Hey guys,

I'm rebuilding my 5.0L HO right now, and since most of the major parts seem to be in pretty good shape (ie. crank, rods, camshaft, etc etc...) What should I keep?

I've heard something about L69 rods being better than regular rods, but I don't know if there is any truth to it.

Is the camshaft a good performance cam? It appears to be in excelent shape, as well as the lifters, but the lifters will probably be replaced anyway.

Is the crank cast or forged? Its probably cast, right? If so, is it worthwhile to find a good junkyard forged 350 crank? I was thinking that if im going to have a crank reground (which mine may or may not need) it might as well be a forged one.

The rebuild will be a mostly stock build, but I will upgrade a few things. Probably intake, and carb will be changed for something a little better, and the exhaust will be upgraded for sure, since I already have a set of headers for it.

The heads will be the stock #416 castings, but will have the ports cleaned up a little bit and will be rebuilt, and I plan to keep the original 9.5 CR.

Any and all input here is welcome.

BTW: This is an '83 original L69 Z/28.

 

the one big weak point in the GM 305 heads is the valve seats. have those check and new seats pressed in. The machine shop said they have run into alot of these heads cracking between the two valves. Port and polish them I sure wish I would have gone ahead and did mine. hind site is 20/20 so they say.

 

Since you have it opened up if you have the money put in all new rocker arms, lifters, pistons, crank, and cam. If you don't have that much extra dough just port the heads and clean up everthing(seals, gaskets little stuff). If you want to keep the stock lifters and rocker arms check them first.

 

Yes, the rods in L69s are superior to the LG4 style.

I would replace the cam with a Comp XE 256 or Crane PowerMax 260 or 266. New lifters are a MUST!

Crank is cast but still good enough. 350 cranks won't work, the clearances are different.

If you use the same parts that I list in my sig you WILL be happy.

Also, follow the link at the end of my sig for lots of how-to on porting and polishing those heads.

 

Mine also went through a full rebuild a couple of years ago..

I'd just make sure you have the heads gone over. Telflon seals wouldn't be a bad idea either.

My cam of choice ended up being a Crane Compucam 2040, and it made a big diff over the stock cam. It does have a higher lift (.440/.454), without problems. Car passed emissions 2 years straight,and performs very well esp. for a 305!

The stock cam is a step up from an LG4, but there are better ones out there. If everything else checks out OK - reuse it.

 

Changing the carb will necessitate changing the distributor to a non-CC, vacuum/mechanical unit. The end result will be zero power increase (although a double-pumper might result in slightly better low-end WOT power). Keep the carb, spend a little money on upgrading the stock ignition (coil & module).

I've got the Crane 2050 compucam and love it. If you go that route, figure on new valve springs (a good idea, anyway), eliminating the exhaust valve rotators, and screw-in rocker studs are a very good idea (or at least pin the press-in). Higher stall torque converter will also be in order with a cam upgrade.

I have never heard of valve seat problems with 416 heads. Worn guides, yes. I've heard of 305 heads that were cracked between the valves, but never 416 heads. However, it would be wise to have them magnafluxed before you do any other work on them.

We'll find out in a few weeks if I'm up to smog-snuff. I started the mods the day it last passed emissions test, I just got the renewal notice this week. I've had a couple of spark plug wire "issues", so a major tune-up is in the works (new wire looms, along with new wires, cap, rotor, & plugs). May also go through the carb, and need to get the A.I.R. re-installed (never had it fully functional since the mods). But, I don't really anticipate any problems getting it through.

 

Actually, at the moment, I don't have any heads for it at all. Sorry for the confusion.

What I meant was that I planned to use some #416's off of another engine. Those too, would be rebuilt. If I were to get a new cam, I would get a kit and use the recomended springs on them.

So why will a 350 crank not work in the 305 block? Its the same stroke, so it should have the same amount of metal on the counterweights, shouldn't it?

I was also thinking about some steel roller rockers, not the stock GM peices. I have quite a bit of time to build this engine, as I do have another in the car that I can use in the meantime.

So... since the L69 rods are better than the regular rods, are they worth keeping?

I want this engine too be absolutely bomb-proof. It has to be able to handle about 300hp, since thats the goal for this engine.

Five7Kid:

Yea, I realized that I'd need a vacuum advance distributor, because I had planned on using a 750 DP Holley on this engine. I just planned on buying a decent used HEI and rebuilding it (bearings, cap, rotor, coil, etc etc...) because the wrecker closest to me sells them fairly cheap.

 

305 & 350 cranks are the same casting, but are machined & balanced to the application. If you put a 350 crank into a 305, you'd best get the rotating assembly balanced.

Whatever rods I used, I'd have the big ends reconditioned, new rod bolts (ARP). Shot peening not a bad idea, either.

I didn't see the improvement I expected going from Holley 650 DP to Proform 750 main body on my 396. If you go with a 750 DP, make sure you have enough stall to "make the chart" on the Holley website.

 

For the 305/350 crank balancing... i'm way ahead of you And glad to hear they will interchange.

I did also plan of doing the rods and replacing the bolts as well.

As for the carb and stall speed... no need. I will be using a manual trans

 

Ah, but you never specified.

Same story exists. It's easy to over-carb with mechanical secondaries.

From http://www.holley.com/HiOctn/TechSer...fo/TI-225.html :

"Greater care ... must be taken in selecting the correct size mechanical secondary carburetor for an application. Double pump, mechanical secondary carburetors initially depend only on the accelerator pumps to provide adequate fuel until enough air flow can be established to begin pulling in the main system. The larger the carburetor the higher the air flow required to accomplish this. If the carburetor is too large, the pump shot will be consumed before the main system starts. The result is a "bog" or a "sag."

"The handy chart, below, will help you to determine the correct carburetor size for your application." (See the website for the chart)

"If your car has a manual transmission, use the lowest RPM at which you use wide-open throttle. This must be a very conservative RPM (on the low RPM side, that is!) and should be found by observing your own driving habits in the vehicle involved. Watch your tachometer! The heavier the vehicle and the lower the numerical axle ratio (higher gear ratio) - the lower this RPM must be."

Etc., etc., etc....

 

Ok... what DP would you suggest? Its a T5 with an open 3.73 rear and in a fairly light Z28 (im guessing 3100-3200lbs). Max rpm would be probably 5500 or so.

 

By the formula (CID*RPM/3456 @ 100% VE), you're looking at less than 500 CFM.

From the chart, if you never floored it with the RPMs lower than 1500, you could get by with as large as a 700. If you chose a 600, you'd bog any anything less than 1200 RPMs; a 750, 1800 RPMs, etc.

Final words from that site:
"When in doubt, select a smaller carburetor size because it will typically give better acceleration times - even though power may fall off slightly at top RPM. You can believe that you'll be happier with the smaller carburetor nearly every time!"

 

Ok, sounds cool to me. I never really stomp on the gas anyway, i doubt my tranny can take it anymore. I just sorta 'roll into it' now to be a little easier on my car, so i'll probably go with a 650 DP Holley.

 

Is it worth the effort to do any port work on the 416 heads? I know its always worth something, but some heads take to it better than others do...