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rabbit 11-22-2007 05:22 PM

Yet another head question
Let me try to tell everyone about what I have now and I would like some advice as to what heads would be a real good choice to go with. I will start from top to bottom. 2 450cfm Holley carbs on a weiand tunnel ram intake.
This on top of a 350 chevy with 2 eyebrow flat tops and Cam is .540-.534 lift 290-304 dur. 106 lobe sep. Center Force Dual Friction Clutch M-21 Muncie 4 speed then ladder bar suspended Dana 60 w/ 4.56 gears and 31x14.5 M&H cheater slicks in a 2900 lb 66 chevy II. The reason I am asking is the heads that are on the car are 72-74 chevy with minor pocket port work done and the car has alot left in it but I think the heads are holding it back. I am going to change them real soon but not sure which would be the best. I have never been much on head (or cam for that matter) choices and don't know what size intake runner would be best or much of anything as to where to start.
All help is greatly appreciated,

rabbit 11-22-2007 05:32 PM

One thing I forgot to add is that the setup now is real (I MEAN REAL) lazy off the starting line and I am wanting some low end power as well. This is a street car and it is driven almost every chance I get so I don't want to hurt the driveability any. I mean what I am after is a very strong and dependable driver of a street car. Due to the lazyness off the line it only runs 8.30's-8.40's straight off the street in the 1/8. I am thinking this thing should probably be in the mid 7's (7.5-7.7) due to everything on the car. Am I wrong on this guess?

Thanks again, Scott

cepx111 11-23-2007 03:12 AM

Tunnel rams love rpms and are notorous for being a dog down low, just the nature of the beast.
Your set-up is begging for more compression and cam, but other than that your gonna have that low end bog, and getting bigger higher flowing heads will only make it worse.
You'd probably get into the mid sevens by just putting on a single plane intake and running a single carb like a 750 double pumper.
Goodluck, Charles

chevguy65 11-23-2007 06:18 AM


what compression is your engine?

Like Charles said that tunnel ram is killing your low end and unless your turning 7200 + rpm you don't need it unless it's on there for looks.

I would junk the tunnel ram and either go to a good single plane or a dual plane and an hvh super sucker underneath and a good 750DP.

You will really wake it up!

rabbit 11-23-2007 07:41 AM

I knew that the tunnel ram is hurting me but it is a part of the car. Look at the pictures below and you will see what I mean. I had this same intake set up on my 55 chevy in high school with less motor and there was very little bog out of it but it was on street tires and nothing sticky but man it sure would run strong. The Nova runs strong as crap after about 2500-3000 and pulls like a bear. I know this is a complicated thing to try to have but I am gonna try I know the heads are 76 cc combustion chambers by looking up the casting numbers so I was thinking compression increase would help alot. I am not sure exactly what the compression is now but with the 76 cc heads and the flat tops I am guessing somewhere around 9:1 maybe.
I really appreciate the assistance, Scott

cepx111 11-23-2007 08:00 AM

With flat tops your compression is closer to 8.5 to 1
if you switched to a smaller cc head like a 64cc you'd be closer to 10 to 1 and much better off.
Try flashing the rpm's higher off the line to get into the powerband of the tunnel ram. Also running that open exhaust is killing some torque too. try running a longer header extention pipe or some racing muffs.
Nice looking old school Nova.
Trick overflow

rabbit 11-23-2007 08:38 AM

Thanks for the compliments. I have already added some racing mufflers. Since the picture I added turndowns to them as well pointing 45* down and out. I was thinking around 60-64 cc heads were what I was needing but still wondering if there is any better than the next.

Thanks, Scott

chevguy65 11-23-2007 08:44 AM

Personally I wouls have the heads taken in and see how much they can take off to get your C/R up to around 10:1
If that doesn't work look for a set of heads with somewhere between 64 and 67cc chambers.

Get a good single plane intake and a 750dp.

You can get just as much out of a good single plane and one carb as your tunnel ram, plus it is easy to tune.

If your willing to change I can see the times you want.

Otherwise you will have a dog until it gets up to around 3000 rpm.

A friend of mine bought a 73 Camaro last season.
It has a 402 bored .040, has a solid roller cam .585 lift 290 dur.
Aluminum heads 220 runners and was topped off with a wiend tunnel ram and dual 450 holleys.

It ran through an art carr tranny and 4000 stall to a ford 9" 3.70 gears.

His best with that setup was 12.80, I think his 60' was 2.1.
I and a few others told him to junk the manifold and carbs and go to a single plane. He liked the look of the manifold and didn't want to change.

This last season he shows up with a vic jr and 850 pro-systems carb, his 1st run was 11.45 with a 1.64 60

To me that's proof enough.

Tunnel rams are designed for high hp high rpm engines, for the street they are useless in my opinion and on a car like yours it is killing your time and street performance.

rabbit 11-23-2007 09:03 AM

I totally understand what you mean chevguy65 but the intake will stay due to the car being mainly built for the look of an old race car from the late 60's. I am not looking for all out performance but I know that there is just more that the car can do and I am just hoping to find it internally without changing the looks of the outside. That is the reason I am looking at the heads as being most of my issue.

Thanks, Scott

cepx111 11-23-2007 10:38 AM

I realized you were gonna keep the old school look and I its killer in my opinion. Are you running drag only? If so you can bump up the compression even more with race fuel.
Dont overlook at cam change either, if you get your compression higher,
things will start to happen in a big way if you get that tunnel happy believe it will come alive.
Goodluck, Charles

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