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By Speedbump - 16 Years Ago
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New guy here. Fortunate enough to have a small shop in my backyard with good but old equipment. In my retirement, I do modest street rod engines mainly the older stuff todays shops don't want to bother with, ie. flathead V-8's & V-12's, early hemi's, 383 Mopars etc, along with the requisite SB and BB chevys. Now....need some info/advice. My current engine is a 292 Y block. Have .040 over SP cast flat top pistons. I'll do the deck close to 0 with a BHJ fixture any my WVN broach, target static compression is 9.0. Heads are ECZC which, according to my research on this and other sites, are good for smaller chambers.? It needs new valves. I can get the 1.920 valves for only slightly more than the 1.780 valves it has. My inclination is to do it (we've always been told size matters) and leave the exhaust 1.510 due to the smaller chamber. I would open up the valve pocket with a 75* hog slightly and finish with a 60-45-30 seat. It would cost slightly more in machine work for the owner, so my question is.... is this the right thing to do for the engine and the owner? He is planning on using an aftermarket cam in the 268-270 adv. range with @.450 lift and a 4V carb. Going in a mid 50"s pick up and will be a moderate driver/ streeter. Sorry for being so long winded. All opinions/reccomendations appreciated. Thanks, Warren
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By Glen Henderson - 16 Years Ago
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Welcome to the site Warren, I'll let the engine experts ( Ted or John or Tim) have the final word on this, but in my opinon a good set of G heads would be a better bet. They have the big valves already and for the additional machine work that you are talking about, I'm sure that you could pick up a set.
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By charliemccraney - 16 Years Ago
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Without more displacement or dome pistons, I don't think you'll reach a true 9:1. With the G heads, you'll be around 8.75. With the C's I think it'll be around 8.15.
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By mctim64 - 16 Years Ago
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You can cut the heads out as you have mentioned, it's done all the time, but if you are going for the best you can get do as Glenn said and find a set of "G" heads (or even 113s). If your customer is looking for a good street machine and nothing more you can just run the "C" heads as configured with the 1.78" intakes, you can also clean up the valve pockets a little to flow better, but it will run very nicely with the smaller valves in those heads. Oh, and welcome to the forum. 
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By PF Arcand - 16 Years Ago
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First welcome to the site. Further to what Charley said, if you want the 9 to1 compression you probably need to cut a few thou off the heads also. The original advertised compression was somewhat optimistic & that was with steel head gaskets. Some here like the "C" heads in spite of the smaller intakes. However, for a more serious engine the "G" or 5752-113 heads are preferred. But a caution with the "G" heads, their decks don't take kindly to heavy milling..
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By Pete 55Tbird - 16 Years Ago
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Hello Warren and welcome to Yblocks are us. Tell us some more about the vehicle that this motor is going into. Is it a stick or a Ford O matic and which rear gears? The reason I ask is because if it is a Ford O matic then pick a cam with good low RPM torque charactoristics. You can put big valves in the ECZ C heads with good results but keep in mind the exhaust of the Y block engine is very restrictive and porting here will pay off more. When guys here tell you not to mill the G heads too much, they mean the unposted ECZ G heads. (look it up) In 1956 Hot Rod Magazine and Edelbrock built a Yblock with ECZ A heads ( similar to ECZ C heads ) and got 300 HP from 320 cubic inches. They used the big valves and milled the heads a lot with great results. Y blocks with an A/T like low end torque over high RPM horsepower. Let us know how it turns out and what you learn. Pete
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By Speedbump - 16 Years Ago
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Thanks for the info/opinions. I may have been optimistic about compression using the advertised numbers from the seal power catalog. I compared the comp ht. from the 292 and 312 offerings and chose the one with the highest which the book showed as 8.7. I intend to leave the piston about .005 in the hole and planned to take about .020 off the heads to compensate for the composition head gasket. The guy is putting this in a 54 pick up with a manual trans and the stock dana rear.(3.91?) He is also going to assemble the engine so I'm just trying to do some good machining on my end so he ends up with a good outcome. My recommendation to him as far as camshaft is along the lines of the Mummert middle cam, about 270 adv degrees and .450 lift. Do you think, considering the ports, there might be an advantage to putting in the 1.62 exhaust valve and leaving the 1.78 intakes? Considering his intended use, staying with standard is probably better, but I'm fighting the urge to tinker for the better. Warren
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By pcmenten - 16 Years Ago
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I would also consider the 1.84" intake valves. What ratio are the rockers? There were two ratios made; 1.43:1 and 1.54:1
If you need valves, I'd at least make the additional investment to get the larger intakes.
