434 engine upgrades ?

[Monza355]

Hello. A friend if mine has a 434 ultra street engine from Scott Shafiroff. It’s a good engine with decent parts but we are hoping we might be able to pick up some power. Maybe with a camshaft upgrade. The engine was sold as a pump gas engine back in the day but with 11.5:1 compression ratio it’s picky on fuel. We have been running it with 100 octane avgas and that works very well.

The engine is a flat top 434 w 11.5:1 compression
Brodix 227 T1 sts cnc ported heads
World Motown 4500 intake and a 1050 cfm Dominator
Solid roller camshaft
254/258 @.050” .634”/.634” lift w. 1.6 rocker arms .396” lobe lift, 109 LSA.
It was supposed to be around 620 hp


The engine is in a 3500 lbs Camaro on 28” tires with 3.89 gears and th400 transmission with 5000-5500 8” converter. It currently runs high 10’s at 126 mph

[PRH]

I don’t see why it wouldn’t respond to all the normal “upgrades”.
Ported manifold, more aggressive cam, more duration, etc.

Valvetrain changes could impact the reliability.

[Monza355]

I don’t see why it wouldn’t respond to all the normal “upgrades”.
Ported manifold, more aggressive cam, more duration, etc.

Valvetrain changes could impact the reliability.

Yes. I wanted to discuss on the forum what direction we should go with the cam.

The car isn’t driven on the streets any more so we are in for some more maintenance if that’s what’s needed for increased power

[BradH]

High 10s at 126 MPH sounds like the 60-ft must be soft.

What are the 1/8 mile #s?

You don't have much gear now; is changing that also an option?

[KnightEngines]

High 10's at 126mph in a 3500lb car is no where near 620hp, more like 540, if that.
They must measure in Shetlands, not clysdales.
Wants more cam & a little hand finishing on the heads & intake.

[novafornow]

You can always pick up a Shafiroff engine. They are not loved on, they are assembled. And by the way, depending on conditions, 620 runs like 540 sometimes. Gears, converter, more cam, love on the heads, you will wake it up.

[PRH]

What size headers are in the car?

I would be targeting a trap rpm of about 7K.
So, a cam, headers, gearing ....... with that in mind, with a gain of 5mph or so.

And by the way, depending on conditions, 620 runs like 540 sometimes.

Also....... depending on how the car is set up.......sometimes 620 runs like 540........ even in good air.

[CamKing]

What RPM do you want to turn it ?

[6.50camaro]

With the 3.89 gears and a 5k to 5.5k stall convertor he's probably seeing 10% to 12% convertor slippage at the finish line because of the 3.89 gears.
At what RPM is the car going across the finish line at know. with 0% slippage it should be about 6k based on gear, tire dia. and speed. I could be wrong but I'm thinking it's about 6600 to 6700. this is based on my own data with a convertor that is much the same to his. Dan

[Monza355]

What RPM do you want to turn it ?

We were thinking about turning it up to 6800-7000 rpm.

The tall-ish gears are in it because he had plans on running little nitrous on an occasion. Maybe 1-2 times per season. But the converter came out looser than we thought it was going to be. So it has never been sprayed. So going with a lower gear ratio is an option at this point.

The headers are 1.7/8” to 3.5” collector.
He also said it has ran a best of 128 mph and is around 6500 rpm’s in the traps

[PRH]

I’d start with having the manifold ported........ maybe have the heads looked over/flowed/touched up.......and set up for about .700 lift........ and get a new cam.

[bob460]

High 10's at 126mph in a 3500lb car is no where near 620hp, more like 540, if that.
They must measure in Shetlands, not clysdales.
Wants more cam & a little hand finishing on the heads & intake.

Never seen a Shafiroff run down the 1/4 with there dyno numbers! ..... always down on power. Would not trust them as far as i can kick them.

[Monza355]

I’d start with having the manifold ported........ maybe have the heads looked over/flowed/touched up.......and set up for about .700 lift........ and get a new cam.

It’s a viable option to port the intake manifold. But it looks plenty big. Especially compared to it’s 4150 counterpart.

The heads do have 240 lbs seat pressure springs that are supposed to be good for .700” lift

[6.50camaro]

Its tough trying to help a friend . You ask question about their set up and tune and sometimes don't get the real answer just what they think you want to hear. Unless you verify ever thing it can be just a exercise in futility . Check ever thing timing ,plugs , is the cam advanced ,retarded , straight up?,, fuel pressure , line size ,pump capacity. Carb fuel level and on and on but you get the picture . Good luck Dan

[1980RS]

Hello. A friend if mine has a 434 ultra street engine from Scott Shafiroff. It’s a good engine with decent parts but we are hoping we might be able to pick up some power. Maybe with a camshaft upgrade. The engine was sold as a pump gas engine back in the day but with 11.5:1 compression ratio it’s picky on fuel. We have been running it with 100 octane avgas and that works very well.

The engine is a flat top 434 w 11.5:1 compression
Brodix 227 T1 sts cnc ported heads
World Motown 4500 intake and a 1050 cfm Dominator
Solid roller camshaft
254/258 @.050” .634”/.634” lift w. 1.6 rocker arms .396” lobe lift, 109 LSA.
It was supposed to be around 620 hp


The engine is in a 3500 lbs Camaro on 28” tires with 3.89 gears and th400 transmission with 5000-5500 8” converter. It currently runs high 10’s at 126 mph

Kinda interesting that the car is not quicker than that, I would put a 300-25 Holley intake and a 4150 hp carb of some sort like that on the car and go from there. With a smallish cam that Dominator setup while quite good may be too much.