PowellSixO

iTrader: (1)

I have a 2007 2500HD Classic 4x4 CCRB that is lifted 6", has 35" tires, 4.88 gears, cat back dual exhaust, and a cai. I just purchased a cam with the following specs:
220/218 Duration @ .050
.581"/.562" Lift
111 LSA

Will the PAC 1218's work for this cam?

I am in the process of looking for a set of 243's that I can swap my 317's out for. I don't plan on doing any porting or polishing, but I was wondering about milling the heads. I know that it's good practice to have the gasket surfaces cleaned up before installing.

Since the price to clean them up is the same to mill, should I take a little off to get a little more compression or should I just have them take enough off to clean them up?

Also if I do have them milled, let's say .025, what push rods should I order?

I'm thinking that since the stock push rods are 7.4 that .025 off the heads would require me to run 7.375 push rods.

Am I correct in thinking so?

I have been wanting to get a set of long tube headers for the truck too, but I've heard that the stock exhaust is allready pretty decent on my truck. Also I can't seem to find a set of headers that will bolt on to my truck.

Do I need a set of headers?

Does anyone know where I can find a set of LT's for my application that won't require a torch and a BFH to install?

One last thought, is picking the right injectors to feed my engine.

What type of injectors will I need?

What size of injectors will I need?

Thanks for taking a look!

batboy

iTrader: (6)

PAC 1218 springs would be perfect for that cam.

The 317 heads flow similar to the 243 heads, but as you have figured out the compression chambers are larger on the 317 head. If you don't plan on any porting, why not just mill the 317 heads? I would not mill 243 heads .025", I know people do, but that's a lot.

Pushrod length will probably require some measurements to determine the correct size.

You really should get headers. Give Texas Speed a call, they should have headers that will fit.

You probably won't need new injectors. When you get tuned after the cam install, have your tuner check injector duty cycle. As long as it's not over 80% at WOT, you'll be ok.

PowellSixO

iTrader: (1)

I would love to just use my 317's and mill them, but I can't get a straight forward answer on how much I can safely mill without PTV clearance issues.

mark21742

With that cam your ptv should be pretty good, but if you clay the heads with the cam before you mill them that will tell you how much you can safely take off.

PowellSixO

iTrader: (1)

Thanks guys I am going to give it a shot. If all else fails I will just stick with the original plan and get some 243's. I should be starting this pretty soon, and I will post the results.

Well I gave in and bought a set of 799's(same thing as 243's). I couldn't pass up the deal. $235 bucks shipped to the house. There are some AMAZING deals on 243's and 799's on Fleebay right now fyi. I also picked up some PAC 1218's for 125 bucks shipped to the house. I allready have the comp cam 220/218 Duration @ .050 .581"/.562" Lift 111 LSA. Now time for more questions.

I am sending the heads down to have the surfaces cleaned up, should I go ahead and have them mill a little off the heads or should I just have them cleaned up?

My truck has 78k miles on it right now, should I replace the oil pump while in there or can I let it ride?

Should I replace the timing gears and chain?

What gaskets will I need to complete the job?

Should I use GM valve stem seals, or aftermarket?

Anything I'm leaving out?

Thanks ahead of time guys!!!!

Also, are the valves between the 317's and the 799's interchangeable?

christiandoy

iTrader: (1)

#36 injectors should do you fine

mark21742

You could see a nice little bump in power if you get more than needed milled off the heads....I like to use http://www.wallaceracing.com/Calculators.htm you can punch your numbers in and come up with just how much you want to take off.
8.5:1 dynamic compression is max safe compression on pump gas (for a daily driver/ street car I'd stay under 8.3-8.4:1), and if you punch your numbers in it will probably take about 11:1 static compression to get there.

Just ask your machine shop to mill it down the the cc you want.

Run your numbers with a .040" head gasket, and run that head gasket. Most of our pistons sit .005" out of the hole, so this will give you the perfect .035" quench.

While you have it opened up you might as well throw in a ported ls6 oil pump and new timing set.

