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Old 11-10-2005, 09:11 AM
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BBC cylinder head question

I have a really good set of GM oval Port head 353049, the are fully ported and polish stage 3, 3 angle valve job and really good matched set of spring.

I have 4 questions:

1- My combustion chamber are around 115CC, when I bought those head, the guy said the already shaved 40 thousand to make this 115CC. How many more thousand I can shave those head, my brother have a set of 990 rectangular port, shave 65 thousand and he have 110cc on his head. Can I go to 110CC or less, 109 or 108, what will be the limit for GM iron head. What is the lowest CC I can go with a set of head like this.

2- A guy at a speed shop near than my house, asked me if I want to make some modification to my head...He want to match all the combustion chamber equals, and make a porting on my exaust hole to match my headers perfectly for 200 canadian bucks, Does it really be a good thing, how many HP I can expect?.. I know if I have better exaust flow, I will probably have a better healtly motor!...Need advice...

3- My last question, I already heard about H pipe or X pipe, I want to know if for the price, it's a good thing to put a kind of pipe to my car...I have 3 inch dual exaust...what will be the benefits, will it be better to put a H or an X pipe...Does it exist negative effect to put a kind of thing like this under my car??? How many HP I can expect from a thing like that...

My last question...I planned to put coated headers like hooker competition, 2 inch primary and 3.5 at the collector...what is the benefits to put coated headers, I heard about the temp reduced under the hood...but what kind of other effects I can see on my motor???

Thanks in advance to answer my question...

Have a nice day everyone...

Stephane
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Old 11-10-2005, 10:33 AM
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Stephane,

When dealing with engines, the words "around 115 CC's" doesn't exist. Have your heads CC'd, so that you know for sure what each combustion chamber is. You will want to equal all chambers to the largest one to start. Then you can measure the head and determine what the heads can be cut down to. You can use a steel shim gasket to cut down on deck height and reduce chamber volume.

A good question at this time is, What are you trying to achieve with this engine. It sounds to me like you should do some more reading and talk with a 'good' engine builder in your area that you can communicate with. It will save you money in the long run.

Also you didn't say what kind of car this was? Or for that matter, which big block Chevy this engine was. There are some great engine guru's on this Board who would gladly give you advice if you detailed your questions a little more. Good luck!
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Old 11-10-2005, 10:54 AM
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Personally I wouldn't fool around with those boat anchors. Get yourself a set of 110 cc heads from Edelbrock. The work is already done and the weight reduction will save you mileage and give you better ET.
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Old 11-10-2005, 11:30 AM
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Quote:
Originally Posted by bracketeer
Personally I wouldn't fool around with those boat anchors. Get yourself a set of 110 cc heads from Edelbrock. The work is already done and the weight reduction will save you mileage and give you better ET.
I didn't have the money to buy another set of head. I was investing too much money on those head. I dont want to lose money and sell it at a ridiculous price. When I was doing the porting and all the stuff on my head, the guy asked 10$/combustion chamber to mesuring the CC, So I was out of money and only mesuring one combustion chamber and it was 115cc, Thats why I was saying around, because I know, all the combustion chamber will not be equals and the same as the one the guy already mesuring. I want to know if it's a good deal at around 160 US dollars to make all the C.C equals and a porting to exaust hole (to matched my gasket headers).

My car is a chevy nova ss 74 with a 468 CI. I want to gain 0.5 CR to reach 10.1:1 CR to match a mechanical magnum cam 595'' lift intake and exaust. Right now, I have 9.5:1 CR and already used 19 thousand steel gasket.

I know, a set of aluminum head will be really good..but ....I'm not rich, and I have to pride some priority

I really dont know the price of aluminum edelbrock head, but I want to know if someone can answer my 4 question and give me some advice if it's will be safe and good to do this.... Too big is my cam right now, I have a radical 10.5:1 CR cam and only have 9.5, it's why I want to go with the cheapest way to reach 10:1 CR and Have a cam matched with every component of my motor..

I hope this information will help the guru's on this hotrodders sites to help me and give me the right way to achieve my goal...

Thanks again...

If question, PM me, no problem.

Stephane
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Old 11-10-2005, 11:45 AM
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heads

You can get those heads down to 110cc's if you have valves that are not sunk way up in the seats, But you are about at your limits. If you go much more then that you run into problems getting the intake to fit,,,,, Even with the additional amount you need to remove you will need to mill the intake mounting surface and slot the holes...unless they were agle milled....


Run as far away as you can from the guy that wants to port the exhaust on those heads.... They are all ready to big....He does not know what he is doing.....If you really feel like grinding on them make the exhaust ports as smooth as you can with-out making the port bigger....

