who knows the most about 177s? looking at building a stockish rebuilt vortec 350 with some better heads (bigger chamber, larger runner, bigger valves) and topping it off with one. i have a partslist I've put together if anyone wants to give me their thoughts on it or what i should/could do differently or better. |
Re: who knows the most about 177s? It's been awhile since someone went this route. If this is really happening, definitely looking forward to seeing this build being documented. Throw up the parts list so we can all compare... - Rob |
Re: who knows the most about 177s? yeah the pro street look is just too cool lol. starting with junkyard l31 out of a 96-2000 silverado/tahoe/suburban swapping heads for a cheap brand i found, power products aluminum heads, 205cc intake 72cc chamber 2.02 intake 1.60 exh comp cams "nitrous cam and lifter kit) comp ultra gold 1.5 rocker arms. pretty stock rebuild kit with chromoly rings and dish pistons some ebay special longtubes (the chinesium stainless ones) arp head/rod bolts and main bolts for peace of mind milodon "diamond stripper" windage tray holley 130gph mechanical pump regulated to 7-8 psi holley 750 blower carb keeping the 700r4 with an overhaul to handle more power and torque and either beefing up the 10 bolt (83 z28 no idea about the rear end) or thinking about the tnt fabrication 8.8 rear end. mostly just want to daily drive this car but i'd also like to track it for atleast a few weeks out of the season (it rains so much here) i have no idea what heat range plugs i'd need, i've read about a few guyus running R44lts plugs and i know blower motors like 112-115* LSA and alot of initial timing and not alot of advance. again i'm a total newb when it comes to FI and any criticism is welcome. |
Re: who knows the most about 177s? Correction to those heads. PROMAXX freedom series heads. 225cc intake runner 62cc exh, 2.08 intake valves 1.60 exh. 72cc chambers. max lift .575. bronze valve guides, 3/8 rocker arm studs, not crazy about that but they're not a huge problem with lower rpms. https://www.summitracing.com/parts/pmx-2122/overview/ |
Re: who knows the most about 177s?
Originally Posted by kmcn47
(Post 6240408)
looking at building a stockish rebuilt vortec 350 with some better heads (bigger chamber, larger runner, bigger valves) and topping it off with one. i have a partslist I've put together if anyone wants to give me their thoughts on it or what i should/could do differently or better. Mine seems to like about 21 degrees of advance at idle, and I have a short timing curve that maxes out at 36 degrees all in by 2800 RPM. I also run a boost retard that takes out anywhere from 1-3 degrees of timing per pound of boost depending on where I have my dial set. I actually have a MSD boost retard sitting in my garage doing nothing that I intend to sell. I switched to a (I think) MSD 6BTM box that not only retards boost, but has the multi spark to help clean things up at idle. Tuning will take a lot of trial and error until you get it dialed in. Every setup will need different amounts of timing advance, rate of timing increase and carb jetting requirements. If you're going to stick to a carb, I'd recommend getting a MSD box. It'll help clean it up at idle quite a bit. You need to keep it on the rich side to be safe, lean it out too much and bad things happen quickly. I ran a carb for quite a while, and switched up to a FItech unit, so I can set cruising A/F ratios and different ratios while under boost. Keep in mind, that when you get a lean backfire with these roots blowers, it sounds like a shotgun going off and it can damage things. Always give the throttle a good shot of gas prior to starting to make sure you don't get a lean backfire when the engine is cold....https://cimg5.ibsrv.net/gimg/www.thi...66a1b4cf56.jpg |
Re: who knows the most about 177s? anyone know how much of a dish i need to get the L31 down to around 8:1 8.5:1? the 72 cc heads will help i know but idk how much they'll change compression. i honestly don't know how to calculate it that well |
