[budsthe3]

When I first started putting my Chevelle's engine/drivetrain together 13 years ago I thought I was doing it right. (I was only 20 years old at the time).
Now that I have learned a lot more since then, I have been thinking the combo I put together may be mismatched. If it is "good enough", then thats fine with me. But if its too far out of wack, then I want to start re-doing it.
I want to make it more of a track car, still occasionally drive it on the street, but gas mileage, comfort, and highway speeds are of no concern to me with this car. Here is my current setup:

1970 Chevelle
Engine:
454 (1975 block, rebuild on the bottom end unknown), cylinder heads are the 3964291 square ports; I had them rebuilt with Manley race flo valves, 2.19 intake/1.72 exhaust, single valve springs which matched to my camshaft I installed, Crane roller rockers, Crane powermax hydraulic camshaft 226/236 duration, 534/553 lift.
Holley 750 4150 carb, Edelbrock RPM Air Gap intake, Accel HEI distributor w/Brute thunder in-cap coil, and Accel module.
Carter Hi performance mechanical fuel pump.

Transmission:
TCI TH400, B&M Holeshot 3000 converter (RPM range of 2800-3200)
Hurst V-Matic 2 ratchet shifter

Rear:
12 bolt, 3.73 posi
Lakewood traction action slapper bars, boxed control arms

Any tips or guidance will be extremely appreciated. I'm just trying to sort out my first creation, as I was only 18 when I first bought the car and started building it (now in my 30's)

 

[Indiansprings]

First, Nice looking car.
Nothing wrong with your combo. Probably runs good doesn't it?

 

[budsthe3]

First, Nice looking car.
Nothing wrong with your combo. Probably runs good doesn't it?

Thank you! yeah it runs real good. I was just thinking lately that my square port heads may be mismatched with my camshaft and rear end ratio, as well as my torque converter.

 

[BillsCamino]

Mismatched? Nope.
Sure an oval port head just might do a little better on the street but IMO not worth the swap now.
Drive and enjoy!

 

[72BBMonte]

Have you run it at track as is yet? You may be happy. Or you may want to start tweaking.

 

[Indiansprings]

Sure some AFR heads and an airflow matching cam would be nice. You can definitely dig around and find some improvements, but if your pretty happy with it dont waste the money.

 

[badrad]

It looks like a pretty well matched combo to me. The only thing I would consider is aluminum heads or good hyd roller cam if you do anything to it.

 

[VinceS427bb]

run it at track to get a baseline on it's performance
then run it some more to fine tune to best performance
then make decision on whether it is good or you need more

 

[Steve R]

X2 what Vince said. You need a baseline before you do anything else.

Steve R

 

[Tom Mobley]

Wild Bill speaketh truth. No reason whatever to tear into that thing unless you just have a burning desire and a bunch of money burning it's way out of your wallet. A nice set of prepped 781s will give you power down low without costing you much of anything up top, but doubtful it'll really make the car run much better unless you're going to start running DRs or slicks.

drive and enjoy.

 

[Tomatolane]

Yeah run it . Maybe get Chris to grind you a hydraulic roller .

Hydraulic rollers, Do very well with your heads, It wakes them up, with more area under the curve.

 

[budsthe3]

Thanks guys for the help. I will be running slicks, dont know if that will affect anything. I was thinking about stepping up to a 850 carb with mechanical secondaries.

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[Rmchevelle]

I want to make it more of a track car, still occasionally drive it on the street,

You need to be more specific. What's the goal at the track? I agree with the others that if it runs good leave it alone but leaving it alone may not meet your "track car" goal. As a "track car" it currently will probably make a decent 12 second to high 11 second bracket car, thus, leave it alone. If your goals are 9 second E.T.'s, though, it's going to need changes.

 

[budsthe3]

I am looking to get it solidly into the 11's. Possibly start with weight reduction, then take it from there for other possibile changes with the engine, maybe slightly bigger cam and bigger carb.

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[LS6 Tommy]

The combo sounds good, but are you sure you have 291 heads? IIRC, 291s had 1.88" exhaust valves. 840s are almost the same, but had 1.72" valves...

Tommy

 

[bracketchev1221]

Mismatched? Nope.
Sure an oval port head just might do a little better on the street but IMO not worth the swap now.
Drive and enjoy!

My thoughts exactly.

 

[jackie schmidt]

The only problem with Chevy OEM square port heads is the potential flow numbers do not match the increase in port volume, reducing velocity at lower and mid RPM ranges.

But that does not mean they will not perform, especially in a drag strip environment where the RPM stays around the upper end.

Like everybody else said, run it, get a base line, and see then contemplate what you want to do.

The thing is probably bumping 550 HP right now. If it hooks, it will be in the mid elevens. A mid eleven car is a real hoot on the street.

 

[blasttime]

Spray it

 

[Tomatolane]

The 3964291s with 1.725 exhaust vales, are Pre 1970 heads,if dates are latter then 1970, they are replacement or crate heads.

But all 396291 heads with 1.725 are for pre 1970 396, or 427 cast iron heads, like the 427/435, or 396/375

The aluminum pre 1970 got 1.84 exhaust.

IIRC in 1970 all HP heads got 1.88 exhaust.

Here is all the info

http://www.nhra.net/tech_specs/engine/

 

[budsthe3]

The 3964291s with 1.725 exhaust vales, are Pre 1970 heads,if dates are latter then 1970, they are replacement or crate heads.

But all 396291 heads with 1.725 are for pre 1970 396, or 427 cast iron heads, like the 427/435, or 396/375

The aluminum pre 1970 got 1.84 exhaust.

IIRC in 1970 all HP heads got 1.88 exhaust.

Here is all the info

http://www.nhra.net/tech_specs/engine/

They are the service replacement heads. The date code is for 1971. When I had them rebuilt, I had the machine shop put in the original exhaust valve size that was already in there....I should have put in the 1.88's, I've been kicking myself ever since