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350 bolt 4 bolt main 6-71 blown.

5K views 30 replies 10 participants last post by  Hudson Crass 
#1 ·
First, I want to thank everyone for the previous responses. And I feel bad it cause so much chaos!
And YES!!!I'm new at this and after speaking with several engine builders in the NYC area i haven't found anyone who did gave some confidence. If any of you are around here or know someone around here would be great to speak to them.

After several great advices I did bought an "010" 350 4 bolt main bare block, and an 6-71 (which just arrived at BDS to be rebuilt).

Now back to my project.
I did find that many people put an 383 stoker kit and run it on a blower. I did find these kit.
http://www.speedomotive.com/ps-524-85-383cid-supercharger-stroker-kit.aspx

1 - When I get the blower back and the block prep, (I will stud it for main and heads, hp bearings) should i buy that kit? buy something similar? it does seems very expensive.
2 - Also I found that some people run it on E85 as it 105 octane. What you guys think?
3 - Should I use the original vette heads?
4 - Serpentine set up?
5 - How much pounds of boost can I add and still run on E85 or gas pump (if I keep the compression around 8)?
6 - Holley, Elderbock or these carbs? http://www.jdrperformance.com/e85
7 - If I put the blower on the original 2 bolt lower while building the 4 bolt and if it "blows", would it damage the heads and or blower?

If anyone is available and willing to chat over this please feel free to call me.

thanks very much guys

victor 646-595-8350
 
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#2 ·
Crazy build

NICE! i all i got to say first off.

Done this build before and you don't want to use the vette heads Bigger chamber CC's are needed. You need to go forged for sure on bottom end. Minimum vaves I'd say 2.02, etc.

Does that kit come with a camshaft? also what specs are they?
 
#3 ·
Focus on static compression in combining the pistons and heads, aiming, in my opinion, for around 7.5:1. That translates to 72-76 cc heads and dished forged pistons. No, Vette heads are a bad idea, if you are referring to older fueler 62-64 cc heads, will not be a wise choice. As for carbs, I have run both Edelbrocks (Carter AFBs) and Holleys on street/strip blower motors. Whichever you run, be certain to boost reference the carbs to the blower manifold. Finally, as I have learned the hard way, ignition timing matters a lot when building a blower motor. In my own case, running a 4:71 with dual 600 Holleys atop a 7:5-1 355 c.i. SBC, required running a locked 32 degrees advance to avoid violent backfires through the carbs. Once you have a blower motor dialed in they are great fun, but dialing it in is crucial.
 
#4 ·
Hi,
No cam on kit. I was thinking in using the vette one. The engine now runs on 8 compression. Its a 1980 L48 vette.
What type of heads should I get?
Thanks.
Victor


355Nova said:
NICE! i all i got to say first off.

Done this build before and you don't want to use the vette heads Bigger chamber CC's are needed. You need to go forged for sure on bottom end. Minimum vaves I'd say 2.02, etc.

Does that kit come with a camshaft? also what specs are they?
 
#5 ·
Hi,
How many pounds of boost can I run before E85 is not enough?
Thanks
Victor

471A said:
Focus on static compression in combining the pistons and heads, aiming, in my opinion, for around 7.5:1. That translates to 72-76 cc heads and dished forged pistons. No, Vette heads are a bad idea, if you are referring to older fueler 62-64 cc heads, will not be a wise choice. As for carbs, I have run both Edelbrocks (Carter AFBs) and Holleys on street/strip blower motors. Whichever you run, be certain to boost reference the carbs to the blower manifold. Finally, as I have learned the hard way, ignition timing matters a lot when building a blower motor. In my own case, running a 4:71 with dual 600 Holleys atop a 7:5-1 355 c.i. SBC, required running a locked 32 degrees advance to avoid violent backfires through the carbs. Once you have a blower motor dialed in they are great fun, but dialing it in is crucial.
 
#6 ·
First of all since you are new to blowers I'd suggest you step back just a little and get some safe first hand experience with them. 5-6 psi boost is all you need to start with. Get a vac/boost gage.

