decisions, decision....

[Cobra power]

When I ordered my chevy350 engine in the US in 2003, I just looked at price and hp's (did not know much about engines). I ended up with an engine with 400hp for about EUR5000. No complaints, it's a good build quality. However, last december I was able to drive my cobra for the first time. The engine runs great, only disappointment was the lack of torque in the lower rpm range (see specs below). Only above 3500-4000 the torque is noticable.

I have discussed my engine specs with several specialist (including on this forum), turns out that the engine is indeed setup for higher RPM's. I got also some comments on mismatched components (carb, cam). Anyway, based on all these comments I decided I would like to modify the engine so that it's more a low rpm - high torque engine. I think this is the most fun for a cobra.

I concluded that I can do two things:
1) modify top end: dual plane intake, different cam/lifters/rockers, different carb.

2) go 383 stroker: forged crank, H-beam connecting rods, etc.

My questions:
- is (1) only enough to make a real difference?
- if I go to 383 (2), will I also need to change the top end (1)?
- how difficult are these modifications? I have no experience but I really look forward to do it myself (new hobby!). But I would like to avoid ending up with an engine that gives lots of troubles later on.
- is it economically smart to go this route? A turnkey chevy383 450+hp is about 8000-9000+ euro's. Assuming I could sell my current engine for EUR 4000 (EUR 1000 loss), than I would have 4000-5000 to spend before it smarter to sell the current engine and buy a new turn key engine (maybe with less potential problems but also without the fun of an own build)

Current setup top end:
Alu Edelbrock Performance heads 2.02 Int And 1.60 Exh valves, TorkerII intake, 600cfm Edelbrock Carb, Crane cam duration @ .050 230 230 Lift .465 .465, hydr. lifters, 1.5 rocker arms.

Bottom end: rather standard, cast crank, I-beam connecting rods

Thanks!

[wilf]

That cam looks to be not too radiacal. You should have plenty of low down torque. Do you know what the lobe centre angle is? If it is 110 degrees or more, then the cam really should not be giving you problems. I disagree that you have an engine "set up for higher rpms", apart from the use of a single plane inlet manifold.

What is your gearing - gearbox type and differential ratio? Has the engine ben properly set up on a dyno/rolling road?

If you want to try a change, first, cheapest, and easiest thing to do would be to swap to a performer RPM inlet manifold. (Dual plane) Just check that you have around 1" spare headroom between the top of the air filter and the underside of the bonnet at present.

[Cobra power]

Thanks for your advice. I will have to check the clearance. COuld be an economical first step.

I also got some negative reactions on the carb, it's supposed to be inadequate and a 750 Holley with vacuum secondairies would be a much better choice.

Do you expect I will get some money for the torkerII (and possible edebrock carb), it's hardly used.

[Cobra power]

which intake should I use?
- Performer RPM
- Performer Airgap
- RPM Airgap

Probably also depends on clearance

[wilf]

I would change the inlet manifold first, and leave the carb as it is for now.

Once you have the car set up again with the new manifold, then connect a vacuum guage to the plenum chamber of the inlet manifold (i.e. use the "always on" vacuum port on the edelbrock carb). At max rpm and wide open throttle, you want to see about 1"wg of vacuum - any more and the carb is too "small", otherwise not.

Don't have too high expectations for the value of secondhand items - 50% of new cost or less is what you are likely to get for them (including your whole engine!).

Performer RPM or Performer RPM airgap is the manifold you want. Check the headroom as we already said. Edlebrock website will give you the dimensions you need.

[Clarkson]

Hi,A 230 degree cam is not radical by any means and is a nice street cam with a power band between 2000/6000rpm and max torque at maybe 4400rpm. But on the other hand, if your a lazy driver and don't like reving your motor, then this is the wrong choice of cam for you. As wilf say's, we need to know what diff and gearbox fitted as this can have a massive effect on your engine performance. A 230 degree cam will not work with high ratio gears and diff's as you engine will never be in the optiom rev range for road use.

I have a 350 chevy 230/236 custom roller with 600tko/.83 5th ratio and a 3.54 diff, and the engine is always on song with a high cruise rpm. ie 3100rpm at 90mph.

I would leave the carb,as by changing it you will only see the difference at high RPM,which that you don't want.

Try a rpm airgap if you have the bonnet clearance,I have one fitted,and as it happends I want to fit the Torker 11 for a little more top end and bonnet clearance.

Just my 2pence worth.

[craggle]

Agree with needing to know the diff ratios.

I started with a 2.88:1 diff and at low revs the acceleration would only dislocate your neck.

Now with a 3.54:1 diff pressing the accelerator at the same revs is enough to break your neck
Completely different car to drive throughout the rev range.

350 chevy with Edelbrock performer Rpm - heads, cam, intake and 750cfm carb.

Craig.

[wilf]

Clarkson old chap - if you want more top end, I don't think a Torker II will give any more than an RPM airgap. For a real difference, you need to go to a Vic Jr. Of course, you need more headroom with that - about 1" more than a performer RPM airgap from memory, but check it out first anyway. I assume you have a cam that will make power up to 6500 to match such an intake?

[Clarkson]

Originally Posted by wilf

Clarkson old chap - if you want more top end, I don't think a Torker II will give any more than an RPM airgap. For a real difference, you need to go to a Vic Jr. Of course, you need more headroom with that - about 1" more than a performer RPM airgap from memory, but check it out first anyway. I assume you have a cam that will make power up to 6500 to match such an intake?

Yeah it would,but I would loose alittle low end torque due to it being a single low rise plane. The Torker II will suite the cam nice,but the vic Jnr will be outside my rev range. My rev range is 2000/6100 upto 6500.

For street use what I have works great,but the bonnet just hits the top of the airfilter.

[Clarkson]

Originally Posted by craggle

Agree with needing to know the diff ratios.

I started with a 2.88:1 diff and at low revs the acceleration would only dislocate your neck.

Now with a 3.54:1 diff pressing the accelerator at the same revs is enough to break your neck
Completely different car to drive throughout the rev range.

350 chevy with Edelbrock performer Rpm - heads, cam, intake and 750cfm carb.

Craig.

Craig,

2.88:1 diff with a Rpm edelbrock cam, with that combo it must of been a real dog to drive!!