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6-17 blower with 781 heads???

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dubs68camaro

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Discussion starter · #1 ·
I am slowly trying to hunt down a blower (will probably just drop the $2,500 for a new one) and I'm wondering if I can get away with the heads I already have. The bottom end will be a 4 bolt main 454-468 with steel crank and forged pistons. The blower is going to be spendy enough and I was wondering if I can use one of the 2 sets of head I already have. They are, of course, early 781's. I was thinking about smoothing out the ports and maybe stuffing 2.19/1.88 valves in them. Do they even make a blower manifold for large oval ports?? I know they were running blowers long before these aftermarket head companies started up, I just didn't know if I could get some good HP from an oval/blown setup. Oh yeah.....for you guys that think blowers are GAY in a Camaro......don't worry.....it's for my '68 swb. Doesn't that make me only a little gay??? LOL

Nothing like just a little Hilborne sticking out of the hood!!!!
 
#2 ·
flow numbers are what its all about there dubs...i dont know what your 781`s are gonna flow, but i know they are a more desirable head design as far as stock is concerned...unfortunately, i`m not versed in the bbc heads much at all...i know that even the best flowing stockers for sbc pail in comparison to some aftermarket jobs...the more efficient the cyl head, the more efficient the blower will be...more efficiency will mean you need less boost to make the same power...less boost means less likelyhood of detonation, or more potential depending on how you look at it...i`m sure jody will have more informative info for you...
 
Discussion starter · #3 ·
......Then Jody needs to get on the ball and post a reply!!!!:D:D:D

I know there is nothing stock like these aftermarket heads. I also know you get what you pay for but it just sucks how much they go for. I was getting excited when I was on Summit's site looking at the do-able prices until I realized that the prices were EACH!!!

As relatively easy as a blower bolts on and unbolts, I can always set a savings budget for some good heads down the road.....I was just hoping to have some fun and the rod-runs this spring and still make some good HP over my current setup. Thanks!
 
#4 ·
there`s no doubt that the heads will work...the issue is how well they will work...the roots blower has been in use since something like the late 1800`s...they didnt have aluminum heads back then!!!your combo will make power over stock for sure, and you can absolutely bolt on better heads later...my post was only to say that the volumetric efficiency of the heads directly affects the ability of the blower to make power...thats the case for any power adder...a blower will make power over stock on most any app...just some more than others...my uncle bolted a 6-71 onto a 1600$gm crate motor...NOTHING special in it at all...just wanted the look for his prostreet 36 ford p-u...it ran fine,although it didnt make 700 hp...but was quite reliable and looked frikken ausumn!!!
 
#5 ·
I would run that 6-71 with 781,s in a heart beat.Match it with a mild hydraulic cam with a wide lsa and it would be a tire fryer on the street.Keep your boost under 10 lbs and buy a spark retard that pulls out some timing as the boost climbs.
 
Discussion starter · #6 ·
fatblock said:
Match it with a mild hydraulic cam with a wide lsa and it would be a tire fryer on the street.Keep your boost under 10 lbs and buy a spark retard that pulls out some timing as the boost climbs.
Click to expand...
I already have a set of retro-fit roller lifters.....so It will be a roller motor. Why a mild cam??? Why not go big?? Then again.....what do you mean by mild? When you say wide lsa...do you mean 112? I have, on the shelf, a comp roller 290 with 110 lsa and 578 lift on each. How would that do? I realize I may need a different cam. Do they make blower grinds like they do turbo and NOS grinds?? Thanks for answering my 52 question. LOL:D
 
#8 ·
You do not need a ratty a$$ cam with forced induction.All big blocks will suck up all the lift you can throw at them..but a tight lsa will have the blower pushing right thru the exhaust valve during the overlap period.Like Mike said..112/114.Less overlap and more cyl fill =hp with a blower.The heads will support 600 hp n/a.The 1.88" exhaust valves and 2" primary header tubes will compliment the 6-71.
 
Discussion starter · #9 ·
fatblock said:
You do not need a ratty a$$ cam with forced induction.All big blocks will suck up all the lift you can throw at them..but a tight lsa will have the blower pushing right thru the exhaust valve during the overlap period.Like Mike said..112/114.Less overlap and more cyl fill =hp with a blower.The heads will support 600 hp n/a.The 1.88" exhaust valves and 2" primary header tubes will compliment the 6-71.
Click to expand...
So are you saying the 2.19/1.88 valve swap would be a good idea since I will probably have to go with beefy-er springs (than the stock single wrap 781's) and have the spring seats cut anyway?
 
#10 ·
dubs68camaro said:
So are you saying the 2.19/1.88 valve swap would be a good idea since I will probably have to go with beefy-er springs (than the stock single wrap 781's) and have the spring seats cut anyway?
Click to expand...
I would say yes.As long as you do not get into coolant with the new seats..the larger valves will have a bigger curtain and you will want more spring on the intake side with boost.
 
#12 ·
My buddy has a 454 with a 6-71 blower with the same 781 heads. They have 2.19/1.88 valves but no porting or blending at all. He has a Isky solid lifter blower grind cam with 2 edelbrock 750 carbs and runs 10.60`s at about 125 or so in a 67 chevelle with a 4L80e and 4.11 gears and 29" slicks. He pieced together the blower and had less than $1000 in it.
 
#13 ·
I built a great street blown 454 using 781 heads, These heads have hard exhaust seats and the biggest exhaust ports of all the factory large oval port heads, If you are still looking for a blower i custom build 6-71 and 8-71 blowers, I have a list and prices for what you are doing if you have not built on as of you, Thanks Ron:hurray:
 
#14 ·
I built a 454 blower motor,and this is the cam I came up with after talking to more than a few engine builders. Its a comp cam roller, cb 288A-R110 246 @50 with 622 lift I was told it would make good power with oval or square port heads, and a nice set of big tube headers.
 
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