High Compression BBC for the street

[Ol69C10]

I'm makin this tread because I was looking for input on my ideal BBC build. I'm going to show what I want and try to make a plan for it.

Starting: I have a 2bolt BBC from '75. Has a 9.8 deck height, stock bores, Large oval heads, casting 781.

Now Im lookin for a 'budget' build but this is what I want: 11:1 compression, stock bores, stock stroke, reuse the heads. I'm gonna be running a Tunnel Ram (for looks) dual 650 holleys, and I'll find a nasty cam that will work with the combo. probably 108lsa, 240-250 dur @ .050 and lift around .515 as I want minimal head work. I plan for around 3200 stall and my current combo is a th350 and 4.11's in a 12blt. I'm looin at a 700R4 and 3.9's eventually.

I've been lookin into a 6.385 rod to try and give some extra piston dwell so I can use pump gas but I can't find a Piston/Rod combo to give the compression I want. I've been gettin a lot of Flak for wanting to run 11 or higher on the street. Some say it'll be too "finniky" or "no fun". I beg to differ.

End statement: 400-450hp, 454cu.in. not worried about driveability from this weekend cruise. Oh, It a 69 C10 and will have a 6/6 static drop.

So, suggestions on compression? Rod/Pistons? Cam? Head work? Block Work?

[70CHEVYBB]

you can not budget build a big block. Why would you go to all that work and not bore the block? I payed the tunnel ram game and you need a higher lift cam to start and usr 450 tunnel ram carbs . You can't go cheap on the heads because your tunnel ram increases the velocity of the air fuel mixture all to be slowed down when it hits the heads. You will spend around 800 to a 1000 just to have the heads done right, thats with upgrading to bigger valves,guide work, millingand grinding the valves. I know this because my 468 that I am building is at the machine shop right now getting all this work done. 11to 1 is to much compression for the street 10to 1 will work fine. What do you mean by extra piston dwell, I have never heasrd of that. .200 longer rods are used for making a stroker like a 489 or 572.

[cdowns]

400hp on a bigblock is easy to do with a pretty standard 4brl carb and dual plane manifold on a 9:1 engine with a 2500 or less stall and easy to run on pump gas and reliable

cant see why you'd throw money away on that nest of problems that u are facing with that combo

[Ol69C10]

70Chevy: Thanks for the info on the heads. Maybe I should look at just runnin a single plane intake. Why is 11:1 too much for the street?

Cdowns: Where's the fun in that? If I wanted a stock bbc I would of kept the engine together. Maybe used an RV cam. I'm looking for something that goin to run hard on a budget.

I've already got a small block at 10:1, .060over, with a comp280 cam, stalled at 2800.

Maybe .030over for the bbc but will be usin the stock stroke.

[jc70chevy]

detitnation on iron heads above 10 to 1 i believe. i know i have 11to 1 out of my aluminum heads but always premium gas

[jocko]

high compression and streetability are mutually exclusive. I've driven 11.25:1 on the street and it pretty much sucked. Gas, and everything else too. 70chevybb is correct - 11:1 IS too much for the street. Even if you are going to drive it as a weekend toy, I'd not even think of exceeding 10:1. With 11:1, you will go broke adding 104+ booster or you'll go broke mixing in local racing gas at the pump. 95 octane by my house is $8 and 100 octane is $10. But, hey, I learned the hard way too... Will never do it again though. I think you would be very happy with streetable compression and money spent elsewhere (heads, cam, intake, carb/FIm headers). Hard advice to give, because I wanted the exact same thing, however, wanted to make the case that I did it and regretted it.

[Redcap]

Originally Posted by Ol69C10

I'm makin this tread because I was looking for input on my ideal BBC build. I'm going to show what I want and try to make a plan for it.

Starting: I have a 2bolt BBC from '75. Has a 9.8 deck height, stock bores, Large oval heads, casting 781.

Now Im lookin for a 'budget' build but this is what I want: 11:1 compression, stock bores, stock stroke, reuse the heads. I'm gonna be running a Tunnel Ram (for looks) dual 650 holleys, and I'll find a nasty cam that will work with the combo. probably 108lsa, 240-250 dur @ .050 and lift around .515 as I want minimal head work. I plan for around 3200 stall and my current combo is a th350 and 4.11's in a 12blt. I'm looin at a 700R4 and 3.9's eventually.

I've been lookin into a 6.385 rod to try and give some extra piston dwell so I can use pump gas but I can't find a Piston/Rod combo to give the compression I want. I've been gettin a lot of Flak for wanting to run 11 or higher on the street. Some say it'll be too "finniky" or "no fun". I beg to differ.

