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By JPotter57 - 17 Years Ago
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I know that many of you here have high HP Ys with superchargers, and that for the most part, boost is the same whether it comes from Centrifigal or Roots superchargers or Turbochargers. The principals are the same, just the methods of delivery, and the amounts of boost differ. Where I run into snags with my research and planning, is what durations do I need to use as a baseline for my Twin Turbo Y project? I don't really want to spend a lot of money changing camshafts, plus the work involved in that, so it boils down to that I want it to be a one or two shot deal, with figuring the best camshaft profile to make the most power out of what I will have. Currently, I have a deal cooking with Glen to snatch a 292 block, go .050, and then either use a 292 steel forging, or a 312 crank. Still pondering the cylinder head issue, have a set of `57 G heads, but would like some of the 113(is that correct?), lower compression `58 heads, or even the `61-`62 heads. I plan on taking baby steps with the boost, starting at around 6 or so lbs of boost. Yes, I plan to get the Probe forged pistons from Mummert, prob have to cut down the domes. I need to keep compression around 8 or 8.5:1, since I eventually want to lean on the boost a bit. My intention is to use the Blue Thunder or even the `57 intake, but, I may fabricate an intake for 1 4V carb, again, still pondering and researching airflow. Probably have some work done to the heads, including 2.02 intakes, but will run many iterations in my software before I buy too much or pick up any tools to see what I need to make what I want. I know I will have to throw out most of what I know about building out to do this, since my experience is all with 302, 351W & C, 390 and 460. 390 is probably as close to the Y as I have ever gotten, but even they are like night and day difference from my 292 project. Some of my many questions about this may be answered in the new book I just bought, if and when it gets here, lol. One of my main concerns is oiling, especially the rockers and lower end. Is this something I need to pay extra attention to? My dad warned me about the rocker trouble, so I am at least aware of it. What about balancing? Is that a particular chore on the Y? I hate to sound like such a newbie, but the Y was discontinued about 3 or 4 years before I was even born, so I havent had that much exposure to it. I do appreciate the help you guys have already given me, and the encouragement to break away from the norm. I guess, I just dont want to look like a novice when it hits the road for the first time, you know...Thanks in advance for any and all help.....
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By Glen Henderson - 17 Years Ago
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OK James, I'll give you my two cents worth, but some of the other guys can talk more about blown engines. No problem with the oiling system, I'll show you some things when you come too pick the block up. Balance just like any other engine, Ted is the expert there. I think the G heads may be a bit much, start looking for a set of 471 heads, may take a bit of looking, but they are out there. I think that in a blown engine that I would leave the intake valves alone and go with larger exhaust valves. Mummert can give you good advice on the heads.
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By JPotter57 - 17 Years Ago
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<deleted, found answer on Mummert's site, JP> I can take a less desirable head, and because the air will be forced in, the only real thing to consider will be chamber volume and whether the chamber can handle the pressure. I'm thinking 12-14 lbs or possibly more if the heads and the gaskets can handle it. I have some printouts from Mummert's site concerning the heads, flow numbers and such, but I am most concerned about the chambers and the sealing ability to deal with boost. As long as it doesnt go lean or I screw up with the timing and dont pull enough out under boost, it should be ok. I will be using a boost controller from MSD, so I shouldnt have the problem with the retard.Now fuel, I may have to figure out a way to use a boost reference fuel pump controller to kick in additional fuel above 7 or 8 lbs of boost. Once I get that figured out, the rest of it should be cake.
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By charliemccraney - 17 Years Ago
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James,
Talk to Mummert about the probe pistons. The ones he has "off the shelf" are not meant for a boosted engine. I have a set of those pistons and spoke with him some on the subject of boost. They probably will not work. I understand that you are planning to run twins. If you're going to go through that trouble, get the right pistons.
Boost referenced fuel pressure regulators are available. You will need a pump capable of providing enough pressure and volume for the amount of boost you plan to run.
