Would appreciate your thoughts, suggestions, input, etc on my upcoming project. I will give you my current setup and then list the mods to be done in November.

1992 Firebird currently with:

1. 350 TBI, stock intake, xtremefi 46mm tbi with 5206 55# injectors, 255lhp fuel pump, CFM-Tech adj fuel pressure reg, open element and all TBI mods, no smog, no EGR, etc.

2. Hedman Shorty, 3" high flow Magnaflow Cat with 3" Magnaflow cat back.

3. UMI Performance LCA, SFC, Adj panhard bar, torque arm, wonder bar


Project Plans: Exhaust will stay the same and most of the other above mods. Continued "chip" work with Brian Harris tbichips.com
1. Current 350 bored .040

2. Edelbrock 3704 Performer TBI intake bored to 50mm

3. 7.4L TBI base with 68# injectors

4. RHS Heads (stated they flow 220-230cfm)
76 CC Combustion chamber 083 / 217 casting style high flow design
new 2.02 One piece stainless steel intake valves
new 1.60 One piece stainless steel exhaust valves
new 3/8 screw-in-studs and guide plates
new stamp steel valve spring retainers
hardened valve keepers
new. 550 lift springs
new valve seals

5. Comp Cam 8-304-8
Basic Operating RPM Range: 1,400-5,400
Intake Duration at 050 inch Lift: 210
Exhaust Duration at 050 inch Lift: 220
Duration at 050 inch Lift: 210 int./220 exh.
Advertised Intake Duration: 266
Advertised Exhaust Duration: 276
Advertised Duration: 266 int./276 exh.
Intake Valve Lift with Factory Rocker Arm Ratio: 0.500 in.
Exhaust Valve Lift with Factory Rocker Arm Ratio: 0.510 in.
Valve Lift with Factory Rocker Arm Ratio: 0.500 int./0.510 exh. lift
Lobe Separation (degrees): 114
Intake Valve Lash: 0.000 in.
Exhaust Valve Lash: 0.000 in.
Computer Controlled Compatible: Yes
Grind Number: CS 266H-R14

6. Comp Cams 1.6 Magnum Roller Rockers

Plus a bunch of other little mods.

Horsepower range should be 350-375.

 

Go with 64cc heads, unless you plan on boosting it. Maybe a bigger cam depending on your goals for the car.

 

Overall goal is still to have a nice "street" vehicle with some power in the 350 range. What is wrong with the 76cc heads? I've already purchased these heads... so....

 

Will they change my compression that much? What will happen if I run them with this overall setup?

 

Yea, your CR will be in the toilet. Why exactly did you choose 76 cc heads in the first place then? Did you even calculate your CR before you threw down $1000 on a part?!?
What pistons did you put in there? the .040" over, what is the part number on them?
Did you deck the block? Need more info to determine your CR. Looks like you'll be able to run 87 octane fuel at least

220-230cfm isn't exactly something to write home about. What's the port size on these?

 

The block is a reman from two years ago. It is a stock 5.7L block that was rebuilt to factory specs etc, but was bored .040 from the remanufacturer. I had no intention two years ago of modifying it, but....

I paid $499 for the new heads and had them inspected by the local machine/race shop in Springfield, IL. They said they are one hell of a nice set of heads for $499 and whoever did the work on them did an excellent job.

From what i understand 230cfm is still better than the stock vortec heads which flow 215-220cfm.

I want to still have a motor that can be easily tuned

I was originally going to just add a stock LT1 cam and keep my stock 191 heads, etc, but I decided to beef things up a little more. That is why i went with the 8-304-8 cam and the 1.6 rockers and the RHS heads.

Comp Cams, Edelbrock and several others stated that with my block and setup the compression will be MILDLY affected. Just spoke with Brian Harris from tbichips.com who assists me in burning my chips and he said the same thing. It was stated that any other motor would be affected much differently, but mine should not be.

It's because of this advice that i went with those heads.

This thread has caused me to dive into my project thoughts more and rethink things and maybe a turbo is in order, lol.

