Inliners International Forums General Discussion Engines GM 4 cylinders 151 153 181

Guys:

Something to check when considering the use of SBC V8 rods. The main dimensions may be correct but the V8 rods have an "offset" that the inline sixes (and I'm guessing the Chevy II 4-bangers) do not. That was one of the issues I ran across when having K1 build a set of 6.2" billet rods for my 250ci L6 project and why I couldn't use widely available "small journal" SBC V8 rods. My understanding is that, using rods with the V8 offset will cause "less than optimal results". If you check with Scat or Crower (or ???) you'll find that's why they have a unique rod for the 194/230/250 Chevy six.

Russ

I thought the difference was that the big end width is greater on the inline rods. I read somewhere they they were even the same forging but of course I can't find that now.

Beater:

I'm assuming the Chevy-II 4-banger being the smaller brother to the 194/230/250 six, nearly everything is the same (only minus two cylinders). With that in mind ...

You're right that the big end width of the six rod is wider at about 1.030" where the SBC width is .940" (as I recall). For the six, the big end diameter is the same as the SBC "small journal" (265/283ci) at 2.000" and the small end is the same at .927". The problem is the beam offset for the V8 where the L6 isn't.

Continued ...

The beam, or the pin eye?

Beater:

Continued ...

If you look at a V8 rod from the side and draw a line down through the center of the beam, you'll see that one face of the big end is closer to that center line than the other. The face (larger if I recall) that is closer to the center line is the one that faces the other rod in the V8 that shares the same crank throw. The L6 (not having a neighbor) has the same distance to either face from the beam center line.

Continued ...

Beater:

Continued ...

I don't have a V8 rod to look at but I'm guessing there is not much of a "bevel" on the big end on the side that faces the neighboring rod and there is more of one on the "outside" to clear the crank throw fillet. The L6 rod has identical bevels on both side since it has to deal with the crank throw fillets on both sides. I suspect a V8 rod used on a L6 crank (even with the right 1.030" width) would bind on the one side and I don't know how the beam offset would affect operations - I'm thinking not good.

Russ

Beater:

PS: Sorry for doing this in 3 parts. Have a strange problem with my email support that limits the size of the text I can send in any one message. Can't get a straight answer as to why from any of the tech support people involved.

Russ

Beater:

I know the "pin eye" is evenly balanced on the L6 rod. I'm not sure if it's offset (the same way the big end is) on the V8 rod or not. If I had to guess, I'd say it probably is.

Russ

I'm sitting here with a mike and a set of Manley aluminum rods for a SBC and I'm darned if I can see a difference from side to side???? Where are you getting you info from???

Jalopy45:

The stock V8 rods I have seen were slightly different and I think the Lunati rods in my son's 406ci Chevy were also slightly offset. I've also read about that somewhere and I'll see if I can dig out the article. As far as aluminum (race) rods are concerned, I'm sure you're right. Maybe the offset isn't a big issue in a race engine but perhaps has an impact if you're trying to get 100K+ miles from a daily driver? Let me see what I can dig up but the offset issue was one that was raised by the folks at K1-Technologies regarding the useability of SBC rods in the 250ci six.

Regards,

Russ

Jalopy45, Beater, and others:

I'm beginning to worry that maybe I completely misunderstood what I was told about rod "offset". If I'm not properly informed on this subject I will be back on this thread to apologize for passing on mis-information - that's certainly not my intent. Of course I can't find the article I remember reading that was in one of my vintage Hotrod "Engines" books - ain't that always the way? Let me check with the K1 folks again and I'll pass on what they tell me. But on the issue of the big end width being wider on the L6 (and so the L4?) than the V8, that alone makes the V8 rod an unusable alternative?

Russ

Russ, you are correct about the offset in the SBC rods. The beam is offset from one side on the B/E of the rod. On aluminum rods, it might not be as apparent because the beam is much wider than the beam of a stock forged steel rod, and the offset might not be as obvious to the naked eye. Also as you mentioned, for use in inlines, a chamfer on the ID of the B/E is required to each side of the rod to give clearance for the radius on the crank journals. A SBC(most any V-style engine as well) only has a chamfer cut into the side of the B/E that faces the radius.If you have ever forgotten to number the rods when you disassembled an engine, thats a good way to tell if you are putting them back in the engine with the correct orientation, by looking at the chamfer and making sure they are facing the radius. Also for racing applictaions involving inlines, the rod bearings are often radiused on both sides as well to clear the radius'.

Ok, So that would make me believe even more that they may all be the same forging and that the material taken from the inside creates the off set and causes the rod to be .094". I still would like to know if the later 181 with the one piece seal and .094 big end width might be a V8 rod. V8, L6, & L4 rod bearings are the same width and are either 2.0 or 2.1 depending on which engine. Beater

Russk, I wish some of the people who email me had your server. Short and sweet!

I'm humbled, been throwing SBC's together since the 60's using all kinds of pieces and never noticed the offset. May explain a few of my fireball displays at the 1000 ft. mark?? Never too old to learn.

Beater:

You're right about sending "short and sweet" emails. But the problem I'm having is a pain at times. Now there's no (practical) limit to the size of messages I can receive ... go figure.

