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Old 11-02-2010, 08:16 PM   #1
Buzznut
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Question GM Inline 6 Interchange Guide? 230, 235, 261, 270, 292, 302 Stovebolts?...

I'm pretty good at searching the internet and all I seem to find with regard to GM IL6 engines is parts for 230, 235, 261, 292, but nothing stating that it will fit 270 and 302 blocks. Will the parts listed for the 230, 235, 261, 292 also bolt onto the 270 and 302 engines? Specifically I'm looking at the aftermarket Offy intake manifolds, distributors, water pumps, exhaust manifolds, etc... Anyone have experience with these?
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Last edited by Buzznut; 11-02-2010 at 09:01 PM.
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Old 11-02-2010, 08:34 PM   #2
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Default Re: Will IL6 230, 235, 261, 292 parts fit the 270 & 302 GMC Stovebolt engines?...

I'm hoping to start stockpiling parts as soon as possible... Anyone?
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Old 11-02-2010, 08:38 PM   #3
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Default Re: Will IL6 230, 235, 261, 292 parts fit the 270 & 302 GMC Stovebolt engines?...

Which engine are you trying to build, and why haven't you talked to the part suppliers?


Nothing interchanges between the 194/230/250/292 Chevy and the 216/235/261 Chevy or 228/256/248/270/302 GMC.

You can modify a 250/292 HEI dizzy to work in the GMC or the 216/235/261 Chevy, but that's about it.

Some parts interchange between the GMC and 235/261 Chevy, but not many.
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Old 11-02-2010, 08:53 PM   #4
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Default Re: Will IL6 230, 235, 261, 292 parts fit the 270 & 302 GMC Stovebolt engines?...

I'm going to be building up the 270 I have and have been looking online at Langdons and Patricks, etc... but finding nothing for the 270. I was mainly looking at the Offy 4bbl intake and some cast exhaust manifolds, and my water pump is missing. I'm also going to go .040 to .060 over and will be needing new slugs, rings, etc.. I'm going to have the head done professionally. I ordered this book and it should be here in a couple days:

http://www.amazon.com/How-Hop-Chevro...ref=pd_sim_b_2
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Old 11-02-2010, 09:02 PM   #5
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Default Re: GM Inline 6 Interchange Guide? 230, 235, 261, 270, 292, 302 Stovebolts?...

Maybe by renaming this thread we can use it as an interchange guide...
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Old 11-02-2010, 09:18 PM   #6
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Default Re: GM Inline 6 Interchange Guide? 230, 235, 261, 270, 292, 302 Stovebolts?...

www.stovebolt.com
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Old 11-02-2010, 09:35 PM   #7
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Default Re: GM Inline 6 Interchange Guide? 230, 235, 261, 270, 292, 302 Stovebolts?...

I have to, I just do!!

You want to look at something different to use, then start looking at the Gimmie V-6's!!

Gimmie made some BIG V-6's through the years.

Hell, maybe a double V-6, V-12 or two??

I never knew about them until my ol' RR Buddy started talking about his ol' Gimmie P/U and just how it's V-6 pulled like a John Deere..

Have you got a copy of Leo Santucci's great as close to a modern 6-banger book that there is??

pdq67
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Old 11-02-2010, 09:41 PM   #8
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Default Re: GM Inline 6 Interchange Guide? 230, 235, 261, 270, 292, 302 Stovebolts?...

I have Santucci's book...it's a great resource, but he doesn't cover the GMC 270's or 302's... I'd love to see an updated version with these engines included.
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Old 11-02-2010, 09:43 PM   #9
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Default Re: GM Inline 6 Interchange Guide? 230, 235, 261, 270, 292, 302 Stovebolts?...

You need to get the old Bill Fisher book if you want to find something printed about GMCs.

California Bill's Chevrolet, GMC & Buick Speed Manual, 1954 Edition
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Old 11-02-2010, 09:46 PM   #10
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Default Re: GM Inline 6 Interchange Guide? 230, 235, 261, 270, 292, 302 Stovebolts?...

Yep, that one is next on my book order list:

http://www.amazon.com/Chevy-GMC-Buic...d_bxgy_b_img_b

makes me feel like a little kid again in grade school when those book order forms came home...

So, it seems that no matter how you slice it, building a 270 isn't an easy feat. The more I search the more I realize parts aren't that easy to find...
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Old 11-02-2010, 10:02 PM   #11
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Default Re: GM Inline 6 Interchange Guide? 230, 235, 261, 270, 292, 302 Stovebolts?...

