Thread: Newbie here with some questions

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First i want to say that ive been reading for a while...Im very selective where i join and this place seems like a cool bunch of guys from all walks of life...Well now down to bussiness..

New to me is a BBC...Its basically a stock rebuild as i comming to find...It has flat tops that are .003 down the hole and 781 heads...I got the heads a 3 angle vale job(just a basic one) and the standard bowl blend done on the machine.I plan on running ferrea valves or possibly manleys..K motion springs, and the retainers and locks that came with it...A comp cams solid xe274 770 is the gring and a Q jet on an RPM intake...

My question is about the heads...When i got my parts back the box had a bunch of shims in it...Im not keen on big block heads so im wondering if useing rotator eliminators will prevent me from stacking up spring shims?

Also what kinda power will the engine makewith the unported 781 heads...I want to port them but cant find any info on them...Ive ported a ton of small block heads from my 15* to my lt1 heads and SB2's but never touched a BBC head...Where can i get some guidance on porting them..

For now it will see a small 200 hp shot of giggle gas but i plan on running a turbo and blow through setup...

Originally posted by philadelphia
First i want to say that ive been reading for a while...Im very selective where i join and this place seems like a cool bunch of guys from all walks of life...Well now down to bussiness..

New to me is a BBC...Its basically a stock rebuild as i comming to find...It has flat tops that are .003 down the hole and 781 heads...I got the heads a 3 angle vale job(just a basic one) and the standard bowl blend done on the machine.I plan on running ferrea valves or possibly manleys..K motion springs, and the retainers and locks that came with it...A comp cams solid xe274 770 is the gring and a Q jet on an RPM intake...

My question is about the heads...When i got my parts back the box had a bunch of shims in it...Im not keen on big block heads so im wondering if useing rotator eliminators will prevent me from stacking up spring shims?

Also what kinda power will the engine makewith the unported 781 heads...I want to port them but cant find any info on them...Ive ported a ton of small block heads from my 15* to my lt1 heads and SB2's but never touched a BBC head...Where can i get some guidance on porting them..

For now it will see a small 200 hp shot of giggle gas but i plan on running a turbo and blow through setup...

You own and have ported some of the best SBC heads out there and you want some guidance on porting stocker 781 BBC heads?You have more in your 15* heads then most people on this forum have in there intire engines.Who are you? and are you messing with us?Don't take take my doubt the wrong way if you are serious.

Nah man im sereous here...Ive long time learned that one doesnt know everything...Ive also learned that one can quickly ruin a set of heads with a die grinder...I like to see stuff with my eyes and go from the on the advice i get...The first set of sbc head i chewed up and i mean boy did i chew them up it cost me...Ive talked to a few local shops and they all want to jump in and hog the short turn on my ports...For light port work id always stay away from that...At this point im just thinking of teardroppibg the guides and cleaning up the rather tall casting ridge running down the port...

Big blocks are new to me since ive only had a mild 9 sec 466 ford in a fox body..I can only do this once so id like to have the most intell as i can.Down here i have a house to pay for anddont make the money i did up top....Living in atlanta is harder for me than when i was in NY,NJ and philadelphia...I had guys from top shops up there to hang around and get advice and help...Down here im surrounded by ford guys...They go pretty damned fast(Tim lynchs shop does my machine work) but they dont know chevy...

Originally posted by philadelphia
Nah man im sereous here...Ive long time learned that one doesnt know everything...Ive also learned that one can quickly ruin a set of heads with a die grinder...I like to see stuff with my eyes and go from the on the advice i get...The first set of sbc head i chewed up and i mean boy did i chew them up it cost me...Ive talked to a few local shops and they all want to jump in and hog the short turn on my ports...For light port work id always stay away from that...At this point im just thinking of teardroppibg the guides and cleaning up the rather tall casting ridge running down the port...

Big blocks are new to me since ive only had a mild 9 sec 466 ford in a fox body..I can only do this once so id like to have the most intell as i can.Down here i have a house to pay for anddont make the money i did up top....Living in atlanta is harder for me than when i was in NY,NJ and philadelphia...I had guys from top shops up there to hang around and get advice and help...Down here im surrounded by ford guys...They go pretty damned fast(Tim lynchs shop does my machine work) but they dont know chevy...

O.K.,fair enough.The reason I doubted you was I own and operate a company that CNC'S cylinder heads.I would never touch the short turn radius ever un-less you have a flow-bench sitting right in front of you.Do a really good bowl blend and tear-drop the guide area and you are on the right track.

Originally posted by DennyW
I just thought I would throw this in, general info, that's all.

