HTT120 Build

[wurk_truk]

There have been a few people (me and Rabos) kicking around the idea of throwing a 120r crank into an engine and building a 120 with bath tub heads.

What do you guys think?   I'm wondering about the pistons needed to do this and still have a 10:1 engine.... with 86-88cc chambers.

To us (me especially...) doing a +10 oversize 'clean up' on SE cylinders and having 120 ci, sounds very appealing.  Big cost saver over other options when all is considered.  Less hassle, too.... if it all can be fitted straight forward like.

There seems to be a LOT of controversy on all kinds of cylinder kits lately.  Not on the SEs, though (if cleaned up).  More than one way to get cubes and that 4 5/8 crank looks appealing with nice rods and all.  Instead of a full Hobans... I think I would go with a Randy weld and be done with it.

Would we need to go like Durwood did, and have some pistons made up?  Is there enough meat on the 120r pistons to shave them down?

Just starting the 'thinking' stage on this.

I, myself, would like to simply use the ported heads I have, along with a set of 54s...  make a 'tractor' engine out of it and move on.  Install using standard rollers and no timken, etc.  SEEMS fairly straight forward???

[Don D]

Your idea is good, cam choice not so good try a number up TW55,
Pistons are off the shelf 22574-10, Use stock 110 heads but have big boyz polish them.
Tune it and go.
Might be surprised how well it runs.
Watched an ol boy over the weekend wax a pretty high end street rod with EFI and all the right stuff with his Cadillac powered 49 Ford Pick-up Rat Rod. Same Theme.

[dennish]

Sounds good to me.  Not sure whether it would be an issue but aren't the rods on the S.E. crank a tad shorter which would mean the 120r pistons would be needed?  I think that was that brought out in Strokers post?

[HV]

Very interesting... Keep us on top of things ... HTT120 !

[HogBag]

 

[FXDBI]

Headquarters has been doing a 120kit with the se 45/8 crank for a few years already, using the stock heads. Thats what the owner Doug runs.......Bob

[FXDRYDR]

You're on to something Wurk. 

[wurk_truk]

Thanks Bob.  I looked at headquarters web page and they do sell pistons for bath tub heads and 4 5/8 crank.  Yes, stroker told me 120 pistons are needed.  Thats why the CPs by HQ look like the ticket to me.... they are made for the 4 5/8 stroke.

10.5:1 comp which sounds OK to me.

So... what valve sizes should one shoot for on the HTT120 build?  Using TC heads and NOT 110 heads.

Ron really started this, and I decided to bring it to the group and see what shakes out is all.

[Admiral Akbar]

With a CR Of 10.5 to one, you could get away with flattops and 92 cc chambers.. While I'd got for a 2 inch intake valve .. Red has a CnC program that will cut 92 cc chambers in stock TC heads.. That will give you about 10.6 with flattops..  Red like to use 1.9 intakes and 1.61 exhausts but you might be able to take him into a bigger intake if he's bored..

Max

[Don D]

what valve sizes should one shoot for on the HTT120 build?  Using TC heads and NOT 110 heads
Probably 2" X 1.61 Would depend on the cam you choose

[ultraswede]

Please keep in mind that the SE 120r 4-5/8" crank has different rod length than any other 4-5/8" after market crank.

So a piston for the Jim's or S&S 4-5/8, will not fit a build with a 120r crank.

I have read about this here on HTT, but just want to post a reminder for us non pros reading this thread.

[FXDBI]

Thanks Bob.  I looked at headquarters web page and they do sell pistons for bath tub heads and 4 5/8 crank.  Yes, stroker told me 120 pistons are needed.  Thats why the CPs by HQ look like the ticket to me.... they are made for the 4 5/8 stroke.

10.5:1 comp which sounds OK to me.

So... what valve sizes should one shoot for on the HTT120 build?  Using TC heads and NOT 110 heads.

Ron really started this, and I decided to bring it to the group and see what shakes out is all.

    Guess that all depends on how much power you want to make and how much gas you want to burn. I notice HQ is making some nice power with 1.9 intakes, along with some nice gas milage properly tuned. His partner Kevin runs Pro-Twin and has a good write up on ther build on his site.
http://protwin.com/120sportperformancepackage.aspx

[wurk_truk]

what valve sizes should one shoot for on the HTT120 build?  Using TC heads and NOT 110 heads
Probably 2" X 1.61 Would depend on the cam you choose

You most likely, Don, will end up being involved in this.

[wurk_truk]

With a CR Of 10.5 to one, you could get away with flattops and 92 cc chambers.. While I'd got for a 2 inch intake valve .. Red has a CnC program that will cut 92 cc chambers in stock TC heads.. That will give you about 10.6 with flattops..  Red like to use 1.9 intakes and 1.61 exhausts but you might be able to take him into a bigger intake if he's bored..

Max

Stroker and I were wondering how much one could hog out TC heads and still be safe.  10.6:1 would be fine.  I think flattops would be the way to go, but the tried and true HQ build sounds appealing.  Have to make sure HQ uses the SE crank, tho., because in what I've read so far, I cannot tell.

Stroker believes the 120 could use more comp.  Me???  Nope.. looking for least amount of comp.  10-10.5 sounds plenty.  PURE stealth.

[Deye76]

I'm running bath tub heads and flat tops in a 113". The heads are 91cc and flow quite well (flow numbers posted here couple years ago.) Static comp. is 10.36:1. Intake valve is 2.00", Ex. 1.625". The 4.060" cylinders were taken out to 4.065" , all that was necessary to straighten out these particular cylinders.  Your project should be a great runner. What about  R&R .615 cams? Would the added lift over the tw55 help?

