OMC XFlow Blocks

[Hooty]

I've got a 3.5" bore V6 xflow block (p/n 388804) that's suppose to be a 235. What's the difference between the 175, 200 & 235 blocks. This is a bubble back block but there's no number on the Welch (freeze) plug and I need to know for sure what it is before I spend a bunch of time and money on it.

Thx. & c/6

Hooty

[Robbie B]

Only the 78/79 235 HP small blocks ( 3.5" bore ) had bubble exhaust with filler blocks.

[Hooty]

Were they the only ones? I know the 200 didn't but did the 150 or 175 have a bubbleback?

Thx. & c/6

Hooty

[Robbie B]

Yes, only the 235, 3.5" bore motors had the bubble. The smaller HP motors were flat back exhaust.
Not sure after 1979 when the 2.6 was introduced though, some of the OMC gurus will be able to help with details of motors produced from 1980 on.
The 78/79 235's are a real strong little motor, you could do a lot worse than one of these little motors.

[dan agnew]

i always liked the 149 cubic inch engines over the later 165 as we could turn it harder and worked real well in sprint racing. always had reliability problems with big blocks

Danny

[B.Leonard]

The 2.6 in '90(maybe earlier??) was called a 175. It was bubble back.

I have a bone stock '80 235 block on my bench right now next to my '84 XP. Many differences in the blocks. I'm not sure if it's an XP/GT thing or they just started making the blocks beefier in '84. The cyl walls are thicker (not the liners) and they have a lot more ribbs and thicker surfaces and bolt holes with more meat around them.

I can't belive the 235 makes the power it does looking at that stock porting. No wonder the torque peak is around 5500. The ports on my ported XP block look like hurricane drainage grates compared to that thing :D

The only reason I can think why the 2.6 may have been harder to keep together when run hard would be the heavier piston. But that can easily be solved.

-BL

[Hooty]

This block is 3.5" 235 and the only difference I can see between it and my 200hp is the exhaust. Porting appears the same.
I'm making some headway identifing the heads though. The part nrs. are 332544 & 332545 and they have the s.l.o.w. temperature sensor. I can't tell if they've been re-worked or not but there's no built up area on the circumference of the combustion chamber. I'll post a foto tomorrow and see what ya think.

Thanks & c/6

Hooty

[Charlie M]

1986 was the first year for the buble back 175. The standard 175 has a more conserative port timing compared to the 235's and the GT 175's.

[Hooty]

This is making me crazy!
Do I have a 70's 235 or a 80's 175?? How can I tell the difference?

Thx. & c/6

Hooty

[wrechin2]

Hooty,
Like Charlie M said. 86 was the first year of the bubble back 175 and it was a big bore 3.625. If you have a small bore 3 1/2 bubble it is a 235.:D

[Hooty]

Thanks wrechin2.
You just saved that last little glimmer of sanity I have left. I'm greatful, as are all my friends and relatives.
I'm attaching a foto of one of the heads with the hope that someone will recognize them and know if they're good juju or not and maybe recommend what work, if any, they need.

Thanks to all & c/6

Hooty

[wrechin2]

Hooty,
Would be better if you posted part number also. B. Leonard has a good list of numbers and will proably be able to tell you good/ bad or what. The numbers on on the side close to the bottom.:D I just bought a 79 235 last night and I am going to run my 79 150 heads on mine. I hope they do well.:D What are you building this for? A lake engine or race? go to my old post and there is some info for 235 mods, but remember this is for a race engine on race gas.
http://forums.screamandfly.com/forums/showthread.php?s=&threadid=20559&perpage=15&pagenumber=3

hope this helps.

[racer]

That head is a 323872/3 It is the good 149 in version.

Wrench, if you have a true 79 235 it will also have these heads and they are much better than the 150 heads.

Hooty, 149 inch 235 78&9, 160 inch 235 80-85 then in 86 with some changes became a 175. These all have the bubble.

Also guys please remember the 9 page mod sheets are for race type engines that will get frequent rebuilds and not meant to push heavy rigs.

Alan Stoker

[wrechin2]

Alan,
I bought just the block. So I only have the 150 heads. Pn# 3323456 and 7. I was told they were almost the same thing as a gt head. Will they be ok if I mill them? Thanks.

[racer]

The 323456 is ok but not as good, especially on a ported engine.

[Hooty]

The part nr. on these heads are 332544 & 332545 and one of them has the s.l.o.w. temp. sensor. Any idea if these are what I should be using?

