stickshift Posted January 9, 2012 Share Posted January 9, 2012 Hey guys, been a while since I posted. I have started back working on my 454. Its comming together slowly but surely. It is a 1972 454 out of a 1972 Chevy Caprice rated from the factory at 270 HP. My goal is a 425 - 450 HP big block. As for as parts go, I have purchased a Lunati Voodoo cam part# 60204 with 554 lift and 276 duration, Edelbrock RPM Air-Gap intake,and MAHLE forged dome pistons. So for the block has been bored 60 over, the crank has been turned,and the oval port heads are being cut out for bigger valves. I still need to get rocker arms,valve springs, fuel pump, water pump, headers, carb and valves. I need a little more advice guys, should I use 1.6 roller rockers or 1.7 roller rockers? Should I cut the heads for 2.19 / 1.88 or 2.25 1.88 valves, and last but not least, should I port & polish the heads or will the bigger valves help get me to my 425-450 HP goal without porting & polishing. Thanks guys and I will keep you posted. Quote Link to comment Share on other sites More sharing options...
wallaby Posted January 9, 2012 Share Posted January 9, 2012 The stock rocker ratio is 1.7, going less will net you a lesser valve lift and duration. I'd stick with the 1.7s. As for valves, bigger is always better, but there is only .006 difference between the 2.19 and the 2.25s....not something you'd notice in the seat of your pants, and it makes it complicated at the machine shop whrn the valves are so close together. I went through this when I rebuilt my engine, and I decided to go with a set of cast-iron merlin heads. The merlins had better port designs and better valve cover sealing surfaces and already had the large valves and hardened seats. It turned out that the replacement merlins were cheaper than having my stock heads rebuilt. My machinist explaned to me that the stock heads have integral flame-hardened valve seats, and that hardened surface would be lost when grinding them out for the larger valves. You really want hardened seats when running unleaded fuel. Anyway, it's something to consider. The only problem I had with the merlins was when I was using stock exhaust manifolds, and the spark plug placement with the new heads caused clearance issues. Headers fixed the problem there. The merlins are also missing a needed bolt hole on the intake manifold mating surface, and I wasn't able to use my upper AC bracket that stradles the valve cover. There wasn't enough metal to drill & tap the needed bolt hole. If you don't have factory AC, this won't be an issue. I really wanted to keep the stock heads and have big valves, but can't live without the hardened seats, so I was able to find a solution that actually saved me money and made me HP...you don't run across that very often! I know the merlins aren't as good as they used to be; there are better head designs out there now, but the price was right. Quote Link to comment Share on other sites More sharing options...
cny first gen 71 Posted January 9, 2012 Share Posted January 9, 2012 What about the polishing of the heads, I was told years ago that polishing heads on a street driven car was a wast of money because they are just going to get carboned up anyhow. Polishing is good for race driven cars only. Is that true or just an old wifes tale? Quote Link to comment Share on other sites More sharing options...
CrazyDavey Posted January 9, 2012 Share Posted January 9, 2012 Hi Ken, good to see you working on the Monte again. First no offense to Mark but bigger is NOT always better. I just went through this with my heads, we tested going from a 2.25 intake valve to a 2.30 and lost too much low lift flow. For your build this is not something you want to do. The 2.19 intake would be a very good valve for your build, that cam is going to want low lift flow and you don't want to kill any low end. Â As stated "polishing" is not desirable, the intake ports need some amount of surface tension to create a good mixture of the fuel and air. You can certainly clean them up but don't "polish" them. You said you have dome pistons, do you know what you chamber size is? Bore size, dome size, chamber size, gasket thickness and piston to deck distance will give you your final compression, I wouldn't go over 10.5 to 1...also an ideal quench is around .040....JMO....Dave Quote Link to comment Share on other sites More sharing options...
wallaby Posted January 10, 2012 Share Posted January 10, 2012 I'm no genius, but in theory bigger valve diameter is better. Then comes the constraints of chambers and cylinder walls and the bigger valves can be too close...they open up alongside a wall on one side and it restricts flow. The term is shrouding. Dave, is this what spoiled the flow on your motor? Any time you go browsing through the catalogs, it's easy to get suckered into believing that a bigger everything means more power. I really thought that bigger valve diameter was a no-brainer (especially at low lift), but flow bench testing is hard to argue with! Â I'm still learning... Quote Link to comment Share on other sites More sharing options...