[Powerglides]

The HQ pistons are dished to give a true 10.5 compression with .030 quench and 83cc chambers. The compression height is based around the use of the earlier TC rod length, not the shorter rods used with the SE 120 crank. The pistons are .005 O/S to allow for honing the SE cylinders to correct their geometry issues.

[wurk_truk]

I was thinking that after looking at the site.  So, then it becomes whether to hog out a set of TC heads to 92ccs or not.

[lonewolf]

I was thinking that after looking at the site.  So, then it becomes whether to hog out a set of TC heads to 92ccs or not.

Why not? I've got some at 89.

[HD/Wrench]

Most of our heads on stock T/C CNC set up come in at 89-90 CC I can get 91 out with a bit of work, And not have to sink the valves,  Valve choice will help you, Instead of a flat bottom valve use one that is a reverse cut ,  You will gain CC volume.

[DaleW]

definitely a different deck height required for the 120R crank, HQ will not be supplying pistons to fit as Doug is anti the shorter rod ratio. I bet one of the piston manufacturers would be willing to make those pistons up on a fairly small order basis, probably would be a few people interested in them.
I have considered it myself as i would pretty much only need the cases, barrels pistons, oil pump/plate assy and bolts etc to have a complete engine and put my original back to stock in case I ever sold the bike.
Is there another SE 4 5/8" crank with the longer rods?

[wurk_truk]

I don't think so.  But a utlrasweede stated, we think the Jims and S&S have longer rods. Doug most assuredly used one of these cranks as the SE has a -10 part number.

But what I DO know is Randy at Hyperformance can have custom pistons made in batches of 4 and up.  Durwood did this for his 104.

What I am wanting to do is like you Dale.  Build something on the cheap.  It does not look so cheap from here right now, though.

But, if I could have some dished pistons made and get the comp closer to 10-10.3:1, with totally stock heads, I might look further.  It's ALL about the money.

I guess I should give out my theory of everything.  I could do a 117 with the cost of pistons and cylinders right now.  I still have that work of art crank from R&R (4 3/8).  But... as a lot of you know, I over think crap.  Sometimes its good sometimes not so good.

MOCO.  What is the largest bore offered ever by the MOCO?  4.060.  Why?  Remember when the 103CVO came out... the first of the 4 3/8 'stroker' cranks?  Why not go over 4" bore?  Now, we see production motors coming out with 4 5/8 cranks and still mighty close to 4" bore.  Why?  MOCO painted themselves into a corner of NO easy upgrades right now... no big bore drop in kits.  Why?

I think there IS something to this.  The total sum of the aftermarket does not have the R&D of MOCO.  I THINK MOCO knows something in relation to the bore size-vs-?  Longevity?   After seeing a rash of all kinds of builds go south.  Not all... not most... but some...  4 1/4 bore is simply too big for any feeling of longevity for ME.  I'm a believer now that 4 1/8 is too big too.  Somehow... there is some kind of engineering thing going on where MOCO refuses to follow S&S, Axtel, etc into larger bores.  I, in no way know any of this and only assume, but something tells them to NOT go bigger.  Piston mass-vs-speed?  Bolt pattern -vs- mass?  Something.   I feel we are right now seeing the next upgrade to a TC...  a 116 sounds about right, and would keep it up with the competition nicely and a 120 would become a CVO model easily.  In any event... since MOCO STROKES and not BORES for size...  I plan on following their lead.

So, this winter I will most likely do a 103 with 54s and ported heads.  But...  my GOAL will be a big dumb tractor engine....  the HTT 120.   CI matters.  But too much compression to where I have to run a race cam to bleed it all off isn't the answer.  A dished piston similar to what HQ may very well be the answer.  I will contact Randy and see.  Or... Don may have hit on it right at the beginning... run 110 heads.  I've asked Don about those in a PM.  I'm stoopid enough to go out and buy some 'program' heads from all the various recalls...  but Don would know whats good and whats not.

As the saying goes... you have bottom; middle; and top... pick any two.  I pick bottom middle and think MVA heads and 266 cams are too much for me and how I ride.

[DaleW]

JE will do sets of 4 to custom specs. Its not much of a job to alter pin locations or mill a dish into the crown.
I think that the bore size the MoCo has stayed at is more to do with the cases dimensions.As I understand it S&S cases are in that area.
Having a narrow angle v twin certainly does leave tittle room for adding bore size without changing all of the overall dimensions to accomodate the pistons at BDC.

[Powerglides]

4 5/8 stroke has always worked well in the Evo. For an econo build, why not consider having pistons made to suit the 4 5/8 crank with bored out stock TC cylinders?. The cylinders are cheap and plentiful and hold up well. So no expensive cylinders to buy, or case boring needed.
Forget that one... the spigots are too short (oops)

[wurk_truk]

BVBob suggested using 110 cylinders, bored to 4060.  But I am just leeery of those leaking.  What do you guys think of 110 cylinders? 

I just sent Randy an e-mail.  What dish was on the HQ pistons, BTW?

[strokerjlk]

there really is no reason to re invent the wheel. the stock 120 r pistons already work,you keep the piston cly relationship the same as a crate motor. rings are good quality, they have huge valve reliefs,they are a flat top. just pick your head and go for it. pick the cam according to static comp.
S&S 625 would give you 10.9 static 9.35 corrected 195 ccp.
mackie 598 9.6 corrected 202 ccp
SE 266 9.2 190 ccp
all with a 89 cc head.

with a diff T/B and cams that 113 would give you something to play with another season. Ron then use the same stuff when you change the crank the next year.