CHEVY Old Heads! Yeah, I'm talking to you...

[Sweet_Johnny]

Hey folks, I have some old heads here that I might be able to put to use, if only I knew which was best for my needs. I've been putting off installing the Stealth intake and different headers on the 305 in my Cutlass since it could really use better heads while I'm in there. Another member who has given me much already offered up some 416s or 601s, but the man has provided a SUM1104 cam kit as well as sent me a rebuilt carb and has his own stuff to deal with so I've given him space. As it turns out, I've got a few good candidates for this head swap (and a few others) already in my own garage.

The 4 best options are some local 416s for $100 or mine with these casting numbers: 3947041 (similar to "Fulie"), 3785896 & 3884520 (Power Pack?), or 354434 (smaller ports/valves than 416 but some like it).

I've read that the 041s have either 60 or 64 cc chambers and are similar to a 186 or 492. They're currently on an engine on a stand so I haven't measured the valves, which are apparently too large anyway at either 1.94 or 2.02. These are not my preference for this 305.





The 434s have 1.72 valves (measured) and I think 60 cc chambers. They came on an engine in an '85 Suburban that I bought at auction & drove around for a while so I know they work. The valves show plenty of meat, and though I've ran these before I don't know a thing about 'em- spring rate, guide/seat condition, etc..





As for the 896/ 520s, they have no accessory holes, sport 1.72 valves (measured), and the valves are pretty even with the chambers- recessed seats? 60 cc chambers? I like 'em but they seem to need more work than the 434s.



Which of those heads is best suited for a 305 in a '78 with a few lightweight items, th350 w/ 2500 stall, and a set of somewhat highway friendly gears (308/323)? Without real porting, blending, spending much $$ (Competition Products Head Improvement Kit is all I want to buy), or buying different heads. Surely one pair has better flow or burn characteristics than another and would be slightly happier with a Summit 1104 cam.



Do any of you guys with more knowledge and experience than me have any wise words that'll lead to good results?

Other heads on hand include 3 pairs of 882s, a pair of 487, and one good 487x + one obliterated 487x. The chambers or valves in all of them are too big for this.

 

[melloelky]

clickbait!!

 

[64nailhead]

Highest compression (smallest chamber) and largest intake valve.

Damn near impossible to get 1hp/cubic inch from that - hmmmmm.

melloelky clickbait? I didn’t see a thong?

 

[Sweet_Johnny]

clickbait!!

Hey, being an Old Head ain't a bad thing, but I like wordplay and if it gets clicks, well, WINNING! I like to think of myself as being one to a hefty degree as well. Plus I'm willing to bet that nobody here under 50 knows a thing about these cylinder heads anyway, thus my need for "Old Heads" to chime in. You've been inside a few smallblocks, any pearls of wisdom you could share or thoughts to discuss? All opinions are welcome and appreciated.

Highest compression (smallest chamber) and largest intake valve.

I kind of figured I'd be happiest with 54 or 58 cc and 1.84 intakes but it looks like I've got 1.72s. Without cc'ing the things I don't know if they're 54, 58, or 60 cc chambers, or what the intake port volume is since online reports vary. I'm open to using steel shim gaskets or the thicker ones to achieve proper quench or compression. The internet is full of experts with misinformation as well as typos, and I definitely trust you guys more than them. I also lack any knowledge about which has the best designed ports, ramps, runners, chamber entry, and such. For instance, between the 416, 601, and 525 Vortec there are a few differences I care about but each has its place. The 601 has a better chamber and intake runner as cast but with porting the 416 can be better from everything I've seen and read. I'm still learning and have a long way to go, and have forgotten more than I want to admit. I have no "pie in the sky" dreams for this, but would like to make the best of what I've got at hand. That "dream" for the 305 would be an M90 on a custom manifold feeding some 76 cc 882s with Manley valves and possibly a stroker crank. The heads are on the El Camino, I have no blower, and would have to make the manifold for it. Realistically, I can drop any of these heads on fairly quickly and notice a marked improvement over what I have, and don't need to blow much $$ since the engine has had an issue or two already. If it blows up, it blows up- then the 350 gets swapped over.

Damn near impossible to get 1hp/cubic inch from that - hmmmmm.

Naturally aspirated, yes. A small shot would hopefully be fine with 114° lobe separation and can stay in the car for the next engine. I know the cast pistons and other factory bottom end parts wouldn't like it much though. I don't currently have a setup, nor a strong desire to hook one up in the immediate future either.

 

[pagrunt]

As for the 896/ 520s, they have no accessory holes, sport 1.72 valves (measured), and the valves are pretty even with the chambers- recessed seats? 60 cc chambers? I like 'em but they seem to need more work than the 434s.

Unless you want to switch to the '68 & older accessory brackets & a short water pump I'd stay away from heads with out accessory holes. I'm guessing you'll just be swapping the top end & leaving the lower end as is. Another thing, you keeping the stock intake? I'd personally would look at what would also work with those heads to get the best set up with a stock short block. There are some good stock intakes out there that could be better flow than the one you have. I have in the stash a EGR cast iron that is per cast numbers what stock class track racers like to run & a '67-'68 one that was the perfect fit for a stock '81 305 that only had Summit can upgrade & Hedman's.

