[fiftyfivegasser]

For those running a 70-72 Z28 with factory 350.....How well do these engines perform?

The specs. indicate that the hp from 70 (more hp) to 72 (less hp) declined due to the valves being choked down to meet smog requirements. Otherwise, mostly everything else remained the same including 4" bore, solid cam/lifters and Holley 4bbl.

Based on your experience, how well do these engines perform (street/strip)?

Are there basic modifications that can increase performance other than going internal?

I will be installing a 72' Z28 - stock 350 in a 55 Chevy backed by a Muncie M21 and 355 gearing. I do plan later to increase hp to 375/400...a far cry from the stock hp.

Information/opinions please on the stock performance. Thanks.

 

[fiftyfivegasser]

I realize you didn't want internal stuff but it was around that time I believe that they started using lazy cams that didn't last long. Do you have the head casting numbers?

Here are the engine specs.:

Casting # Block 3970010 4 bolt main, suffix codes: CKT Crankshaft 330550 Forged steel Heads 3998916 76.18 cc, 2.02/1.6 valves, screw in studs & guide plates Cam 3972182 3972178 square Solid lifter - 0.458(I)/0.484(E) lift, 317I/346E duration Pistons Flat w/valve relief - yields 9.0:1 compression Intake 3959594 Carb (M/T)3999263 GAHolley List 6239, 780cfm , 4150 series - 4BBL


As you can see, the valves have low cc ratings, but the cam number, etc. matches the 70-71 engine specs. (from what I've been able to find).

I have been told that the cam used in these engines was similar to the Duntov 30/30. Not sure if that's good or bad?

 

[fiftyfivegasser]

1972 Performance Question

For those running a 70-72 Z28 with factory 350.....How well do these engines perform?

The specs. indicate that the hp from 70 (more hp) to 72 (less hp) declined due to the valves being choked down to meet smog requirements. Otherwise, mostly everything else remained the same including 4" bore, solid cam/lifters and Holley 4bbl.

Based on your experience, how well do these engines perform (street/strip)?

Are there basic modifications that can increase performance other than going internal?

I will be installing a 72' Z28 - stock 350 in a 55 Chevy backed by a Muncie M21 and 355 gearing. I do plan later to increase hp to 375/400...a far cry from the stock hp.

Information/opinions please on the stock performance. Thanks.

 

[fiftyfivegasser]

Thanks for the feedback.

The reason for my inquiry is that the car I'm placing the engine in is an old school gasser. I planned to run the stock 350 until an upgrade and it will be street-worthy.

Two concerns was the solid lifter set up (never had this) and secondly, I just wanted some input on how this engine performed.

I would hate to be bruised by a "ricer" due to a sick running stocker. In other words, I would like for the engines performance to back up the cars looks:yes:

It is planned to upgrade hp at some future date, but I want to get it on the road until funds are available for this. The head change will be the first consideration...I already have fenderwell headers for the install.

BTW, what would be the gross hp for this engine at 255 net? Would it be 310 gross?

 

[fiftyfivegasser]

Even with a stock '70 LT1 making 360 hp you are setting yourself up for bruses if you start playing around with even a half serious tuner. It's all about hp to weight ratios and gears.

255 net would be 306 gross based on the 330/275 numbers...

Got what you're saying Dennis....I'll stay clear of the ricers till the hp upgrade is complete.

I am heavy at around 3200# (pure steel). Plan to move up to close to 400hp and hope the 355 gears holds up; along with a fiberglass tilt nose and trunk to lighten things.

Thanks for the advise.

 

[fiftyfivegasser]

Re: 1972 Performance Question

Thanks gentlemen.

What is your rear gearing ratio?

 

[fiftyfivegasser]

Re: 1972 Performance Question

Posi 373's...4 speed

Hey Wiskee; I see you have or have had a 55 2 door. A stocker or modified?

I have a gasser I'm setting up for the 350 install.

Can see progress at www.picturetrail.com/fiftyfivegasser