I will do more research.

 

230 is about the same as stock vortecs... Which cost about $400 or less. If you only paid $500, you're doing ok then.

Check your deck height, and what pistons are in it. I have a funny feeling you have a 8:1 CR wonder with terrible quench in your hands

 

Everything is still stock. Have not started on the project yet. When I spoke with the re-manufacturer two years ago (Recon) they stated the compression ratio is 9.5:1.

 

You're looking at between 8.65:1 to 9:1 compression with those heads and flat top pisons. The range is from .025" to .005" deck height. If you make deck height .005" and shave enough off the heads to make the chambers 68-70cc you'd be looking at around 9.6:1. This is all with figuring in a standard .040" thick gasket.

 

I was just talking with Brian Harris and to be safe I am going with a .015" thick head gasket instead of the .039 stock gasket. This will raise the CR 3/10 over a stock gasket and I am going to shave .030" off the heads and the same amount off the intake to match as to not have alignment issues.

 

Well, since the heads are going to the machine shop any other suggestions on what to do with them? While they're out I might as well make the best of it.

 

Another quick question after a ton more research... The stock 191 heads are 76cc. I can't imagine how the RHS 76cc heads will be a problem.

 

Are you going to run 55 pound injectors?? The biggest you need for a na motor would be 30 pound. Thats what I run and does not lean out at any point in the power band

 

It will be a 7.4L TBI base and 68# injectors with fuel pressure at 30psi

 

What are 191 heads?
If you're talking about stock 350cid TBI heads, they are 64cc. 76 cc heads haven't really been made since the '70's.

Is the block disassembled yet, or is it still in the car running? I'd wait until you disassemble it, find out what pistons are in there (flat tops right? 5cc dish?), check the DECK HEIGHT. Measure it yourself! Numbers like deck height have a funny way of changing themself from what you think it might be, to what it is in the engine

Check how flat the decks are on the block. Feeler gauge and straight edge. If at all possible, deck the block!

I'm sticking with my first guess you'll be at ~8:1 CR.

 

14102191 is the casting number on my current heads. Several told me that those heads are 76cc. Who knows!?

The engine is still in and I'm still driving her. I will not start my project for about another 3 weeks. I am just trying to make sure all is well before I dive in.

I have a local machine shop (Springfield, IL) who is in the NHRA circuit and builds engines for a lot of the drivers, etc. and they are checking my new heads out and giving me ideas of what to do to get the compression where it needs to be without tearing the entire engine down.

They say shave them down which will bring the heads down to 70-72cc and go with a .015" head gasket set and that should give me close to 9.5:1 compression.

So, we will see what happens.

 

This is my current setup and the pics were taken 2 years ago. Enlarge the photo and you will see the casting number.

 

Just so everyone is updated. I am currently running the 14102191 heads. The 191 head IS already a 76cc combustion chamber. This engine is a re-manufactured engine and you never know why they do what they do.

So, installing the RHS heads that I have listed above will not be an issue and will not make my compression ratio take a dump. Even with the 2.02/1.60 valves and the 170cc runners these heads will work awesome. Obviously, the deck height and type of piston is already setup for the 76cc design.

These RHS heads will flow 27 more CFM @ .500" lift than 906 heads.

I spoke with Comp Cams and Racing Head Services, Edelbrock and Tim Wilkerson's master engine machinist. They all agree that with my setup and these heads it will do great. They all said it would work great even if i was currently running a 64cc head. They stated that there are differences with the RHS than a typical 76cc chambered head. Who knows guys, lol!

Thanks so much for your input and making me dive into more research.


Here's the data for future use: It was all in caps when i copied and pasted. Sorry for that.
CASTING NUMBER 14102191

SWIRL PORT INTAKE PORT DESIGN

76cc COMBUSTION CHAMBER

1.94" INTAKE 1.50" EXHAUST VALVE

VALVE SPRING PART NUMBER IS 3911068 (SAME SPRING USED WITH THE OLD 300H.P 350 CRATE)

INSTALLED HEIGHT 1.70" PRESSURE @ INSTALLED HEIGHT IS 80 LBS * PRESSURE WITH VALVE OPEN IS 267 LBS.