End statement: 400-450hp, 454cu.in. not worried about driveability from this weekend cruise. Oh, It a 69 C10 and will have a 6/6 static drop.

So, suggestions on compression? Rod/Pistons? Cam? Head work? Block Work?

Are you specifically wanting to run AV gas? You will be with a 11:1 comp ratio. That stuff is $6+/gallon around here.

400hp is stupid simple with a 454. 700R4 and a bigblock don't mix very well, unless you dump a TON of money into the trans.

[huahuamick]

This is exactly what I want to know .

[1project2many]

Tunnel ram intakes are great for getting fuel and air into the cylinder with no restriction but they're lousy at mixing said fuel and air and they're even worse at vaporizing the fuel so it's in a ready-to-burn state when it gets to the cylinder. You can switch to small carbs (I'd use 350 cfm units for only 400 hp) but now you're looking at twice the cost and twice the maintenance and all you've really gained is looks.

Increasing compression ratio produces more heat in the combustion chambers. If you make enough heat your fuel's gonna start burning before the spark plug fires. This is called pre-ignition. Octane ratings are a way to tell how resistant a fuel is to pre-ignition.

There are ways to get compression up and run street fuel but you're not gonna do it with 1960's design heads. Modern fast burn style closed chambers with a very tight quench area is the key to keeping pre-ignition away. Aluminum heads help to distribute heat away from the combustion chambers quickly so it can't build up but ceramic thermal barrier coatings applied to the chambers and piston tops will help keep heat out of aluminum or iron heads parts.

Increasing piston dwell at TDC means it takes more time for the crank to rotate through TDC and move into a position where force on the piston can actually do more work. A talented guy might try using extended dwell along with fast burn heads and later ignition timing to "find" lost power but it will not prevent pre-ignition.

IMO there's a lot to be gained by switching to fuel injection, or even by using a computer to control ignition timing. With EFI you could use a tunnel ram style intake with a large TB and keep all your driveability. Good heads, big intake, and mild cam would easily generate 400hp. Properly tuned and with quality components your truck should be trouble free for years.

[PanelDeland]

If you're looking for "WOW" just build a fairly mild BB with aluminum heads and use a supercharger.The tunnel will work on the street with FI but you're still gonna have to feed it.You will be running in a less than optimm rpm range on the street causing driveability problems.A tunnel ram intake needs to run in the higher RPM range to keep fuel/air velocity up of you will probably see raw fuel dripping out the tailpipes.If you run FI it will need to be TPI style rather than TBI or the fuel problem will probably just be less rather then eliminated.400 HP is so easy with a BB you can probably use all factory parts to get it.It's not really hard to get 400 hp from a smallblock and retain good street manners.

[GASoline71]

Originally Posted by Redcap

400hp is stupid simple with a 454. 700R4 and a bigblock don't mix very well, unless you dump a TON of money into the trans.

Agree 100%. Heck... 450hp is still pretty simple with a few "upgrades" and still using a single 4bbl.

Gary

[big d's red67]

I built my 454 with pro comp aluminum heads, 9.7 to 1 compression, roller cam roller rockers, stock crank turned 10/10, stock rods, cylinders bored 30 edelbrock air gap intake holly 850 cfm carb. It dynoed out a 528 hp and 630 ft pounds of torque. I have a real good machine shop that answered all my questions so I could reach these numbers with out spending a lot. I spent about $4500 total.

[Ol69C10]

Thanks for everyone's input. This will be my third engine build, first bbc, so i'm grateful for all the help. Sounds like through most experiences the Alum. heads ran better with the comp, thats good info.

Any input on the 6.385 rods? Or should I just run a stock length rod? Looking at rod/piston combos the price is still very similar but is there an advantage there?

Also, even if i run comp at 10:1, I'm lookin at runnin a cam @ 108lsa/106icl with the dur around 245@.050. Single plane int with a 750/850 holley. Any thoughts on streetability? Would a larger lsa help keep it from detonating/pre-ign? I want that rough idle but don't like the mutha-thumpr...expensive. Any one using a specific grind?

Big D: those are some great numbers, no doubt that roller cam is helping! Ha, I'm goin to have to stick with a Hyd.tappet. Do you mind postin your some of your cam info?

Jocko: what sucked about runnin the 11.2? besides the fuel booster, how did it drive/feel?

I'm really goin for that old rat look/feel so the engine build is important. It's why i'm lookin to run the tunnel ram, more comp, rough idle. Any cam suggestions for a T-ram? Longer lobe sep? I'll be limited on lift so maybe a longer dur too?

[big d's red67]

Originally Posted by Ol69C10

Big D: those are some great numbers, no doubt that roller cam is helping! Ha, I'm goin to have to stick with a Hyd.tappet. Do you mind postin your some of your cam info?

