choice on cam

[shadowbandit]

Well loyed had given me two options hard to choice witch one 231/239 .622/.606 109 LSA that's the first one 235/243 .629/.613 110 LSA and that's the second one car will be a fully forged 355 and get the gun with 250 so please what do you guys think

[Chopstix]

2nd

[popo8]

Did he give u pros and cons to both. Im sure there are pros to each and thats why he gave u options.

LTXtech.com is my Drug...

[Injuneer]

And he was aware you were going to spray?

[popo8]

NightTrain66

LTXtech.com is my Drug...

[NightTrain66]

whats the vehicle weight, gear and stall?

What RPM are you OK taking the engine up to (6400, 6600, 6800, etc)?

Lloyd

[shadowbandit]

Well car is going to be full interior car so I'm not sure I know motor can spin up to 6750-6800 4:10 3600-3800 tight converter threw a cpt built 4l60e

[NightTrain66]

If you are worried about N/A times, get the 231/239 cam.

A converter made for nitrous will be execting a cpl of hundred more ft lbs of TQ to launch well and multiplt TQ well so it feels like a much tighter converter and the N/A track times will suffer quite a bit.

You could lose 2 tenths from the 60 ft with a nitrous converter compared to a N/A converter making the car 4 tenths slower N/A. The extyra TQ made down low of the 231/239 cam will "help" to get the car moving.

The 235/243 cam will like a looser converter (3600-4400) and has the potential to be 1 tenth quicker compared to the 231/239 cam if using A LOOSE CONVERTER or if using the nitrous converter AND spraying nitrous. The tighter converter will make the 231/239 cam faster N/A.

Really depends on hopw often you are gonna spray nitrous and/or run N/A.

most will be happiest with theresults of the smaller 231/239 cam.

Lloyd

The

[Injuneer]

I guess what surprised me a bit for a nitrous application was only an 8* split on the exhaust, and the narrow LSA. But my experience is very limited.

[NightTrain66]

I would up it to 10-14 degree split (depending on RPM range, etc) with some AFR 227's (offset intake rockers, larger cross section at PR pinch) and single plane intake but still use a 110 LSA if on a 250 shot.

If widening the LSA like to 112-114 you would have to put more advance (an extra 2-4 degrees) to get the ICL where you want it (107 for instance would have 5-7 degrees of advance) and then the ECL would be even higher (117 to 121). This would open the ex valve WAY early and blow down the cylinder (stop pushing down on piston sooner on power stroke) so it would be very sluggish with no spray.

In order to get the EVC to end where you want it to allow exhaust to escape you would need to use a MUCH bigger exhaust lobe (16-22 degrees larger than exhaust). If you do not delay the EVC enough to get exhaust out you pretty much end up with a big EGR valve if the valve is at too low of a lift at end of ex stroke and start of intake stroke. Adding exhaust duration is the only way to get the get the EVC working well (valve still at a high lift at end of ex stroke) if you have a wide LSA and advance the intake lobe (thus advancing ex lobe too).

Other option is to run very little advance and just let the IVO and IVC happen real late and that results in a real lazy engine (unless boosted). The nitrous will make the cylinder pressure come up and you will see a good "increase" over the N/A ET's but from my experience on 10 to 12 second LT1/SB Chevy running 250 shot it is better to have the cam closer to a N/A cam and run faster N/A and even though it doesn't see as much "increase" by using the nitrous, it still ends up being just as fast and some times still faster than a "nitrous cam" with a wider LSA, more split on these 10-12 second LT1/SB Chevys.

example -

231/239 duration 110 LSA cam runs 11.30's N/A and 10.20's on 250 shot (1.1 sec diff)

231/243 duration 114 LSA cam runs 11.60's N/A and 10.30's on 250 shot (1.3 sec diff)

ET's and increases are just pulled out of the air but that is the kinda results that i have seen from doing the cam both ways.

If running enough cubes (410-434 ci), using heads with offset rockers, better flowing intakes, more nitrous and really just focusing on the ET with the nitrous being used (and no concern of N/A ET) I agree, more split and wider LSA is gonna be faster.

If using 250 shot or less and running 10-12 seconds on nitrous (like "most" on this board are) I have seen this info to be correct.

