Which GO engine for OB conversion ?

[CapeTown73]

Hi guys, I remember reading somewhere that the OB conversion kit that is made by ‘Lights’ for the Novarossi T21M, will also fit one of the GO marine .21 engines ? I have one of these conversion kits that I originally used with my T21M Nova as an outboard but have since built the Nova into my JAE21 rigger as an inboard engine, and I now have the conversion kit free. I would like to fit this kit into a GO engine and mount it on a spare Lawless leg that I have.

Can anyone tell me the model code or name of the GO engine which will accept my spare conversion kit ?

 

There is a GO engine distributor here but I need to give him the right code to ensure I get the correct engine.

Thanks for any assistance.

 

[Jerry Wyss]

I think it this one Wennie

http://www.massivemods.com.au/product_info.php?cPath=2&products_id=271

 

[CapeTown73]

I think it this one Wennie

http://www.massivemods.com.au/product_info.php?cPath=2&products_id=271

Thanks for your quick response Jerry. And I believe you are correct in that someone said the right entgine has a black casing !

So it's their .21 PRO 7-port.

Kind regards,

 

[RodneyPierce]

I think it this one Wennie

http://www.massivemods.com.au/product_info.php?cPath=2&products_id=271

Thanks for your quick response Jerry. And I believe you are correct in that someone said the right entgine has a black casing !

So it's their .21 PRO 7-port.

Kind regards,

Yes, these are the ones. The GO PRO versions. I have the 5 port myself, and its a pretty decent runner.

 

[Jerry Wyss]

They're also calling it a "Marine" version Wennie . I really don't know how much an equivalent "Buggy engine" would differ from the Marine,, speaking of internal timings. I heard of a exhaust port timing of 170* on the marine. In my world thats at least 8* (degrees) too low for current O/B "J" pipe use.

 

[CapeTown73]

They're also calling it a "Marine" version Wennie . I really don't know how much an equivalent "Buggy engine" would differ from the Marine,, speaking of internal timings. I heard of a exhaust port timing of 170* on the marine. In my world thats at least 8* (degrees) too low for current O/B "J" pipe use.

Jerry,

I appreciate this information and I will lift the exhaust timing to around 178/180* when I get the engine.

Cheers,

 

[RodneyPierce]

the marine and buggy version are the same timing numbers. cranks close around 55*, exhaust at 172, transfers at 126 boost at 122. only diff is the marine crank is fully threaded, water cooling head, and rotary carb and flywheel. everything else is the same.

 

[Ray Sametz]

This is what's so cool about IW, in less then a hour a guy in South Africa has an answer and timing numbers to boot. B) B) ==={}

 

[CapeTown73]

This is what's so cool about IW, in less then a hour a guy in South Africa has an answer and timing numbers to boot. B) B) ==={}

Hello Ray,

Yes you are right ! IW is a wonderful facility and I have received excellent advice and assistance each of the previous times that I've asked!

Thanks to all for sharing !

Cheers,

 

[RodneyPierce]

wennie, let me know if you need any further assitance. I have been playing with these motors here this summer. Stock button volume is .19cc including squish, and they need to be turned down, as the stock clearance without any shims is around .022, which as we all know, is way higher then we want to run. Im currently running the stock button, at .006 head space. My exhaust as at 187*, raised the boost port up to match the transfers. have a blowdown of 30.5. motor runs pretty decent

 

[CapeTown73]

wennie, let me know if you need any further assitance. I have been playing with these motors here this summer. Stock button volume is .19cc including squish, and they need to be turned down, as the stock clearance without any shims is around .022, which as we all know, is way higher then we want to run. Im currently running the stock button, at .006 head space. My exhaust as at 187*, raised the boost port up to match the transfers. have a blowdown of 30.5. motor runs pretty decent

Thanks Rodney, I appreciate that you are there to help ! And thanks also for the numbers that you are currently running. I have a friend who runs a precision engineering business and I will talk to him for assistance to maybe replicate what you run. Well see !

Cheers again,

 

[Jerry Wyss]

Ok Rodney I'm a little concerned with the 187* Ex port timing displayed up there :lol:

CapeTown probably runs lower nitro, (just a guess) and you can afford to run a much higher compression ratio than you can using high nitro. A .19cc button volume is on the high side for 60% nitro, along with the lesser compressed stroke of 187* Ex port timing will give you.

I would estimate that Rods compression ratio is in the 8.?:1 area. It will work but your missing out on the coup de gras of engine performance.

If your engine was mine, running say 30% nitro, I would not let the Ex port timing go above 181*, 182*. The idea here is to get that .19cc button volume to work for you with the less potent 30%. The best way to do that is to increase the compression, to generate more heat for ignition of that larger volume of less potent fuel. Detonation has not been a problem since I switched to 30, 35% nitro while utilizing higher compression ratio's. Medium plugs will work better here with the higher methanol content. It helps to retard the timing slightly for the lower flash temp of the greater methanol content in 30% nitro fuel.

