Rusty Bowtie
General Category => General Discussion - Intros => Topic started by: 28chevyguy on December 30, 2019, 09:35:59 AM
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What do I need to do to run the 57 intake and valve covers on a later (70's) motor? I know I can physically bolt them on but whats up with the breather systems on the older motors? obviously they dont have the cross ventilation/PCV setup which is the main obstacle, the oil cap in the front is the breather and there was a funky tube coming down the intake in the back to suck the ventilation out ? Not sure how I would get the newer motor ventilated with the old style intake and covers. Would be nice to have the motor look sort of correct in my 57 when you pop the hood, but if its too much trouble I don't have to bother. Im sure im missing a bit of info here.
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What do I need to do to run the 57 intake and valve covers on a later (70's) motor? I know I can physically bolt them on but whats up with the breather systems on the older motors? obviously they dont have the cross ventilation/PCV setup which is the main obstacle, the oil cap in the front is the breather and there was a funky tube coming down the intake in the back to suck the ventilation out ? Not sure how I would get the newer motor ventilated with the old style intake and covers. Would be nice to have the motor look sort of correct in my 57 when you pop the hood, but if its too much trouble I don't have to bother. Im sure im missing a bit of info here.
Those were the days before PCV = positive crankcase ventilation. The oil filler tube and the oil filler breather were the same thing. It the tube with breather was how things worked from way back.
The funky tube in the back of the motor was called a road draft tube and allowed excessive internal pressure to escape facing the road. Again all this before the EPA got involved.
The 421 cubic inch 57 olds motor with lots of end gap on rings and clearances in my 35 coupe with 12-1 pistons, the blow by the rings used to knock the tube filter cap off unless I used braided stainless strap screwed to cap and bolted to intake.
Now whether you could get that setup passed by air management might be another story. But if running a pre PCV motor that's what they had.
The crate 383 I bought I have made an aluminum tube that goes across the front of heads , 4 holes are tapped with aeroquip fittings and 4 small motorcycle air filters are used.
mike lynch......... HAIRBALL
mike lynch
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You got a couple options on the valve covers. First is to buy(or make) an adapter plate, they run around $100 on the net. They are 1/4" or 3/8" thick and require 2 sets of gaskets, and sit up higher. Second option is to get a set of '60 to mid '60s 283 valve covers. They are still "Chevrolet" scripted and are straight across holes.
On the crankcase vent, worst option is to modify or buy an oil filler tube (leaving vent cap on) with fitting for pvc to go to base of carb. I've seen guys run like this, but don't think it's too effective.
Others have drilled a hole in the left rear of the intake for a fitting and pvc valve, then to base carb. You leave stock filler/vent on front.
The other was to modify/buy oilfiller with sealed cap and pvc fitting to carb base then drill hole in left rear intake and plumb a line to the bottom of air cleaner.
I'm sure there are other ways, just what I've seen.
Geezer, hope that made sense. 😜
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Thanks for the great info . I just got home from the shop... yep never noticed the staggered bolt pattern, now I see they would have to be lifted anyway... all that primitive ventilation im hearing about is non appealing . Im just going to run regular cross vent/pcv . It was worth a thought I know a lotta people have attempted buts its all just for visual anyway...
thanks you guys are great !!
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most newer valve cover gaskets have the straight .......early , and the later staggered holes. Use gasket new style as template to drill new holes. Unless your running 1.6 roller rocker arms instead of the stock 1.5, clearance is not going to be a problem. They were 1.5 all the way up even most of the roller crate motors SBC.
1986 and up SBC has stock center bolt valve covers. The aluminum heads on 350--383 depending on motor heads will have both side bolt holes in them.
mike.............HAIRBALL
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hmm , Im going to be running an early 70's 350 , I read I can remove the plug for the road draft tube and add a pcv valve there , some how making/ fitting a grommet . then run vacuum to base of the carb ? allowing me to run the 283 intake and script covers... and so being 1.5 valves they should fit not problem besides redrilling upper holes . would be pretty cool if I could pull it off without too much trouble .
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I thought by the 70s the hole was gone on the 350 blocks. If you have the plug....easy pezzy. Should just be a soft plug (I think). Remove plug (or get new one)and drill hole, tap back in, install grommet. Speedway sells a 2- grommet set for $4.99, you only need the piece for the pcv, (and not the vent grommet) the one on the right is for pcv and has a built in oil deflector. Says hole size between 1.22" and 1.25". Plug the pcv valve in and hose to carb base....done.
Add**just looking around the net, that grommet may be the right size to just push in the hole once plug removed.
Never thought of redrilling valve cover, but make sure to fill the old hole. Like I said, '60 up 283 scripted cover is the same except has straight across holes.
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I didn't recall either of my '69 Vettes having the hole prevision. I did read some 327/350 large journal engines /blocks were sold as over the counter GM replacement/warranty that had the hole?
Dang, I cut the top out of a few for adjusting valves through the years. Nobody was using Scrip covers at the time. I might still have a pair somewhere.
I read somewhere a guy drilled the back (by firewall) of a script cover and installed the baffle/defuser style pcv grommet and to carb. But I guess you could put it any where it wasn't obvious. The higher the better I would think, and leave oil fill vent cap.
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According to a google search, GM developed it and the usa gov mandated it be used starting in 1964.
So if any whacko from HAMB questions your use of PCV valve not conforming to their 64 and down parts manifesto credo and threaten to toss your boney ass off their site , you got defense against any oppressive edits from the grand pooh bah operating there.
mike lynch...........HAIRBALL
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28ChevyGuy....got this post back on topic.