Keith
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Old 11-10-2005, 12:11 PM
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I agree on leaving the exhaust ports at the size that they are now. I think opening them up that far would be a bad idea. It would not be a bad idea getting the combustion chambers set to the same size. If the heads are fully ported, they should already be really close to the same size though. As far as the exhaust goes, I think it is pretty well accepted that an X pipe is better than an H pipe. I am not how much hp you would gain. The money could probably be better spent elsewhere. As for the coated headers, along with lowering under hood temperatures they also keep heat in the headers which will maintain exhaust gas velocity. They look cool too. I would stick with the 049 heads. I have a friend with a 9.5:1 468 with a set of cleaned up 049's (flowed 290 max) and a fairly mild hyd roller cam that made 560 hp and 560 tq. Also, I just had a set fully ported with 2.19 1.88 valves and they ended up flowing a max of 325 cfm. Thats not too bad. Compare that to the flow numbers that CHP got for the edelbrock performer RPM heads, and I think the 049's are going to out perform them.

http://chevyhiperformance.com/techar...98/index8.html

Adam
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Old 11-10-2005, 12:17 PM
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Coating headers just makes them look good and last longer. A thin layer of anything is not going to reduce heat that much (if at all). And no real HP to gain there. Just a better looking engine. Rusted up headers do look bad.

You might only be down 10 or 15 hp with the lower compression. Try advancing the timing chain 4 degrees to make up for the lower cr.

Port matching (intake or exhaust) does next to nothing.

No real perforamce gains with an X or H pipe. Just a more quiet cab. When comparing the two, I read the X's make a higher exhaust tone and H's make a lower tone. And the lower tone gets on most people nerves during long road trips. No problem with that under your car except for maybe more places to bottom out. Have a good installer do the job.
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Old 11-10-2005, 01:00 PM
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exhaust

I forgot about the X pipe... I have not had a chance to test mine but a friend put one on his 415 ci small block chevy. The car always ran a low 10.30 after the X pipe it went 10.17 with no other changes in the same weather..... But the car only picked up a tick in the MPH so that tells you the car is working better in the lower end. His 60 foot time dropped also but i can not remember how much...

Keith

Last edited by k-star; 11-10-2005 at 01:49 PM.
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Old 11-10-2005, 01:17 PM
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As far as coating goes, Calico claims a 25%-30% recuction in underhood temps. I have never seen any tests done, but you could talk to them about it.

http://www.calicocoatings.com/index.phtml?coatings

Adam
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Old 11-10-2005, 02:04 PM
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Keep the .049 heads


You can cut your heads up to about .080" and still be safe on most BBC iron heads,(not including intake valve seats over 2.19) but, why? As stated above. At minimum you will have to slot your intake and not run end rail seals. Usually you will have to have the intake milled. Shim the distributer hole up. Not only expensive to have four surfaces milled on the intake, but also makes the intake unusable on anything else.. Been there with customers!!

You really don't want aluminum heads for your situation. They would only save weight. Back in the day. To get serious Horsepower from my aluminum head BBC bracket car I had to turn the pumps off (electric) at the starting line and flip them back on at the mph lights to make any power. Heat is energy and aluminum draws it away from the chambers.

Forget the exhaust porting, pay attention to the bowl behind the valve and if you must cut/smooth something do the roof of the port only. Make sure your headers/gaskets don't hang over the top of the port. 2" exhaust tube with a large collector are good for this setup.

Coatings can lower underhood temps and do keep your headers from rusting thru in a couple of years. I have never used an X pipe, but I know an H pipe works well with 2 1/2-3" exhaust.
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Old 11-11-2005, 06:37 AM
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Come back with number

As I said previsously, there is the flow chart of my head.

Intake Exaust
.100 69 55
.200 146 99
.300 214 127
.400 266 169
.500 293 189
.550 302 192
.600 308 201
.650 312 204

This is really good for GM ported 049 head???

I really want to put another cam...I want to know if this one will fit perfectly if I up my CR by 0.5.

Cam Style: Mechanical flat tappet
Basic Operating RPM Range: 2,500-6,500 RPM
Intake and Exaust : Duration 050 inch Lift: 248
Advertised Intake and Exhaust Duration: 294
Intake Valve Lift with Factory Rocker Arm Ratio: 0.595
Lobe Separation (degrees): 110

With this flow number, can I choose another cam? I already heard about dual pattern cam....but I dont understand what is a dual pattern cam...I think is High energy by comp cam!!!

If I shave my head to 110cc, will I be able to reach 10.0:1 CR?
There the other information for my motor:
4.00 stroke
4.310 bored
10.5cc Dome piston
19 thousand gasket.
Deck??? Never touch, maybe 20 or 25 thousand..(I heard that is the number for a stock desk on a 73 block if noboby never decked it.)

Thanks everyone for the other reply...I probably put an H pipe under my car next summer....here is Winter and it's really cold and full of snow everywhere....

