RHS 170cc Vortec Max Cam Lift?

41Sprint · #1 (**permalink**) 07-07-2010, 09:16 PM

We recently installed a set of RHS Vortec heads on our 358 back up engine, The engine has a flat tappet cam with a .555 lift. We used .+.100 valves with ..060 base shims with .060 shims (.120 total ) and got the necessary spring pressures and with no retainer to guide clearance problems. .The power increase was very impressive so much so that we want to install another set just like them on our 383 primary engine. It has a roller cam with a .645 lift. I would like to know if anyone has installed a set up like this with the RHS 170cc vortec heads successfully and what was necessary to make it work. I know we will have to machine the spring seating area but there are limits on taking it deeper.
Any help would be appreciated that will keep me from buying a bunch of parts that won't work.

iwannagofaster · #2 (**permalink**) 07-08-2010, 03:45 PM

We really don't recommend that you go over .600" lift on those heads. Besides the fact that they don't flow over .600", you are going to cut really close to water on those heads if you cut them. You can use a .200" long valve, but that will throw the geometry off quite a bit. I have heard of people cutting the pockets about .050" deeper, but I have never tried it and don't recommend it. If you want to give it a shot, go for it, but there is not much metal there. The way it looks, you could pull the shims out and run against the head, and that would clear you for at least .650 with the right spring, you would just have to check the retainer to guide clearance on that, but that would be up to you. You could even squeeze .030" shim in there and be okay from the looks of it.

41Sprint · #3 (**permalink**) 07-08-2010, 06:36 PM

William,
Thanks for the info and prompt response. It seems I need to rethink our plans for the vortec heads. We may have to consider using the Pro action 180 heads instead if we want to keep our current camshaft configuration. Running the numbers on the computer dyno shows a slight improvement using the Pro Action 180 heads with the .645 roller cam over the vortec heads with a .theorical 570 lift. Will have to play a bit with durations to see what improvements can be made before finalizing our decision though. I have to admit the performance increase we saw on the 358 with the vortec heads has made me a believer in them.
Thanks again for the info!
Dick Talley

iwannagofaster · #4 (**permalink**) 07-12-2010, 02:27 PM

No problem at all. I am glad you got the results we were shooting for from those heads. If you need anything else, you can email me direct at; whood@compcams.com; or post and I will reply as soon as I can.

keithnh · #5 (**permalink**) 02-14-2011, 05:43 PM

I am currently gathering parts for my GM 302 project motor. Chasing the torque turkey instead of HP. My crank is done and nitrided along with 6.0 Scat I-beam rods. I decided to use Vortec heads as I saw reference to possible fuel economy improvements in reviews of them along with significant power gains. Their operating range is right where I need it given the cam I have selected which is the 252 XFI roller. I did several mock-ups on Cam Quest and came up with numbers that were extremely pleasing to me ... 464 ft-lbs @ 2500 / 344 HP @ 5000. It appears to me given my goal RHS 64cc castings are the most intelligent way to go as they have several desired machining operations done and are supposedly stronger than factory in the cracking arena as well as slightly better flowing not to mention at a reasonable price. Am encountering some resistance to my plan am not sure who to trust for good info. Everybody thinks Im wacky for destroking a 350, maybe I am ...there's only one way to find out.

Since most of the engine will be CC parts I am hoping to bend your ear a bit to get things as good as they can be given my plan. I am repowering a cherry 84 Cutlass 3.8 carb with the GM 5.0 (89 350 roller motor/L99 crank) converting to tbi-FI and 5spd manual. Looking for a very strong daily driver that gets decent fuel mileage. The 6 only got 18mpg and was gutless. I will be close to @ 10 to 1 with 64cc heads and will be using a Weiand 8151 intake and TBI adaptor with a factory p/u throttle body and custom chip.
I have 2 questions for you ...

1. Is there a reason given my particulars why the heads wouldnt flow enough for the cam ?? The machine shop said " the heads dont flow enough for the lift of the cam" ... are they right? Sounds kinda silly? I know I can use 1.5 rockers and was considering it in the fuel economy quest although the cam is designed for 1.6 ... I still want a smile at what happens when I put my foot down tho. The shop Im going to is one of the best shops in NH and have had builds in magazines and are still reasonably priced. They may just not want to put together a "wrong-way" motor like mine seems to be in their opinion. They've told me it wont be a high performance motor ... they've also said Cam Quest numbers arent fairy tales and are close. High performance is in the eye of the beholder, 464ftlb/344hp is high performance to me. I think the motor will want to rev too being smaller displacement needing less air.
2. I talked to a fella at Tech assistance last week who said I could order the castings direct for the same price as summit with free shipping which I intend to do. Does CC also have a machine shop that would assemble and possibly tweak the heads as needed, maybe flow them too and send the numbers with the heads ... (I have the CC titanium retainers for 26918 springs and Ferrea + .100 5000 series valves Both NIB.) That would be a pretty cool deal.

Thanks for your time and input Keith

amick · #6 (**permalink**) 02-15-2011, 11:03 AM

1. No sir that is not correct. I know what they are thinking in saying that but they just don't have all the info. Those heads (12410) flow up to .550 lift they simply peak at .500 lift which is why the given flow chart stops there. Even the 12407 will carry flow out around the .520-.530 mark, which is as much lift as your valve train is going to see any way after deflection is accounted for. I do agree with them that the CamQuest HP/TQ numbers are favorable. That is not say they are useless but they will predict high. That is because the program does not have your exact head flow numbers, intake flow numbers, and it can not account for atmospheric conditions. Here is a link to a similar cam in a 9.25:1 350 engine. This is not an exact apples for apples comparison but it will give you and idea. http://www.compcams.com/v002/Pages/392/XR252HR-10.aspx

2. Yes sir you can order the heads direct from us if you prefer. We do offer free shipping on the purchase as long as you are in the continental 48 states. We unfortunately do not have a machine shop facility.