Big block oval port cast iron heads were made in two different configurations. The large oval port heads found on many passenger vehicles and trucks and the small oval port heads (which are also sometimes called peanut ports or round ports or truck ports) found on many big block 454 truck engines made after '76. Each of the oval port head sizes used a matching intake manifold. If you are building a motor for pulling or towing on the street, the small oval port heads will make their power at low and mid range rpms, but run out of breath at rpms over 4500. If you are building a strong street performer or a bracket racer, the large oval port heads are the ticket up to about 6500 rpm if you do some bowl porting and add the 2.19"/1.88" valves. Some of the better performing cast iron large oval port castings are the open chamber designs like the "781" or "049" casting. You can get an aluminum version of the large oval port, open chamber head under casting number "391" from GM/Performance Parts.

He already has a set of 781's.

Originally posted by DennyW
I know that, but he said he was new to BBC, so when ever your new to something, it's good to go from basic understanding of what you are working with. And I don't know where he is at.

This is true.Did you see the list of SBC heads he has.I think he knows alot more than he is letting on to.

Originally posted by DennyW
Well, that's possible. Some people like to test others to see what they know. But also, they may have read books and talked to people about different things, but not actually did any redo work, or fully understood what all that means. I try not to think they are playing me, but that does happen. All and all, I don't have much going, so talking and helping, even if it's for fun, or to test me, is ok with me. I try to keep a happy face, and help anyway. I try not to expose more than needed.

You are right.I think I should try and help more than I do also.

What are these 15* heads you guys are talking about, and what is so special about them? Cost?

I'm basically a Ford guy, so this term is lost on me. Bet others are wondering too.




Don

Originally posted by Itoldyouso
What are these 15* heads you guys are talking about, and what is so special about them? Cost?

I'm basically a Ford guy, so this term is lost on me. Bet others are wondering too.




Don

The 15* raised runner heads by Brodix sell for about $2600 bare and are for late models and sprint cars.They require 15* pistons intake etc.The sb2's sell for much more than this bare.

So the only application is roundy round kind of cars? Not drag and certainly not street? I wondered, because you site late models and sprints.


Don

Don, here's an explanation of 18 degree heads. 15 degree heads are just more of the same......
Dyno Testing Trick Flow's New 18 Degree Chevy Heads




If there is one constant in this big, crazy, spinning-wildly-out-of-control world, it's this: horsepower wins races. Oh sure, racers will tell you stuff like suspension settings, driver skill, and plain old dumb luck are important. But deep down in the furthest corner of their souls, they know it's raw, screaming horsepower that takes the checkered flag.

The cylinder head crowd at Trick Flow Specialties understands this Primary Law of the Universe—their famous Twisted Wedge and R-Series aluminum heads are ample proof of that. Now they've gone to an even greater degree in the search for more power. Actually, make that 18 degrees, as in their new 18 degree aluminum heads for small block Chevy. And do those heads make power—we have the dyno tests to prove it.

Why 18 is Better

Before we get to the dyno results, let's get into the theory behind 18 degree heads. The number refers to the angle of the intake and exhaust valves in relation to the head's deck surface. By contrast, conventional small block Chevy heads have a valve angle of 23 degrees.

So what's the big deal about 18 degrees? The shallower valve angle allows the cylinder head designer to use a smaller volume combustion chamber to help boost the engine's compression ratio without going to large-dome pistons. The combustion chamber on the Trick Flow 18 degree head is 56cc versus the 64cc chamber on most high performance 23 degree heads.


CAPTION
The Trick Flow heads, like all 18 degree heads, require shaft mounted, offset roller rockers. Trick Flow used these Jesel 1.6/1.5 ratio shaft rockers for the dyno tests.

Another big advantage of the 18 degree valve angle is valve location. The valves in a conventional 23 degree head are .275 in. from the cylinder bore centerline. When the valves are close to maximum lift, they become shrouded by the combustion chamber and the cylinder walls. That hurts the engine's ability to breathe--and that hurts horsepower.

In 18 degree heads, the valves are right on the cylinder bore centerline. The valves are also relocated to position the intake valve closer to the bore center, and the exhaust valve closer to the cylinder wall. This unshrouds the intake valve at maximum lift and allows the use of bigger valves.

The Trick Flow 18 degree heads are machined for 2.150 in./1.625 in. valves, and can accept intake valves up to 2.180 in.

To fully take advantage of the highflow characteristics of the shallower valve angle and larger valves, 18 degree heads have raised intake runners; the runners on the Trick Flow heads have floors raised 1.15 in. from the deck. And when you combine big, unshrouded valves with raised ports, you get gobs of power-building airflow at high rpm.

The one drawback to 18 degree heads is that they can't use standard 23 degree head components. For example, the 18 degree head's intake manifold mounting flange is angled at five degrees (standard is 10 degrees) to accommodate the raised intake runners. That requires a special 18 degree intake.

The 18 degree heads are also taller than their 23 degree cousins, and require longer valves and special head studs. Eighteen degree pistons with domes and valve reliefs matched to the combustion chamber shape and valve locations are needed. And then there's the big kicker—18 degree heads must use shaft mount, offset rocker arms and mechanical roller cams with offset lifters. These components are readily available, but often cost more than 23 degree stuff. Nobody said going fast was gonna be cheap.

