Has anyone had much luck running a 6-71 blower with only a single keyway in the crank snout? I have a 4340 forged crank and already have this engine together. I had been running a little 144 b&m blower but I've finally saved up enough for a REAL blower. Any comments would be appreciated, thanks. By the way this is for more of a show than go deal, street time only, not for strip. Probably only going to be running 5 pounds of boost. This is on a 377 SBC.
I ran a single keyed crank on my old 283 with a 6-71. running about the same boost you mentioned. Never had a problem, but didn't abuse it too much either. Just drove the shit out of it. Although it's strongly suggested to have it done, you probably won't have an issue with how you will be using it. The blown 327 i'm doing now is doubled keyed though.....it'll be abused a bit more ps: what ya gonna do with that little 144?????? Tony
I know one guy who has run a blown Chevvie with a single key for years and another guy with a blown Chevvie that didn't make it through the cam break in with the single key.... My advise is this...wait untill this winter...take the engine apart, get the crank double keyed, toss in some new rings/bearings/gaskets and be ready for spring with an engine you don't have to be worried about in the back of your mind. (how much is a rebuild kit for a Chevvie anyway, like 39 dollars???) While we are on the subject, do you have some good forged pistons? Cause 5lbs of boost is going to be just fine....for about a week before maybe 10lbs could be better... I have run my little blown 389 Pontiac for almost a billion miles at 10lbs of boost with no issues. (double keyed, nice pistons, mind my fuel and timing) You can too. Good luck, -Abone.
Just got done going through the whole thing!!! 6" forged crower rods, Manley ultralite forged pistons full floaters, entire rotating assembly has been balanced, has fluidampr, haven't even broke in the new cam yet, comp cams Turbo extream suppose to work good with blowers too. Has a new set of patriot freedom series aluminum heads with 7/16 screw in studs, guide plates, pro magnum roller rockers, gear drive, windage tray and crank scraper, all ARP studs for mains and heads, and I run an MSD digital e-curve distributor. Unfortunately comp. is 9 to 1 which is why I chose the low boost levels.I REALLY don't want to tear this thing apart again.
Well...you have yourself a dilema...If the engine is in the car and running, I would say go ahead and risk it and keep it under 6lbs of boost and be prepared for the possibility of having to walk home someday with your balancer in your hand. But, if the engine is on the stand, I would take the time to peel the crank out of there and get it keyed. AND, ditch that balancer for a real blower style crank hub. In a perfect world, you should double key the crank, get your compression to 8:5 or under (with a thicker Cometic gasket or larger cc heads) then give her the boost without fear. Or...you could run it and see what happens. You never know...that little motor could live at 6lbs of boost @ 9:0 with a single keyway for the next hundred thousand miles, or you could spin the balancer and pop a head gasket just going around the block... I'm in the try it and see what happens camp. Mind your timing and air fuel ratio and your 9:0 should be fine. Oh, wait a minute...aluminum heads...yea, 9:0 wouldn't scare me, just keep an eye on your tune. The single key on the other hand....well, it will either be OK or it won't. I say give it a shot. Good luck, -Abone.
I picked the patriot heads because they were 72cc and everything else in aluminum was 64cc other than a set of $1800 AFR's! I'm also running a set of Fel Pro .051 head gaskets to achieve my 9 to 1 comp. Since the engine is still on the stand I guess I'll probably pull the crank back out and have it double keyed. I'll also put the fluidampr on a different project. The Dyers kit I'm looking at comes with the correct crank hub anyway. Now if I can just learn to live with 9 to 1 comp cause I'm not ready to pull the pistons out just yet, wish me luck with low boost and 93 octane. Thanks for convincing me to do what in the back of my mind I knew I needed to do anyway....dang it!
Make sure the hub is really double keyed, last one I got from Dyers only had one. It was about 10 years ago though.
I Just purchased a SBC Dyer's 6-71 and Gary recommended a steel aftermarket balancer out of summit for around $145.00 and told me himself that the single keyway would be fine. Let's hope, I guess I will find out.
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ VERY INTERESTING!!! I was trying to decide between Dyers and Hampton, the Hampton wad $100 bucks cheaper but for some reason I liked the Dyers better. Thanks Oh and as far as the 144, I think I have it traded off for a set of E.T. 10 spokes and a set of 5 windows for the rear with 30" Hurst pie crusts. Should change the look of the 26 T!
The folks at Dyer's were really helpful on my set up. The quality of everything was top notch packaged really well with attention to detail and a free shirt. They are custom made to your specs. I ordered a low boost cast finish 6-71 blower. It took a few weeks to build it and then Gary called me to let me know the day it was being shipped and when to expect it, I thought that was great customer service.