THESE SPRINGS ARE GOOD FOR .550" LIFT BUT CLEARENCE BETWEEN GUIDE AND RETAINER MUST BE DOUBLE CHECKED BEFORE ATTEMPTING.

7 BOLT EXHAUST FLANGE

CENTERBOLT VALVE COVER FLANGE

1987-1995 INTAKE MANIFOLD BOLT PATTERN WITH CENTER INTAKE BOLTS CANTED @ 72 ANGLE

THIS CYLINDER HEAD IS NOT A PERFORMANCE ORIENTED CYLINDER HEAD. IT IS CLASSIFIED AS A HIGH SWIRL HEAD THAT WAS INTENDED FOR GOOD BOTTOM END TORQUE AND FUEL ECONOMY. THE INTAKE RUNNER IS RESTRICTIVE BECCAUSE IT HAS A RAMP CAST INTO THE BOTTOM OF THE BOWL TO PROMOTE HIGH SWIRL.

 

Sorry, I wasn't familiar with 191 heads. Once you remove those heads, MEASURE THE DECK HEIGHT! Rebuilder engines could be anywhere! best to measure and then you'll know! dial indicator, base, steel straight edge, feeler gauges and you're good.
Find out what pistons are in there now.

76 cc heads, and 3.48" stroke (like a 350 chevy has) means terrible compression, unless you have pop up dome pistons. The math doesn't lie. With a small cam and swirl port heads, it'll help you have good bottom end. But with bigger heads, bigger cam, etc, then it'll be lazy down low. Please at least measure. If need be, you can shave the heads a bit, or at least you will KNOW what your actual CR will be. It's not like the car will stall at stoplights, you're just leaving some HP on the table, that's all.

27cfm more? Vortecs flow more then 198-205cfm bone stock. You're lucky if you're outflowing the stock vortecs by 15cfm at .500", and the kicker is what is your flow at .300" or .400", where vortecs REALLY shine? You're getting the heads for cheap, so I can't argue, but don't try to doll them up as something they aren't. They're entry level truck aftermarket heads. Meant for low RPM torque and low CR for towing and the like. Not really 'camaro' heads in my book. They'll work, i'm just saying you're hammering a round peg into a square hole eh?


Good luck, and please let us know what pistons are in there, and the deck height.

 

Sonix..

You're absolutely right. For my average application they will do great. They are not a set of $1500 AFR heads, lol. Comp Cams compared them to the vortecs that so many TBI users upgrade to. my 230-240 minimal cfm flow is adequate for 375hp

You bet that i will measure before i install!!! LOL. I have seen blocks from remans that have had .030 and .040 pistons in them. NUTS

I really appreciate your input. I wasn't trying to make them out to be something that they are not, just trying to show what they actually are and that is better than a vortec for mild-mod upgrades.

 

Here is the pdf tech info for anyone who cares, lol.

Thanks guys!

 

Not to burst anyone's bubble, but the 14102191 heads are in fact 76cc combustion chamber heads.

Talked with National Cylinder Head, Engine Builder Mag, Chevy 350.com, etc etc etc. They are 100% state they are 76cc.

I pulled them off, took the buret, measured and they are 76cc heads.

FACT 14102191 are 76cc combustion chambered heads.

Also Pure Stock Rules state that all cylinder heads must be 76cc combustion chamber or bigger and guess what...? GM casting # 14102191 is listed. I contact the entities involved with making the rules for Pure Stock and they stated that the 191 heads are 76cc.

I guess I said that enough? LOL!

SOLVED!