I will tell you a quick story, hope this doesn't send us down the wrong path.
Against my machinist advice I didn't use a roller cam, I built the motor ran it on the dyno put it in my truck and after a whole 11 miles the cam shaft broke and I had to do a total rebuild again plus a valve job on brand new heads.I said all of this to give you this warning, you may already know this I learned the hard way. Make sure you have enough zink in you oil so this doesn't happen to you.
I made the same HP and torque numbers on the dyno with the flat tappet cam, here are the specs from it. 112 degree lobe centers Lift intake .295 exhaust .310 duration at .050 214 intake 224 exhaust. the dyno sheet shows 628 clb-ft at 3500 rpm and 528 HP at 5000. the torgue is over 600 till you hit 4400 RPM the HP is at 418 at 3500 and climbs quickly from there. sorry so long. hope this helps. by the way I dynoed the engine on 91 octane from my local gas station with 10% ethanol at 36 degree all in on the timing.

[Ol69C10]

Big D: I've heard that about the oil, so strange but i'm aware. I def don't want to go through a whole rebuild a second time. Thanks for sharing the specs, are you sure those are @.050?
Posted via Mobile Device

[big d's red67]

Originally Posted by Ol69C10

Big D: Thanks for sharing the specs, are you sure those are @.050?
Posted via Mobile Device

Yep, read them right off the cam card.

[79shortbed]

Quote:
Originally Posted by Ol69C10 View Post
Big D: Thanks for sharing the specs, are you sure those are @.050?
Posted via Mobile Device
Yep, read them right off the cam card.

Those sound like the lobe lift numbers, not lift numbers after the lifters and rocker arms. Multiply those numbers by the rocker arm ratios to get the total cam lift.

[Ol69C10]

Originally Posted by big d's red67

Yep, read them right off the cam card.

Big D: Sorry, I read it backwards. Now that I'm on my computer I can see what you wrote clearly. I read it as 295/310 @ .050, thought you may be runnin a ProStock cam! Lol.

Here's a vid of my truck from 2009 w/ the small block...I miss-stated the comp ratio. It's at around 9.5

[b454rat]

I built my big block for about $3k. 781 heads were already done, 10:1 comp, two bolt, cast crank, small rods w/ARP bolts. Can't remember what the specs are on the cam, but it's not big, but it does have a nice idle to it. It's not a complete fender shaker, but IMO how a car should sound. Every car or truck I get that is carbed has carb issues, this one is no different. I don't really know how to tune them to get them to run the best, but gonna have to figure it out on this. Right now has a 600 Edelbrock on it, but gonna put a 3310 on soon as I get some money. I run 93 in it, and other than the carb no issues driving it. Sucks now that it's getting cold out, soon to have snow, and can't drive it as much. Engine builder told me it's about 350-375...

[SSC's76]

I was reading this post last night just dident get a chance to comment. like jack said high compression and street is terrible. I ran 11.5:1 383 on the street in and it was just a nightmare to get good fuel I could test the quality of the gas in 2 blocks after I filled up. most the time I was running with the timing so retarded all the power advantage was lost. now its strange that engine is now in the wifes appolo and it its fine with midgrade. the weight difference between the truck and the car seem to allow the engine to run happy. what exactly are you wanting to do with this setup? everything I seen here with the dual feed tunnel ram and the cam choices I've seen are not streetable. you can drive it on the street but I sure would not. I like the idea mentioned above about a milder build with a blower that would be my choice for a street friendly yet insane power output build


Posted from 67-72chevytrucks.com App for Android

[Ol69C10]

Vid didn't post the first time.

YouTube - Shanes Truck

SSC: thanks for the info, I hadn't thought about weight. I need to make sure an
idiot consider that for my bbc build.

Rat: that sounds like a solid build. What are you runnin it in?
Posted via Mobile Device

[b454rat]

79 Malibu factory 4-speed 3.42 posi rear...

[Redcap]

Originally Posted by b454rat

79 Malibu factory 4-speed 3.42 posi rear...

That is a bad ass looking Malibu. Here is my '78 project.

[b454rat]

I've had a bunch of Malibu's and other G bodies, but this one takes the cake. Factory stick, tach dash w/clock, black interior, buckets, console, and factory power "sky roof". I've only seen two, this one and a 78 I had when I was going to school in FLA. Never knew they existed. I have new front fenders (two guesses what the louvers are off) and found a set of doors. Still tweaking it, but runs and drives, goes pretty good, but the carb is tickin' me off....

What's under the hood of yours??

[clinebarger]

Originally Posted by b454rat

two guesses what the louvers are off??

Late 2nd gen Camaro??