Testing the Trick Flow Head

The Trick Flow 18 degree heads we dyno tested came with as-cast 250cc intake/100cc exhaust runners, 56cc combustion chambers, 2.150 in./1.625 in. stainless valves, and 1.55 in. dual valve springs. The flowbench data on these heads was impressive: maximum intake flow was a steady 328 cfm from .550 in. to .700 in. lift; max exhaust flow was 255 cfm at .650 in. lift. In the hands of a skilled head porter, the Trick Flow heads can be made to flow a bunch more.


CAPTION
The dyno test engine is a 358 cubic inch small block with a relatively mild 9.5:1 compression ratio. Testing was conducted with an 830 cfm Holley double pumper and a Demon Carburetion 825 cfm Race Demon/RS.

Dyno Engine Specifications

Displacement and Compression: 358 cubic inches, 9.5:1 compression
Block: Bowtie iron, 4.125 in. bore
Crankshaft: Trick Flow forged, 3.33 in. stroke
Connecting Rods: Trick Flow forged, 6.125 in.
Pistons: JE forged, -19cc dish
Camshaft: Iskenderian mechanical roller, 264/268 degree duration @ .050 in., .645 in. lift
Intake Manifold: Bowtie single plane
Carburetion: Holley 830 cfm double pumper (Test 1), Demon Carburetion 825 cfm Race Demon/RS (Test 2)
Ignition: MSD Pro-Billet distributor, MSD 6AL ignition box
Exhaust: Dyantech step headers (1 3/4 in. to 1 7/8 in. primary), 3 1/2 in. Flowmaster mufflers

The test engine was a relatively mild 358 cubic inch small block with 9.5:1 compression. Set up like a late model circle track engine, it has a Bowtie 4-bolt block, 3.33 in. stroke Trick Flow forged crank and 6.125 in. forged rods, JE dished pistons, a .645 in. lift Iskenderian roller cam and lifters, Jesel shaft rockers, and a Chevy Bowtie single plane intake. Two carburetors were used—a tried and true 830 cfm Holley double pumper and a Demon Carburetion 825 cfm Race Demon/RS. This was the first time we had seen a Demon in action, and we were anxious to see if it performed as good as it looked (see "Caution: Demons at Work" for details on the Race Demon).

The test results were as impressive as the flow bench data, especially when you consider the mild compression ratio. With the Holley, the 358 made 607 HP at 7,250 rpm and 472 ft.-lbs. of torque at 5,750 rpm. With the Race Demon/RS bolted on, horsepower edged up to 620 HP; torque stayed about the same at 474 ft.-lbs. Trick Flow plans on dynoing the heads on a more serious 12 or 13:1 compression engine, and fully expects even more dramatic power figures.


CAPTION
The 18 degree valve angle allowed the Trick Flow designers to put the valves on the cylinder bore centerline, and reposition the intake closer to the bore center. That unshrouds the intake at maximum lift, and allows the use of bigger valves. The small 56cc combustion chamber lets you run higher compression ratios without going to large-dome pistons.

Trick Flow 18 Degree Head Flow Data
Head tested on Quadrant Scientific Flowlab 1400 flow bench at 28 in. of water pressure
Intake Flow Exhaust Flow
Lift CFM Lift CFM
.300 in. 217 .300 in. 152
.400 in. 276 .400 in. 198
.450 in. 298 .450 in. 209
.500 in. 316 .500 in. 219
.550 in. 328 .550 in. 225
.600 in. 328 .600 in. 231
.650 in. 328 .650 in. 255
.700 in. 328 .700 in. 237

There's no doubt that Trick Flow's 18 degree heads can make serious power--power ideal for high rpm circle track or Super-class drag racing. While they're not bargain-basement heads by any means, they are a good deal when you consider the large amounts of time and money you would spend on making a set of 23 degree or other 18 degree heads perform at these power levels. It seems as though the Trick Flow 18 degree heads are a bargain after all....



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as you guys will get to know me you will see that im down to earth and pretty humble...I always speak on my own experences and not what ive seen or heard...While i may have lotsa experence building pretty wild small blocks i saw after reading here that this is a good place to go for help...As well as a great place that i can help out others...

Philadelphia,

I am from NJ as well, and then I moved to Atlanta for 6 years. My point being there is a machine shop on the corner of South Cobb Drive and Pat Mel Road; right behind the corner (just one lot in). Its called "Chix Machine Shop." Located on the Marietta Smyrna border. Very fair prices, for machine work! Have a full parts storeas well with very fair prices. Finally they have a couple of guys in there that Race their cars. Both Chevrolet and Ford. The owner and his main machine man there I have seen them help out people by showing them how to port thier heads etc. They typically dont do high perfomance port work for business purposes for off the street customers, but do it for selected racers in the Atlanta area. Nice shop with clean high tech up to date machining equipment. Maybe swing by there and pick some brains. Chances are they may have a set of 781's with some street strip port work already done!