Domed top pistons in a flat top piston engine? (2 Viewers)

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I have a Canadian 2f with the flat top pistons that I am rebuilding for my 1977 FJ45. I know it is original block and head with the flat top pistons, as are the other two 2f's I have. I also know that the US models may have had dome top pistons for those years. My engine needed boring so I ordered new pistons and the ones the supplier got for me (ITM ENGINE PRODUCTS) are domed, not flat like original. Apparently these are the only ones listed for the 2F. Can any of the engine gurus out there tell me if I will have head/valve clearance issues if I use them??
 

FJ40Jim

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Yes, they will not fit. The piston dome will interfere with the head.
Just order the correct flattop pistons cataloged for 81-87 USA 2F.
 
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I've wondered about this. Could the dome be relieved in the appropriate areas so as not to interfere with the head? Or if the valve lift high enough that there would still be a piston/valve interference issue?
 

FJ40Jim

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Valve interferenc isn't the issue.
Flattop engines are 8.3CR stock. Bore 1mm over and it's 8.5.
Mill .50mm off the head and CR is heading for 9:1, which means premium gas.
The last thing the engine needs at that point is a pop-up piston raising CR to 12.0
 
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Valve interferenc isn't the issue.
Flattop engines are 8.3CR stock. Bore 1mm over and it's 8.5.
Mill .50mm off the head and CR is heading for 9:1, which means premium gas.
The last thing the engine needs at that point is a pop-up piston raising CR to 12.0

Whoa, I had no idea that the dome was so high.
 
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Pretty sure it would be north of 12:1 , dome height off the top of my head would push it over 13...ugh . Been there , done that on a Suzuki engine - never use two different machine shops 1500 miles apart to build the same engine .
Has anyone really looked into the quality of the ITM pistons ? Kind of curious as some of their other offerings seem pretty well done .
Sarge
 
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Figures . Had a talk with a local machinist buddy here last week and mentioned Toyota discontinuing the pistons for these engines . His answer is always the same - have them made by one of the reputable US makers , which I'm sure with domed tops is going to hurt quite a bit .
The issue in my mind is that the later 2F's with flat tops had head cracking issues that were commonplace , correct ?
Hate the prospect of not being able to properly rebuild my engine down the road ...ugh .

BTW - I love that thread of yours , seen so many similar issues over the years and some were quite creative .

Sarge
 

FJ40Jim

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A set of forged Wiseco pistons, 1.5mm OS, with wrist pins is around $760, IIRC. Search and ye shall find a thread with some pics and pricing from the last time I got some.
 

RockDoc

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"best" 2F

Mark W made reference in this thread to a Canadian 2F having flat tops and "open" chambers in the head. I take that to mean the head would suit domed pistons. Do we know for sure the head in question in this thread won't suit domed pistons? What is the part number / casting number on this head @PG45er?
 

FJ40Jim

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I have seen plenty of 2F engines with flattops and open chamber. The have 6:1CR and no power. Toyota didn't build em that way. It's the result of cracking one of the relatively crack- prone close chamber heads and replacing with an indestructible open head from the JY.

At least, that's what I've seen.
 
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Hmmmmmmmmm. Pretty sure that my 2F has flat tops and an open chamber head.... I wonder if Toyota might not have built them that way for third world markets so that they could run on a 50:50 mix of turpentine and shoe polish if necessary?

All the more reason to use my F-135 engine with its weird half open/half closed chambers, I guess. At least its CR is supposed to be 6.8:1.
 
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As long as Wiseco doesn't use their usual short-azz skirts , that would be fine and a lot cheaper than what J&E Racing charged for 4 forged 10:1 pistons for that banzai Samurai engine we built . I would be curious just how hard it is to find a closed chamber head in good shape and not cracked - the real numbers of what's available is what drives the market . I'm just looking for solutions for a good , solid and reliable "recipe" engine so I can gather parts for later - my 2F is still in solid shape for now although starting to suspect some cam wear . No non-Toyota and I really prefer the torque band and reliability of a solid straight 6 .
Sarge
 

FJ40Jim

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No short ass race skirts. Since 2F is based on the 256/270/302 jimmy engine that is popular for LSR, they machine the 2F piston from the 270 forged blank. The pistons are big & heavy, in case you need to run boost. And methanol spray. And a little more boost. Because LSR.
 
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That's excellent news Jim , appreciate that and I know your input is something I can trust - which I don't give out easily from being burned before .
Since every decent machinist I've used around here has retired , you'll probably get this 2F just shipped to your place...lol .
Sarge
 
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Yes, they will not fit. The piston dome will interfere with the head.
Just order the correct flattop pistons cataloged for 81-87 USA 2F.

Bump
I"ve got my flat top pistons. The block was bored .050 over for the dome tops, so I checked the fit of the flat top pistons in the cylinders. They meet the manual specs, 2.4 lb to pull the .002 strip gauge. The rings I'm not 100% sure on...ring end gap in the manual says .008-.016 for 1st and second ring. I've got .020 on the top ring and .017 on the second ring?? My machine shop guy says he is comfortable with that. Mine is the first 2F he's seen so thought I should get another opinion.
Thoughts????
 
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Stick to the service manual specs on those rings - aftermarket rings are commonly off a bit and I don't give ***** what the machine shop claims as to lapping rings in a controlled manner to make them all identical - I always check ring gaps . Rebuilding my last Suzuki engine took 5 separate kits to get a set that fit all 4 pistons - it's rare to see one of those engines hit the magic compression pressure specs , that one was dead-nutz on spec at 200psi cold , perfect . I always had to fight with customers and rebuilt engines that were broke in properly and were well below wearout spec in the service manual (170psi) - it results in a weak engine that my carb setups could never help . Telling them their new engine was junk produced some serious Sh** Storms with the rebuilders , some of them reputable vendors from out forums . It's all about paying attention to those specs and stick to it - otherwise you'll regret it later with an engine that is either weak , burns oil or won't last nearly as long as it should .

Ok , rant off....


Sarge
 

FJ40Jim

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You will find that piston rings will always specout w/ too large a gap, because the ring mfg doesn't want to take any chance on the rings butting closed. The way to get perfect minimal end gaps is order 1mm O/S rings for the .75mm O/S bore, then file to fit.
 
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Yeah , we've done that before as well with several different engines and I hated it . Guess I expect far too much from parts that are suppose to fit .
Q - @FJ40Jim - Are Toyota's oversized rings a better out of the box fit ? Or , same game - oversize and file...?

I know I'm going to wear out this engine sooner or later , if nothing else it will need a refresh and right now it seriously needs a reseal - rust proofing itself pretty heavily as-is . Looking to start compiling parts while I have the chance...

Sarge
 

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