Looper exhaust porting

[Captain75]

I listen to you racer, it won't be any WOT before I have the jetting checked and corrected!

Any of you guys out there who knows where to find recirc check valves, w/o paying 23bucks each!?
I have managed to get a couple of dead ones to come alive by removing the end screen, and work the inner part back and forth and at the same time lube with weapon oil. After this they close when exposed to compressed air, but still leaks a bit if you blow by mouth. Any other tricks out there?

My boat

[olboatman]

Nice pic!!! I new you were on the other side of the planet ---but I didn't realize you were that far over! Gary

[Captain75]

Drilled my mains to 1,8mm(appx 0,0709....)
switched back to stock idle air bleeds (#48),
removed the 22" Raker, and mounted a 19" vented, heavily cupped alu prop.
Now it really came alive! Jumps up on plane, revs appx 6000rpms, still break in process so I don't want to stay at WOT and start trim out to gain rpms. It reaches 6000rpm fast, in only a couple of seconds. Just a small bit of "four stroking" when you stab the throttle when on plane, plugs look chocolate brown. After these last adjustments I can clearly say the port work described in this thread made a huge difference in power, every hour was worth the effort, a big thanks to all you guys who gave me pointers and tips!
Right now I don't se any problem in reaching my goal of 50knots with a killer holeshot. If I want to go faster than that I need another 100hp and a huge setback because the boat is bow heavy due to the hard top, and it don't respont very well to trim adjustments.

A couple of remaining questions;
1. Should I be looking at an even smaller pitch to reach the area of the most hp's?
What kind of rpms should I be looking for( no duration changes made )
2. I have another set of untouched 2,7L heads that I want to mill if its possible while staying on pump gas, any ideas on how much I can shave?

Best regards!
Anders

[Captain75]

It seems to differ .025" when it comes to head depth when comparing an 87 200xp, and an 87 225!? Is that correct? Despite this difference it seems to me that Jetting is the same in both motors? Does that mean that I can mill .025" without worrying about jetting.

The removed airbox baffle together with a 12size jet increase must improve something?

[TomAprilsswitzers]

Does anyone know what the max PSI for a blue printed V8 should be? Before we blue printed and evened out the ports on it the PSI was 135, this is an original 3.6 punched out to 4.0 liters. We now have 150-152 psi after raising the ports and the motor has not been broke in yet , only about 30 minutes at the dock, and this is with stock 4 liter heads, I have a pair of Taylor Marine and Machine heads and I am afraid to put the on with the PSI at this level? anyone? I have been told that the max PSI should be 145 to 155, but I have also been told that stock V6's are usually 150...HELP!!!!

[TomAprilsswitzers]

Here are some pictures of the port job we did (my first attempt) plus we opened the rod slots too.Attachment 298785Attachment 298786Attachment 298787Attachment 298788Attachment 298789

[wanagofass]

It seems to differ .025" when it comes to head depth when comparing an 87 200xp, and an 87 225!? Is that correct? Despite this difference it seems to me that Jetting is the same in both motors? Does that mean that I can mill .025" without worrying about jetting.

The removed airbox baffle together with a 12size jet increase must improve something?

I'm not sure how many psi different .025" would show, but if I remember I ended up 4 jet sizes bigger going from stock closed deck heads to 2.7L heads. That's about 20 psi tighter but with a better chamber also so be cautious.

[wanagofass]

Does anyone know what the max PSI for a blue printed V8 should be? Before we blue printed and evened out the ports on it the PSI was 135, this is an original 3.6 punched out to 4.0 liters. We now have 150-152 psi after raising the ports and the motor has not been broke in yet , only about 30 minutes at the dock, and this is with stock 4 liter heads, I have a pair of Taylor Marine and Machine heads and I am afraid to put the on with the PSI at this level? anyone? I have been told that the max PSI should be 145 to 155, but I have also been told that stock V6's are usually 150...HELP!!!!

Are you checking the compression with the same guage? Porting can only lower the compression. Unless you ended up with a bigger cc' dome or the 4.0L heads have smaller cc' chambers than the 3.6L heads then the only gain in compression should be from a fresh bore and rings.

[TomAprilsswitzers]

Used the same gauge each time, will try another gauge in the future.The new rings have not seated yet...

[baja200merk]

There has never been a stock v6 with 150 psi. Try another gauge

[TomAprilsswitzers]

This is not a V6 it's a V8. I was only told that some stock V6's had 150....So what about a V8 and it's stock PSI?

[baja200merk]

Yes I understand. I don't know what v8 was but id guess 110-115 at most. Who ever told you there was a stock v6 rude with 150 psi either had a bad gauge or was clueless. Hate to see you try it on pump and hurt a motor. We have run 160 on pump with no load and small prop jetted safe and low timing it was on accident

[Captain75]

I need some pointers when it comes to using the right prop pitch.
I went down 3", which made a huge difference on holeshot and cured the small off idle bog.
Still a bit of "fourstroking" when you open up full, I believe that is due to the mains is a bit to big, 0.071" compared to stock 62D. Thinking about removing the airbox to se what it does.
Right now motor revs appx 6000 at wot, seems a bit low? I believe the limit is 6700!?
Shall I go down another 2" and gain like 500-600rpms?

Pointers please!

[wanagofass]

I doubt that there's more mph to be had in reducing pitch.

[NosBoss]

The early loopers had the limit at 6100-6200. That can be changed with aftermarket power packs.