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Old 11-02-2010, 10:37 PM   #12
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Default Re: GM Inline 6 Interchange Guide? 230, 235, 261, 270, 292, 302 Stovebolts?...

Can I ask anyone who might know what the specific differences are in exhaust and intake manifold design?
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Old 11-03-2010, 01:51 AM   #13
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Default Re: GM Inline 6 Interchange Guide? 230, 235, 261, 270, 292, 302 Stovebolts?...

GMC manifolds do not interchange with 216-235-261 Chevy sixes or 195-215-230-250-292 Chevy/GMC sixes. 228-248-256 and most 270 GMCs have smaller intake ports than 302 and 270H heads. So the port alingment rings don't interchange. Did you join Inliners International? It was started to promote 270-302 GMC engines.
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Old 11-03-2010, 03:17 AM   #14
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Default Re: GM Inline 6 Interchange Guide? 230, 235, 261, 270, 292, 302 Stovebolts?...

Cast headers for the 216-261 fit the GMC 228-302. Port matching should be done.
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Old 11-03-2010, 09:06 AM   #15
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Default Re: GM Inline 6 Interchange Guide? 230, 235, 261, 270, 292, 302 Stovebolts?...

The GMC is the most expensive of the three engine types to build.
Yes, you can get parts for them, but you need to inquire, not just surf the internet.
Patrick's and Tom Langdon are your best bet for rebuild parts. Speed and dressup parts are mostly limited to vintage, but they still make the Howard 5 carb intake, and Fentons are available for it. Jim Carter Truck Parts has some parts listed for it. You could also try Larrowe & Sons truck parts...
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Old 11-03-2010, 09:28 AM   #16
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Question Re: GM Inline 6 Interchange Guide? 230, 235, 261, 270, 292, 302 Stovebolts?...

Quote:
Originally Posted by 302GMC View Post
Cast headers for the 216-261 fit the GMC 228-302. Port matching should be done.
Hmmm, now I know that the intakes for the 235/261 don't interchange with the GMC, so it would seem that the port spacing for the exhaust would be different as well. In an old Patrick's catalog I remember seeing the Fentons for the Chevies and the GMC as being listed as two different items. But I've never gone and measured the port spacing on my GMC to compare to the Chevy.


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Old 11-03-2010, 01:29 PM   #17
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Default Re: GM Inline 6 Interchange Guide? 230, 235, 261, 270, 292, 302 Stovebolts?...

Jim Carter lists two different Fentons...
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Old 11-03-2010, 09:20 PM   #18
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Default Re: GM Inline 6 Interchange Guide? 230, 235, 261, 270, 292, 302 Stovebolts?...

I believe the castings are the same - the machining is different. The port spacing is close enough that if all you try to do is split the difference between the forward/aft single ports and the middle siamesed ports . . .

I spent a day at Langdons(meant to say Patricks) and among other things watched shopping carts full of rough castings being machined on jigs. One shopping cart of castings rolled in - and boxes were packed with Chevy versions off of one machine and GMC versions off the other machine.

I have been snagging GMC speed parts whenever the opportunity affords - if you keep your eyes open, stuff pops often enough to make a build up possible.

I ran across a 40 ft container stuffed with innumerable NOS GMC parts and carted home all I had money for a few years ago. Lots of Vietnam era NOS parts for military GMC engines that fit the civilian versions just fine.

If a 270 is what you want to build - and you don't need everything tomorrow - just be patient, watch eBay and craigslist - and be ready to buy when the parts surface.

Last edited by motion guru; 11-04-2010 at 07:43 PM. Reason: up too late
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Old 11-03-2010, 09:57 PM   #19
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Default Re: GM Inline 6 Interchange Guide? 230, 235, 261, 270, 292, 302 Stovebolts?...

id be quite keen on a twin carb manifold and some headers for a '61 261...
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Old 11-03-2010, 11:03 PM   #20
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Default Re: GM Inline 6 Interchange Guide? 230, 235, 261, 270, 292, 302 Stovebolts?...

If they're that rare then I'm not parting with this engine any time soon... I'll build it. so far I really only need a resource for intake manifolds, water pump and fuel pump. I'm likely going to alter the HEI unit mentioned above, I'll find the Fenton exhaust and will keep the original GMC scripted valve cover. Jims Chevrolet is about 1 hour from me and I know Jim pretty well from building a few 55 thru 59 pickups. I'll pick his brain about parts..
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