V-Twin Forum banner

1 - 12 of 12 Posts

·
Premium Member
Joined
·
93 Posts
Discussion Starter #1
HTCC CNC heads w/ flat top pistons??


I have experienced and have read others problems with the HTCC heads regarding the proper squish/quench and the tendency to ping these heads seem to have. Not to mention the difficulty in tuning.

I also noticed that the MOCO lists in the S.E. book flat top pistons that can be used in the 103”

Now my question

Is the problem really with the heads? Or is it a matter of the pistons/ heads design combo. Let’s say you would put in flat tops or dished pistons, now the combustion chamber is basically no different than any other. Or am I wrong here? And should not be as tricky to tune by removing the SQUISH issue Again, am I wrong here?

Think of this

110 ci engine built with
4 3/8 flywheels
Axtell 4.0 cylinders w/ dished pistons
HTCC heads – 84 cc chamber ( MOCO figure )
0.30 head gasket

Assuming 0.00 deck height this should give about 10.0 -1 comp. a reasonable number and should work with most High performance cams, of course I am thinking mostly of the TW400G I am presently running.

Or this

117 ci engine built with
4 3/8 flywheels
Axtell 4.125 cylinders w/ dished pistons
HTCC heads
.040 head gasket

Again assuming 0.00 deck height this should give around 10.30 – 1 comp. Again a reasonable number so as not to eat starter parts and be able to run on pump gas

I know there are a lot of guys with a LOT of motor building experience on this forum I just wanted to throw this out there and see what the opinion on this type of build would be.
I am considering this since I already have the heads and if I can make them work I would rather do that than replace them. AND if they don’t work,… well I will already have the bottom end done and it would just be a matter of sending out my old stock take-off heads and having the ports done to compliment the rest of the build.

BTW this would be a BAGGER motor so I am willing to give up peak HP for stump pulling torque.

So let’s Brainstorm this a little

 

·
Premium Member
Joined
·
2,566 Posts
We do two things to those heads:
Weld the combustion chambers back to stock bath tub and cnc port or weld and cnc port to take out the core shift and change the exhaust to intake flow ratio so that they better scavage. This drives up the low rpm torque and cools the engine down. The flat top pistons have the fastest burn that we have found. If your riding a lot thru mountains or ride 2 up with a lot of pulling the welded and cnc ported are the best, for open road out here in the midwest and if your on a budget the cnc ported heads work fine.
 

·
Premium Member
Joined
·
93 Posts
Discussion Starter #3
Would this be better starting out with stock heads and having the mods done to them or using the HTCC CNC heads as a starting point? ( I still have the stock heads in a box somewhere )
 

·
Registered
Joined
·
3,201 Posts
Using flat tops with HTCC heads I'll bet would cause even nastier detonation.
Check out Axtell. I had them machine a 20° squish band in my HTCC CNC heads and they provided matching pistons. The "humps" in the combustion chamber are nearly eliminated and now displace 89cc. You can get them in 95", 113" (4.060" bigger bore) which is what I have, and 117". Going this route your squish will be where it needs to be. If your going to go with flat tops use your stock heads and have them ported. Not an expert but I have been around the block with HTCC CNC heads, ... a few times.
 

·
Registered
Joined
·
487 Posts
i Have used the httc cnc heads on 117-120-124' builds with flat tops without issue
 

·
Long Rider
Joined
·
160 Posts
The stock rods on the 07 96" are a bit shorter than the previous years, leaving the pistons "down in the hole" a bit and you must remove some stock from the bottom of the jugs to get the deck height right and the squish. If you don't do this, everything is off and you will lose a lot of hp, tq and it will ping like hell. Don't ask me how I know.
 

·
Registered
Joined
·
168 Posts
Dalton said:
The stock rods on the 07 96" are a bit shorter than the previous years, leaving the pistons "down in the hole" a bit and you must remove some stock from the bottom of the jugs to get the deck height right and the squish. If you don't do this, everything is off and you will lose a lot of hp, tq and it will ping like hell. Don't ask me how I know.
i have heard this before
i have not seen a 96 inch mill apart yet
hoping to get one this winter to build
i am a small one person shop and only do mill work in the winter months
my question is this
did they move the wrist pin hole on the 96 inch pistons as well or are they still just using the 88 inch pistion
i am assumming by the drisprciption you posted
that the new 07 4-3/8 stroke wheels are the years before 07 cvo wheels with shorter rods and 88 inch pistons
 

·
Banned
Joined
·
3,694 Posts
KingofCubes said:
We do two things to those heads:
Weld the combustion chambers back to stock bath tub and cnc port or weld and cnc port to take out the core shift and change the exhaust to intake flow ratio so that they better scavage. This drives up the low rpm torque and cools the engine down. The flat top pistons have the fastest burn that we have found. If your riding a lot thru mountains or ride 2 up with a lot of pulling the welded and cnc ported are the best, for open road out here in the midwest and if your on a budget the cnc ported heads work fine.

You can find a set of R&R Stage 4 Heads on ebay if anyone is interested in a set of heads like the King Of Cubes describes above...



{salute( :spank: {salute(
 

·
Long Rider
Joined
·
160 Posts
SNUFFY said:
i have heard this before
i have not seen a 96 inch mill apart yet
hoping to get one this winter to build
i am a small one person shop and only do mill work in the winter months
my question is this
did they move the wrist pin hole on the 96 inch pistons as well or are they still just using the 88 inch pistion
i am assumming by the drisprciption you posted
that the new 07 4-3/8 stroke wheels are the years before 07 cvo wheels with shorter rods and 88 inch pistons
For the build I did, went with the HD "Stroker" flat tops pistons, the same ones that hae been used for years. When I put it together I could not get the quench right and didn't feel like pulling it back apart and milling the bottom of the jusgs so just put it together, Ended up being about .045. It ran ok, but hated hot weather and pinged like hell, I had to pull an awful lot of timing out of the tune to get it where it was manageable. Pulled it back down, milled the bottom of the barrels and got to .035 quench. Ran a lot better, could put more timing into it, fuel mileage went upfrom 35 to 41mpg and it was ok even in 100+ heat.

Rods are about .006 short for whatever reason. SE cranks are not short, only the stockers. Anyone building an 07 could have issues due to this.
 

·
Registered
Joined
·
487 Posts
depending on the head sometimes you have to deck slightly to correct the step Gasket to angle to correct the squish the last set of httc heads i CC'd where 86.6cc's but have seen 89cc's for large displacement engines the volumes are good for correct and resonable compression ratios
 

·
Premium Member
Joined
·
2,566 Posts
Last August when I was out at R&R Reggie was testing different quench areas
by testing the by-products the same way he did the EPA certified engine test he performed and found that the more the quench area (to a point) the less hydrocarbons were in the exhaust gas. This is why we have to run a special cnc piston dome program on the domed pistons we use with his heads because they have a tighter combustion chamber.
 
1 - 12 of 12 Posts
Top