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 Post subject: 993 heads info?
 Post Posted: Sat Feb 12, 2011 9:00 pm 
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I am looking at getting a set of these from a member. 993 heads They have 2.02/1.6 valves and some port work done. (fully ported intake runners and gasket matched). I was wondering if they would improve my set up. Looking to drop my E.T. I run 12.50's now looking to improve 3-4 tenths. I am running 305 heads now that have real small chambers. I think something like 58cc or smaller. I built the motor for 11.1 w/64cc. so I figure my CR now is 12 something. I know my CR will drop but I will gain flow on the big end.

355
.530 lift cam
Weiand Team G intake
750 DP race series carb
Super Comp headers 1 3/4"
TH 350 w/3800 stall
4:10
Car is gutted, lexan frt and back windows, glass hood,glass frt bumper w/LW brackets. Should weigh less than 3000. Give me your opinion if these will improve my ET.

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 Post subject: Re: 993 heads info?
 Post Posted: Sun Feb 13, 2011 2:28 pm 
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Hey, Not sure if this helps.
3998993
1968-79
307-350
HP 115 -175
CFM in 150.8
CFM ex 91.1
CC 75.5

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 Post subject: Re: 993 heads info?
 Post Posted: Mon Feb 14, 2011 1:19 pm 
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I had a set of those before and ran into the 12's and could have gone quicker with a few things. Mine weren't fully ported either. You will do better than those 305 heads.

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 Post subject: Re: 993 heads info?
 Post Posted: Mon Feb 14, 2011 7:42 pm 
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Thanks for the info. I knew there would be someone out there that has run these heads in the 12's. I am looking to run in the low 12's with these.

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 Post subject: Re: 993 heads info?
 Post Posted: Tue Feb 15, 2011 12:08 am 
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That would be NO - You will not have enough track to notice the difference. KEEP the compression as Most small block chevy heads are good to 6000 rpm easy.

You need the low end torque to get the car out of the hole to bring down the ET.

Unless they are cheap. Save money and buy NEWER heads. It is NOT the valve size that determines ALL the flow. The amount of compression loss will well over come the gain you will get from the porting that someone could have done to that head. 993 is a VERY common 70's head.

993 heads are like 76-80 cc combustion chambers. as far down as you can afford to go is 64cc. 041 heads converted to 2.02 would work well. The problem here is the amount you would spend to get this machining done ...you might as well by aftermarket heads.

AGAIN your choice and you can try BUt I can pretty much guarantee slower ETs Jim

P.S. IF YOU WERE SUPER CHARGING OR TURBO CHARGING WE MIGHT BE TALKING A DIFFERENT OUT COME.

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 Post subject: Re: 993 heads info?
 Post Posted: Tue Feb 15, 2011 12:42 pm 
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monzaz wrote:
That would be NO - You will not have enough track to notice the difference. KEEP the compression as Most small block chevy heads are good to 6000 rpm easy.

You need the low end torque to get the car out of the hole to bring down the ET.

Unless they are cheap. Save money and buy NEWER heads. It is NOT the valve size that determines ALL the flow. The amount of compression loss will well over come the gain you will get from the porting that someone could have done to that head. 993 is a VERY common 70's head.

993 heads are like 76-80 cc combustion chambers. as far down as you can afford to go is 64cc. 041 heads converted to 2.02 would work well. The problem here is the amount you would spend to get this machining done ...you might as well by aftermarket heads.

AGAIN your choice and you can try BUt I can pretty much guarantee slower ETs Jim

P.S. IF YOU WERE SUPER CHARGING OR TURBO CHARGING WE MIGHT BE TALKING A DIFFERENT OUT COME.

These 993 heads are a 76 chamber head, and no way they cannot be taken down to 64cc head. I had mine shaved .045 and that brought it to about 70-71cc. My heads were only pocket ported and had no tuning done when i took it to the track. (hockey pucks for slicks) and i still ran a 12.80's. So with a full port job and better tuning with the right combo theose heads will get into the mid to low 12's.

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 Post subject: Re: 993 heads info?
 Post Posted: Tue Feb 15, 2011 9:26 pm 
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Ok here is another question. I am selling my Bu as a roller. I was going to put those heads on my 355 to lower the CR so it would be streetable. I was wondering if these would be good on a street motor or would it run like a dog due to the same fact as stated before. I would be happy if these heads made the motor run the same; that way it would be a kinda hot running car for some one. I was thinking about putting it in a S 10 or 80's Camaro and sell it to a young kid. As stated before I built the motor 11to1 CR w/64cc heads so the 993's should lower it enough to run pump gas. If this isn't going to work then it isn't going to work and I will come up with something else. Thanks for your time and effort guys.

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 Post subject: Re: 993 heads info?
 Post Posted: Tue Feb 15, 2011 9:39 pm 
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If i had to guess i'd say you'd be around the 9.5-1 comp, which you can still make that 355 turn pretty good. If you want to keep a bit more compression get thinner head gaskets. I droppeed my compression down when i put a blower on and it still ran great with the blower belt off and it still ran strong and even stronger with the belt back on.
Do you already have these heads and how much?

