Engine questions (warning - long)

[Ikom]

I am getting ready to take the engine plunge and have been talking to a very good local engine shop. They do their own dyno work and the owners personally, meticulously build and run each engine before it leaves their shop. They are also in the process of using dedicated CNC machines to bore and hone all of their engines which will make their output extremely consistent – read very high quality control and repeatability.

Their stock (series II) engine is a 383ci which puts out a modest 442HP 488ft lb and costs $6859USD. See:

www.promaxperformance.com/Products_Chev_383_series_II.htm

However they have a brand new rare (400) block from GM which can easily accommodate 421ci (and more) displacement and I have to make a quick decision to secure one of these blocks.

I do not want real crazy horsepower but these blocks mated with the correct internals will easily produce and handle up to 700HP.

My own requirements are modest at around 540+HP.

This complete engine will however hit my wallet for an additional $3000USD but will include a forged steel scat crank, scat H beam rods, forged Keith Black pistons, 850cfm carb, air gap single plane manifold, Pro Topline aluminum heads with 2.020 intake and 1.600 diameter valves. 10.30:1 compression, steel roller cam and roller lifters, MSD digital six ignition and pro billet distributor. And a bunch of other goodies.

It should easily make about 440 ft lbs of torque at 2000 RPM and peak at 500ft lbs at 5000 RPM. The 550 horsepower peaks at 5500 RPM and is still at 520 around 6000+RPM.

I will be using the 993 Transmission - G50/20 - six speed - Limited Slip Differential with the following gear ratios:

1st 3.82
2nd 2.048
3rd 1.407
4th 1.118
5th 0.928
6th 0.775
reverse 2.857
final drive ring and pinion 3.444 (Hypoid bevel-gear drive with 16 mm offset)

According to gear calc charts – the car should be doing 180mph at 6200 in sixth, which is plenty for me (My Porsche did about 164mph and was scary fast for me) see:

www.geocities.com/z_design_studio/transmission_993_bit.html

Now the questions:

1) Is this overkill for the car and tranny? I guess what I really want to know is - if there is an ideal engine/tranny combination for the car or a good rule of thumb to go by? Where should the power and torque ideally be at various RPMs for a street ULTIMA?

2) What is the size of the factory exhaust headers - headers and collectors? I need to make sure the exhaust flow is adequate for the engine.

All opinions are welcome.

[B1 ECC]

Checked out the website and the video! the engine in the video is running on a test bed and not a "dyno", looks about as impressive as a Ford Fiesta undergoing an emission check! If you can visit the factory o.k. If you can't, what's the the Pre-emtor thingy!! Oh' buyer beware.

[Ikom]

B1 ECC said:

Checked out the website and the video! the engine in the video is running on a test bed and not a "dyno", looks about as impressive as a Ford Fiesta undergoing an emission check! If you can visit the factory o.k. If you can't, what's the the Pre-emtor thingy!! Oh' buyer beware.

"Caveot Emptor" - You meant to say.
Thanks for the heads up.

Their workshop/factory is not far from me and I have visited them several times - a very highly regarded and credible operation with a long list of satisfied hot-rodders.

Agreed, the Video is of an engine on nothing more sophisticated than a test bed, however, they do have access to an engine dyno.

My questions though are:

1)Best power/torque curves for the Ultima engine/drivetrain application?

2)Diameter of factory exhaust - individual pipes and collector?

Thanks

[steve_D]

Ikom said:

1)Best power/torque curves for the Ultima engine/drivetrain application? 2)Diameter of factory exhaust - individual pipes and collector? Thanks

I was advised to aim for an engine producing higher revs with little or no low down torque. Reason: The light weight of the Ultima, 5 or more manual gears and the perception that the car is for high speed rather than drag racing. Correct choice of cam and large intake flows are the order of the day.

