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I have stock Gen IV 454 & 781 Heads, Compression ????

70K views 59 replies 11 participants last post by  wild_man84 
#1 · (Edited)
Im going to be working with stock 4 bolt main 454 Gen IV bottom end.. ( in vehicle) I have a set of stock 781 heads.... I'm ready to send the heads off to a machine shop for work ( if needed/recommended) for new parts to match cam and for port&polish job.

Ive been searching and it looks like the cc's of the 781 are 115-118 cc's. not sure on the valves.

The cam im looking at recommends CR to be 9:1+.
Can I and how do I get my CR up without bottom end work?

Should I get the bigger valves 2.19 and 1.88?
What should I tell the machine shop to do with my heads ( mill? cc? P&P )
Should I use 0.020" shims (read that) Port match gasket?
The the cam recommends 2 different valve spring sizes, how Would I determine the answer. so in the future, I can figure it out for myself instead of having to ask. here is what it offers/recommends for the cam

Single Outer Valve Springs: 1.524" O.D., 1.110" I.D. OR
Dual Valve Springs: 1.509" O.D. Outer, .697" I.D. Inner On a guess, Id say the Dual valve springs BC of High RPM and my cam is .51 lift int & exh. and my rocker ratio is 1.72? is that right


Not a daily driver.. Looking to get high tq. rpm range (2200 to 5800)

Any input/advice/direction would be appreciated.... thanks in advance
 
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#27 ·
cobalt327 said:
Sorry, matts37chev- I didn't see the first page of the thread before responding. The comment about the heads was more to add something on-topic instead of just flakking the guy for the street racing comment.

In any event, wild man- check out this build to get an idea of what kind of flow (CNC ported AFR Magnum 315's w/2.25" x 1.88" valves milled to 110 cc chamber volume, being fed by a Vic Jr.) and how much cam duration (254º/260º @ 0.050") is needed to make 738 HP/666 TQ based on a Gen. VI 502 short-block (GMPP p/n 24502619)- an engine w/a lot larger bore diameter and a 4" stroke (giving less piston speed) than an engine based on a BBC 427 TD.

If you lower the power expectations by at least a hundred or so, things will become much more "doable", IMO.
you dont need to be sorry, i'm just glad i'm not the only one thinking this way :thumbup:
 
#28 ·
http://www.airflowresearch.com/articles/article076/A-P1.htm

This is where i began my search a few years back. Thats really more of a conversation I'd rather have when the time comes. Dont want to put the cart in front of the horse. And yes, i will be talking it over needing help from the guys here. For now though...


Should I go for the bigger valves . Not the 2.19/1.88 bigger. Nows the time to get the head work done. If i should go bigger then what size? Alao what other valve wkrk should I get. Basically, what work should I have done to put these heads at full potential for what im using it for. Not dragging.
 
#29 · (Edited)
cobalt327 said:
In any event, wild man- check out this build to get an idea of what kind of flow (CNC ported AFR Magnum 315's w/2.25" x 1.88" valves milled to 110 cc chamber volume, being fed by a Vic Jr.) and how much cam duration (254�/260� @ 0.050") is needed to make 738 HP/666 TQ based on a Gen. VI 502 short-block (GMPP p/n 24502619)- an engine w/a lot larger bore diameter and a 4" stroke (giving less piston speed) than an engine based on a BBC 427 TD.

If you lower the power expectations by at least a hundred or so, things will become much more "doable", IMO.

Wow Cobalt, thanks for posting that Article, I have been searching for builds like that, as I am building a 540 w/AFR 315's (with a Gen VI Block)-my Cam is close to those figures, so this gives me more material to day dream about- :drunk:

sorry to hi-jack this Thread-

To the OP, I am waiting for the Heads from AFR now (ordered about 5 weeks ago), and used 2.25" valves and PAC Springs-I started out building a 496 for the street, bought some Edelbrock Heads (290cc w/2.19") and realized I wanted more-those Heads you have can build power though-I have a friend who gets big power out of them, and goes 2.25"-

http://www.vortecproperformance.com/engine_combinations.html
 
#32 ·
cobalt327 said:
Much beyond 500 NA HP, the chassis and attendant parts and modifications to hold up to the the power and hook it all to the ground starts to cost more than the engine. HP means nothing if all it does is spin the tires. Just something to consider... ;)

For me, its a lifelong project. Im never getting rid of this truck. So racing tranny or just a beefy one, drive line, and rearend up grade.? For sure. Torsion bars. Race tires. Im wanting it to be a hell'a show truck someday. After getting all the engine and drive train complete and like it. Tear it all back down, frame up restore.
 
