115 vs. 140 crossflow heads - telling the difference.

[iwombat]

So I have a set of what is supposed to be 140 heads (w/ the built-in coil mounts), but damn if they don't look identical to the 115 heads I pulled off. Given who I bought my parts motor from, it's not unlikely that the 115 was retrofitted with the high-compression heads already. How do I tell what's what? Are the casting numbers different?

 

[emdsapmgr]

Re: 115 vs. 140 crossflow heads - telling the difference.

In most years the 140 heads were a different part number from the 115 head. 1977 was an exception. Some heads will look identical, yet have had different part numbers in different years.... In order to know for sure, I'd match the part number on the heads with the BRP parts lists and see how it compares to the 140 head part numbers of that year. In 1977 the 115/140 both used a 322215/321900. From 78 into part of 1981, the 140 heads (322864/865) were different from the 115.

 

[R.Johnson]

Re: 115 vs. 140 crossflow heads - telling the difference.

You could measure the volume with a hypodermic schringe, they will measure in cc's.

 

[ezeke]

Re: 115 vs. 140 crossflow heads - telling the difference.

Do all of the heads have the small numbers cast inside circles on the top coil bracket?

 

[iwombat]

Re: 115 vs. 140 crossflow heads - telling the difference.

Yes they do. Do those correspond to a part number, or are they casting numbers? They're not very easy to read, so I haven't tried matching them yet. I'd probably need to take a rubbing or sand blast the old paint off.

 

[gotboostedvr6]

Re: 115 vs. 140 crossflow heads - telling the difference.

just to give you a heads up the 77 140 heads are the ones you want for high compression

 

[iwombat]

Re: 115 vs. 140 crossflow heads - telling the difference.

Just to be clear again. I know what part #s I want, I just don't know how to match the heads I have to those numbers. I'd assumed any number I find on the heads is going to be a casting number and not a part number. Was that an incorrect assumption?


So, after a spot blast on the embossings I come up with

324528/9 - 85hp-115hp

and

329538/9 - 110hp

so, looks like I'm still looking for a set of high-compression heads.

 

[emdsapmgr]

Re: 115 vs. 140 crossflow heads - telling the difference.

You are correct.

 

[ezeke]

Re: 115 vs. 140 crossflow heads - telling the difference.

Look for 326502/503 or 322864/865

 

[gotboostedvr6]

Re: 115 vs. 140 crossflow heads - telling the difference.

here is some OMC crossflow info for you some may help some may not


To make a 140 you need the tuned exhaust housing and 140 carbs [carb are 1 3/8 vs 1 1/8-+]. the hard part is finding what is called the filler blocks. They are wedged shaped blocks that made a flat surface for the tuned exhaust to mount to. The 135 and 140hp motas all had the blocks. OMC would never sell them as a part. The difference between the 135 and 140 is a 1" gap in the center web under the tuned exhaust.

I have a 1983 Johnson 115 and did the conversion this past summer. . The 140's had small changes through the years. Only the 78-79 140's had the 1-3/8 carbs all others had 1-5/16.

The 85, 90, and 100 hp V-4's had even smaller carbs

A little cross flow V4 history.

Starting with the 1973 135hp V4, basically the first motor to offer performance using things learned from the racing programs KC and KR engines.
The 73 135 is a unique year using different internal engine parts than the later motors but stock performance is about the same as the other years. Hottest head on a production V4
The 1974-76 135hp changed the internal engine parts to be very similar to the later model engines. Slightly Looser heads than the 73.
1977 was the first year of the 140. Better gear case design all though still hydro mechanical shifting. Internal rams on the Trim and tilt, Different exhaust tuning. Slightly looser heads again, some had coil mounts but the ones I have seen were not tapped.
1978-79 140s are thought to be the strongest of the 140 in stock form because they had 1 3/8 carbs stock. The exhaust system changed again to what was used for the rest of the V4 Xflows built. Heads are the same as the 77 140 with coil mounts.
1980-84 140s were back to the 1 5/16 carbs, some had intake stuffers, some didn't. Heads were slightly looser again from the 78-79 heads but great for pump fuel and easy to find.
In 1986 all OMC Engines were changed to the prop shaft rating. The 140s became 110hp. Along with power head to prop shaft ratings the heads went very soft. Known as the Bathtub heads.
I believe in 1990 the 110 became a 115 along with the SLP models being a 112. Built until at least 1998.
Basically the same as the 1980-84 140s with soft heads and no intake stuffers.