That cam seems a little 'sporty' for a truck. The '57 cam is another good choice.
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By 46yblock - 16 Years Ago
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I have a 292 .060 os with 113 heads, 72 cc originally. I cut the heads .035 and decked .028 to get .004 in hole flat top pistons. Ended up with 9.2 static cr. If it were me I would stick with the orig. intake valves, take .020 off heads, and deck it .020, hoping the intake would line up ok. If not ok then some material removal would need to come off head's intake flanges, approx. 1.4 times the net loss from heads and deck, in this case .028.
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By charliemccraney - 16 Years Ago
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Speedbump (11/17/2009)
Do you think, considering the ports, there might be an advantage to putting in the 1.62 exhaust valve and leaving the 1.78 intakes? Considering his intended use, staying with standard is probably better, but I'm fighting the urge to tinker for the better.
I'd stay with the stock size on the exhaust and go with 1.84 on the intake.
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By Bigwin56F100 - 16 Years Ago
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Find yourself a December 1956 Hot Rod Magazine as there is a several page layout on obtaining 300 HP from 312 with "C" heads
Kevin
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By Speedbump - 16 Years Ago
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I take it the 1.84 valve you all refer to is from the late 302? Has the same basic spec with the keeper groove being a little further down the stem. Could be used with the matching spring which would handle the .450 lift and give a little better closed and open numbers for a performance cam. Sounds like a great compromise and it's readily available for a moderate price. I know the cam sounds a LITTLE zoomie for a truck but I'm a street rod guy and I believe if it's ultimate job is to be a cruiser/street rod, it should sound like one. And I think with the target compression of about 9 being possible, it will support the extra duration nicely.
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By charliemccraney - 16 Years Ago
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I don't know if there is a specific application for the valves. John Mummert sells some.
I think the cam will be fine at whatever compression you're able to get. I'm running a cam that is similar. I did not notice any difference in the characteristics using the same cam in 2 different builds, with a difference of about 1 point in compression. It simply felt stronger throughout. It's not a totally fair comparison, though because the compression is not the only thing that was changed. The first was running about 8.3:1. Now it should be around 9.4 to 9.5. Even at 8.3:1 it was an improvement over stock, though it was more hotrod than truck, and it still is. And if he's looking for a hotrod it should be fine. I might even go bigger, depending on just how much hotrod your customer wants.
Think about ignition upgrades in addition to those which you are already planning. I only recently upgraded to a Duraspark based system and there is a huge improvement at the lower end. There is a noticeable improvement at the upper end but it is not nearly as significant. Looking back, I really can't believe I put the ignition upgrade off for so long.
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By Speedbump - 16 Years Ago
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Update. Ended up using 1.840 intakes and 1.540 exhaust in combo with a 1.650 seat in the exhaust. They are readilly available valves for a 351W. Combustion chamber looks great, valve wise. I also cleaned up the short turn on both the intake and exhaust which was much easier after opening it up for the valves and seats. I'm not going to do any more to these heads but was wondering..... I don't know what the (G?) head looks like but it appears to me the combustion chamber wall shape on this C head is a real detriment to flow. Has anyone laid back the chamber wall toward the gasket to see if there is flow there? Would the loss in compression more than negate the gains, if any? Is the newer head better in that respect? Thanks again for the insight on this build. Warren
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By PF Arcand - 16 Years Ago
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Warren: If you're lucky, John Mummert (El Cajon CA)may come on and make a suggestion or two on what works & what doesn't with the Heads. If not you may want to give him a call in CA. You sound like you have fairly extensive experience with various buildups, but many rodders have misunderstood the design of the Y-block heads. Unfortunately, many builders think because they aren't SBC like in design, that they cant work well.. Not true..
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