at what point do you throw old heads in the scrap bin?

grumpyvette

Administrator
Staff member
I got asked to comment on how you decide when repairs on an old set of cylinder heads is just not worth the time and cost vs replacing them with newer cylinder heads?

Obviously there's a cost vs value ratio,and theres surely a reason you think the old current heads need either repair work or replacement.valve guides valve seats, valve seals can all be repaired.
cracks, in most aluminum heads are easily repaired, cast iron is a different story

I'd be the first guy in line to tell you, that, if your determined to upgrade for the performance advantage of the newer head designs ,I'm sure you can rationalize a bit higher cost to do so
, and if you have extra machine work invested into a cylinder head like porting or combustion chamber machine work,angle milling, decking etc. those factors come into play when considering replacing a cylinder head vs repairing it. and while Ive rarely bothered rebuilding old stock production heads, if the cost exceeded about 65% of what new similar or better heads cost, youll need to weight the costs vs replacement, simply because older rebuilt heads will always have had wear items retained and have the basic castings that may be corroded or micro stressed, in areas you might not suspect so they do tend to have slightly more long term durability issues than new heads.
ID also point out that before you start swapping cylinder heads Id be sure that its the heads that NEED to be replaced, and to look carefully at the costs.
yes some heads are not that easy to replace and youll want to rebuild or refurbish those, but don,t get emotionally attached, THINK LOGICALLY, many times you can buy bare castings and swap parts from old heads to new castings to save cash
I recently got a call from a guy I know concerning rebuilding his muscle cars engine and during the brief discussion he , mentioned that he dropped off a set of cylinder heads he had that were in need of repair work at a local cylinder head rebuilder and was shocked at the $800 price he was quoted to have a set of older cast iron big block heads rebuilt,with new valves, valve seats, new valve guides and valve springs ,with a multi angle valve job. yes $800 may seem excessive but if you calculate the parts cost, of decent quality parts, vs cheap components it generally won,t seem quite so outrageous (obviously youll need to verify the quality of the parts being used in any rebuild) and then subtract that the cost of the SKILLED labor, that price , seemed at least too me rather cheap,for what he claimed was being done, in fact Id bet money the $800 quote was a low/ball to get the job and when he went to pick up the heads they would have tacked on a bit more for "UN_FOR SEEN, BUT MANDATORY REPAIR WORK" so as I've stated numerous, times when dealing with any machine shop get everything in writing and take lots of pictures and get signatures and valid signed agreements, listing exactly whats to be done and what it will cost and when it will be ready for pick-up and a list of everything youll supply and what the machine shop supplies and will do. before dropping off work because verbal agreements are rarely adhered too ,if the machine shop feels there's more money to be made, a valid point,you'll learn the hard way eventually if you only make verbal agreements and don,t get things in writing before work starts.
at some point it should become obvious that the cost to refurbish older heads will depend on what needs to be replaced and repaired , what previous custom port work has been done and the comparable cost of replacing those heads with new heads having similar work already done.
yes some older heads are no longer easily available and it might be your only option to have the work done if you choose to retain those heads, in functional condition.
if you have original 392 hemi heads or pontiac ram air V heads ford tunnel port 427,bOSS 302, or sohc 427 HEADS YOUR GOING TO PAY BIG BUCKS BECAUSE THOSE ARE RARE AND HARD TO REPLACE, BUT IT WOULD MAKE LITTLE ECONOMIC SENSE TO REBUILD LETS SAY 396 bbc CAST IRON OVAL PORT HEADS FOR $800, if you could buy new replacement heads for nearly the same cost. and even the legendary "FUELIE HEADS" are 45 year old technology that's been easily out paced, in potential performance by the better head designs now available.
and Id point out that repairs on aluminum heads tend to be faster, easier and cheaper than when your dealing with cast iron as aluminum is easily TIG welded and machined, unlike cast iron
I can supply a few tips ,and bits of info for anyone willing to jump down the rabbit hole, when your looking to machine cylinder heads for different valve springs, keep in mind your machinist needs to be careful as enlarging or deepening the valve seat depth and diameter, if done too much weakens the heads and installing stronger valve spring load rates adds considerable stress, so its possible to run into problems rather easily , if machine work is too extensive, ID suggest calling the cylinder head manufacturer for info on that! along with having a discussion with your machine shop.