 

i realize everyone is picking on your heads. But 2.02 intake with 1.60 exhaust? the way i learned is the more air/feul your moving in with the bigger intake require a bigger exhaust valve to move it out. 1.60 sounds a bit small to me all i have ever used with my 2.02 intake is 1.90 exhaust thats what most major heads have too.. You asked if 76cc chambers are really a problem. Not if you want low comp ratio. but most perf. engine builders tend to want to kick the comp ratio up its more power period. even if you deck the heads your still only lookin into the low 9.2:1 comp maybe a bit higher.

Do your heads have heart shaped chambers?

 

The new RHS heads don't have heart-shaped chambers. Here is a pic.

 

The 2.02/1.60 is a very typical/common combo.

 

eh i had 1.90 on my edelbrock heads and my world. and my current procomp on my daily driver has them too. but i just went and looked a bit i found a few 1.60 so your right there. there really isnt anything wrong with the old style chambers but heart shaped chambers seem to have better combustion efficiancy. thats why i asked

 

Again, what's confusing to me is the conflicting opinions. National Cylinder Head, Edelbrock, Comp Cams, Tim Wilkerson's master engine machinist, etc have all stated that my comp ratio should be 9.5:1 at the lowest with my setup including the RHS heads.

Each one of them have been give DETAILED information regarding my setup.

I guess the proof will be when i turn the key for the first time after it's done.
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You're right about the heart-shaped chambers. They are better for many applications from what i'm told

 

what style pistons? i skimmed through the previouse posts but didnt find if you said it or not. even with flat tops 9.5 with 76cc seems a bit high

 

I've never heard of 1.90" exhaust valves on an SBC. Not unless it's a super custom setup. I don't even think 2.02 / 1.90" valves will fit on a 350 bore actually. I've heard of vizard building a custom nitrous motor, and he used 1.94/1.70" valves. He had to shrink the intakes, to fit the big exhaust ones.

ok ok, 191 heads are 76cc, good. The main reason I brought it up (a long time ago!), was that 76cc heads on a 350 will have dismal low compression. He mentioned dished pistons long ago, that's why I made that comment. It's not like it won't run, it'll just be down on power, and will happily burn 87 octane. Not a "bad" thing per se, but just not usually what most members on here go for.

Power to you tho doc. Have you did the math on your actual measured CR though?

 

I am going to measure the deck height this weekend if time permits. I have taken all of this advice into consideration and believe me I will make sure the pistons, deck height etc and head combo will make a reasonable compression ratio.

This has been a great learning experience for me. I am definitely a novice at this and this is turning out to be a fun hobby. I knew absolutely nothing about TBI's prior to 2 years ago. Still don't know much, lol...
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I am told they are a flat top piston.

 

Despite what Comp Cams and all those guys say... is there a better head that I can put on my application that is under $600 new for a set?

Just curious...

 

Sonix you beet me to it. I have never heard od 1.90 exhaust valves.
SBC standard valve sizes are
1.94in/1.50 ex
2.00in/1.55ex LT1
2.02in/160ex

Flat tops with 76cc even with a thin head gasket you'd be lucky to hit 9:1
do you know what they said the cr was when you got the engine.

As far a s heads everyone agrees on the vortecs. I'd like them but i want to put a lt1 intake on my car and was told no go with the vortecs.
not many heads under $600

 

Recon Engines stated that the engine I purchased was 100% GM stock specs with exception of being bored .040. They said they will match the pistons to the heads and vise/versa and they keep in at stock compression ratio.

Those are their exact words. I will find out more when i dive into it.
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I was just told this week that the Pro-Torker RHS heads that I have will flow 270cfm as they sit now. This was from a machinist who has installed a number of these heads and flow tested them before and after machining. He was surprised I had a set of these heads and that they were new. RHS replaced this head with a newer style a few years back. I paid $499 plus shipping. Had them inspected by Tim Wilkerson's machinist and he said "damn nice set of heads for $499 and nice work" That's about all i know, lol.

 

Everyone makes it sound like I have a $499 set of paper weights, lol.

They are by far better than the stock 191 and 193 heads. I know that for sure and with the cam, intake and TBI setup they should work fine for the $$$$$.