The rotating assembly you are looking at is probably pretty good. Get the 1/4" keyway and a 1/4" tool bit for a key. Might as well get it balanced too. I don't use a damper on my blown motors and I have a lot of miles this way. A serpentine belt will really complicate things. Just use v belts for accessory drive. You can get the blower drive for any number of them 2 or 3 is usually all you will ever need.
Get the lower compression pistons. 8 to 1 is ok for pump gas. E-85 is wonderful if you can get a reliable source. The problem as I see it is that your fuel mileage will be such that you will have to plan regular stops around stations that have E-85. Here in Minn we have lots of E-85 but our cruises are often out in the country and are often in the 100 to 150 mile range so you will need a huge tank. I have a 16 gal and have to carry a 2 gallon back up just in case with 93 oct gas. I go on 3-5 cruises a week all summer so E-85 can be a bit expensive too. Tune for 93 and you will be happy.

Get a set of aluminum heads. 70+cc. I have Edelbrock Rpm heads 70cc and they work just fine for me. 3 inch exhaust all the way back.

If you want to run a 2 bolt block stay around 5 pounds boost but be sure you have AAA just in case. If you do break it you could lose the block, heads, cam and dist shaft and worst case maybe have a fire. Carry a 10 lb fire extinguisher just in case. I do.

You can run a lot of boost with E-85 but be sure you have sourse as noted.

Get an Air Fuel Gage (AFR) for tuning and learn to use it. Save yourself some grief.

Get a pair of Holley 750 blower carbs brand new. These will come with manifold reference ports for the power valves. Get a BDS scoop for best looks.

Get an MSD or other good dist and have it curved with 12 deg all in by 2000 motor rpm. Set it at 28 to 30 total advance. You also need a good ign. box . 6AL or similar. You should have a rev limiter and set it around 5600 to start. Really fancy would have a built in boost retard.

You don't really need too wild of cam for the street. A 234 deg @.050 and .510 lift works pretty well to start. I'd use a roller cam if you can with today's oil. You can use a little more lift with a roller cam too.

This should get you started.
 
#7 ·
if you want pm me and i will give you the number to he guy who builds my blowers and he can answer all your questions he has crew cheifed for pro mods and outlaw altereds. also helpful buy the book street supercharging. everybody wants to make this stuff sound complicated and its not. a blower expecially below 10 lbs boost doen't beat up parts . forget the holleys go to the edelbrocks no power valve! one gasket and they perform flawlessly no tricky linkage and the 2 bolt will be fine like i said pm me for the right info.
 
#8 ·
Hi Bantam
would be great to get the contacts, you can send it to victorcesarbota@gmail.com or call me at 646-595-8350
thx
victor


1932bantam said:
if you want pm me and i will give you the number to he guy who builds my blowers and he can answer all your questions he has crew cheifed for pro mods and outlaw altereds. also helpful buy the book street supercharging. everybody wants to make this stuff sound complicated and its not. a blower expecially below 10 lbs boost doen't beat up parts . forget the holleys go to the edelbrocks no power valve! one gasket and they perform flawlessly no tricky linkage and the 2 bolt will be fine like i said pm me for the right info.
 
#9 ·
A Fluidampr isn't what I would choose, but Speedway has a lot of experience, so take it for what it's worth. The additional 1/4" keyway with the original OEM keyway is a good idea, in any event- even though 1:1 ratio 6-71 on a SBC w/~8:1 CR seem to get away w/less. I wouldn't try it, personally.

ATI makes supercharger dampers w/the outer hub designed as a belt drive, but this will require coordination w/the provider of the drive pulley set up to get it all to coexist. I'd just as soon use a v-belt to run accessories.

AFA a 3-3/4" stroke crank set up, don't forget to get the correct hub or damper if it's externally balanced. Internally balanced will use the "standard" neutral balance (like a 350) parts.

In addition to bentwing's sound advice, BDS can answer any tech questions you may have.

