Hi guys, I am looking for some opinions on my build, mostly with help choosing a cam. I own a GM sedan, factory LS1 and I am building a 415 LS3 for it, this is what I have so far:

415 iron short motor - purchased from Schwanke - it has Mahle flat tops, Eagle h-beam rods, Eagle 4" crank, iron block 4.065" bore. I also ordered a cam and LS7 style lifters (more on this later)

LS3 heads - these came as a package from ebay, CNC ported with stainless valves and double springs

Ported factory intake, 92mm throttle body, 80LB injectors

Built 4L65 trans with 2500 lockup

I have owned a few large cube combinations and being a daily driver I am planning to keep the diff gears street orientated. From previous experience the larger motors pull the taller gears really well, Im not really worried if I lose a few tenths at the drags and if it does become a concern I can always change the gears anyway. Factory ratio is 3.07, with the low first gear its the same overall first gear ratio as a TH400 with 4.5 gears, and stall makes all the difference. These 4A cars pull off stall speed very quickly so I dont think gearing is a big issue provided it isnt cruising way under cam.

I had Schwanke choose the cam and assemble the short for me but the motor arrived with a gouge in a deck so I dismantled the motor and had it decked, now its apart I am rethinking my options. The cam supplied is:

271280/290- Isky
.530 int./ .540 ext. Lift
232 int./ 242 ext. Duration @.050
110 Lobe Center

I bought 1.8 rockers knowing that the lift is on the low side but I am looking at a modern spec cam since I have it out, so what would you guys suggest? I really want to make 500rwhp, that would be a very big deal for me, and my second goal is to run in the 10's but the car isn't set up for drags so any 120+mph terminal speed will be close enough.

I have seen some discussion on this cam:

SpinMonster Cam
230XFI /234XER 114+2
intake .612 lift
exhaust .598 lift

Its a more aggressive grind while having less overlap so it could work out very well, but its a street car so I need it to last a while, how hard is this on springs?

While at the machine shop I took my heads to have them looked at, what I found out is that my ported heads flow less than unported L92 heads at all points below 0.600 with the difference being 30cfm in the 0.250-0.350 range so I am going to get another pair of heads and start again. What comp should I be aiming for? All build forums speak of 11.3+ but the head guy reckons its way over rated and he has built many with 10.5 comp (street motors), I just dont think its a good idea to go too low on comp. It will be running 95/98 PULP.

I have been advised that 80LB injectors will be too small, should I get 100LB instead?

I realise its a lot of text but please read through it, ask questions as needed and any advice would be greatly appreciated.

 

Your first Isky cam would be pretty gentle on valvsprings w/1.7 rockers but the 1.8s you mentioned would add lift as well as kick to what the spring has to deal with. Your second cam seems like a decent stick, however the LS3 style heads which flow so well on the intake side tend to like alot of exhaust duration to help the E/I flow ratio. The intake lobe duration you're looking at would be really docile and street friendly in an engine that large...plus the stall being on the lower side will rely on the long stroke/low rpm torque manners. I'd bet this Tooley cam would perform quite well for you and he may even suggest a few tweaks to it (custom) for your rectangle port engine.
http://www.briantooleyracing.com/nat...-camshaft.html
As for heads, I'm sorry to hear that yours don't flow better given the CNC porting that was done to them. Are you going to try to sell them and find a new LS3 GM head/s or possibly an aftermarket LS3 style ????
Texas Speed has a nice set of ported GM castings....which can be upgraded with either the GM or stainless hollow-stem lightweight valves and some .650" dual springs.
http://www.texas-speed.com/p-1179-pr...ted-heads.aspx
A friend of mine really loves his PRC aftermarket castings. On his Texas Speed 416 with a cam about the same size you're looking at, he's in the 570 RWHP range. Here's the link to those......
http://www.texas-speed.com/p-4010-pr...der-heads.aspx
I know shipping costs an arm and a leg to you folks down under but these are just some suggestions to help ya out.....

 

Stainless Ls3 valves are very heavy and require serious valvesprings and gentle lobes to be stable. This sounds like stuff you're just pulling from the shelf with no consideration for how the combo works.