Because your engine will be relatively unique, you may want to have a custom cam ground. Choose a target power level and know as many of the other dimensions and specifications of your engine - bore, stroke, chamber volume, and whatever else may be needed. Again, it's probably best to talk with Mummert about this. Most importantly, pick a goal and stick to it.
P.S. Since you want to run twins, why not aim for 550 to 600 hp? Twins just seem excessive for 450hp. I don't know how well a 600 horse Y would stay together, though.
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By JPotter57 - 17 Years Ago
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450 rwhp, should be close to 550 at the flywheel, and will get me low 11s with my `57. I am also leary of how long it will last at elevated power levels. The good thing about turbos, is that you can adjust the boost down and use premium for normal driving, then wick it up with race gas for getting stupid at the track. I had spoken with a couple people, still havent gotten with Mummert yet, but was under the impression that there was enough material to machine the domes from the pistons....But, unless I can find the 471 heads, I will need a dish...That would be where I would need a set of Wisecos like Teds I suppose.... To begin with, just to get a feel for how this Y will perform, I will be using a pair of small turbos, Garrett T3s, similar to what is used on Mustangs, T-Birds, and later 4 bangers. From the calculators and compressor map figures I have come up with, that is pretty ideal for a 540 hp 299 inch Y, max rpm of 6500, boost set at 14 lbs. I will have to use an external wastegate to reach the 14 psi, stock wg will maybe go 8-10 psi. Once I get fuel and ignition bugs ironed out, I have a pair of T04B turbos lined up, better turbine housings, bigger compressors, good for more power, but still, its only as good as its foundation, which is why I am trying to get the best shortblock together I can. Not really afraid to drop some bucks on a good stout setup, just want to take it slow and learn the Y.. Thanks again for the input. I will be contacting Mummert before I start buying stuff, well, except for the main hard parts, block, heads, etc.
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By Hollow Head - 17 Years Ago
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Speedmaven, not sure if you have already read all this stuff about us here in Finland learning how to make it work? Oiling is not a problem, because oil pressure does not drop dramatically with even two turbos. Fuel pressure must be high enough and the pump must deliver enough fuel. Our cam is about 270 degrees with 0.291" lift measured from the lobe and it makes 0.437" with 1.5 rockers.
We have not gone even near the limits, because we haven't had as many testing possibilities as we wanted and because our Hollow Machine is not road legal here in Finland.
Keep on doing the next Twin Turbo Y-block 
http://www.y-blocksforever.com/forums/Topic4180-3-1.aspx
And here is something about our next setup 
http://www.y-blocksforever.com/forums/Topic9084-3-1.aspx
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By Glen Henderson - 17 Years Ago
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I don't have any experience with a boosted engine, but from what I have read on this site and other sources, the biggest problem with high boost will be keeping head gaskets in it. I think that Jerry Christinson had to go to copper O rings with his "Blackbird" engine. I think Ted and John may have gone with the larger FE head bolts.
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By Hollow Head - 17 Years Ago
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And Speedmaven, Alan Allards great book about turbogharging & supercharging states that 10-25 psi boost pressures give you about 250 hp per litre, so 292 should give you over 1000 hp if all the parts will stand that. 7-15 psi gives you 40 -50% increase in power .
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By JPotter57 - 17 Years Ago
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Hollow Head, I have been reading on your combo. That ought to be one scary ride with such a light weight. Glenn, the head gasket issue is at the front of my thoughts . I was wondering if it were necessary to go to o-rings..There is a machine shop here that can do it, just another cost to add to the pile I guess. Tell me more about the FE head bolts. If there is enough meat in the block to go to the bigger bolts, and the lengths are useable, one could also go to ARP head studs for an FE, right? That sounds good to me..Any ideas there Ted or Jerry?
