Arctic Chat : Arctic Cat Forum banner
1 - 20 of 36 Posts

·
Registered
Joined
·
1,634 Posts
Discussion Starter · #1 · (Edited)
Well now that the chassis is done its time to get the engine ready to go. See 97 Zrt600 Project...

http://www.arcticchat.com/forum/z-zl-zr-zrt-tcat-ext-jag-cougar/361871-project-97-zrt600.html

This summer I Split the cases and had the crankshaft rebuilt and welded all 3 throws. I told my crank guy that this was going into a high RPM race engine and I wanted it right. It came back with 7 new bearings, 3 new rods and rod bearings and fully welded. When I set it up on V-blocks it was with in .001 from one end to the other. So after the case mods i put the bottom end together.

Now its time for the cylinders to get ported. This is going to be a very hot lake race engine on pump gas but will see most of the time in the woods of Michigan blasting from one corner to the next.

I started with a degree wheel to see where the stock port timing was set. The very first thing I noticed after putting the piston on and rolling it to BDC was the bottom of the transfer ports were lower than the top of the piston. When I checked the port timing it was clear this would be a pretty easy mod to a point. Just raise the cylinders and cut the heads to match. I opted to call Cometic gasket and bought a set of .020" shims and another set of Cat base gaskets. Stock base gaskets are .018 so adding a .020" and another base gasket .018" basically raises the port timing 1mm which is perfect for a set of aftrmarket pipe that turn 9300 Rpms. Now that the cylinder is raised the bottom of the transfer ports match the piston at BDC. At this point I noticed i had to lower the exhaust port 1/2mm.

So now the port timing is set at 202 degree's of duration on the exhaust and 134 degree's of duration on the transfer ports. Wow that was easy. Just use 2 sets of base gaskets and a .020" aluminum shim from Cometic gaskets.

All that is left to do is to widen the exhaust a touch and match the exhaust flange to the manifold. Then cut the heads .038" each.

So after the air compressor pumped up it was time to dig out my handy dandy die grinder which is very well worn. lol. Over the last 25 years i think I have wore out 8 or more of them.
 

Attachments

·
Registered
Joined
·
1,634 Posts
Discussion Starter · #2 · (Edited)
So I needed to add some red lay out die in to the cylinders. I check the height of the piston from the top of the cylinder when I get the crank angle where I want it. I also use a sharp flat tool bit to scribe lines in the cylinder wear i put the lay out die. This way I can physically check the port heights top and bottom with a set of calipers and have the lay out die to grind close to.

Now that the exhaust is where I want it to its time do do some Top Secret Porting that I figured out on my TSR racing software. Sorry guys but you wont see that info on here. A guy has to have a edge some where. lol.

Other goodies for this engine include 39.2mm bored carbs, v-force reeds, 9300Rpm pipes, and a 2 degree timing key.
 

Attachments

·
Registered
Joined
·
1,634 Posts
Discussion Starter · #3 ·
Here is a few pics of the case tunnel porting I did as well.
 

Attachments

·
Registered
Joined
·
1,352 Posts
Very nice Al. I know I have the ability (after you gave me the knowledge), I just pray every night that I maintain the patience needed for the task at hand.
 

·
Registered
Joined
·
1,634 Posts
Discussion Starter · #5 ·
Thank you and you are very welcome. Porting is tedious work. The more you do it the easier it gets. It this case getting the nicasal off with out gouging was very important on the exhaust height. I only wanted to clean the nicasal off after I raised it up with shims.
 

·
Registered
Joined
·
10,403 Posts
Come on now Al, be honest, you have done so much work to this sled in just a few days along with other projects, you have to have at least a cot or spare sofa you sleep on out there don't you? I bet you have a kitchen out there too. LOL :lol:

Nice work I must say! Are you planning on doing a dyno on it?
 