#33 ·
I believe there's something to be said for building a project up from the rear, forward. Doing things this way, the engine will be one of the last things done and there's no way it shouldn't be a perfect match to the rest of the truck.

But building the engine often takes priority. Thing is, then rest of the truck has to be built around the engine, and if a particular part is center stage- like the heads in this case- you'll find you're basically building the entire project around a set of heads.

Anyway, that's just one guy's opinion. There is more than one "right" way, so kudos for wanting a strong running vehicle and good luck w/whatever you decide to do.
 
#34 ·
cobalt327 said:
I believe there's something to be said for building a project up from the rear, forward. Doing things this way, the engine will be one of the last things done and there's no way it shouldn't be a perfect match to the rest of the truck.

But building the engine often takes priority. Thing is, then rest of the truck has to be built around the engine, and if a particular part is center stage- like the heads in this case- you'll find you're basically building the entire project around a set of heads.

Anyway, that's just one guy's opinion. There is more than one "right" way, so kudos for wanting a strong running vehicle and good luck w/whatever you decide to do.
Im picking up what your layin down big guy. Lol heres how i see it. Lets say i build the bottom end, with x type pistons. Now im ready to select top end components and realize i should of used xy pistons. See my point.... i just think that an engine is built around itself in theory. It's a big equation and until you match the components to what the person is looking for. I know hotrods cost money. Its expected. But its cheaper or convenient to swap heads in my situation.

I dont want to get the body and chassis ready and interior. Then get a scuff or stain. Just my opinion. Any advice i really enjoy and take in. Dont want to give off the wrong idea
 
#35 ·
wild_man84 said:
Should I go for the bigger valves . Not the 2.19/1.88 bigger. Nows the time to get the head work done. If i should go bigger then what size? Also what other valve work should I get. Basically, what work should I have done to put these heads at full potential for what im using it for. Not dragging.
yes, I think the 2.19/1.88 are what you want
I dont think you want the 2.25 intakes, they are too big for 781s
 
#36 ·
cobalt327 said:
I believe there's something to be said for building a project up from the rear, forward.
X2^
Simply changing the rear gear ratio from, for instance, 2.73 to 3.73 will make it seem like you've put a power adder in the motor. So, if a fellow was satisfied with the performance from a gear change only, he could save himself a lot of money, have a faster car and the motor is still stone reliable.
 
#37 ·
techinspector1 said:
X2^
Simply changing the rear gear ratio from, for instance, 2.73 to 3.73 will make it seem like you've put a power adder in the motor. So, if a fellow was satisfied with the performance from a gear change only, he could save himself a lot of money, have a faster car and the motor is still stone reliable.

its 373 rear gears now. 14-bolt limited slip. but! I do see your point...

Well, tomorrow I have to talk to the machine shop about what work needs to be done. so.... Im going bigger valves.2.19/1.88. competition valve work milled for cc's ( figuring since my pal on here recommended not to bore to 496. rather a 468. if i mill heads to a smaller cc, that could compensate a bit for the lesser cubes) am I correct as that goes. basically, your taking less volume into a lesser area.

Im wishing I would have taken pictures before I sent them off. Really excited to get them back.

any recommendations on type of valve to order. materiel/manufacturer. im sure it comes down to preference on some parts as oil. but some oil works and some doesn't. any history of certainty on working valves that's satisfied one.
 
#40 ·
wild_man84 said:
( figuring since my pal on here recommended not to bore to 496. rather a 468.
.060 over with 4" stroke gives you 468. The same .060 over with a 4-1/4" stroke gets you 496.

Why not stroke it to 496 and get the 28 extra cubes? This is an excellent way to get closer to the power you're looking for and higher compression in one shot.
 
#41 · (Edited)
123pugsy said:
.060 over with 4" stroke gives you 468. The same .060 over with a 4-1/4" stroke gets you 496.

Why not stroke it to 496 and get the 28 extra cubes? This is an excellent way to get closer to the power you're looking for and higher compression in one shot.

Awesome, That what I initially wanted to do but was told bad idea. So, I backed off. now!! Im back on it_____ full speed... Heading back to south Carolina where I have the same stocker engine in my storage to build while the one in the truck is still drivable. So, after reading your post today at work. stole a few minutes from the man... haha..... did some googleing about rotating assem. and eagle, scat, oliver, carillo...

"H" or "I" beam rods??? Yes, I could possibly add a supercharger DTR. with that in mind....

