355 TBI build help.

**old truck guy** · 12-13-2014

Continuing purchasing parts. Looking for input on rocker arms. Was originally planning on gmpp 12495490 1.5 stamped but I've heard they can be really inconsistent with ratio and while I've read some places that they are long slot, I can't find anything to support this. Don't know if they're capable of my .520 lift. Also considering crane 10800c and comp 1417-16. Looking for opinions.

**old truck guy** · 12-13-2014

Also has anybody used the crusader marine intake? Looks pretty identical to the gmpp intake without the egr provisions and its cheaper.

**Roadknee** · 12-13-2014

Originally Posted by old truck guy

Continuing purchasing parts. Looking for input on rocker arms. Was originally planning on gmpp 12495490 1.5 stamped but I've heard they can be really inconsistent with ratio and while I've read some places that they are long slot, I can't find anything to support this. Don't know if they're capable of my .520 lift. Also considering crane 10800c and comp 1417-16. Looking for opinions.

That XFI cam you've selected has very aggressive lobes. I think you really should run rockers with the roller fulcrum together with some min 0.080" wall pushrods.

**Roadknee** · 12-13-2014

Originally Posted by old truck guy

Also has anybody used the crusader marine intake? Looks pretty identical to the gmpp intake without the egr provisions and its cheaper.

I've looked at that intake and think it would work well. Take a close look at the throttle body mounting pad. The throttle bores look closer together than a 2bbl TBI. You might be able to re-drill the flange and offset-grind the bores or just find an appropriate adapter plate.

**BLG355** · 12-13-2014

Originally Posted by old truck guy

Continuing purchasing parts. Looking for input on rocker arms. Was originally planning on gmpp 12495490 1.5 stamped but I've heard they can be really inconsistent with ratio and while I've read some places that they are long slot, I can't find anything to support this. Don't know if they're capable of my .520 lift. Also considering crane 10800c and comp 1417-16. Looking for opinions.

I'm not sure if others have had too many issues with this, but with my 95 K1500, I tried full rollers at first, and they were noisy and giving me excessive knock counts, On a ten minute run I could get upwards of 10,000. I switched to comp cams magnum roller tip rockers and the only knock counts I get now are during initial startup, they other day I ran a 18 minute log and it have 246 knock counts, which is what it had during startup.

From what I understand there are ways around it and you can change things in the tune to reduce them or change for an LT4 sensor or something, but I just wanted it to be able to run without issues and I'm a new tuner so I changed them out and had no more issues.

http://www.jegs.com/i/COMP-Cams/249/...arentProductId=

This is what I have on right now, they are more money than the regular stamped rockers, but they are good for higher spring pressures and lift, plus are very tough. I used the 1.6 ratio on my Isky 252/257 Hyd Roller cam to get just under .500" lift. The only issue with them is that they are thicker than cheap rockers, so you will need a very thin socket to turn the lock nuts because of this. If you don't have them already, good screw in studs will almost me a must, like ARP.

BLG

**old truck guy** · 12-14-2014

I went with comps rpm1417-16 magnum roller tip rockers and magnum 1 pc hardened .080 pushrods. These are comps recommended items for my cam. I already have a new set of gmpp 12371042 roller lifter kit. Are these lifters gonna hold up to the aggressive lobes of my cam?

**Roadknee** · 12-14-2014

Yep, those are good lifters.

**old truck guy** · 03-25-2015

Ok been away for a few months but still making progress. I got my heads back from the machine shop and the port and polish, fresh mill and new springs look awesome. Gonna throw in a set of screw in studs just for a little added insurance. Sold the Edelbrock and bought the crusader marine intake. Bored it to match the 46mm throttle body and I also machined in a boss on the front, right corner of the plenum so I can utilize the stock vacuum brake booster line.

Converted my fpr to adjustable one by removing the stock set screw, retaping the hole to 10-24 and installing a 3/4" long allen head cap screw with a jamb nut. Drilled a 1/4" hole in the base below the fpr between the fuel line bosses. The head of the cap screw fits snuggly in this hole and I'm pretty confident that I'll be able to adjust it on the vehicle. Also I finally found a 92 caprice cop car in a junk yard a couple hours away. I made the journey and thankfully it had the 68lb injectors in it. Sent them to Mr injector and had them cleaned and flow tested and im good to go :-). I'm hoping to get by with 15psi fp because i just replaced the pump with a new ac delco less than a year ago lol but if not I'll be buying a new fuel pump and spring. Guess will find out when I fire it up and do some data logging.

Have pretty much all my parts and hopefully will be pulling the motor in the next couple weeks to get the short block done. Have laptop and will be downloading tuner pro rt. Mark w is going to do my initial tune but I will need to be able to do data logging and I guess make final revisions. What all do I need to get?

Thx, Mike

**old truck guy** · 03-27-2015

Bump

**PJG1173** · 03-27-2015

http://www.gearhead-efi.com/Fuel-Inj...-and-Tutorials under hardware should get you started

**old truck guy** · 03-31-2015

May be a dumb question but I don't know. Do both injectors fire at the same time or is one for 1, 4, 6 and 7 and the other 2, 3, 5 and 8? I've noticed that different intake manifolds vary on which side feeds what.

**brian617** · 03-31-2015

TBI injectors each fire every other DRP.

**old truck guy** · 03-31-2015

Originally Posted by brian617

TBI injectors each fire every other DRP.

So there is a specific injector (wire harness) for each of the two groups of cylinders then? I suppose all I have to do is look at a stock manifold to see which injector harness feeds which group of cylinders. Are they polarity sensitive?

**PJG1173** · 03-31-2015

you have inj A (two wires) and inj B (two wires). one wire form each injector goes to fused power and the other wire goes to the computer on its own pin. each injector fires every other distributor ref pulse. they are not dedicated to any particular set of cylinders. the computer does not know which is feeding which cylinder. or even which cylinder is in what position. it is very basic injection.

**old truck guy** · 04-01-2015

Originally Posted by PJG1173

you have inj A (two wires) and inj B (two wires). one wire form each injector goes to fused power and the other wire goes to the computer on its own pin. each injector fires every other distributor ref pulse. they are not dedicated to any particular set of cylinders. the computer does not know which is feeding which cylinder. or even which cylinder is in what position. it is very basic injection.

I agree that the computer doesn't know which cylinder when but it's clearly a mechanical relationship. If you look at how an intake manifold is divided, one injector supplies cylinders 1, 4, 6 and 7. Firing order being 18436572, those cylinders are all 180 deg apart. The other injector cylinders 8, 3, 5 and 2, also 180 degrees apart from each other and 90 degrees apart from the other group. As #1 begans the combustion stroke, #6 is begining the intake stroke so it makes sense to me that you would want the injector that feeds #6 to be firing on the #1 spark pulse, every thing else falls naturally into succeeding order. If the wrong injector was firing, everything would be 90 degrees off of the corresponding intake stroke.

Now back to my previous question. I understand that there are two wires to each injector. My question was are the injectors polarity sensitive?