I'd look at a HUC or XE lobe cam and run stock LS3 rockers w/trunion upgrade. I'd then run PAC-1905 valve springs.

An XE 232/248 114 would work well with LS3 heads in a big motor.

 

Thanks A.R. its just the stuff I am after.

Jake - the cam was chosen by the builder of the short motor, the rockers chosen to try to compensate for the low lift and the heads were too good a deal to turn down. Even after shipping these heads would cost me more than twice as much if sourced locally.

Aftermarket heads are way out of the budget, so I will be selling these and starting again with some factory heads.

I understand your point about the larger exhaust duration but I was reading what spinmonster was discussing on the corvette forum and he is dead against large overlap with factory LS3 heads due to reversion. The Tooley cam you recommended has 10 degrees of overlap which is way above what spinmonster recommends. I know there are many different ways you can build this motor and all will work to some extent but a small time tinkerer like myself will never have the resources to buy-try-test different cams, different heads etc etc so you pretty much have to hope you bought a decent selection of parts and that it performs satisfactorily when its all done.

Shipping actually isnt too bad, GST and import duty add 15% and the exchange rate is pretty poor at the moment, but after all that it is still cheaper to buy from overseas.

 

It's not a Tooley cam. It's just a cam with a wide split. Overlap sensitivity is important on the LS3... but it's been out for 6 years now. The way you're thinking is what people saw 4-5 years ago when they tried to cam like a cathedral head and went too far in the other direction when overlap/reversion killed power.

And you have a 415... not a 376. You can't go by Spin's cam choice there. You have a longer stroke and more cubes. Spin's cam is going to drive fine but leave a lot of power on the table. The reversion aspect also is with stock, unported heads. Once you port them, you change the I/E ratio. I know folks have used a 232/240 or 232/242 cam in the 400cid LS3 combos with luck as well. So you could tone it down a bit and run the 232/242 114... which is close to what Schwanke set you up with.

And I would not run heavy rockers and stainless LS3 valves. I assume the rockers are roller rockers? That's going to eat itself unless you swap out PAC 1208X springs or something to control all that valve weight.

 

Thanks mate, I meant AR in second post, he linked a Tooley cam. I will have a look again but I believe the thread where I saw spin talking about cams was in relation to a stroker. I am re-assesing my combo now while its apart as I want to do it properly the first time. Yes the rockers are rollers and the current springs have 150 on the seat. The last thing I want to do is choke the top end with the wrong cam.

What rev limit would you put on solid stainless valves?

Cheers

 

6400 Max with the stainless valves and only 150lbs seat pressure. You probably need closer to 180lbs. Shim the springs to within .050" of coil bind.

 

Good luck you need some help picking parts. The people you have had doing it for you are all very lost.

Pick one capable person and listen to them.

Tim

 

Who is a capable person? Everyone has confidence in themselves then someone else tells you that their ideas are rubbish ....

How much does your Mustang weigh Tim?

 

Proven results. I am not talking Dyno queens.
Cars that go down the race track, road, driven in traffic.

The major issues I see is the cam is not even close even with 1.8 rockers. Not going to make power due to no duration or lift.
Injectors are way to big. I run 80 in my car on pump 93 they are at 50% on e85 80%. Makes 750 hp
Compression is way to low
The solid stem valves are too heavy. Beats up on springs

My car weighs 3000lb going down the track.

Flowtechinduction.com does my cylinder heads and valve train. The results do the talking.

Tim

 

OP how was the quality of your short block other than the gouge in the deck? I was thinking of going with schwanke for my next engine..

 

I will PM you.

 

Ok guys, an update on this as things have changed. I have sold my Pro Comp heads and bought some GMPP cnc heads. These are still a budget option but now have hollow inlet valves, titanium retainers and Tooley 660 springs. The smaller chambers with my 0.040 gaskets give me 11.5:1 without milling. I sold the roller rockers and bought a set of cryo treated stockers wih trunion upgrade. I sold the cam and am doing more research before buying another one.

I have started a thread on cams but feel free to chip in here if you like.

 

We offer a custom cam service and have a pretty long list of satisfied customers! Let us know if we can help get you what you are looking for!