 

[iwombat]

Re: 115 vs. 140 crossflow heads - telling the difference.

I'm not looking to make a true 140, but something in the 120-130 range would really be ideal. What I'm looking for here is better hole-shot for pulling skiiers and tubers and not necessarily top-end speed. I rarely get up over 3/4 throttle anyway. To that extent, I don't think the tuned exhaust will get me much. I'm also not really looking to sink a pile of $$ into searching for rare parts. This is more of a fun project than a necessity anyway.

So far, I have a set of the 1&5/16" carbs and it appears a set of the "bathtub" heads as well as the stock heads as described above. I'm putting in boyesen reeds, and I think a set of the high-compression 140 heads would complete what I need to do.

 

[ezeke]

Re: 115 vs. 140 crossflow heads - telling the difference.

Last summer I rebuilt the 1994 Turbojet 115 using the block from a modified 1979 115 flatback. The original bubbleback had both leaf valve shims and exhaust fillers, and we left the exhaust fillers out, but mounted the bubbleback. There was no change in top end whatever, and I could detect no visible or performance change.

I'm a little sorry that we didn't leave the leaf shims out as well because I don't think that they do anything either.

BTW, The V4 exhaust filler blocks were always available as a set as part # 322684, and now as part #392000.

 

[Dhadley]

Re: 115 vs. 140 crossflow heads - telling the difference.

We've found the same thing that Ezeke found. Don't get so hung up on the head configuration and hp numbers. At the rpm you're talking about and the intended use you're not going to see a great deal of difference. In fact the general comment is that all the work & worry wasn't worth the result.

The V4 crossflow is never, ever going to have the torque the V4 looper has. If you're after gut wrenching low end power, get a 60* V4 looper.

If you're looking for pulling power, we've always found the smaller carbs are better but the larger carbs will allow more top rpm. For skiing we've always ended up with the 1 1/4" carbs. The same with the heads, the 115 heads allowed for better acceleration. However, the difference may be so slight it's hard to tell.

The reeds that are shimmed on one side help if you're approaching the rpm where the reeds start to flutter and quit flowing properly. On the other hand the Boyesens don't have that problem anyway.

 

[iwombat]

Re: 115 vs. 140 crossflow heads - telling the difference.

Thanks Dhadley. That's some good information. I think I'll run the upsized carbs (up from 1") and the new reeds and call it a day. I'm doing a full rebuild (have the short-block all back from the machine shop and ready to assemble) and figured I'd make any meaningful upgrades I can lay my hands on w/o spending a lot of $$ for stuff I wasn't going to really make use of. Sounds like the reeds and carbs were the good choices, and I should stick with the heads and exhaust that came with it.

 

[Dhadley]

Re: 115 vs. 140 crossflow heads - telling the difference.

The Boyesen reeds, in my opinion, are the best bang for the buck for a motor that's going to be used for skiing.

BTW - fortunately the casting number on the V4 head is the part number. Doesn't always work out that lucky.

 

[iwombat]

Re: 115 vs. 140 crossflow heads - telling the difference.

BTW - fortunately the casting number on the V4 head is the part number. Doesn't always work out that lucky.

I've been down that road one too many times before. That's why I really didn't think they'd correspond.

Something that makes sense and is useful, who knew?



This is kind of a fish/ski setup, but given the wind and chop where I normally fish, top-end performance is kind of meaningless except on the rare morning. Even so, at sometimes 20min to the fishing grounds 3/4 throttle saves a pile of gas.

 

[gotboostedvr6]

Re: 115 vs. 140 crossflow heads - telling the difference.

IMO do it correctly the first time or dont bother...
or just find a 140 Power Head.. if you do this and not that you will be just wasting fuel..

 

[johnny lightning]

Re: 115 vs. 140 crossflow heads - telling the difference.

Another thing that bears mentioning.If you go with the high compression heads you must run 92 octane premium or higher or you will melt her down !