Waiting for some advice....
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Old 11-11-2005, 07:01 AM
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The secret may be to check the deck height and cut the block to a reasonable dimension.

Block decks on Chevies are seldom close to "Book". I have seen some as low as .080" and as high as .008". Sometimes on the same block, sometimes on one side. Just depends on who was running the broach at the plant that day, and how many blocks they needed to make production.

The 400 SBC in my S-er was .045 down left front,tapered to .018 at back edge of no.4, then went to .024 the rest of the way down. I'm sure the original owners had head gasket probs from the day the motor left the factory. I found it on the scrap pile. Cleaned it, cut it to .005 deck, and set the "Squish" at .040.. Runs great.
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Old 11-11-2005, 07:30 AM
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The intake flow looks good but the exhaust flow looks weak. A dual pattern cam would help the exhaust (more duration on the exhaust lobe).

Why do you want to run a cam that big for? What gears, transmission, converter, etc do you have in the car? What is the intended use of the car?

Maybe a compcam xs274s would be a better choice for the current compression. 274/280, 236/242/, 0.568/0.578, 110 lobe centers, solid 0.016/0.016, 2000-6400 rpm. A dual pattern cam for a 2500 stall converter. Or maybe one step up to a xs282s, 282/290 cam for 2400 to 6800 rpm and a 3000 stall converter.

FYI, a lot of lift can really reduce the life of the valve train (springs, cam, lifter, and rockers).
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Old 11-11-2005, 08:58 AM
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advice..

Quote:
Originally Posted by 454C10
The intake flow looks good but the exhaust flow looks weak. A dual pattern cam would help the exhaust (more duration on the exhaust lobe).
Why do you want to run a cam that big for? What gears, transmission, converter, etc do you have in the car? What is the intended use of the car?
Maybe a compcam xs274s would be a better choice for the current compression. 274/280, 236/242/, 0.568/0.578, 110 lobe centers, solid 0.016/0.016, 2000-6400 rpm. A dual pattern cam for a 2500 stall converter. Or maybe one step up to a xs282s, 282/290 cam for 2400 to 6800 rpm and a 3000 stall converter.
FYI, a lot of lift can really reduce the life of the valve train (springs, cam, lifter, and rockers).
What I have to do for the exaust flow, ask the guy to ported the exaust side more???

I want to run a small cam than I have right now, I have the 305H magnum hydraulic 575 lift both sides and 305 duration. The cam is too big, I have a great power outputs, but I have to choose a cam for 10.0:1 CR to have the maximum hp from my motor... I have a 3500 stall, my transmission is a TH350, right now, I have a 3.73 but I'll put a 4.10 in a couple of month...I have a 468 CI and run pump gaz....I want to be a monster on the street and Have a really good time in the quarter miles...with my current setup, I make a 11.68 and 117 mph with the wrong cam....

Right now, I run on my spring a set of full roller rocker 1.7 crane (aluminum color), with a dual spring matched my cam (more larger than my original one) I was oblige to put valve lash cap on my spring (retainer) to clear both sides of the rocker. If I go with a mechanical cam with valve lash, will I have to change those rocker to a roller rocker with a thin end (I mean the part who go on the top of the retainer), like scorpion 1.8 or something similar...

Stephane

Last edited by Ratoflic; 11-11-2005 at 09:12 AM. Reason: mistake
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Old 11-11-2005, 09:41 AM
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As you know already, the solid cam will make a lot more valvetrain noise than you have now. And will require much more frequent adjustment as compared to your current cam. Buy a few extra valve cover gaskets. That hyd. cam may have spoiled you a little.

Yes, the exhaust flow needs some help. I would leave the port alone and concentrate on unshrouding the valve and some bowl work (directly under the valve). I have a set of old style small port BBC heads that flow 200 cfm at 0.500 on the exhaust side so there is room for improvement for you.

I have run the compcam 292H in my sbc with good results on the street and strip. Maybe just going down one cam size would do the trick for you.

Those are good times. I think you set up is well matched, but just the compression is a little low. A 3500 stall would be a little high for a smaller cam than what you have now. Just something else to consider.

With your current set-up you are most likely hitting the end of the 1/4 mile at 6200 rpms. A 4.11 would increase that to 6800. I'm not sure lowering both the gear and installing a smaller cam would be a good idea.

Maybe you should just advance the cam a few degrees, work on the exhaust valve, and install a 4.11. Or work on the exhaust valve, install one cam size smaller, and leave the gear alone. Either one should net a better et.

Also, your low compression could allow for a little N20. I have seen some very mild 100 hp shots that just spray down through the top of the carb. Could add another 7 or 8 mph to your 1/4 mile trap speed.

You can use your current roller rockers with a solid cam.
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