Re: who knows the most about 177s? Calculating static compression ratio is pretty straight forward. It is the total volume of the air space inside the cylinder and combustion chamber with piston at bottom dead center, divided by the volume with piston at top dead center. The hard part is getting the data you need to make the calculation. You need to know, * Cylinder bore diameter. * Crankshaft stroke length. * Height of piston above or below deck with piston at top dead center. * Piston dish or dome volume. * Head gasket bore diameter and compressed thickness. * Cylinder head chamber volume. This will give you a reasonable estimate without going to the gnats *** with other fine details. I can help you with the calcs if you get the data. |
Re: who knows the most about 177s? stock 96-00 L31. the heads i mentioned. 72cc chamber. anyone recommend a head gasket? stock copressed for a l31 is 0.28 thickness. i know most fel pro replacements are .38 or .41 compressed thickness. that should help with CR. anyone know the stock dish on the l31 pistons? how much more to get it to around 8, 8.5:1? stock l31 CR is 9.1-9.4:1 from what ive read. hard to get straight answers. |
Re: who knows the most about 177s? Earlier you mentioned rebuilding the engine. That could change bore diameter and deck height too. You can fiddle with gasket thickness to alter compression ratio but really the gasket thickness should be more focused on minimizing quench. |
Re: who knows the most about 177s? If you can find a copy of the engine service manual it will have all the specs in it. |
Re: who knows the most about 177s? i was planning to rebuild yeah but not overbore or undersize the rods. there are alot of low miles 90s chevy trucks in pick n pull here (wa state) so i was hoping to find a good low miles example. stock specs 9.4:1 CR from GM, bore x stroke: 101.60 x 88.39 mm, stock vortecs are 64 cc chamber. my heasd are 72cc chamber. stock gasket is 0.28 compressed. stock dish on pistons is 11cc from what i can find. |
Re: who knows the most about 177s? Still missing some info. Walk down the list I gave you. |
Re: who knows the most about 177s?
Originally Posted by kmcn47
(Post 6242949)
anyone know how much of a dish i need to get the L31 down to around 8:1 8.5:1? the 72 cc heads will help i know but idk how much they'll change compression. i honestly don't know how to calculate it that well It won't get out of it's own way! -- Joe |
Re: who knows the most about 177s? Not sure of the stock dish but 11-12 cc sounds right. 12 gives 9.5-9.7 to one on stock vortec depending on actual chamber volume. going to 72 cc head and same .028” gasket i assumed that gives you 8.95:1. Honestly would leave it there for few psi boost. Much more torquey cuz those heads are really big for a 350” motor. I would try a 6 heat range ngk plug. Stock is like 4 so two steps down is perfect for few psi. Could try a 5 if its fouling plugs alot tho but if the tune is good it will not |
Re: who knows the most about 177s? Not sure if this is entirely correct but this info is what I found in a few minutes on Google. L31 engine Bore: 4.00 inch Stroke: 3.48 inch Compression Ratio: 9.4 Head chamber: 64 cc Piston: -12 cc Deck height above piston: 0.025 - 0.030 inch Gasket diameter: 4.10 inch Gasket thickness: 0.028 inch These numbers give about 9.2 compression ratio but it goes up to 9.4 if you tweak the deck height to 0.015 inch. Close enough for government work. Looks like a 72cc head would deliver somewhere around 8.7 or 8.5 compression ratio. |
Re: who knows the most about 177s?
Originally Posted by anesthes
(Post 6243044)
8:1 ??? It won't get out of it's own way! -- Joe
Originally Posted by QwkTrip
(Post 6243189)
Not sure if this is entirely correct but this info is what I found in a few minutes on Google. L31 engine Bore: 4.00 inch Stroke: 3.48 inch Compression Ratio: 9.4 Head chamber: 64 cc Piston: -12 cc Deck height above piston: 0.025 - 0.030 inch Gasket diameter: 4.10 inch Gasket thickness: 0.028 inch These numbers give about 9.2 compression ratio but it goes up to 9.4 if you tweak the deck height to 0.015 inch. Close enough for government work. Looks like a 72cc head would deliver somewhere around 8.7 or 8.5 compression ratio. |
Re: who knows the most about 177s?
Originally Posted by kmcn47
(Post 6243250)
thats BEFORE the blower goes on haha -- Joe |
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