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 Post subject: Re: 993 heads info?
 Post Posted: Tue Feb 15, 2011 11:15 pm 
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[quote/]
These 993 heads are a 76 chamber head, and no way they cannot be taken down to 64cc head. I had mine shaved .045 and that brought it to about 70-71cc. My heads were only pocket ported and had no tuning done when i took it to the track. (hockey pucks for slicks) and i still ran a 12.80's. So with a full port job and better tuning with the right combo theose heads will get into the mid to low 12's.[/quote]

I think you read my reply wrong. I did not say to cut your heads...I said that he should not go under 64cc head to purchase if he was going to keep his ET relatively unchanged.

I do not doubt what you are say on YOUR car. But he wants to know about his car and combo. IT ALL depends on the short block combo with the heads.

QUOTED) Ok here is another question. I am selling my Bu as a roller. I was going to put those heads on my 355 to lower the CR so it would be streetable. I was wondering if these would be good on a street motor or would it run like a dog due to the same fact as stated before. I would be happy if these heads made the motor run the same; that way it would be a kinda hot running car for some one. I was thinking about putting it in a S 10 or 80's Camaro and sell it to a young kid. As stated before I built the motor 11to1 CR w/64cc heads so the 993's should lower it enough to run pump gas. If this isn't going to work then it isn't going to work and I will come up with something else. Thanks for your time and effort guys.

The heads will bring the compression down enough to run High test gas, But even on a HOT day you might have some detonation issues.

You can not expect to take out compression and have the same running and feeling motor. Period.

The car with out the high stall will run pretty doggy until the cam gets into its power band. You have a all or slug set-up It is a drag race car. Right?

AGAIN I do not have duration of the cam either. BUT with a .530 lift I am sure you are in the 240 and up range unless you are using a ROLLER cam. Solid lift cam? Hydraulic?? roller cam???

What are your shift points when you race this car? What is your trap rpm and speed/ mph?

What also is your 60 foot time ?

Remember to if the car is sold to someone that has NO idea how fast the car went and has never had a faster car this is all a moot point to the buyer. It maybe doggy to you but to the buyer it may be the fastest, torquey machine that they have even been in...???

Hopefully you an offer more engine info to hash out a lot of gray areas

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 Post subject: Re: 993 heads info?
 Post Posted: Wed Feb 16, 2011 5:39 am 
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The cam is a hydraulic. .510 intake .533 exhaust duration @.050 244/254 lobe centers 107int/117exh it is choppy
I don't have a killer stall in it. 3800 and it kicks in before that. Shift points 5800, I have tried higher but with the 305 heads it doesn't help.
60ft- 1.72-1.75 alot of 1.73-.74
Trap speed: 105-107

I kind of figured that lowering the CR would hurt it some. Just kinda hoping it wouldn't kill it. If it ran 12.90-13.10 with these heads in a street car then I think that is respectable. Will the 3800 be to much on the street? I had a B&M 3000 holeshot convertor in the car before and it fell on its face. Not sure what the power band is but I know it is over 3000 for all out hammering it.

After looking at my cam card it looks like I will hopefuly find someone looking for a good drag motor(cheap). I know it has alot more in it if it had better heads, those 305's are killing it. I am just moving on to something else so if this street car thing don't work out then on the stand it goes.

Yes the heads are cheap. $200 That is bolt on. They have been cleaned and new springs,locks,guides,studs ect... It has rockers on it but I would put my roller rockers on. I figured I would put on a thick gasket on to get the CR down some. I agree if I take out all the CR then it will hurt the motor.

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79' Malibu
MOUSE TURD MONSTER
355 w/305 iron heads
best to date: 12.39@107


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 Post subject: Re: 993 heads info?
 Post Posted: Wed Feb 16, 2011 8:50 am 
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Ok this helps, Do your 305 heads have new springs or original springs?

I do not believe your heads are killing the time. You just have too big a cam with not enough stall for THE DRAG RACE TRACK (this is to optimize your 60 foot. ) With that combo and heads and supposed compression you should be well into the 1.60 sixty foot times


The duration is just too much for your Intake and stall to overcome at low end. The cam you picked pulls to 6500-7000 and you shift at 5800...??? SO yes the potential for more power and torque are there but your combo is off. SINCE you are drag racing TORQUE IS KING
You need as much torque at at least 1000 into stall speed.

SO if you have a 3800 stall you want at least 2/3 of your full torque out put in the 2800 range on the cam. (THIS IS FOR DRAG RACE optimal launch)
Your cam probably has good torque starting at 3000-4000 range- you need a 4000-5000 stall for the launch and 60 foot you need.

JUST not much you can do with the wrong combo you have to deal with it - make the best of it as you are selling it anyway right.

AGAIN the heads should not be the issue- try looking into your ignition What is the initial timing (balancer) and what is your totally timing? (when all your timing comes in on the mechanical distributor)
What ignition are you using this will be another area to help on your cars power and all around performance with ANY HEAD combo?

We ran a 274 comp cam with roughly the same set-up better heads little bit more compression (12-1) 11.40 all day on a 3000# car.
4.10 gears 4000 stall 1.40 60 foot.