I've seen where some guys just completely internally balance the motor and run a crank hub and do away with the harmonic balancer.. have any hambers done this and ran no balancer with their 671 motors?
Yes. Most blower engines have a hub and no balancer. I was worried about it not having a balancer for teh first 80 thousand miles or so, but after that, I kinda quit thinking about it... -Abone.
I read on a different forum where a guy painted his cast finished blower with a cast grey colored engine paint to help with keeping it clean, just an idea.
Mine sees 15-20K miles a year and sits outside all day long at work in the rain/snow etc. I wash her off at the carwash a few times a year, but that's about it. It stays about as clean as the rest of the car... -Abone.
^^^^^^^^^^^^^^^^^^^^^ Mmmmmm tasty!!!!! Are those AFB's? Normally I'm a Holley guy, but I've been thinking of trying a set of Edelbrock's. I've been trying to research running them on a blower and it seems like everything else, people either love em or hate em cause they don't want to learn how to figure them out. From what I've read so far you might be leaving some H.P. on the table, but I'm not going for that. I'm just wanting a nice driver that starts up easy and don't leak fuel everywhere. Any comments out there about carbs? Thanks again.
Yes, I ran a couple of swap meet Edelbrocks with quick cheap rebuild kits after I soda blasted them for a retro look. No regrets, easy to tune and all my plugs are reading good. My set up is low boost for the street, If your going to drag race or want max power I would go with Holleys. Also the linkage was easy to install running Edelbrocks and inexpensive. Good luck.
Did you just follow edelbrocks recommendations on the carbs for a blower? What size are you running 650's? SBC?
If you feel you want dual keys you could pin the crank. http://www.racepartsdirect.com/product_info.php?cPath=563_1156&products_id=4841
followed edelbrocks recommendations, pair of 600's on a 383 chevy. dynoed it and it was perfect, we didn't change a thing, just a tad rich which is where you want to be anyway. Yah holleys woud be best for max performance, but i like the fact afb's are easy to mess with, cheap cores can be picked up at swaps for 40 bucks.
A 350 is already internally balanced. My 454 is externally balanced, it has a weighted steel crank hub driving the blower. 100k miles, still works.
Yes, I have been using Gmc 6-71 and 4-71 blowers on various small block engines for the last 35 years.All street driven and running stock dampers.I've never had any problems.
My 354 has 8 to 1 comp and is a single key crank. I built this five years ago but haven't fired it yet but Gary Dyer and others don't think it will be a problem with 8lbs. of boost.
I think I'm more worried about the 9-1 comp. than I am about the single keyway on the crank now.....geez
I had 9-1 comp on my 283. You will just have to spin the blower in respect to the comp ratio to get your desired boost.. In other words, underdriven a bit more.
The real problem with Chevys isn't the single keyway, it's the lack of any keyway. Early 283's & some 327's had a real keyway but that went away and two half moons replaced it. One half moon for the timing gear & one half moon for the balancer, Folks this is not & I repeat not a keyway. Most shop cut a full keyway 180 from the half moon and tell the customer that now you have duel keyways = not !! Now you have one real keyway. What I do is put the crank up in the mill and just open full cut the half moons to a full keyway all the way to the end. This is all that is needed to end any issues with the blower hub. Fake duel keyways just weaken the already to small crank snout. I see on the import Chevy cranks a added third half moon & I just machine those out to a real keyway also. A real purpose built SBC blower crank has either a BBC or Chrysler snout with a real keyway or a real pair of keyways, No half moons Almost forgot, on SBC redrill the bolt to at least 1/2 to keep things tight.
Is Edelbrock/Carter, going to be a problem, not being referenced to the manifold for metering rod operation? I went with Demons because of the blower referencing. I know that there is a potential for problems wth "Lean out" when taking the vacuum signal from above the blower. I personally like the Edelbrock/Carter, but avoided them because of this.
Has anyone tried the Edelbrock thunder series AVS? Says they are for dual quad setups, I know you would still change a few things according to the manual for blower applications, but wondered if they were a bit easier to tune with the different secondary adjustment?
Just to let everyone know I called Dyers yesterday and HIS OPINION is, for a SBC 4-5 lbs of boost stock keyway should be fine, anything more up to 10-12 lbs you need a fully cut keyway (single) should be fine. Anything over 10-12 lbs of boost needs double keyed. All need SFI balancer. Hope this info is of help to someone other than me.
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