Since it looks like the transfers and boost ports are in the 130* area, I would open the crank to 215* total open time to take advantage of the higher transfer port timings. Get at least a 65* ATDC closing timing on the crank. I'd advise you verify the 130* transfer timing,, thats on the high side,, any more would probably be unhelpful.

Now the hard part,, its likely that its going to take extra heat to get this thing to tick off correctly. As a rule, I always break my engines in without any water (to the cooling head)on a .21 O/B power head. In fact I never use water, air cooling is about as cool as I give. For most engines its a long process for break-in but you gotta do it.

Another problem is that I don't know what the climate is like in your area. If its hot and humid most of the time I have heard that after breakin its a good idea to use a small amount of water going thru the head. Just a fine spritz coming out the head is enough.

An adjustment that I would expect, would be that you may need a bit more compression. On a lathe, turn the outside edge of the angled squishband and make it a "partial angled squish" so you will have a small flat area on the outside of the squishband. Just remember that whatever amount you turn off (in thickness) you will have to turn that same amout off the area where the button seats on the sleeve flange. This will have to be measured out ahead of time to make sure you have enough "meat" to lose on the button seating area.

I have been using head spacing as low as .004" using the lower nitro and have went as high as .006".

Tally-Ho

 

[RodneyPierce]

Jerry, I hear you. I was simply stating what I run for numbers in my motor, and what works for me. My compression ratio is actually at 9.4:1 TCR. Transfers at 126, not 130. The total duration (after opening closing to 65* ATDC is 218*) And these motors are very hard to get temp in. I partially blame this on the cooling head. The passage is HUGE. Great motors though im my opinion. I love mine.

 

[Jerry Wyss]

After all this talk I don't remember hearing what pipes he has. Sure hope its not a car pipe h34r:

 

[topfuel443]

Hes got pipes, hoppers and some others.

~ James

 

[RodneyPierce]

good to hear. Also, TD said he runs 45% nitro, so I guess I just assumed it was available there in South Africa also. It def makes a difference.

 

[topfuel443]

If I remember right, Wennie has run 50% before on some engines. Been a while since we have caught up.

He will chime in though.

 

[CapeTown73]

If I remember right, Wennie has run 50% before on some engines. Been a while since we have caught up.

He will chime in though.

Hello Gabe ! So nice to see your posts. Its sure been a long time since we last talked. I almost feel guilty for not having made any progress with my 7.5 F1 OB tunnel boat, but the 'rigger fever' got a good hold of me a few months ago and its taken virtually all of my time and resources since then. I’ve got both my .21 and my gas JAE riggers running respectfully well! But I havent abandoned the F1 project and I will more than likely complete the boat before end of this year. I'll let you have some photos as I progress. Elza has been visiting friends in Redding, California for the last few weeks and will be back this coming Friday. I've really missed her!

Its now just gone 04:00 in the morning here, the two French poodles do a tap dance on me around this time each morning which tells me that they want to go outside to do their ablutions ! So while they’re busy I usually have a quick look at anything interesting on IW ! So here I am !

Jerry and Rodney, yes James is right! I have both versions of the .21 HTB pipes and plan to run the ‘power’ pipe on the GO OB engine after I take the exhaust duration up to 180 and will also do the lathe-work on the button to get the head clearance closer to what it should be. Unfortunately nitro is very expensive here so I’ve run all my nitro engines on no more than 40% for this past season.

I must also thank both of you for the excellent, and valued, information on timing numbers etc, but I have to be honest and admit that I don’t have any experience with changing (or even measuring) the numbers for intake, transfer, button volume etc. So my work on this engine will probably be limited to the exhaust timing and head clearance. I would also be OK with increasing the nitro content to 50% if this will make a meaningful difference ?

But first things first. Later this morning I will contact the local supplier of GO engines to find out if has the 7-port Pro Marine engine in stock. I’ll keep you posted!

Gabe I’ll send you a longer letter this week directly to your OER e-mail addy if thats all right.

Thanks again for all the help,

Kind regards,

 

[Jerry Wyss]

Just a re-cap,, I think you would be better off with the two exhaust ports timings that you expressed, 178* to 180*. Thats if you can get the pipe length short enough. With the HTB "HP" you would have a better chance getting down to at least 8 & 3/8ths inches. Thats not an exact length I'm giving here, it's just to have the ability to get that short. The "hot spot" length is something you'll will have to find by running the thing.

JW

 

[Mark Leyde]

Wennie, The PTO housing diameter that fits into the crank case will need to be turned down to about 1.002" to fit the Go engine. The bolt holes will also have to be sloted just a bit to fit also. Other wise every thing will fit great. I have done up a couple of Go OB's now.

Mark