You shouldn't be splashing your info out like that, IMHO- it's an open invitation to get spammed, etc.
 
#10 ·
hi fluidampr
thanks very much,
I will do the keyway, balancing advised and will also BDS.
so many option it is a bit confusing.
thx again
victor


cobalt327 said:
A Fluidampr isn't what I would choose, but Speedway has a lot of experience, so take it for what it's worth. The additional 1/4" keyway with the original OEM keyway is a good idea, in any event- even though 1:1 ratio 6-71 on a SBC w/~8:1 CR seem to get away w/less. I wouldn't try it, personally.

ATI makes supercharger dampers w/the outer hub designed as a belt drive, but this will require coordination w/the provider of the drive pulley set up to get it all to coexist. I'd just as soon use a v-belt to run accessories.

AFA a 3-3/4" stroke crank set up, don't forget to get the correct hub or damper if it's externally balanced. Internally balanced will use the "standard" neutral balance (like a 350) parts.

In addition to bentwing's sound advice, BDS can answer any tech questions you may have.

You shouldn't be splashing your info out like that, IMHO- it's an open invitation to get spammed, etc.
 
#11 ·
hi bentwings,
thx great info.
thx
victor


bentwings said:
First of all since you are new to blowers I'd suggest you step back just a little and get some safe first hand experience with them. 5-6 psi boost is all you need to start with. Get a vac/boost gage.

The rotating assembly you are looking at is probably pretty good. Get the 1/4" keyway and a 1/4" tool bit for a key. Might as well get it balanced too. I don't use a damper on my blown motors and I have a lot of miles this way. A serpentine belt will really complicate things. Just use v belts for accessory drive. You can get the blower drive for any number of them 2 or 3 is usually all you will ever need.
Get the lower compression pistons. 8 to 1 is ok for pump gas. E-85 is wonderful if you can get a reliable source. The problem as I see it is that your fuel mileage will be such that you will have to plan regular stops around stations that have E-85. Here in Minn we have lots of E-85 but our cruises are often out in the country and are often in the 100 to 150 mile range so you will need a huge tank. I have a 16 gal and have to carry a 2 gallon back up just in case with 93 oct gas. I go on 3-5 cruises a week all summer so E-85 can be a bit expensive too. Tune for 93 and you will be happy.

Get a set of aluminum heads. 70+cc. I have Edelbrock Rpm heads 70cc and they work just fine for me. 3 inch exhaust all the way back.

If you want to run a 2 bolt block stay around 5 pounds boost but be sure you have AAA just in case. If you do break it you could lose the block, heads, cam and dist shaft and worst case maybe have a fire. Carry a 10 lb fire extinguisher just in case. I do.

You can run a lot of boost with E-85 but be sure you have sourse as noted.

Get an Air Fuel Gage (AFR) for tuning and learn to use it. Save yourself some grief.

Get a pair of Holley 750 blower carbs brand new. These will come with manifold reference ports for the power valves. Get a BDS scoop for best looks.

Get an MSD or other good dist and have it curved with 12 deg all in by 2000 motor rpm. Set it at 28 to 30 total advance. You also need a good ign. box . 6AL or similar. You should have a rev limiter and set it around 5600 to start. Really fancy would have a built in boost retard.

You don't really need too wild of cam for the street. A 234 deg @.050 and .510 lift works pretty well to start. I'd use a roller cam if you can with today's oil. You can use a little more lift with a roller cam too.

This should get you started.
 
#12 ·
i will email you the number. far as the damper run the correct crank hub ex or in. balance .the belt will take out harmonics. if your getting a gm blower rebuilt find out if it is a big or small 6-71 there are two! look identical on the out side in the 70's they all went to the smaller rotors rough estimate the big will turn 15lbs at 1.1 the small will give around 7 lb @ 1.1 this is right on the bds web site.camshaft and heads will play a part in this but this is close.camshaft you want wide lobe centers more lift on ex.if you will compare the blower cams lift ,duration ,lobe center and try to find one close you can save some money and will make good power. double keyway is good also and I also have had them drill into the crank all the way back to the 1st main bearing and use a head stud for a little added extra strength but not really necessary for street. I would keep the hub as close to the crank as possible one v belt pulley behind hub to drive alt and water pump. also good valve springs is a must and rotella oil (good stuff) they keep taking everything out of the oil you will wipe out a flat tappet quik.
 