Sam (Bones) Posted January 10, 2012 Share Posted January 10, 2012 I like stock heads and valves for a street engine, I love my 9.5:1 454, awesome little street engine, sure it's not my 12:1 468 but it sure surprised me Quote Link to comment Share on other sites More sharing options...
Mike 57 Posted January 10, 2012 Share Posted January 10, 2012 I think I would go with a set of 2.19 intakes and leave the stock size exhaust. I would find a good set of exhaust valves with a back cut, or ask your machine shop if they can do the back cut on your stock valves. That way you my not have to worry about the hardened exhaust seats if they can clean up without getting past the induction hardening. The exhaust seats are the only ones that are hardened. If you do go with the 2.19 intakes the throats will have to be blended. Quote Link to comment Share on other sites More sharing options...
CrazyDavey Posted January 11, 2012 Share Posted January 11, 2012 I'm no genius, but in theory bigger valve diameter is better. Then comes the constraints of chambers and cylinder walls and the bigger valves can be too close...they open up alongside a wall on one side and it restricts flow. The term is shrouding. Dave, is this what spoiled the flow on your motor? Any time you go browsing through the catalogs, it's easy to get suckered into believing that a bigger everything means more power. I really thought that bigger valve diameter was a no-brainer (especially at low lift), but flow bench testing is hard to argue with! Â I'm still learning... Â No Mark it wasn't a shrouding issue, it had to do with some of the runner short turn areas and throat diameter...with more port work it could have been made to work but we didn't want to make the ports any bigger as they are boaderline too big as they are...they probably did increase slightly from 305 to 310....if I was going to turn it 7500 and utilize the high lift numbers that would have also been different...70% of my needed head efficiency is from .200 to .500 lift.... Quote Link to comment Share on other sites More sharing options...
Blue502 Posted January 12, 2012 Share Posted January 12, 2012 Nice MC.Listen to Dave.He knows his stuff.I test him on a regular basis. Quote Link to comment Share on other sites More sharing options...
stickshift Posted January 12, 2012 Author Share Posted January 12, 2012 Thanks a lot guys. you guys are awesome. I called the shop yesterday and the valves had already been installed. He installed the big 2.25 intake valves, not sure about the exhaust, i think 1.88. I wanted to have the heads ported but i guess if he has already installed the valves its too late. He says when we finish the build we should be at 10.5 to 1 compression. Does this sound like a good start to get me to my 425 - 450 HP goal? Quote Link to comment Share on other sites More sharing options...
dbreese Posted January 12, 2012 Share Posted January 12, 2012 450 hp and then some!! Â Nice build and I like the color on the car. Looks great! Â David Quote Link to comment Share on other sites More sharing options...
Andy's Auto Posted January 12, 2012 Share Posted January 12, 2012 The 2.19 intake valves are all you will ever need with 454 inches. Save the 2.25s and 2.30s for the bigger strokers. I can see 375-400 horse with your cam selection but not 450. But HP only sells cars, torque makes Montes go. You are well on your way to a mid 12 second land yacht. Â Mark, funny you mention the AC issue on your Iron Merlins. I had a similar issue on the #1 intake port holes where the lower bracket attaches. They truly screwed the pooch on them. The headers cover the holes. But at 269 CFM they were worth 3 tenths over a worked over set of 820s that are on the 402 that came out of my 68 Velle. Yeah, kept the old 9 second 496 intact and threw it in the 68. Just finished the rear end. Whoa! If not for my 19th tomorrow I would bolt some seat belts in it and head to the track. Quote Link to comment Share on other sites More sharing options...
green_monte Posted February 6, 2012 Share Posted February 6, 2012 go with a hyd roller cam, even with a very mild one you can make very good power. my 468 with only 9.0 cr, zz502 cam, edelbrock rpm heads, rpm intake and holley 750 carb makes 470hp. Quote Link to comment Share on other sites More sharing options...
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