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By 62f250 - 11 Years Ago
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Hi guys I'm looking for some advice on increasing the performance 312. I have a combo in mind and was hoping to get some feedback from guys more familiar with y's. The base for the build is a 57 312 with the g heads and a b intake. The combo i'm thinking of is .030 over with mummerts pop up pistons on stock rods with a stock crank, i'm looking at mummerts y 292 s camshaft. Mild home port clean up of heads and intake with a 750 holley on top. Its going in my f250 and wont see much street use. I'd like to see 325 horse and 350 lb ft out of this engine. Any advice would be greatly appreciated thanks in advance
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By speedpro56 - 11 Years Ago
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With a .030 312 and mild porting to the heads AND intake I'd keep the cam around say a comp tight lash rated duration 264 @.050 234degrees with a lobe sep around 110 degrees and carb in the 600 to 650 cfms. More cubes and more porting on the heads etc then a bigger cam and carb maybe?
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By 62f250 - 11 Years Ago
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I'm lookin for as much bang for my buck as i can get but unfortunately a stroker is'nt in the budget. I'm not very familiar with the how the y block responds to camshafts. Do the smaller mid .400 lift cams really wake them up?
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By slumlord444 - 11 Years Ago
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I am thinking more like a 600 or 650 CFM carb. Headers and a large exhaust system will be a big help and will also help gas millage.
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By 62f250 - 11 Years Ago
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I planned on using reds fenderwell headers on the truck but think i'm going to go with the speedway kit with 2.5 inch pipes to flowmasters or the thrush welded mufflers. As far as the carb goes i've found that fords kinda like a bigger carb. I've run stock 302s with 670s with good resultsthats why i figured a 750 would be a good choice for a hotter similar cubic inch engine
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By speedpro56 - 11 Years Ago
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This really depends on the head and intake flow. Stock heads on a y-block G heads flow around 155 to 160 cfms and the B intake around 170 cfms per runner thus 600 and smaller carbs. Offerings for the 302 flowing more cfms can get away with more carb. porting the iron heads up to 200 cfms say at 500 lift means the intake has to be upgraded as well because the intake will be flowing less than the heads. Here comes the aftermarket, mummert or blue thunder and with the extra air a bigger carb can be used.
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By charliemccraney - 11 Years Ago
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My engine is similar to the one you propose. The significant differences are that I have a smaller cam, but potentially better flow (intake and heads). I run a 570 which works great for the street, and with a 91mph quarter mile, not too bad on the strip for a street truck.
The 750 may work, if it has vacuum secondaries but even so, it will be bigger than necessary. You say it won't see much street use. Does that mean it won't be driven much or it will be primarily for racing? Racing is the only place you may actually benefit from the bigger carb.
Here's a "recipe" for your goal:
http://forums.y-blocksforever.com/Topic70388.aspx?#bm70417
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By 62f250 - 11 Years Ago
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The truck will be used for truck pulls and the occasional trip to town. I guess i left some of this stuff out of the original post. The truck will be equipped with a standard trans and 4.10 axle ratios. I've come to the conclusion that my b intake is probly not going to suit my needs and i should just get a mummert or blue thunder.
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By 62f250 - 11 Years Ago
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Charlie, a 91 mph trap speed puts you in the mid 15's right? Thats impressive for a street y block in a truck.
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By charliemccraney - 11 Years Ago
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15.60 and the gearing's all wrong, not enough traction. So there's more in it once those are worked out.
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By 62f250 - 11 Years Ago
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Not to get off track but 15.6 at 90.xx mph is the fastest time i ever got with the original 352 in my 63 galaxie. Everything was wrong with that though. To much cam not enough anything else. I was young and thought big cam equaled big power lol
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By slumlord444 - 11 Years Ago
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15.6 is none too shabby. My 57 Bird when the engine was fresh and we had better gas only got into the high 14's once, cool night at Alton Dragway probably 1969. 312 .040 over, Crane street grind cam, factory dual quads, 3 speed, 3.89 rear end and 7" recap cheater slicks. It turned consistent 15.1-15.2's. Good enough to beat a lot of "so called" muscle cars. 396 Chevel, 389 GTO, lots of street rods with basically stock 350's. Had a lot of fun with it. Will again when I get it back together.
