BORE SHROUDING TEST: 4.03" vs 3.91" Edelbrock RPM Heads Really Fit a 318? Project Mission Impossible
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I've seen a 305 VS 350 flow bench comparison and the loss was a lot smaller but I think it was 1.9? valves, always wonder how a 318 bore would effect it, killed more than I thought it would but a 318 especially with an overbore is still capable of making decent hp, wonder how bad a 273 does
Back in the day, bolting X-heads on a 318 was one of the oldest tricks in the book. Every 318 loved them.
Even though it killed a decent amount of cfm but it's not like most are taking advantage of all the cfm in the 1st place. A 250-450 hp+ sbm recipe's seems fairly the same to me whether it's a 318 or 340 or 360.
Always a good topic of discussion with cylinder heads. What makes more power if you could only have 1 of the following? Compression? (closed chambers), larger valves, or larger ports?
Depends on exactly how much cr vs how much overall airflow gain (VE%), Airflow generally has way more potential.
It really comes to the matter of "did it help" in the real test? Real test is they are bolted on and how did the engine respond. Remember, science at one point said the bumble bee's wings were too small/light for its mass of body, yet it amazingly enough flies.. and really well !! LOL
The test was a good idea. Like he said, measuring shrouding and notching the bore for improvement hasn't been done. (that they have seen) We knew all of the testing to be true but didn't know how much as far as numbers go. It was an interesting test.
It's kind of like the folks that say "don't put a 340 intake on 318 heads because of reversion". Yet, the engine responds very positive to the swap. In fact, I've never seen a 318 sized-port 4bbl intake outperform the "mismatch" ports of the 340 ports on the 318 heads. This is where information becomes just "info" that the engine doesn't seem to care about. If the engine doesn't care, I don't.
But yes, neat test.
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100%It's kind of like the folks that say "don't put a 340 intake on 318 heads because of reversion". Yet, the engine responds very positive to the swap. In fact, I've never seen a 318 sized-port 4bbl intake outperform the "mismatch" [ ports of the 340 ports on the 318 heads. This is where information becomes just "info" that the engine doesn't seem to care about. If the engine doesn't care, I don't.
Just a test with numbers to prove what we've known all along. 
Agree, I think for most especially doing around 400 hp or less 318 this info don't change much.It's kind of like the folks that say "don't put a 340 intake on 318 heads because of reversion". Yet, the engine responds very positive to the swap. In fact, I've never seen a 318 sized-port 4bbl intake outperform the "mismatch" ports of the 340 ports on the 318 heads. This is where information becomes just "info" that the engine doesn't seem to care about. If the engine doesn't care, I don't.
I'm glad Andy is doing these tests, and there is certainly info there, but then one would ask "what do I do about it?" I mean, notch the cylinders is minimal. Going .060 over would be the best remedy, but adding bore size is always a good thing regardless if it's 1.88 or 2.02.Just a test with numbers to prove what we've known all along.
It's kind of like the folks that say "don't put a 340 intake on 318 heads because of reversion". Yet, the engine responds very positive to the swap. In fact, I've never seen a 318 sized-port 4bbl intake outperform the "mismatch" ports of the 340 ports on the 318 heads. This is where information becomes just "info" that the engine doesn't seem to care about. If the engine doesn't care, I don't.
Agree. My Power-Wagon has the 360 spreadbore with an 800 cfm quadrajet atop of 318 heads and a mild Delta re-grind.
Truck will cruse at 75+ or crawl across the tundra without a hick-up.
The internet can be the misinformation superhighway at times...
I was disappointed after watching the video .
Not because of the results, but because of the way it was done .
I had anticipated the bore being sleeved down with a real insert,, not a big ring of tape .
And then to have a notch cut out of the tape reminiscent of something from the Slate Rock and Gravel company .
I turned it off after that .
That was not a real test in my opinion !
Yes,,,All of the OEMs relieved bores in the past to increase flow ,(usually to clear the valves really ).
But any backyard guy can relieve an iron bore by hand much smoother .
And all of the flowbench guys know that sharp or abrupt corners kill flow .
Those look like good heads,,,but I still think an overbored 318 with a judicious bore notch would flow very close to the larger sized baseline .
Of course,,,I love the 340 as well and most here Poo-Poo on that also .
Lol
Still really good heads in my opinion for the money,,but we already knew that before the video .
By the way .
The S R & G company was the quarry where Fred Flintstone worked .
Tommy
Not because of the results, but because of the way it was done .
I had anticipated the bore being sleeved down with a real insert,, not a big ring of tape .
And then to have a notch cut out of the tape reminiscent of something from the Slate Rock and Gravel company .
I turned it off after that .
That was not a real test in my opinion !
Yes,,,All of the OEMs relieved bores in the past to increase flow ,(usually to clear the valves really ).
But any backyard guy can relieve an iron bore by hand much smoother .
And all of the flowbench guys know that sharp or abrupt corners kill flow .
Those look like good heads,,,but I still think an overbored 318 with a judicious bore notch would flow very close to the larger sized baseline .
Of course,,,I love the 340 as well and most here Poo-Poo on that also .
Lol
Still really good heads in my opinion for the money,,but we already knew that before the video .
By the way .
The S R & G company was the quarry where Fred Flintstone worked .
Tommy
this ^^.
The valves won’t clear a 273 bore sizeI've seen a 305 VS 350 flow bench comparison and the loss was a lot smaller but I think it was 1.9? valves, always wonder how a 318 bore would effect it, killed more than I thought it would but a 318 especially with an overbore is still capable of making decent hp, wonder how bad a 273 does
That’s been covered before, more or less, flow out powers compressions
People say they have with notches, Plus I was half joking, wouldn't be against seeing the results if someone did though
Bitches for a 1.88 IIRC
Now that's something I haven't seen a video test comparison done on. I am sure flow out performs compression. But by how much?
You can run like a 100 hp of air/fuel through an engine to 1000's of hp of air/fuel, compression generally is gonna make those numbers vary like 0-25%. So if you run a 100 hp of air/fuel at 7:1 and crank it to 17:1 you might gain like 20-25% + power.
FWIW: NASCAR tested low compression in the Truck Series years ago. I believe the Ram was running W5 Cylinder Heads.Now that's something I haven't seen a video test comparison done on. I am sure flow out performs compression. But by how much?
"Both employ carbureted 358-cubic-inch pushrod V-8s, but in presaging Winston Cup rules, truck compression ratios are limited to 9.5:1, slicing 60 horsepower from Cup cars' 720."
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