eurotrash

Rod Ratio vs. Displacement. Is there a choice to be made?

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So, I have been pondering all the things. s14 block and crank vs. m10 block with s14 crank vs. m10 block and crank.. all with long 146mm rods, as a theoretical study. 

 

When it comes to rod ratios, I understand that anything over 1.6 is wonderful..so I did some online calculator..ing. 

 

80mm stroke with 146mm rods renders a 1.82 rod ratio.  In a 91mm bore at 2081cc. 

84mm stroke with 146mm rods renders a 1.74 rod ratio.  In a 91mm bore at 2185cc

 

OR

 

84mm stroke with 146mm rods renders a 1.74 rod ratio.  In a 94mm bore at 2317cc

 

The numbers are quite interesting, but the question becomes more about the weight of the s14 crank, the rod ratios, and the final displacement.. which is the most balanced build?  Does the added displacement of option #3 make it the clear choice?  Or no?

 

It should be noted that I am not using the 16 valve head if I use the s14 block, but either a built e12 or 1.8 head with a 292 or 300 degree cam.. so as traditional knowledge maintains, I will not be spinning to 7k effectively. Nor do I wish to.. The concept is max torque for a quick car on the street and 3rd gear back roading. 

 

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In my incredibly limited and anecdotal knowledge, I sure like the long rods on my stock crank at 91mm bore.  I am also using a slightly warmed up 1.8i head (gasket matched and a little smoothing) with +1mm valves.  I had everything balanced.  I've had a couple of people comment on how smooth it is.  I'm currently on the stock cam and stock exhaust.  Exhaust is getting ordered and I need to change the induction to get a bigger cam...

 

I think the saying about no replacement for displacement is working here as well.  That's a lot more motor at 84/94.  I'm interested to hear from people with personal knowledge.

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2 hours ago, eurotrash said:

It should be noted that I am not using the 16 valve head if I use the s14 block

If you are thinking about mounting an M10 head on a S14 block, you will be either the first or one of the chosen few that could make it work.  Water and oil passages are different between the two.

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Jim, isn’t the head gasket the same? I use an S14 head gasket on my m10. 

 

John

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Quote

max torque

Biggest displacement, longest throw, and longest rod you can manage.

 

Balance is an exponential concern as revs rise.   If you're not revving, you don't mind the less- ideal balance.

 

So the benefits of good rod ratio, displacement and stroke win.

 

If I wanted torque, I'd fit an M20 eta motor, which are available for approximately free.

 

Or an M54B30, and do some real surgery to the tunnel to run the 6 speed.  And maybe reinforce the shell while I was at it...  after I put in a 188mm diff.

 

t

 

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1 hour ago, Harv said:

Jim, isn’t the head gasket the same? I use an S14 head gasket on my m10. 

 

John

Close but no cigar.  I just overlaid the M10 on a S14 gasket and the S14 has some extra holes.  I didn't identify what the holes are for, it would be research that the OP should do if he is designing a system.

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For max torque below 7k it's #3 for sure.

#2 being still nice lower budged option while #1 would target >7k to gain anything from the rod ratio.

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(edited)

The problem with running a S14 head gasket on an engine with a M10 head is the water flow from the block to the head.  If you look at a S14 head you will see that the water comes OUT of the head on the exhaust side, the M10 exits on the intake side. The water on the S14 is ported into the head on the intake side (biased toward the back of the head) so the water moves through the entire head especially around the exhaust ports. If you use the S14 gasket on the M10 the water enters the head on the intake side and flows directly to the outlet at the front of the head on the same side.  You don’t get effective flow through the exhaust side of the head. It turns out that mild street driving this is not as big of a problem but high loads and rpm’s we had serious overheating. 

 

Also so if you are using the stock S14 front timing cover on the block you will need to modify the timing cover on the head to match, they don’t line up perfectly. 

 

There have ave been many S14/M10 hybrids built over the years, the 1st one I saw was in 1996. This is also the one where we figured out the head gasket problem. 

Edited by Preyupy

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(edited)
2 hours ago, Preyupy said:

Also so if you are using the stock S14 front timing cover on the block you will need to modify the timing cover on the head to match, they don’t line up perfectly. 

And the S14 front cover tensioner oil reservoir is missing on the chain side so there is no pocket to hold oil for the tensioner hydraulics for M10 service.

The chain oiling on a S14 is a different concept and doesn't get spill oil from the M10  no. 1 cylinder rocker area.  The lower tensioner shoe gets oil from the lower pivot pin (ask me how I know,  The engine builder didn't put new orings in the new shoe, it doesn't come with orings)

Edited by jimk
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(edited)

@JimK, I was hoping you would ring in here.  But I will tell you that there are several of these motors on the streets of LA currently.  New builds that Le Tran and I built on paper years ago (by no means implying that we were the first to look at the idea).  He has customers with 2.3 and 2.5 evo blocks.  Last I heard there was a 2.7 in the works...  Jeff Dietch is pretty proud of how his turned out. He started with Dellorto 45s and is now moving to the Jenvey heritage TBs.

 

 Point is, via the wide-eyed guys who volunteered their checkbooks to fund the proof of concept, we know it IS possible.  As well, a gentleman in Europe has reported numbers of 200+ with a 316 cam and 45s. But he probably did a ton of head work. 

 

Right now,  I have the s14 block and crank, and I know that..

1. I need to either turn the crank nose down, or open up the chain cover seal hole.   

2. Close up the hole in the left rear corner of the block and maybe a few other tweaks.

3. Custom pistons for the bore/pin height/combustion chamber/CR

4. MLS M10 head gasket for a 94mm bore. 

Edited by eurotrash

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If had to be sold at a later date, unless all the parts p/ns and modifications with dimensions are well documented, the buyer surely have a wonderful time with any repairs/overhauls.

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(edited)
4 hours ago, eurotrash said:

@JimK, I was hoping you would ring in here.  But I will tell you that there are several of these motors on the streets of LA currently.  

 

I would love to see a couple different dyno results and some actual numbers.  Given your experience, do you have/know of some?  Seems interesting.

Edited by AceAndrew

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@AceAndrew    

 

I have been asking for anyone who owns one to put up numbers.. no one will step up.  I am about to offer to pay for the dyno pulls..  I don't know if you saw it, but it became a spat on Facebook a while back.. when I got jokingly serious about how weird it is that no one will do so.  That being said, the wild one over in the EU that put up like 225/175 (IIRC) was posted, I just can't find it. I hate all the lost info on FB.. 

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(edited)

@AceAndrew

 

Ok, I found the man in question.  Walter Thomas.. Here is is response to my questions. But I am waiting to hear if the numbers were at the wheels.

Hi Jason, my old engine was a 2,3L S14 combo. 206PS and 230 Nm. The actuell engine is a 2,5L S14 combo with 225PS and 255 Nm. The 2,3L had a 304° SCHRICK and 45er WEBER. The 2,5L has a 336/328 SCHRICK and 48er WEBER. I miss my old engine very often. It was the right engine for me. The 2,5L is too rought!! Endless power abouve 4500 rpm.But under 4500 rpm no culture! I sold it last month and in the winter time I built a new engine. It will be a 2,0L with 304° or 300° and 45er WEBER. The 2,3L was the best!!! Sorry for my bad english, I hope you understand what I mean!

EDIT:  that was crank power numbers, and when asked if it was worth the expense.. 

... and YES it is worth!

Edited by eurotrash

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