Hi guys,

 

Recently obtained a 5K block with the O dished pistons (referred to as flat tops), and have a D dished head in really good nick. I know this combination will seriously increase the compression, but does anybody know by how much and if it will work?

 

Just not sure if the thing will explode or not!

 

Thanks

Look up philby's build thread for his wagon. The answer seems to be a lot, and even with a cam with a lot of duration it was still a bit of a pain to get right. You'll probably go through quite a few head gaskets.

Measure it and see- A thread popped up recently about it, I think it was the same problem. Blowing head gaskets as soon as it was run and he had almost flat-top pistons with a high comp head. Someone will remember...

 

A burette or pipette will measure the head combustion chamber volume, the gasket gives about 5-7cc and the piston dish I think was 5cc.

OMG! Where were you 35 pages ago Zoidy??

 

Is this your problem??

 

http://www.rollaclub.com/board/topic/48931-help-on-5k-motor-head-rebuild/

OMG! Where were you 35 pages ago Zoidy??

 

Is this your problem??

 

http://www.rollaclub.com/board/topic/48931-help-on-5k-motor-head-rebuild/

 

Hahha, I should've been on here a few weeks ago by the sounds of it!

 

After reading the thread, I don't think mine would be as bad because the dish in my pistons look deeper and the head has not been molested (not skimmed). It appears double head gaskets and spacers are frowned upon, so I think some sort of thick copper head gasket would work for me. If you can help me with the number crunching I reckon we can work this one out. My head is in very good condition, so I want to go ahead with it.

 

Now why did this guy have trouble with water jackets not lining up on the gasket? Are the D dished and O dished blocks different? I thought the 5K uses only one type of head gasket?

 

Thanks

Forgot to clarify this earlier...

 

I have not run the motor yet. I got the block on its own recently, and have had the D dished type head for a while now. I thought I should inquire before slapping them together in case she goes boom. Ironically the bloke who sold it to me reckons the motor (running D dish head) blew a head gasket, which totally makes sense now!

 

Also it has solid lifters with adjustable rocker gear, and these weird ball and cup pushrods which are roughly 147.5 mm long. The setup differs completely to my other 5K solid lifter setup, and I've not heard of this length pushrod before.

 

Does anybody have a picture of the factory Toyota 5K solid lifters? I reckon I may have them.

 

Cheers

Look here

 

147.5 sounds really weird. They would be too short for a solid lifter that doesn't have the additional guts. You could do something freaky like run the hydro lifters with those rods plus adjustable arms and a 4K head and you'd be OK, as the 5K's that run the normal head and "flat top" pistons run 150mm push rods.

 

It sort of misses the point of running hydro's, but if it works... :)

Zoidburg, my guess is that your pistons are the aftermarket ACL/Mahle items, they will measure at about 8-9CC

 

Your D Dish head will measure about 22cc, so your compression will be high.

 

As mentioned in the other thread, if you're worried about it being unworkable, you could probably get the head volume increased slightly.

Look here

 

147.5 sounds really weird. They would be too short for a solid lifter that doesn't have the additional guts. You could do something freaky like run the hydro lifters with those rods plus adjustable arms and a 4K head and you'd be OK, as the 5K's that run the normal head and "flat top" pistons run 150mm push rods.

 

It sort of misses the point of running hydro's, but if it works... :)

 

Yeah I know, they are weird length pushrods.

 

However the lifters are very tall and the pushrod sits right on the top, so I reckon the height difference is made up there. I have all the different 5K pushrods and lifters, so I can check the heights before I put them in anyway. The solid lifters in it are weird, never seen them before either.

 

Also ACL appear to make a head shim, so I'll inquire about that.

 

Thanks

Okay ACL make two head shims for the 5K, one is 0.8 mm thick and the other is 1.5 mm thick. This plus the head gasket may get me out of trouble, but then I'm not sure if I'd need longer pushrods or not.

 

Went in to a head shop today and the bloke there recommended hollowing out the combustion chambers in the head. Will take the head in next week to have that looked at. After that I gotta decide what rocker gear and pushrods to use, as I have a few combinations here.

 

Not really sure which way to go at this stage, so many options!

Edited March 11, 201115 yr by Zoidburg

Measured up a few bits today...

 

The 147 mm pushrods with those weird solid lifters measure a total of 188 mm, from the bottom of the lifter to the top of the pushrod. The previous solid lifter setup I used on my other 5K (same head) has 186 mm pushrods, and measured 190 mm from bottom of lifter to top of pushrod. So pretty much the same outcome, and with adjustable rockers it wont be a problem.

 

Also my piston dish looks to be around 6 cc.