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By Hoosier Hurricane - 17 Years Ago
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James: I tap the head bolt holes to 1/2-13. Don't drill them first, just let the tap take out the old threads. Start with a starter tap, then finish with a bottom tap. I use a junk head with the bolt holes drilled to 1/2" for a tap guide. If you don't have a junk head, drill one of your intended for use heads to 1/2" for a tap guide, you will need to drill them to 17/32 for the 1/2" bolts to clear, so you won't hurt one to use it for a guide. I go to the local Fastenal store and buy ten 1/2-13 x 2 for the lower row, six 1/2-13 x 4 for the shorter long bolts, and four 1/2-13 x 4 1/4 for the longer long bolts. All grade 8. I torque them to 85# on the top row and 80# on the bottom row. Retorque after several warm up/cool downs. You may need to find a thinwall 3/4" socket to fit the larger bolt heads and clear the counterbores. 1/2" studs would probably be even better, but I have had good luck with these and 14# boost at the top of each gear. John John
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By JPotter57 - 17 Years Ago
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Thanks, John, that's just what I needed to know. 14 psi is about what I was looking to make, dont want to get too greedy, you know? Hopefully I can get up to Glen's place in the next week or so, and get the 292 block. It's starting to come together, at least in my mind, lol
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By Hollow Head - 17 Years Ago
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Just take your time... We started planning (drunk as hell  ) our combo in 2003. First with 239 with twins, but finally in 2007 ended up with 292 and twins. Well thought, half done... Take a lot's of photos and keep us informed.
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By Ted - 17 Years Ago
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When boosting an engine, be sure to use ‘posted’ heads. These have the extra support built into them so the decks of the heads will not flex under pressure. Only a small percentage of the G heads were posted while all the 113 and all other heads cast starting in 1958 are posted. As Glen mentioned, using 471 heads or re-valving some of the other 82+ cc smaller valve head castings would make for a better starting point as far as compression ratio goes. Here’s a link showing how to identify posted heads. http://www.y-blocksforever.com/forums/Topic6711-3-1.aspx More information on posted heads can be found by simply putting ‘posted heads’ in the search bar. Blower cams have been talked about in detail on the site so a search should yield some of these discussions. Here are some of the links on the subject. http://www.y-blocksforever.com/forums/Topic8997-3-1.aspx http://www.y-blocksforever.com/forums/Topic8191-3-1.aspx http://www.y-blocksforever.com/forums/Topic3108-3-1.aspx I’ll add to John’s ½” head bolt discussion in that I’ve experimented with up to 130 lbs of torque using ARP bolts with oil. No issues with the threads with this much torque and this was the torque actually recommended by ARP for their hardware when using oil on the threads. For my roadster engine with 13.0:1 CR, I’m currently torquing the ARP ½” bolts to 105 lbs on the top row and 100 lbs on the lowers with oil on the threads. Fe bolts are the right diameter but not all the correct lengths.
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By JPotter57 - 17 Years Ago
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Thanks, Ted...I was speaking with John Gambill and Pat Fleischman about heads, and they told me about the 471s, which is probably what I will use. I am currently working on getting a set of those, so, at least that part of the combo will be had.. Thanks for the info and links on the headbolts, etc. I will have the info printed and in my binder tonight.
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By charliemccraney - 17 Years Ago
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There is a set of 471s on ebay right now:
471-heads
I was going to ask some questions and bid on them but it sounds like you can put them to use sooner than I.
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By miker - 17 Years Ago
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Having built a couple of blown street motors, I think you're right to worry about the head gaskets as that was a problem on my first one. I picked up oil thru the PCV valve, and the detonation blew the gasket instantly on the dyno. I used ARP studs on the second motor, and repulled them about 7 times before I got no more movement. I was pretty worried about that, but J Mummert told me that wasn't unusual. Both motors have boost retard with the MSD, but as street cars I can't depend on the fuel, and don't reset the timing for ambient temperature, so I really want to aviod detonation. When I bought the cams from Mummert (one custom 274 he had, and a 284) he had some interesting thoughts on the effects of lobe centers and the rpm that the boost levels occur at. Turbos and centrifigals tend to make boost at higher levels than roots set ups, and Mummert was more likely to go with n/a lobe centers than what you might see advertised as "blower cams". It would be worth talking to him about that, he's very knowledgable. Aero Motive makes a couple of regulators that will reference fuel pressure to boost, just get the carb model, not the fuelie one. Summit
Racing has them.
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