Did some searching/reading. both have pro's/con's... weight/strength
scat crank with eagle rods... hows that sound???
Positive and negative feed back on experience with or know about exp. with bottom end components...

also, seeing Im pretty much going 100% complete build... should I get a GEN V or VI block? Im talking and searching and GEN IV's have high oil use issues... I dont drive it a lot. so would that be just as good. Meaning, No sense in buying another block since I have one

http://www.camaros.net/forums/archive/index.php/t-839.html

can I bore my Mark IV safely .60 over and not hit the oil gallery??
 
#42 · (Edited)
Update On The Heads

Called the machine shop first thing this morning before making my 300' climb to work ( yes wind turbines ). Let him know the heads should come in today or Monday.

We talked briefly due to the fact he was the only one on the phones for the weekend b/c two others were off to a race or something. He was really nice and apologized 10 times or more bc he kept having to put me on hold...

Basiclly we kinda discussed what I was looking a getting done. ( And to give y'all a laugh, didnt finish everything and was around $1200 without parts, wanted to share that to give you a laugh on that 800 conversation haha)

So, Because hes going to be short with time and not be able to focus his undivided attention to me. He ask if he could just wait untill the heads came in, so he could look at what route we/I may wanna go. And, he would be fully staffed again, he'd be able to talk with me and not get interupted... All which made perfect sense to me and completely understandable. Plus, give me another day or two to talk here and look around.

While talking briefly though, He asked me what kind of intake I was going to be using? I told him " Was going to use the Holley 9901-202 - Holley EFI Intake Manifold" He Kinda chuckled and asked the purpose of the build. I told him "mainly just Sunday and car shows" He then tells me about the intake from the company he works for and how more efficient it is AND it would be different at shows and would get more attention. Goes on to add that they can powder-coat it also. And would port match it to the heads ..
Sounds good to me for one reason, cheaper than the efi 3000 system but!!! also sounds like he is doing his job, being a salesman. Also, If I go carborated, I then, Have to figure out a way to hide all the wires in the engine bay.....

Let me here y'alls input-------- :confused:

http://www.steveschmidtracing.com/sniper-jr-intake-manifold.html
 
#43 ·
wild_man84 said:
He then tells me about the intake from the company he works for and how more efficient it is AND it would be different at shows and would get more attention. Goes on to add that they can powder-coat it also. And would port match it to the heads ..
Sounds good to me for one reason, cheaper than the efi 3000 system but!!! also sounds like he is doing his job, being a salesman. Also, If I go carborated, I then, Have to figure out a way to hide all the wires in the engine bay.....

Let me here y'alls input-------- :confused:

http://www.steveschmidtracing.com/sniper-jr-intake-manifold.html
look up some info and it says its operating rpm range 4000-8500... Im not going to be matched to my cam or heads or what I want to be. So, to me I should pass on "this" intake.. Just doesnt match my setup Im going for.. what yall think
 
#44 ·
123pugsy said:
.060 over with 4" stroke gives you 468. The same .060 over with a 4-1/4" stroke gets you 496.

Why not stroke it to 496 and get the 28 extra cubes? This is an excellent way to get closer to the power you're looking for and higher compression in one shot.
I am building a 496 because (just like the 781 heads) by the time you pay to have the crank checked, turned, polished, rods resized, pistons hung on the rods, etc.
for a little more, you can just by a new scat rotating assembly
then you are spending your money on new parts, not checking and maybe fixing and reusing old parts
the only real difference for me, was paying to have the block clearanced for the extra stroke (this you could do your self if you want)
 
#49 ·
123pugsy said:
Glad to see you've slowed down.
I almost couldn't keep up to your posts, you were talking so fast. :p

Getting Excited, Been wanting to do this for some time now! Not only that, actually have had a few minutes lately.

Just ordered 5 books.. The three you recommended and one about blue printing and another one also...
 
#50 ·
wild_man84 said:
Getting Excited, Been wanting to do this for some time now! Not only that, actually have had a few minutes lately.

Just ordered 5 books.. The three you recommended and one about blue printing and another one also...

Right on.

Read them all before buying any parts or getting any machining done.
 
#51 ·
Unfortunately, the heads are already at the machine shop. I will be discussing work and prices tomorrow. If it gets too close to $2,000 then, Im just going to have them basically worked and just keep on hand for a back up. And just buy Aftermarket, again, as ya'll tried to tell me lol.... Mistakes/learning curves always have a price tag. Ill be getting those books Thursday and Friday.
 
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