I think you can get a "cam swap" gasket kit (water pump, timing cover and a few other small gaskets), but I'll recomend just spending the $250 or do on the complete gasket kit, plus the .040" mls head gaskets. Give Texas speed a call, they should gave everything in stock for you

PowellSixO

iTrader: (1)

Thanks for that. Does anyone know off the top of their head what injectors will be compatable with my truck? I have read a lot about people using ford injectors. Is this an option for me? Also I have read that the 8.1 marine injectors will work. Is this true? Also if you haven't noticed I'm trying to do this on some what of a budget if possible. I don't want to do go cheap, if it means not doing the job right though. Thanks again.

Thanks for the info. I will now add an oil pump and timing set to my list of "need to purchase". Thanks for the Texas Speed tip too, they have a good looking kit that should provide me with everything I need including push rods. I will play with the numbers and see what I need the machine shop to remove to get the best compression ratio. The heads are in the mail right now being shipped to me. Once I get them I will send them down to Phoenix the next day to be machined. I plan on having this whole job done within 3-4 weeks.

Thanks again for the tips.

Well I was playing around with numbers, and figured out that if I have the machine shop take .020" off of my heads I will have 61.5 cc chambers. If I run this with the stock .051 head gaskets, I will be right at 10.5:1 cr.

This should be a pretty big difference over the stock 9.6:1 cr right?

I would take a little more off but I don't want to have to worry about ptv clearance. I know the best way is to put everything together and check it, but I don't want the truck to be down for very long. I would like to get everything together and get it all put together in one weekend if possible.

Does any one have experience milling 243s?

How much can I safely take off without having to worry about ptv clearance?

Also I would run the .040" head gaskets, but they are exspensive.

Plus can't I achieve the same goal with stock hg's and just milling more?

batboy

iTrader: (6)

Since you are going to use single beehive springs, GM valve seals are your best bet.

Max you can mill the 243/799 heads is subjective, but a conservative limit in my opinion is .030". PTV clearance also depends on the cam duration and lift, so it's not so simple to decide how much to mill. Your plan to go .020" sounds reasonable to me, a nice compromise.

For head gasket, it's hard to beat the GM MLS. They are more forgiving and seal easier than Cometic.

PowellSixO

iTrader: (1)

Found a good deal on some non marine 8.1 injectors (31#). Do you guys think that these will be enough for my engine or should I go with 36# as suggested?

mark21742

If I had the choice to go with more milling and thicker gasket, or less milling and thinner gasket I'd mill .010", and go with the thinner .040" gasket.....this will give you a better quench srea and make the engine less prone to detonate.

Oh, also....for every point you raise your compression (9.5-10.5 in you case) you see an average of 3-4% gain in torque and HP all across the whole tom range.

PowellSixO

iTrader: (1)

I'm looking at this site:

http://www.rceng.com/technical.aspx

Using a BHP of 450, 8 injectors, brake specific fuel consumption of .50, maximum injector duty cycle of .80, and fuel rail pressure of 55 psi, it calls for 31.27 lb/hr injectors. Is this info correct?

mark21742

Your stock injectors (28 lbs if I'm correct) should work, but if you nerd to upgrade go ahead and drop in a set of 36 lb injectors do you have some room to grow later.

I can't see buying things twice when if you just go slightly bigger you only have to buy once.....I have more motor and rpms than you, but I went with 60 lb injectors in mine with future plans of turboing my 408

PowellSixO

iTrader: (1)

Stock is 25lb/hr I believe. I found a set of 31lb/hr for $115 thats why I was asking. I allready have my truck tuned and they said I am now over the 80% duty cycle. I figured with the cam I would surely need to go bigger.

mark21742

Oh ok....if you only have 25 lb stock, then 31 will put you in the clear

PowellSixO

iTrader: (1)

My bad stockers are 24lb @ 3bar (43.5psi). So 8.1 truck 31lb/hr injectors @ 3bar should support 400hp at 80% duty cycle. My combo shouldn't put anything over that right?

mark21742

You should be close