Cam Selection for AFR 205/SBF 347

[Mac VABCH]

I am in the process of switching from World Products Cast Iron Windsor Sr. Heads currently with a Ford Racing E303 cam to AFR-205 heads with the Nitros exhaust ports and a aggressive cam not selected yet. Here are both head specs:

WP Windsor Sr.------------------------AFR-205 (1452)

Intake runner Vol.: 200cc-----------------205cc
Valves: 2.02I/1.60E x 11/32" stem---------2.08I/1.60E x 11/32" stem
Chamber: 64cc---------------------------58cc
Max Lift: .560"---------------------------.710"

Flow# for AFR 205:
.200-141I/121E
.300-201I/173E
.400-251I/208E
.500-291I/231E
.550-301I/236E
.600-308I/240E
.700-310I/244E

Head Gasket:
Fel-PRO 31011-1 compressed thickness = .041"

These will be going on a 347 Eagle stroker kit w/ a 1985 5L HO block 4.030 bore and 3.40 stroke. With the WP heads and the head gasket listed above the CR should be 10.36/1? CR with the AFR heads should be 11.16/1? I didn't have the engine built but it was sold to me by a very close friend and he can't remember what the pistons where notched for but most likely for the 2.02/1.60 valves. I would like to not have to tear the motor down past the short block. I know that I must check the piston/valve clearance and most likely will have to cut bigger reliefs in them for the 2.08I valves. Additionally I will have to measure for push rod length for the new cam/head combo. Also I would like to stay with a hydraulic roller cam/lifters. I have 4 questions:
1. How do I determine the max lift I can have. I would like to take advantage of the max lift of the AFR heads to help determine the cam.
2. What are your informed cam suggestions as this is STRICTLY a R/R track car. I haven't had it registered in 3 yrs. I don't what to turn the motor more than 6500ish. Gears are 3.63 with a T-5 (.73 5th gear) and a 25" rear tire. If I need to use a vacuum pump or accumulator i will. Also if I need to run race gas I will for the extra performance of the cam.
3. After the cam is selected, installed and degreed what order should I check P/V clearance and push rod length? How do I get accurate push rod length if I have P/V interference before I cut new reliefs and how do I know how deep to cut reliefs without the correct length push rods?
4. Are my CR calculations correct?

I am not a engine builder so I might be reading to much into this, if I am I apologize up front...I have put as much info as I can in this thread if I am missing something please let me know. Thanks for the help....Mac

[blykins]

That will be a good head for a road race car if you have the cam and intake to back it up.

Here's some answers for you:

1. You can't really see how a new cam will interact with the pistons until you get the new cam installed. Due to the valve timing events, one cam may get close while another cam may be a little further out. You can get a general idea by checking valve/piston clearance with the current cam. Since it's an E303 cam, you know the lift. Check the P/V clearance and you can get a general idea for how much lift you can shoot for. If the pistons came with the stroker kit, you could probably assume that they will take some lift....probably close to .600". This will vary of course depending on how the pistons are made....domed, flat, dish, etc.

2. You will need a nicely sized cam to take advantage of the flow from the AFR heads. For off the shelf hydraulic rollers, I like to use Comp's XFI series. They are designed for strokers and I think that it would be a good choice for you. Since you don't want to turn any higher than 6500, I would look at the XFI236HR-14. I sell Jones Racing cams and if you wanted a custom camshaft for your application, we could talk further about that.

3. Set up your camshaft first. Degree it and time it the way you want. Once you set the cam timing and degree it to double check it, then you can check piston/valve clearance. Since P/V clearances change when you advance (intake valve clearance goes away, exhaust clearance grows) or retard (intake valve clearance grows, exhaust goes away), then you must set the cam timing first. When you get that set then you can check your piston valve clearance with an adjustable length checking pushrod. You set them to different lengths and then you can see what length works best. It's best to use a solid roller lifter when you check p/v clearance so that you get an accurate result. Either that, or bottom out the plunger on the hydraulic lifter so that the plunger doesn't mess with your results. Use clay to check radial valve clearance and it's best to use a dial indicator/mag base to check depth clearance.