My exhaust is away for coating at present but I believe its 1.75" into 3". The exhaust may not be ideal as the whole system is somewhat truncated. The collector is probably only about 10" where I have heard the Chevytalk forum recommend 22" minimum.
Steve

[B1 ECC]

Oh yeh! That's what I meant!
I agree with Steve's reply, if you want a top speed in excess of 160mph, then you will need an engine that will pull all the way to, and perhaps beyond 6500rpm.Your camshaft choice will be the main dictate of this and as a consequence, will dump the peak torque around the 4500 mark.(At this point most 383 are producing 470-500 bhp)
The factory exhausts are good and cosmetically very good, but if I was doing it again, I would go for custom built, to better compliment the engine characteristics!

[steve_D]

If you have it in mind to do other than factory exhaust then speak to Andy and possibly Clive about the systems they have. Andy has an 'H' system and other mods resulting, I believe, in lower sound levels and a smoother, less harsh note.
Steve

[G Man]

To get a v8 sbc to rev i went 4 a 377 ci an overbored 350, my red line is now 7800 rev and it loves a spanking

G Man

[builder]

G Man said:

To get a v8 sbc to rev i went 4 a 377 ci an overbored 350, my red line is now 7800 rev and it loves a spanking G Man

Hi Gareth,

I agree with the 377 size. My research has pointed me exactly in that direction. Would you be so kind as to share the build details of your 'lump'? I have built SBC engines, but never for this type of duty.

Thanks!
--Scott
Reno, NV

[G Man]

377 ci 10.5 comp Chapman 18 deg alum heads, scp 4 stage dry sump, holley 750 carb 1 7/8 headers, mSD dist, Edelbrock 18 deg manifold, jesel 1.55 rockers, comp cams cs252/256 roller cams , dart aluminium block. Childs and albert light weight billet crank and rods, JE flat top pistons.
Head flow numbers
Edelbrock/Chapman 6105
Intake Port Volume: 255cc
Exaust Port Volume 105cc
Chamber Volume 47.5cc
Valve sizes and Lengths
Intake Valve 2.180 5.640 Long 12° 33° Backcut
Exhaust Valve 1.625 5.660 Long 25°

644 BHP at 7200 rpm

>> Edited by G Man on Wednesday 14th April 08:52

[builder]

G Man said:

377 ci 10.5 comp Chapman 18 deg alum heads, scp 4 stage dry sump, holley 750 carb 1 7/8 headers, mSD dist, Edelbrock 18 deg manifold, jesel 1.55 rockers, comp cams cs252/256 roller cams , dart aluminium block. Childs and albert light weight billet crank and rods, JE flat top pistons. Head flow numbers Edelbrock/Chapman 6105 Intake Port Volume: 255cc Exaust Port Volume 105cc Chamber Volume 47.5cc Valve sizes and Lengths Intake Valve 2.180 5.640 Long 12° 33° Backcut Exhaust Valve 1.625 5.660 Long 25° 644 BHP at 7200 rpm >> Edited by G Man on Wednesday 14th April 08:52

That's a thing of beauty. Curious with that cam... Can you describe your torque curve? Are you happy with the balance, or would you make any changes?

-- Scott
Reno, NV

[G Man]

I have over 500 ftlbs of torque from 3000 rpm to 6000
The pickup from 3500 to 7700 is just unbelievable
Under 2500 it is a pussy cat which saves on the gearbox.

[andycanam]

Have to agree, my own personnel view is that you need revs in an Ultima and G-mans engine fits the bill perfectly..... just don't forget the LSD.

[builder]

G Man said:

I have over 500 ftlbs of torque from 3000 rpm to 6000 The pickup from 3500 to 7700 is just unbelievable Under 2500 it is a pussy cat which saves on the gearbox.

SWEET! That about ices it for me. I know the direction I am heading now. High revs with very respectable bhp and torque with a rock-solid bottom end and a limited slip dif.

This Ultima board is awesome. Thanks for all of the time you guys put into helping others. Ted at Ultima has been very helpful as well. It's his job to reply to builder qustions, but I know all of my questions were repeats of those who have gone before me. I wouldn't be this far "down the road", if not for this well-spring and the excellent builder's Websites. Thanks all...

-- Scott
Reno, NV