·
Registered
Joined
·
1,634 Posts
Discussion Starter · #7 · (Edited)
Come on now Al, be honest, you have done so much work to this sled in just a few days along with other projects, you have to have at least a cot or spare sofa you sleep on out there don't you? I bet you have a kitchen out there too. LOL :lol:

Nice work I must say! Are you planning on doing a dyno on it?
No cot, sofa, or kitchen in my garage. Its made for working. lol. The step daughter and grand kids moved in :Bangin: so I moved out to the garage!! Praise God as they are moving back out tonight!!!Cat happy

I have no intentions of dyno'ing it any time soon. If I cant get a handle on it then I will but I am pretty good at getting a handle on a mod engine. I have been tuning and modding engines sense 1979. I only had one that gave my fits and that was a 87 eltigre 6000 with a 530 engine that I modded. Ity would not go 1/2 mile before it banged out the plugs, I ended up changing ignition timing 1 degree for 7 days and testing it. That sled taught me what timing does.
 

·
Registered
Joined
·
38 Posts
Do you think raising the cylinders and machining the heads to get the squish back to spec is a worth while thing to do during a top end rebuild with stock pipes?
 

·
Registered
Joined
·
1,634 Posts
Discussion Starter · #9 ·
do you think raising the cylinders and machining the heads to get the squish back to spec is a worth while thing to do during a top end rebuild with stock pipes?
Yes Yes Yes
 

·
Registered
Joined
·
1,634 Posts
Discussion Starter · #10 · (Edited)
Well, I got the cylinders finished up yesterday, gave them a hone job, Gaped some new rings to .014" and assembled the top end with new bearings, pins, etc. except for heads. Then I got out the solider and checked the squish gap. After raising the cylinders the squish gap was at .090".

Then cut all the heads and rechecked the squish gap. They are now back to .052". After that I gave the heads a bath to clean the dust off of them. So they are ready to be installed today as is the V-force reeds, intake and oil pump. Then its time to drop this small block Zrt into the chassis.

FYI, I did not show a pic of it. But I drilled the holes out bigger in the piston to .083" where they feed the exhaust port bridge. This will help keep the bridge cooler and save ring life. If I would have had more time i would have relieved the the exhaust port bridge .0015-.002". I will do that this summer. The exhust port bridge gets hot and actually swell's towards the piston. The correct cure for this is what I described above. Doing them will save piston and ring life.
 

Attachments

  • Like
Reactions: CatFever900

·
Junior Member
Joined
·
5,963 Posts
Any one know why my pants got a litte tighter?
 

·
Registered
Joined
·
1,634 Posts
Discussion Starter · #12 ·
  • Like
Reactions: seanod76

·
Junior Member
Joined
·
5,963 Posts
Yea I might be lol
 

·
Registered
Joined
·
1,634 Posts
Discussion Starter · #14 ·
At least you are willing to entertain that. Some guys have no sense of humor.:chug:
 

·
Junior Member
Joined
·
5,963 Posts
It's because I have a stupid sense of humor
 

·
Registered
Joined
·
1,634 Posts
Discussion Starter · #16 ·
Well a little more progress tonight. Now that the engine is done I will be posting on my project thread until i start tuning. At that point I will put the tuning notes in this thread in case some one else wants to build up a Zrt600. AL
 

Attachments

·
Registered
Joined
·
1,634 Posts
Discussion Starter · #18 ·
Thanks Rusty
 

·
Registered
Joined
·
436 Posts
Al,you can relieve the exh port bridge up to .002 without breaking thru the nikasil? Also your exh porting "edges" won't peel? Will it run 91oct? Hdal
 

·
Registered
Joined
·
1,634 Posts
Discussion Starter · #20 ·
Al,you can relieve the exh port bridge up to .002 without breaking thru the nikasil? Also your exh porting "edges" won't peel? Will it run 91oct? Hdal
I figured about that as for relieving. Thanks for the confirmation.

I am not sure on the 91 octane with a 2 degree key. With out it I would say yes no problem.
 
1 - 20 of 36 Posts
Top