 

[Sweet_Johnny]

Unless you want to switch to the '68 & older accessory brackets & a short water pump I'd stay away from heads with out accessory holes. I'm guessing you'll just be swapping the top end & leaving the lower end as is. Another thing, you keeping the stock intake? I'd personally would look at what would also work with those heads to get the best set up with a stock short block. There are some good stock intakes out there that could be better flow than the one you have. I have in the stash a EGR cast iron that is per cast numbers what stock class track racers like to run & a '67-'68 one that was the perfect fit for a stock '81 305 that only had Summit can upgrade & Hedman's.

Thanks for the tips! I definitely don't want to fuss with other brackets that I don't have, even though Alan Grove Components has some nice ones. One goal is to utilize stuff I already own unless the 416s are better than that, I can stomach paying $100 for them. At the time of posting I was looking into drilling my heads for accessories- not happening.

You're correct, I would be swapping the top and leaving the stock bottom end with double roller chain and 1104 cam kit. The intent is to pair it with a Weiand Stealth I modified to accept a Rochester via a spacer. The Stealth has a big plenum necessitating better heads, and the cam wants more of both than I currently have. I'm running an aluminum GM manifold now (14057053 iirc) that I believe to be milled, and I have a vacuum leak even after multiple gasket changes- this manifold is likely never going on another engine of mine. I also have a Vic Jr. & a Typhoon from when Professional Products first hit the scene, but of the 4 the Stealth is my choice unless it's just too much since the Typhoon is on another engine. The factory carb is just about done but Eric set me up with a better one, and I'd be installing a knockoff "ready to run" billet distributor w/ the module pulled out wired to an MSD Street Fire box. There's also Accel shorty "groove" plugs if they're the correct heat range, Accel wires, and different headers to go alongside mello's old rockers. Originally I wanted a stock look but now I'm going for a stock experimental vibe with lots of aluminum- radiator, intake, t-stat housing, valve covers, heat shield, and I might do the pulleys later. I really want L98 heads but don't want to pay $500 for a pair currently on eBay, I think I see corrosion on them that they've carefully avoided picturing well.

I was operating on the assumption that any of my 1.72 valved options would be good for my combo as would the 416s, but the smaller valves would limit rpm to 4k. The bigger valves of the 416s breathe better but I wonder if it's a moot point due to other factors like CR, port volume/flow, or something else. I think the early heads are now out of the question, leaving my 434s vs some $100 416s as the 2 frontrunners.

 

[pagrunt]

I was operating on the assumption that any of my 1.72 valved options would be good for my combo as would the 416s, but the smaller valves would limit rpm to 4k. The bigger valves of the 416s breathe better but I wonder if it's a moot point due to other factors like CR, port volume/flow, or something else. I think the early heads are now out of the question, leaving my 434s vs some $100 416s as the 2 frontrunners.

I'd look at it for how much you need to let it suck in to the chamber to get what you need for your power out put. I'm no expert on this but with the '86 305s (LG4 & L69) for example, they both have 1.84/1.50 valves & 9.5:1 compression but the LG4 is rated 150 HP @ 4000, the L69 is 180 @ 4800. Your 305 alredy have 1.72/1.50 heads, 8.4:1 compression & pushing 160 @ 4000. Now for the chambers I don't have that info handy at the desk right now.

 

[Sweet_Johnny]

My heads are # 376450 and Eric said "64 to 58 CC depending on who you ask. Not known as great flow."

Some other guy online said "they're either 55 or 65cc."

Well, 6 cc's is manageable but 10 cc's is quite a difference and if I've got 55 now I don't think going much bigger is wise even if it breathes better. But maybe someone knows if 0.015" gaskets on an undecked block with stock dishes will garner enough with the spare heads I have. Again, I've encountered conflicting numbers and hoped a member would have first-hand knowledge of them.

I looked up the cam specs for LG4/ L69:



I've got 20° more duration and 0.050" more lift than the L69, but what happens when my valve opening/closing points are factored in? It makes a direct comparison difficult and I'm not sure which is more important in my situation: compression, valve size, or runner/ chamber design? Does it matter at all? I say yes. Details matter even when it's a 305 & spare parts- it's still an engine.

The 041 chamber may be too big (if 64cc) & the valves will rub anyway, the 434 runners might not flow like 416s but would definitely be an improvement similar to porting my current heads, and even if they have 60cc chambers I'm still good. I like their bigger 1.84 valves but they cost $$ and I don't know their history, adding more cost to check for damage then overhaul. I could probably just slap the 434s on after cleaning, saving $$. The old "Power Packs" have the best internal design and flow but need brackets and and maybe seats + everything else, eating time & $$.

I guess I'm asking the forum if I'm better off switching to shim gaskets with 60cc chambers & good flow (if I currently have 55cc chambers), or if the smaller valved 434s still flow well enough above 4k to support the CR bump (if I currently have 65cc chambers). Or are the 416s definitely worth it for some reason? I'm also asking if there are inherent issues or bonuses to using any particular head mentioned due to design. In a perfect world somebody can say "Use these for this reason, but these are better if modified. This gasket will get your quench where you want it. Your setup wouldn't respond well to the runner of these heads, ever."

It appears that I can raise the CR with 434s if I currently have 65cc, flow more air with them at a lower CR if I have 55cc, or possibly just move more air at the same CR for the cost of head gaskets. If I have 65cc right now the 434 is the clear winner. If I have 55cc right now then the best flow with 60cc or less points to 416s. But is the cost justified when the 2 are compared? The issue is me not knowing the details that matter.

 

[Sweet_Johnny]

More digging says the 416s might outflow the "Packs", and the 434s don't breathe after 4k just like what I already have due to valve size. So I'm still torn between using what I've got or spending $$ for better and not being sure it's justified.