Lloyd

[shadowbandit]

Okay so since your going to building the top end for this 355 I just want your best advice I'm trying to run bottom nines maybe really high 9s

[NightTrain66]

vehicle weight and 60 ft are gonna be a BIG part of track times.

With a light enough car, the right converter and suspension you could possibly run low 9's with a Hot Cam and some out of the box Edelbrock heads, LOL.

Send me an email about your exact set up

cubic inch
compression
heads
intake
headers
exhaust
weight
gear
what trans
stall
tire ht
DFI, 24X, LT1 PCM and Opti, etc

if the car was running before at track and what ET's it ran with what set up, etc.

The average 3300 lb car with 1.40 60 ft, LT1 intake, LS1 air lid, 58 MM TB, LT1 PCM, 7000 RPM shift point, 355, 12 to 1 compression, ported GM LT1 heads (or ported 21 degree TFS heads) with 1 3/4 LT's, ORY, cat back exhaust, 4.11 gears, 28" tire, TH 350, 4500 stall, 250 shot of nitrous, etc, etc,

If this describes your set up I would suggest something "around" 251/261 .688/.688 108 LSA depending on what springs you are willing to buy and how often you want to change them.

More weight and/or slower 60 ft will need more HP to run the same ET.

Lighter car and/or better 60 ft (suspension, converter, etc) will make the car faster with the same HP.

Things like 24X conversion, higher shift point (more cam), better heads, 1 7/8 headers, 3" True Duals, more compression, single plane with elbo and LS1 TB, etc all will lead to more HP.

Any car is not gonna be fastest the first trip down the track. Cars that are together for a while get dialed in. Tweak the tune with a lil less/more fuel up top, a lil less/more timing up top (NOT on the dyno, on the TRACK where it matters) Play with suspension & converter choice, etc and help 60 ft and efficiency up top.

Cars that have been together a while get faster by the owner taking steps to make them faster at the track. They dont get faster just by leaving things alone and making passes. Look at just about anyones build and from the time they get it together with the heads/cam set up and go to the track often you will see the cars speed up over the weeks/years from them tweeking things to make it faster.

People that just throw the car together and go run it do not see the cars speed up if they do not change anything. This is not because everything is already so perfectly dialed in that it can't get any better at the track, it is usually because they do not have the budget to change things, the knowledge to know what to change or are just content with the way the car runs anyway.

Email me your set up and Ill get you some better info. (nighttrain66@msn.com)

[NightTrain66]

quick example of my 97 T/A LT1 car (3820 lb race wt) and the few tweeks I made to it and track times.

Got 383 with used LE2 heads and cam installed, chased problems for about 2 months that ended up bieng bad 02, opti and plug wires.

Went to track with stock 80K trans, Yank SS 3600 stall, stock suspension, 3.42 gears, stock 17" wheels with M/T Drag Radials, PCMforless tune.

1.63 60 ft, 12.70 @ 117 MPH - Had OBD2 PCM and hit "stall wall" or what ever it is called. Left good, shifted to 2nd and hit nuetral. Had to let off gas and then slowly apply gas to shift to 3rd. Went 1st, then nuetral on shift point, then to 3rd.

Got ODB1 PCM and mail order tune from PCMforless.com but still 80K stock trans and it would occasionaly tag the 6800 RPM limiter on 2/3 shift even though shift points were set at 6100 RPM.

1.62, 7.5x @ 90 MPH, 111.55 @ 117 MPH

Blew apart 7.5 posi unit, installed heavy ass 8.8 ford with 3.55 gears and posi unit, CPT trans, got dyno tune (went from 410 to 436 RWHP)

1.59, 7.11 @ 94 MPH, 11.13 @ 121 MPH

Sold it to guy that works with me. He weighs 30 lbs less, installed LS1 lid (getting rid of CAI and 90* elbo) aftermarket TQ arm, control arms, shock/springs.

1.51, 6.81 @ 97 MPH (1/8 mile track only).

Just shows all the little tweeking done (and extra $$$ for trans, rear end, suspension, etc) and how it shaved a lot from the ET.

Put 15K miles a year on the car until elec WP went out and wounded the engine. Some "at the track tuning" playing with timing, fuel, shift points coulda/woulda/shoulda made the car faster (everyone has this story) but it never happened and the car is only as fast as the time slip says it is.

Lloyd