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By PF Arcand - 11 Years Ago
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Sounds like you're going to be giving the engine a real workout.. What kind of RPM are you planning on? With pop up pistons & all, you might want to consider H.D. rods of some sort. Mummert has them or you could go with truck rods, but some say if they need a complete redo including a crack check, that it may be just as well to go with Mummert's. And if you don't have a good knowledge of porting basics, be careful what you do with the heads & intake. Mummert has spent many an hour doing tests on Y heads & intakes. "G" heads aren't Chebie heads. Also, you need to know if your heads are the later posted ones?. If not, they need to be retro posted or according to Ted Eaton, best forget the High compression pistons.
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By 62f250 - 11 Years Ago
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I was proud of the 15.60 as there was much improvent between that pass and its first and the engine had lots more in it,converter,shift kit deeper gear car woulda gone mid 14s. That was the first engine i put together for that car still have the car 20 years later.
I have considered upgrading the rods,couldnt find any info on how much power stock rods will take. Max rpms would probly be around 6k. I plan on balancing the piston and rod myself and having the crank done. The extent of my knowledge porting heads is really limited but i know that and wasnt going to do anything to these heads i wasnt comfortable with and was only gonna do a mild bowl blend and smooth the ports. I believe the heads are unposted but will have them posted. I looked quick when i bought the engine but havent looked again
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By 62f250 - 11 Years Ago
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So after so more research i think i've found the combination that suits my needs and my budget.
.060 over for a total of 322 cubes
Mummerts dome pistons and upgrade rods zero decked block.
Heads milled .025 with stainless stock size valves mild bowl blend and port match.
Mummert dual plane intake and holley 750
Mummerts 228@50 .500 lift cam.
My static comp ratio ends up at roughly 11.37-1
Combo loosely based on ted eatons dyno mule which with mild porting of g heads less compression and less cam made 288hp and 344lb/ft of tq.
Using teds formula of 6% increase per point of compression puts that combo at 322 hp without factoring in the added lift.
If the added lift nets 25 hp then the combo would actually exceed my expectations
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By Y block Billy - 11 Years Ago
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For that much lift you may have to take down your guides a bit, I think Ted or John can tell you how much.
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By 62f250 - 11 Years Ago
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I read on one of their websites that i would have to shave roughly an 1/8 inch of the guides to run that much lift.
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By charliemccraney - 11 Years Ago
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You'll be able to determine just how much to trim once all parts are in hand. Also, the .500" lift is with 1.54 rockers. You may want to set the heads up for 1.6, .520" just in case you decide to go with aftermarket rockers in the future.
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By 62f250 - 11 Years Ago
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I will be checking the piston to valve clearance before anything gets fired up to. Anybody know off hand what the dove rocker arms go for?
Charlie, I was reading a post over on fte that you wrote about the duraspark conversion,is it really as easy as it sounds?
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By charliemccraney - 11 Years Ago
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How easy it is depends on which distributor you start with. There are many posts on this site about it.
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By 62f250 - 11 Years Ago
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I found one lastnite while i was looking around the forums. Sounds like thats the way i'm going to go i've never had trouble with a duraspark system
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By Y block Billy - 11 Years Ago
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Check with Ted on Harland Sharp rockers, I think they have had better luck with them!
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By 62f250 - 11 Years Ago
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Ok thanks for the tip. I have harland sharps on my 390 and have not had any trouble with them as long as you dont try to use the old umbrella seals. Car wasnt hard to find at least when it was running !
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By 62f250 - 11 Years Ago
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Whats are you guys using for valve spring locks and retainers? I just got my new valves and i'm looking to send my heads to the machine shop was just curious if stock is ok or if i should upgrade? Thanks
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By Hoosier Hurricane - 11 Years Ago
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I use 429/460 retainers with the stock Y keepers. 289/early 302 retainers also will work. Both are single piece retainers. They are not machined for dual valve springs, but single springs with or without dampers are OK.
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By 62f250 - 11 Years Ago
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Ok thanks i'll get some 460 retainers.
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By 62f250 - 10 Years Ago
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Update to what's happening with my old truck, she's been successfully converted to 4wd. I used a 73 f250 for its axles and running gear. Sadly the trucks not y block powered but is 360 fe powered. She's been on the road for the last 6 weeks enjoying the road again for the first time since the 90s
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