Thx & c/6

[wrechin2]

Alan,
So I really need to find the original 235 heads. It will be ported. Not as heavly as your 9 page block would be. Just squared and all the rough spots ground out. Thanks for the info. What all pn# heads would be good? You proably have 50 sets of them don't you. Email me a price of a set of good heads. Thanks again

[B.Leonard]

What's the part # on that head Hooty? 332544 or 323872? I'll save the picture w/part # in my database. If they're the same I'll record it as such.

It looks similar to the good big bore head just smaller diameter chamber. Also notice how thick the cyl walls are on that block. That tells me small bore without even pulling the calipers out. The early 2.6s are real thin.

-BL

[racer]

Hooty, If that head is a 332544 it has been cut a fair amount as that normally had a ridge where the gasket seated, with it cut the main difference to the 323872 would be the exhaust side deflector, and slightly less compression at the same chamber depth.

[Hooty]

The part nr. for the head pictured is 332544 and I thought they had been cut because there was no ridge. Should I use these heads or try to find the others mentioned? B.Leonard has a good eye. It is a small bore. What has me concerned is the ports. Were all the small bore V6 ports the same or are the 235 ports different? I sent wrechin2 an email asking him to measure the distance form the deck to the top of the int. & exh. ports and the hight of the ports on his 235 but if any of ya'll have these dimensions, I would appreciate knowing them. I also appreciate the time and trouble ya'll have spent helping me.

c/6

Hooty

[B.Leonard]

I'm sure the ports are different from a 150 to a 235 small bore.

Did they ever make a big bore 150?

I think one of the advantages of the big bore is that you can have more port area. Kinda like the 4 stroke world, big bores allowed big valves, less shrouding of the valves by the cyl walls/sides of chamber.

-BL

[Hooty]

That's whats got my knickers in a twist. I've got the bubble back exhaust o-k, but I don't know what block or heads I have. All this stuff came to me in boxes. The part nr. on the block is 388804 . Would you happen to know what it is? Would you happen to have the port dimensions of a 235?
Thanks for any and all help.

c/6

Hooty

[Hooty]

I hate doin' ignorant stuff. It was all right here. Ya'll told me it was a small bore 235 block because it was a bubbleback block. I just didn't "get it". It's on its way to the machine shop to get bored and maybe align bored because the crankcase cover is a different part nr.
All I need now is a little guidance with the heads. Should I use these heads (332544) or try to find the 323872 heads.
After this, it's orderin' parts and start assembly.

Mucho Garcius ya'll!

c/6

Hooty

[wrechin2]

Hooty,
Do you still need the specs for the port heights? Go check out B.Leonards build up on his XP. Gave me a few good Ideals.

[Hooty]

Yo wrechin2,
I don't think so. The main reason I wanted them was be insure I had a 235. But, as you and a few others pointed out, if it's a 3.5" bore block with the bubbleback exhaust, it's a 235. It just took time for that to sink in.
Thanks for the help wrechin2 and if I can help you out lemme know.

c/6

Hooty

[B.Leonard]

Ok... breakin out the old notebook here...

1979 140: I- 2.16
E- 1.80

1979 150: I- 2.175
E- 1.675

1980 235: I- 2.060
E- 1.58

1981 235: I- 2.120
E- 1.55

1984 2.6XP: I- 2.050
E- 1.55

Interesting diff between the '80 & '81 235. I wonder if it was intentional :rolleyes: OMC was known for some very very sloppy tolerances.

-BL

PS

Remember all '80 and later 235s/2.6 motors were big bore 3.625". The 150 and 140 listed are small bore 3.5s

[Hooty]

Add This to the book

1979 235: I- 2.060 + - .005
E- 1.58

Any thoughts on those heads I've got?

c/6

Hooty

[B.Leonard]

Thanks Hooty. I think I see a trend here. Maybe they lowered the intake in '81 to to make 'em a little more torqy, need to measure a few more blocks before jumping to a conclusion.

I'd run those heads. Use good gas (92-93), start with the timing around 20-22 and work up if it looks ok. See what your cranking compression comes up at.

-BL

[Bill Gohr]

Appear to be 150XP's from 84 or5 that had the lip cut off. They'll be ok to use for all around boating, pretty close to original 235's. That has to be a 235 block if it's a 3.5 bore with tuned exhaust, that part number you keep giving out on the block is just a casting number, disregard it.