupid question, but would rebuilding a pre 87 350 bew easier than rebuilding 1 with the oe hydrauilic cam (87 and after)? it seems like more parts are available for pre 87 motors than 87 and up motors. seems like there are barely any valve train and top end parts for 87's+. Also, under the comp cams website just about every xfi i click on says that machining is required on the cylinder heads. what kind of machining are they talking about?

 

To a certain degree what you are finding is true. 87-up engines use rail-guided (self-aligning) rocker arms instead of "standard" ones + guideplates/machined pushrod holes, like on 86-down head. They also have a different intake manifold bolt pattern than the more common 86-down heads. Other than those things, however, the differences are nothing to write home about.

The "machining" they refer to with the XFI cams almost certainly refers to having the guides cut down to accomodate more lift. The factory heads (both 86-down and 87-up) usually poop out around .470". More than that the retainers will contact the top of the guides/seals. Spring upgrade to match the XFI cam would be required regarless of what year heads they are.

The "advantage" to the 87-up motors is that the block is built to take a (factory-style) roller cam. That makes a roller cam upgrade much cheaper- just swap the cam for an aftermarket unit built for 87-up engines. Earlier 86-down non-roller blocks will chew up the better part of $800 to retrofit a roller cam into them.

 

ok thanks damon. is one cheaper than the other? how much does it cost to get a pair of heads machined? if i were to build an 87 block are the heads the only place that will need machining? does an 86 need any machinging if you were to put a hyd roller in it? i wanna go XFI

 

Is the pre '87 block a 4 bolt block? I am asuming the '87 is from an f-body, so I will also assume that it is 2 bolt block?

Just food for thought.....

 

its an f- body block

 

I assume you are referring to the post '87 block? As far as I know there were no 350 engines in thirdgen f-bodies until '87.

Your pre '87 either has to be pre '82 if is from an fbody, or its not from an fbody, or its not a 350.

Someone throw the BS flag if I am wrong. Really it all depends on what you want to do with thing, and how fast you want to go.

If you wan to do an XFI cam, you don't have to go roller. I don't know what your budget is like, but if money is concern, you can build a healthy engine with less money using a hydraulic flat tappet setup.

There are TONs of variables that are not covered here though. What heads are you using? pistons, rods... yada...yada...yada

If you put up some more info, you might get some more responses.

 

i just want to go roller. and all third gens except 92 i belive came with the 5.7 auto combo.

 

You are WAY off. I know that for sure. Checkout the tech articles on this site.

 

As much as many of us on this board wish it were true (all engines being a 350), I believe the 305/4speed auto was the standard V8 for our cars.

 

so if a pair of heads say max lift .650 then if you have a cam that has max lift of .550 then no machining will be needed correct?