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5k Head Vs 4k Head


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Hope this isnt bleeding obvious, but I was wondering if 4k head can be used on a 5k engine, with 5k rocker gear and pushrods etc.

 

I am looking at getting some head work done, and have a 4k head that I can use, so I can keep the car on the road while the work is being done, and then just change the heads over.

 

Would the 4k head change the compression in the 5k all that much? Have just been reading a similar thread about 3k heads on 5k blocks, but didnt want to hijack that one..

 

Also wondering if a 4k cam is the same as a 5K cam, so I can send a spare 4k cam off to Tighe for a regrind, then just chuck it straight in my 5k...?

 

Cheers

 

Davros

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Seeing as a normal 4k head has about twice the combustion chamber volume of a dished 5k head, you will drop the compression ratio quite a fair bit. Probably will come in at under 8:1, so she will be a bit of a dog.

 

With regards to using your rocker gear with the 4k head, keep in mind that a normal 4k head is taller. You will end up with less hydraulic lifter preload, which may or may not be a problem? If you were to pop out the circlips in the top of your lifters you would have a big problem.

 

I'm pretty sure that the dished 4k and 5k cams have a shorter rear bearing journal than the normal 4k cams. Not sure if it would cause a problem, but if you did happen to have the rear of the cam butt up against the welsch plug at the back of the block it wouldn't be good. You should always check for cam endplay after installing a cam and tightening up the front retainer plate. I'd be sending off the original 5k cam to be reground.

 

With the regrind, make sure you get the base of your rocker pedestals skimmed to match the reduction in the radius of the base circle diameter. This maintains lifter preload. Tell the regrinders that you will be using hydraulic lifters so you don't end up with a potential cam/lifter incompatability. You should also get the lifters refaced to ensure a proper break in and long life from your cam.

 

Make sure when you reassemble your motor with the new cam you use a good quality thick cam lube (should come with your cam, but doesn't always) on all the cam lobes and dizzy drive gear to help with break in. When you first start it, keep the revs to above 2000 RPM for the first half hour and don't drive it. This will help to seat in the cam and lifters properly and help to prevent chewing off a cam lobe in the first 1000 kays or so.

 

I think it would be best to park it until you get your cam back. Really you should send off your rocker pedestals (disassemble your rocker gear and number them for correct reassembly), and your lifters with your cam for machining. It is best to do it once and do it properly. Saves a lot of time, money and frustration in the long run.

 

Doug

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Thanks for the replies guys..

 

Doug - thanks for taking the time to provide so much info, its really appreciated.

I have been spedning so much time sifting through info in the FAQ and the various forums and starting to piece together a plan for my engine,

and tips such as yours and others I have received from other members make it so much easier to (hopefully) avoid making mistakes the first time round.

 

And I agree with doing things right the first time....

 

Engine will be getting pulled apart asap..

 

Cheers

 

Davros

Edited by Davros El Davros
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  • 1 year later...

What model 4K head is it or 4K block and what model 5K gear?

 

All depends.

 

Some 4K heads are 100% same as a 5K head factory others are different.

 

if it is a stock normal ADM 4K head 5K head is HEAPS better but the 4K will drop compression if it is a normal flat top piston head so id jsut not drive the car..LOL

 

As for the cam rear bearing clearance yes Felix is right some are smaller so you can damage a welsch plug.

 

I use a 4K cam in my 5K no problems just make sure it is the same as the original 5K one first. I in a previous 5K also rana 3K cam with a re-grind to suit hydro lifters so yes cam swap can be done first messure it up but.

 

I run. Stock 4K cam in 5K, twin row timing chain, 3F lifters, 4Kc push rods on 3K rocker gear slightly modified according tot eh TRD book and all this on a dished piston 5K running a 5K head that is shaved to up the compression. Run about 210 PSI each cylinder.

 

Cheers

Cameron

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what about swapping a 4k for a 4k-e how easy is this and is it worth doing and putting a turbo on it

or can i put the injectors on a good 4k block

 

this has been covered a fair bit over the years

 

if your in nz swapping in a 4k-e should be easy, if not in nz check out nz kp61 forums or trademe.co.nz and pray that a complete system comes up for sale (happens rarely) or better yet just fly to nz with a shopping list and hunt down parts in car yards

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  • 3 years later...

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