manufacturers can supply info , similar too but not limited too info ,like this
that DIFFERS with each head design.so don,t blindly start machining heads for larger springs with higher load rates , ask and get the CORRECT answers first!
millboss1c%20(2).jpg

http://garage.grumpysperformance.co...-the-rabbit-hole-with-alice.10933/#post-66925



http://garage.grumpysperformance.com/index.php?threads/valve-springs.9613/#post-50556

http://garage.grumpysperformance.com/index.php?threads/two-loose-valve-locks.9687/#post-36006

http://garage.grumpysperformance.co...oper-valve-spring-seats-shims.1005/#post-1818

http://garage.grumpysperformance.co...-loads-and-installed-height.10709/#post-46658

http://garage.grumpysperformance.co...e-springs-and-setting-up-the-valve-train.181/

http://garage.grumpysperformance.com/index.php?threads/valve-seat-angles-and-air-flow.8460/

http://garage.grumpysperformance.co...d-high-spring-pressures-don-t-work-well.1489/

http://garage.grumpysperformance.co...ring-installation-questions.12833/#post-66431

http://garage.grumpysperformance.com/index.php?threads/what-springs.11352/#post-51835

http://garage.grumpysperformance.co...train-clearances-and-problems.528/#post-46440

http://garage.grumpysperformance.com/index.php?threads/removing-valve-seals.4283/#post-44287

http://garage.grumpysperformance.co...lve-seat-angles-and-air-flow.8460/#post-29682

http://garage.grumpysperformance.co...ide-issue-on-new-crate-motor.7979/#post-27508

http://garage.grumpysperformance.com/index.php?threads/valve-spring-installation-questions.12833/

http://garage.grumpysperformance.com/index.php?threads/busted-valve-spring.7716/#post-29797

http://garage.grumpysperformance.com/index.php?threads/testing-valve-springs.1751/#post-4387


Some of the More Popular Gen I Cast Iron GM Cylinder Heads

http://www.onedirt.com/tech-stories/engine/a-guide-to-vortec-vs-oe-small-block-chevy-heads/

#3767754 – Manufactured from 1959-1961 on 283 Cubic Inch engines. Called the “Power Pack” cylinder heads. 1.72˝ intake valves and 1.50˝ exhaust valves. 60cc Combustion Chambers.

#3774692 – Manufactured from 1958-1964 on 283 Cubic Inch engines. Called the “Power Pack” cylinder heads. 1.72˝ intake valves and 1.50˝ exhaust valves. 60cc Combustion Chambers.

#3795896 – Manufactured from 1963-1965 on 283 Cubic Inch engines. Called the “Power Pack” cylinder heads. 1.72˝ intake valves and 1.50˝ exhaust valves. 60cc Combustion Chambers.

#3782461 – Manufactured from 1964-1966 on 327 Cubic Inch engines. 161/62 cc port volumes, 62cc combustion chamber. Identified by Double Camel hump symbol.

#3782461X – Manufactured from 1960-1963 on 283 and 327 Cubic Inch engines. 172/64 cc port volumes, 62cc combustion chamber. Identified by Double Camel hump symbol.

#3890462 – Manufactured from 1966-1967 on 302, 327, and 350 Cubic Inch engines. 64cc combustion chamber. Identified by Camel hump symbol. No accessory mounting holes.

#3917291 – Manufactured from 1967-1968 on 302, 327, and 350 Cubic Inch engines. 64cc combustion chamber. Identified by Camel hump symbol.

#3932441 – Manufactured from 1969-1970 on 350 Cubic Inch engines. 161-165cc intake port. 76cc combustion chamber.

#3932441X – Manufactured from 1969-1970 on 350 and 400 Cubic Inch engines. 161/65cc ports. 80cc combustion chamber. 1.94″ intake/1.5″ exhaust valves.

#333881 – Manufactured from 1974-1975 on 350 Cubic Inch engines. 76cc combustion chamber. 2.02″ intake/1.6″ Exhaust valves.

#3991492 – Manufactured from 1970 on 350 Cubic Inch engines. Available on the LT1 engine and over the counter. 64cc combustion chamber. Either straight or angled plugs.




yes well worth the time to read the links and sub-links, the answer your looking for may be in the links or sub links
any time you buy new cylinder heads it makes a great deal of sense, to verify they are designed to match the block youll use, the piston dome shape, and to look for several independent reviews, from previous purchasers, that are NOT on the manufactures web site and to read through the fine print on specs on valve size,valve spring load rates , max valve lift, port cross sectional area, combustion chamber volume,suggested head gaskets, intake manifolds, and look for advice on matching cams headers etc.
It certainly won,t hurt to shop for vendors selling at a lower price, but be aware component quality in valves, retainers and machine work do vary wildly as does the care taken in the machine work being done, so you tend to get what you pay for!


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