12.90 combo street car 3000# weight - 280 comp cam Magnum hydraulic cam, 327 true flat top 9 to 9.5 to 1, 041 heads (like fuelie heads 1.94 1.5 valves (NO PORTING AT ALL stock just reconditioned, seats springs guides etc...normal stuff) RPM Edelbrock intake, unilite distrib (12-14* initial / 38* total advance) 2500 stall, 3.73 rear gears 24" slick (real gear ratio 4.10 most likely because of the undersized slick...we were trying to keep a 7.5 rear together here...lol :D) 700 cfm dble pump holley carb This is a great street strip combo VERY FUN ON THE STREET... ET is respectable but will not impress the real drag race guys.

WHEN you build any car you really have to make a choice as to its MAJOR use...if it is every weekend to the track and that is most important to you, BUILD THE CAR TO RUN THE TRACK and suffer with the street low end- sluggish shifts on standard around town driving.
IF you want a exciting street car, you want the cam that gives you the most lift with little amount of duration (215-235 @ .050. 1.6 rockers help on a 260-280 lift cam get even more lift on the intake valve - NOT affecting the duration. Tinkering with initial timing will also create low end torque quicker, LIGHTER distributor advance weight springs will to again help the cause. You need a distributor that can be adjusted as you do not want your full advance over 40* timing at full throttle - unless your engine is modified to take it. (usually never needed over 40* anyway)
REMEMBER - with all this tinkering other things will suffer gas mileage being one of them - some time heat (advance etc. so do what your car can handle) Be reasonable as there is a LIMIT for every motor.
For all you know your could be at your limits and have done everything you can with your combo to eek the last bit out... (I doubt it on this one )

IF you get caught up in the TRACK ET's you will kill yourself on the street driving... (naturally aspiration motor) ET's get quicker and street ability will go down.

There is a tolerance level for each person. we are all different and will all have a different level of what we think is acceptable for a street car. My guide line is if you can not freeway drive for a 1/2 hour WITH FREEWAY NORMAL SPEEDS it is NO LONGER A STREET vehicle driver.

This is where OVERDRIVE trannies have become the norm and give cars advantage to race and drive to the track.

I am rambling on now...lol

If the heads are that inexpensive and you have the time Go for it and see what happens WORSE case you will have that knowledge first hand. That is how GOOD REAL knowledge is learned. Just try not to learn the same thing over and over...lol. :) JIm

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 Post subject: Re: 993 heads info?
 Post Posted: Thu Feb 17, 2011 12:41 am 
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If my cam makes power up to 7000rpm and my heads are done flowing by 5500 rpm then how could it not be my heads that are not killing me? I should have but in a bigger convertor but I think the heads are the biggest issue on my motor. I didn't know anything about Bowtie stuff until I did this Malibu and I didn't find this site until after the car/motor was done.
Not even the point , I am asking if this motor will be a decent running street motor with the 993 heads. I will not be racing this motor anymore just want to put it into a 80's rear wheel drive car and drive it on the street.

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 Post subject: Re: 993 heads info?
 Post Posted: Thu Feb 17, 2011 1:31 am 
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Those heads will work just fine on the street aswell at the track. I had no problem taking mine to 7200rpm and they will out flow those 305 heads.

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 Post subject: Re: 993 heads info?
 Post Posted: Thu Feb 17, 2011 1:46 am 
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I am asking if this motor will be a decent running street motor with the 993 heads.
Answer- (As stated - IF you keep all the same parts identical trans stall gear ratio etc. It will have less torque than with the 305 heads . As far as it running good on the street THAT is entirely up to your liking as YOU personally will find that out when you swap the heads.I am comparing what you have and are use to .(YOUR LOW SPEED OPERATION WILL SUFFER PART THROTTLE WILL SUFFER)
IT WILL STILL BURN OUT ON FULL THROTTLE NO PROBLEM AS YOU HAVE A 3800 STALL. :)
-AS I stated LOWERING the compression LOWERS the output of the motors power period.
-Of course the car will drive and run... as to how good on the street is to be determined by what you think.


I will not be racing this motor anymore just want to put it into a 80's rear wheel drive car and drive it on the street.[/quote]
-If you are adding weight (80's car heavier than your race lightened car) to the car AGAIN that will kill more power from the motor.

IF you are looking to decompress the motor for the street and sell YES it will work for you just fine.

If your ever going to build another motor with stock GM heads FACTORY keep the cam lift under .500 lift and 230 -235 .050 duration and a good dual plane intake like rpm or stealth etc.
If your using over .500 lift cam use a 200cc runner head at least with 2.02 valve. at least. and the single plane.

Obviously if you are running pump gas you need to match the cam, head combustion volume with the compression you will be using. (which unfortunately you did not do with the 305 heads) But that may have been the best you could get at the time and that is fine also...)

I will have to let this go as I think we are beating a dead horse. :)

I do wish you the best on your choice. Please let us know how it goes. Jim


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 Post subject: Re: 993 heads info?
 Post Posted: Thu Feb 17, 2011 9:20 am 
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Thanks Monza for your time.

I have decided on not using the other heads and use this Bowtie motor as a boat anchor as all chevy motors should be used as.

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