#13 ·
I would very strongly suggest that you Google up Speedomotive before you buy ANYthing from them. I've read enough bad press about them to be cautious about them. For good quality stuff, you can't hardly beat Summit. There are plenty of GOOD supliers out there, that have spotless reputations. All it takes, for ME at least, is a couple of bad raps, and I stay away...
 
#15 ·
Hi guys,
I'm buying the drive set up for the blower. I'm thinking in having he compression at 6.5 and run 16~17 psi on blower. The guys at BDS recommended to set up for gas/E85 as E85 stations are rare and mpg get much lower on eE85.
How low can I set the compression before I start to run issues? Is 6.5 ok?
thanks
 
#16 ·
That's what i will do.
Tuned for gas. Can I get away with 6.5 compression on a 383 stroker. so I can put 16 psi and still pump gas?
thx

bentwings said:
First of all since you are new to blowers I'd suggest you step back just a little and get some safe first hand experience with them. 5-6 psi boost is all you need to start with. Get a vac/boost gage.

The rotating assembly you are looking at is probably pretty good. Get the 1/4" keyway and a 1/4" tool bit for a key. Might as well get it balanced too. I don't use a damper on my blown motors and I have a lot of miles this way. A serpentine belt will really complicate things. Just use v belts for accessory drive. You can get the blower drive for any number of them 2 or 3 is usually all you will ever need.
Get the lower compression pistons. 8 to 1 is ok for pump gas. E-85 is wonderful if you can get a reliable source. The problem as I see it is that your fuel mileage will be such that you will have to plan regular stops around stations that have E-85. Here in Minn we have lots of E-85 but our cruises are often out in the country and are often in the 100 to 150 mile range so you will need a huge tank. I have a 16 gal and have to carry a 2 gallon back up just in case with 93 oct gas. I go on 3-5 cruises a week all summer so E-85 can be a bit expensive too. Tune for 93 and you will be happy.

Get a set of aluminum heads. 70+cc. I have Edelbrock Rpm heads 70cc and they work just fine for me. 3 inch exhaust all the way back.

If you want to run a 2 bolt block stay around 5 pounds boost but be sure you have AAA just in case. If you do break it you could lose the block, heads, cam and dist shaft and worst case maybe have a fire. Carry a 10 lb fire extinguisher just in case. I do.

You can run a lot of boost with E-85 but be sure you have sourse as noted.

Get an Air Fuel Gage (AFR) for tuning and learn to use it. Save yourself some grief.

Get a pair of Holley 750 blower carbs brand new. These will come with manifold reference ports for the power valves. Get a BDS scoop for best looks.

Get an MSD or other good dist and have it curved with 12 deg all in by 2000 motor rpm. Set it at 28 to 30 total advance. You also need a good ign. box . 6AL or similar. You should have a rev limiter and set it around 5600 to start. Really fancy would have a built in boost retard.

You don't really need too wild of cam for the street. A 234 deg @.050 and .510 lift works pretty well to start. I'd use a roller cam if you can with today's oil. You can use a little more lift with a roller cam too.

This should get you started.
 
#17 ·
16 PSI!???
I don't understand why you think you need that kind of boost on a street-driven vehicle. :confused:

If it's even possible to make those kinds of boost numbers, you'll have to spin that blower very fast, and it will make all kinds of heat.

I'd stay in the 7.5 to 8.0 CR range, and under-drive the blower so that you're making 5-6 PSI of boost. The engine and the blower will both thank you, and you'll have all the torque need for frying tires.

If you head for the strip, *then* maybe swap the pulleys for higher boost.
 