4. It's hard to get a very accurate compression ratio calculation without knowing the piston volumes and how far the pistons are below deck at TDC. I suppose you could backwards solve to get it, but I'd feel a lot better to have all the numbers.

For a strictly race application, I'd look at a solid roller camshaft. Then you don't have to worry about valve float at higher rpms.

[Mac VABCH]

Brent,

Thanks for the reply. I thought that I put every thing in the tread but I forgot to say that the intake is a Edlbrock Victor Jr. used with MassFloEFI. The piston are flat top. Yes I would be interested in a custom cam. Are you available. I am currently in Kenya so I would have to call you...Mac

[olddog]

I have a similar engine, with the same intake and EFI. While you have the engine apart, check the intake out closely. Some of my fuel enjector bungs were 1/4" into the air flow path. Most of the bungs were no longer round where the welds were at. It took very little work to clean that up. Also port match the intake to the heads.

If you need to machine the pistons for the valve clearance (and you will if you go near the .7" mark) it will change the ballance. If it were me I would get it re-ballanced.

My engine wants to idle about 500 rpm cold and comes up to 900 rpm warm. Does yours do the same thing? I'd like to know if it is typical, before I continue to dig into this.

[CHANMADD]

You can work out the max cam specs with a little patience. Remember that the valves also can only be pushed sofar before you get coil bind, Max Valve Lift ,the head manufacturer will give you those specs (You need 0.060 clearance between the coils) although I do run mine a little closer. The rocker ratio is the next thing, Divide the max Valve lift by the Rocker ratio and that will give you the max cam lobe lift. A solid roller cam with rev kit and roller rockers works good.If you would like to email me I can help walk you through the process.
John

[vector1]

looks like you're intent on what you are doing, so i would pull the heads and look at what you have regarding piston to deck height, eyebrows, etc., you can also alter your head gasket thickness to help with the compression ratio. if you have to cut valve reliefs i wouldn't worry about the rebalance.

you might look into the new competition afr185's as potential heads. with your small bores i'm not so sure you would benefit from all the potential airflow of big valves so i wouldn't get too excited about that aspect. after you pull your heads put some soft springs on a cylinder and check what your current p to v clearance is, this will give you an idea of how far you can go and how much more valve you can use with current pockets if you put some clay in there.

definitely get a cam made specifically for your combination and application. with your rpm you should be able to run hyd roller pretty easily. blykins works with a good cam guy and he can give you an idea on how much lift and duration to expect, then put a degree wheel on your engine and check your duration and lift values against your current setup.

good luck.

[blykins]

Mac,

Just shoot me all of your engine specs and I'll talk with Mike about his thoughts on a custom grind spec. Would you be interested in a solid roller? For road racing where you may spend a lot of time at higher revs, I would lean more that way. If you stick with a juice roller, I'd recommend some very lightweight valve train components to reduce the weight on the lifters.

You can reach me at brent@b2motorsportsllc.com

[Mac VABCH]

Brent,

I will send you a email...Thanks Mike

[Mac VABCH]

Well,

Instead of doing a lot of work to th 347 that I have now, I decided to buy a new engine and sell the current 347. Following Blykins advise I went with a Keith Craft Long Block. The motor will be a Dart block 363cc with AFR205 heads with ~13/1 Compression....Thanks for all the advise, can't wait to get it in the car...Mac

[Mac VABCH]

I should mention that Brent Lykins not only steered me in the right direction for selecting the motor but was particularly helpful providing a custom grind cam that should work great for this combo and how I use it.... He was very knowledgeable in education me as to the process of good cam selection which is what I was originally asking for....Thanks again...Mac

[blykins]

Glad I could help, Mike. I think you'll be extremely pleased with this combination.