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#42867 08/08/08 12:00 PM
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The head was acid dipped to remove some rust, but the water jacket didn't come up as clean as I had hoped. However, what you see on the combustion surface is wipe away rust dust. The PO had the head gasket matched,ported and polished, and the chambers slightly contoured.The springs are dual 115# with .095 spacers as the head was milled an equal amount.The keepers are of unknown(so far) make, but are light weight. The cam is a 60's vintage Clifford "290" and Larry at Cliffords has recently provided info on that cam, but I haven't profiled or degreed it yet.
I'm rebuilding this 261 with all that I received with it,just to get it running again.Any changes I'll make later.Certainly any and all suggestions,comments,or critizisms are welcome from you all. By the way, this motor came with a home built aluminum intake and the 2 4bbl carbs it ran on.That rebuild work is a ways down the road, but this has been a new fun experience for me.



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wow looks like from this angle that someone did a big porting job on those intake ports, and look great, could you tell us what they measure across, the intake port diameter that is, looks like they polished up those combustion chambers too, very nice looking unit!


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It must be the pic angle because they are stock 1.75" with a 3 angle valve cut.


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Drew,

It's great to see another 261 go together. I'm on my fourth one now. Are you familiar with the Racer Brown article in the May 1955 issue of HRM? The Bob Duggan article in the Jan/Feb issue of the 12 port News. Is your block the later version with the full flow filter fittings built in?

dbane,

How is yours progressing?

Best wishes!


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well if the intake ports are 1.75 inch diameter then someone did a real big port job on it being that the stock port is 1.5 inches across, right guys? I thought that the gmc heads were more desirable because the H head and the 302 head had the larger 1.75 intake port diameter and this lends itself to better power than the stock jimmy head, and chevy heads which are 1.5 inch across, is this accurate, I thought I picked this info up here but maybe I am mistaken? Oh and as for my motor hoyt, it is just about ready to go, got the block done, just got to put in the oil pump and lube the cam lobes and pop in the lifters and finish my 250 HEI distributor for it by making a colar for the hold down, and when I get my truck back and finished from my body work guy (and that is a whole other can of worms and me just being furious with him for what I have paid thus far and how long its taken for what I have got so far, AARRRRGGGGGHHHH) and then I am going to port and polish my 848 head and have it ready to go, got my webers mounted on the offy. So back to these ports, if he has ports that have been done out a quarter inch from stock, can this be done? I thought that only 1/8 could be done and the ports hogged out to 1.625 until you got into water? whats the skinny here guys?


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Okay,It's obvious to me that I need some education on this motor or the head at least. I have a 261 shop manual print out that says the stock Intake Valve measures 1 7/8 inches head diameter and the stock Exhaust Valve measures 1 1/2 inches head diameter.And I mis-typed in the earlier post and should have typed 1.875 inches(1 7/8).Am I right or wrong?

Thanks Hoyt, I've read those articles,but better read them again I think.And yes again, it is the later block with the fittings built in.The progress isn't too slow ,and while I'd like to see this motor running soon,I'm not pushing it.Currently I'm degreeing the cam which is a new experience for me.So I'm taking my time and getting help with that.The PO built his own dual aluminum intake running 2 750cfm Holleys! He swears it wasn't over carburated for drag racing.So that will be the next part of the project to work on after the head is mounted.The PO has been very helpful, but he travels alot in his job,so it's usually short emails for info. Anyway progress is progress no matter how slow.

Last edited by Drew, II # 4211; 08/10/08 09:53 AM. Reason: Spelling

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Drew,

I believe that dbane was asking about the intake port diameters at the intake manifold interface. Are they still sized for the stock alignment rings?


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and there we have it, it seems like a said a lot to ask for a little, and overtalked the heck out of it, well this is what you get when your 25 years old, so here we are, but yes that is what I meant to ask without saying so much, more or less.


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Geez,Louise! My bad. dbane,it's not your youth that confused me.More like my senioritus. \:D Anyway, of course you are right.Stock would be 1.5".The intake manifold port area measure out at 1.585",just enough to remove the alignment ring shoulder,I think.The rings will not be used. I've included a pic of the aluminum dual 4bbl intake that came with this project.The ports are a match to the head intake ports.It might appear there is a shoulder for alignment rings, but that is just where the tube and flange mate each other.
http://pic19.picturetrail.com:80/VOL1061/3611363/20102173/329809116.jpg


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very cool looking intake, that thing would be awesome if it were polished or chromed, two 750 cfm four barrels, that sounds a lot for a motor of this type, thats just me, this sound normal to anyone else? but nonetheless very cool looking!


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Well,I'm with you in that I think 2 750's is way too much.But,we'll see. After the 261 is actually running I promised the PO that we would get together and maybe he can give me some of his tuning tips. The manifold does need a good cleaning and polishing plus the welds could be dressed up too.It's been in damp storage for 20+ years and looks way better then the block and head did when I started this rebuild.
I have to scout up or get someone to make some decent headers too. The PO ran nearly straight drop downs off of each cylinder to a single open collector out the wheel well, but they weren't available. Unfortunately they went with his '50 Chevy coupe to a junk yard about 2 weeks before I bought the engine.The buyer then, just wanted the modified chassis and rear,but not the body.Too bad for me.I might have been able to strike a deal for it all as the PO wanted it gone.


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 Originally Posted By: Drew, II # 4211
The PO built his own dual aluminum intake running 2 750cfm Holleys! He swears it wasn't over carburated for drag racing.


Well, maybe not for that, but if you sawed the plenum off and used the manifold stubs as ram stacks (and fed it fuel somehow) that wouldn't be 'overcarbed for drag racing' either .

Manifold is definetly a nice looking piece though.


My, what a steep learning curve. Erik II#5155
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The Valve spring retainers are aluminum and were made by Offy. I have a set on my 235. Some say aluminum is too soft for retainers and it is tougher to keep the valves adjusted. Could be, I don't know. They are pretty though and as you said, very light. Offy also made an inner valve spring and special pushrods also. I have an old Offy catalog that lists the stuff.

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Greg,
Thanks for that info.The head goes back on this weekend and the intake is nearly ready. This sure has been a learning experience for me and lots-o-fun.


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1500 cfm? How much HP can an all out drag race 261 devolop? 300 maybe? Dual 750 CFM 4 bbls will support 600 plus HP on a V engine no problem.


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Tony P,As I've said before I think it's too much,but this process is to put the 261 back the way it was raced in the late 60's, early 70's. I'll make decisions changing anything like the carburetion after it's running once again. It ran many years at Maple Grove,PA with this set up.The PO is checking his home/garage for more info and once it's actually running he'll help with tuning.


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I used aluminum retainers for a time and the only problem I had with them was wear. It was prior to having roller rockers. The stock rockers always "worked" the valves causing wear to the spring retainers and valve guides. I found evidence of this when cutting open the full flow oil filters.
All of it looks great...............Good Luck


216.158 MPH 12-Port 302 GMC on 70% 171.0 MPH 302 stock head on gasoline 7 years later

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