#21 ·
I think you are pushing it. 550 maybe but that's it.
Here are some of my cruises this week. I've been to 30 events so far this year since mid April. These are pretty typical of the events I have been to this year.

Early this week,
20 miles of country cruising. Stop and wait for the last 10 cars to catch up. Idle for 15 minutes. 20 more miles in winding hills. Stop and wait again. Idle for 10 minutes. Go 10 more miles on country road then turn down a gravel road for 7 miles. 20 cars in front 10 in the rear. Stop at event. Leave and go 2 more miles on gravel road to county road. 15 miles to the interstate. 75-80 mph in bumper to bumper traffic. Yes we can go fast here in the midwest. get into town and get caught in rush hour traffic. Sit still for 20 minutes idling next to 2 semi's. Spend another 45 minutes slowly moving. We finally break out and start moving at 30-35 mph for the next half hour before the highway opens up and I can dash home for early dinner.

Cruise later that afternoon. Caught in traffic again. It took an hour and 45 minutes to go 40 miles. It poured rain all the way home. The car was a mess. Need to clean the air cleaners again.

Cruise tonight. 950 cars at the event.
I took 3 1/2 hour trips around the grounds and never got above 800 rpm except for the 1/2 block to my parking spot. The temp never got above 205.

So far this year I can probably count on one hand the number of times I have stepped on the gas enough to get into the secondaries. Total time at 5 psi boost is probably 5 sec.

My point is you really need to look at how you are going to be using your ride. I find that it is nearly impossible to use the power that I have except for a very short time. You can get a kick in the pants but that's about it. The whole blower thing becomes an image thing. If it looks fast it probably is but you will not be able to prove it. haha
Blowing the tires off at an event likely will get you banned and tossed out.

spend some time designing a good cooling system. Plan on coated headers. You will need them.

8 to 1 comp ratio would be ideal. I see no reason to go below this. It will run very nicely and start easily. If you want to push it up to 8 pounds of boost, it will work ok since you can only spend a few sec at full boost on the street.
 
#22 ·
8.1 engine @ 7lbs boost is better than a 6.5 @16lbs on the street spin the blower slow as you can to keep the heat down . I read an article on don garlits in the 60's he ran more compression and less boost to keep from trashing the 1/2 pitch blower belts. you start spinning these things they take a lot of power to turn simply not needed for the street . its more of a statement gives the car ATTITUDE
 
#23 ·
You are not running 8500 rpm and 60% od on the blower.

You won't have to worry about belts wearing out on the street. Even a 2 in 1/2 in pitch Gilmer belt will run 20% overdrive all day long. The only thing that will break one is if something gets caught in it like a rock or tool or you don't adjust it correctly. I run a 3 in (75 mm) 8 mm belt and it is still like new. I haven't even adjusted it since I started the year out.

These blower don't take as much power to drive on the street as you might think. Some blowers are driven by a muliple vee groove belt and they last forever.
 
#25 ·
I'm thinking in running it 2% over, on a 350/383 it makes ~12 psi
and to run 12 psi on 93 octane, I need a static of 6.5 to 7
It will be city/highway ridden. With very few times on high rpm
is that low to start and or run on street comfortably?

If I'm going to do this and spend all this money I prefer to run it at max within pump gas limits

thanks
 
#26 ·
You know, there's an old saying...."You can lead a horse to water, but you can't make him drink".

Victor, Bentwings has lead you to water 3 different times in the course of this thread, trying desperately to shine the light of truth on your project. You have continuously ignored his sterling advice and rushed headlong into your own ignorance. Were I Bentwings, I would have blown up before now. I guess he just happens to be more of a gentleman than I am.

If you don't learn pretty quickly to pay attention to those who have been there and done that and been there and done that and been there and done that, you are going to be doomed to repeat all the mistakes that others have made doing the very same things that you intend to do.

Geez guy, wake the hell up and pay attention!!! :spank: :spank: :spank: :spank: :spank:
 
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