Russ

Jalopy45:

I wish I could say my "heads up" on the V8 vs. L6 rod was due to years of hands on experience and sage wisdom. Sadly, it's far from it. My "insight" was due to the fact that just a few weeks ago I was wandering down the same garden path, thinking I might use "small journal" V8 rods in my 250 project. I wrote K1 asking if they would sell six of them and they replied with an explaination as to why that was NOT a good solution (big end width, beam offset, and such). I ended up sending them an OEM 250 rod so they could take all the critical measurements (except for the 6.200 c/c length I requested) to ensure the finished billet H-beam rods I ordered would be correct. So, more of case of dumb luck on my part.

Russ

Looking more closely at the V8-6 rods I can see that one side has been machined than the other. This would account for the off set and the narrower overall width. I would like to know if any one has a V rod with #7755 in the top above the wrist pin bore. If we could get the forging before they were narrowed? Beater

Here are the cams we worked up a few weeks back at Erson. I went by Monday and Steve and I discussed a suggestion Tlowe made. That was to use cam #3s lift on cam #2. I just decided to go with #3. It is the hottest of the three but still quite streetable. It should be fun in a light car. I'm still 1 rod short of a set.

Beater,
Might be able to help you with a rod, soon. We can PM about that.

Got my cam from them. Solid lifter 220 dur @ .050 , .510 lift after the lash. It should run real good in the farm buggy. The boy and I tore down the shortblock and took it in to get machining going.

What did Steve say about the different lobes? I ran into problems wanting a different lift. Tom

Steve said he could do if a lobe plate existed. He even said they could make a new plate but it would cost more. I just went with cam #3. It's a bit hotter than #2 but in my application it will work well. If I doesn't I'll get another one. I've got guys here who are contacting their boat builder friends searching for rods. Tahoe has lots of boat stuff around. We didn't have an Inliner meeting this month so I didn't see the guys. Will see them in January. Mean while I have plenty of work to do. Thanks, Beater

"I'm still 1 rod short of a set. "

I don't know what to say.

Will6er

That's all changed. Now my rods runnith over. I got a full set with pistons on eBay for $75. I'm not sure they are the ones for the 2 piece seal crank buy if not I'll stroke the 151 with a new style 181 crank. They are plentiful.

153 head on eBay. This head must be early. The center exhaust ports are Siamese type. Cast #3788518 or 618?

does anyone have the specs for Corvair rods?? I know some parts interchange with 6's and 8's like the lifters and some of the bearings and pushrods with 8's.

Looks like the standard 5 port head to me. I'll take some pix today of the ones I have and post them.

Check the center port on this one. The exhaust ports are not Siamese. On the eBay head the boss is set back like the intakes.

2 heads only a few years apart, , ,

Mine Is a third form. It has the emission tubes in the exhaust ports. The manifold mating flange on the ends is different.

I got my 181 rods today. I can put the 181 crank in the 153 block and see what deck height I have with the 250 pistons. It should be close.

Bet they will be sticking out of the hole, just barely. Just file them, better yet use a sawzall! Goodluck, keep us posted.

My pistons have a .060 dish. I'm hoping most of that is sticking out. If it isn't right up there I'll have to take the sawsall to the block!

A bastard cut file will do wonders also. An added bonus is that will make a really flat surface.

MBHD

Who did they name those after? They called them that long before any of us were around. Did they know we were coming?

Here's a couple of shots from my phone on an altered V8 HEI to use on a 4 or the 90 degreee V6 could be changed the same way. The housing is shortened and a sleeve placed over the reamainder to match the 4/6 cyl. distributor mount and the 4/6 cyl. gear installed farther up the distributor shaftr to line up with the cam.

Here's what an 8 port 181 head looks like, thewre is one on EBay now with large v alves and screw in studs still @ $200. http://cgi.ebay.com/ebaymotors/Marine-Ch...=item4cf4639cb6 ,

I don't understand. Do you use the 8 cyl cap for the 4?
Jan

You could just using every other post.9 I'm using one V8 distributor to fire 2 four cylinder engines running in tamden, but I'm converting some Mallory Unilites which you just have to change the cap and rotor to a 4 or 6 cylinder.

I got a pretty hot lil 181 out of a 1950 Willys that I found for a buddy. He didnt want the 4 banger and offered it to me. I have wanted one forever for a lil T modified project that I have been collecting parts for. Anyways mine came with an Erson cam but its done, few lobes are toast. So Beater what were Ersons prices like? I am thinking of cam #2, what lifters are you running?
My mill came with a Clifford 4 barrel intake meant to go on a 153 head, but someone built an adapter to mate them up?? It came with a header too, and a Mallory dual point dizzy too. The Clifford intake has way smaller ports then the 181 head, making it restrictive for sure. I am going to sell the Clifford intake to a 153 owner to pay for the Erson cam and lifters.

-Shiny

Shiny, It sounds like you got a sweet deal! I paid $160 something for my cam out the door. I don't know if that was a deal or not. I didn't ask. Steve said stock lifters would be fine. I'm sure Steve Tanzy kept the profiles we worked up if not send him a copy of cam #2. I drive by there all the time if you need my help let me know. I'd like to see pictures of your engine. I didn't know the 181 ports were bigger. Is yours like the one in Gary's post or does it just have two intake ports? A friend gave me a 181 head but I haven't picked it up yet. I don't know which one it is. I'm getting my 153 head ready to send to Tom Lowe for a treatment. It will get 1.84 intakes and 1.60 exhausts. lumps, porting . and screw in studs. That will make my build, Beater

Jalopy45: I like that distributor mod, thanks for the photo.