Valve To Piston Clearance Question

C

CaptainJack_7

New Member

Dec 21, 2014

9

0

1

Dec 21, 2014

#1

• Dec 21, 2014

• #1

I'm building a 347 stroker stock block scat full forged rotating assembly with +5cc dished pistons. I will be running 93 cobra r gt40 heads with the stock crane 1.7 rockers. My question is with the fr x303 cam with the calculated lift with the 1.7rockers being .575 will I have a problem with the valves hitting the pistons?

 

A5literMan

At least it is lumpy...

5 Year Member

Jul 30, 2011

4,674

2,343

194

Illinois

Dec 21, 2014

#2

• Dec 21, 2014

• #2

You will have to check it

 

C

CaptainJack_7

New Member

Dec 21, 2014

9

0

1

Dec 21, 2014

#3

• Dec 21, 2014

• #3

Should I do the Plato method or just spin it by hand? Anyone familiar with this set up though, just wandering if I'm on the border line?

 

addermk2

5 Year Member

Aug 25, 2009

308

87

49

Dec 21, 2014

#4

• Dec 21, 2014

• #4

Heads are too small. The car will barely make 320whp. PTV won't be an issue with the tiny valves that are in those heads. Also, running the amount of spring tension needed for the X cam on a 5/16" rocker bolt... not smart. You'll have a lot of valve train flex, and you CAN rip those bolts right out of the heads.

My advice... save for some good heads (190+cc) and get a custom cam.

 

Reactions: f8tlfiveo

C

CaptainJack_7

New Member

Dec 21, 2014

9

0

1

Dec 21, 2014

#5

• Dec 21, 2014

• #5

So any good head recommendations for a decent price? And could I get better Rocker bolts and not worry? The gt 40 heads have a mild Port job on them. If I port match the heads with my rpm air gap will it make decent power? I do understand with these heads I'll run out if breath around 5500 rpm. I really want to just get an ots cam any recommendations?

 

A5literMan

At least it is lumpy...

5 Year Member

Jul 30, 2011

4,674

2,343

194

Illinois

Dec 21, 2014

#6

• Dec 21, 2014

• #6

Look for some used trick flow or afr heads. If you are going to buy new go with the tfs 11r 190-205 or afr 185-205cc heads. For a ots cam I would look into comp cams,Anderson ford makes some descent grinds. It really depends on what your after for the combo. A custom cam is money well spent imo. They actually are only about 100$ over a ots grind. Don't skimp on the heads! That's where all the power is made.

 

C

CaptainJack_7

New Member

Dec 21, 2014

9

0

1

Dec 21, 2014

#7

• Dec 21, 2014

• #7

Are the 93 cobra r gt40 heads that horrible?

 

A5literMan

At least it is lumpy...

5 Year Member

Jul 30, 2011

4,674

2,343

194

Illinois

Dec 21, 2014

#8

• Dec 21, 2014

• #8

Short answer? Yes

Longer answer is if you want it to perform like a 302 put the gt40's on. If you want to get the most performance buy some heads. A head swap will net you anywhere from 50-100rwhp!!

 

addermk2

5 Year Member

Aug 25, 2009

308

87

49

Dec 21, 2014

#9

• Dec 21, 2014

• #9

A properly setup 347 with the right cam and the right heads, can easily make 500hp.

The parts that you have are such a hodge podge and Mish mosh, you'll honestly be lucky to break 300.

 

TOOLOW91

If you're the village idiot what's that make me?

20+ Year Stangneter

Nov 29, 1999

8,483

8,687

234

S.I.NY

Dec 21, 2014

#10

• Dec 21, 2014

• #10

These guys are spot on . You want to make power the motor needs to breathe ! And a decent OTS cam vs a Custom cam is prob like 80 bucks diff in price for something made to work for your exact combo .

 

mikestang63

SN Certified Technician

Aug 27, 2012

11,606

8,859

214

In the garage

Dec 21, 2014

#11

• Dec 21, 2014

• #11

Sell the heads , cam. and rockers. You are setting yourself up for major dissapointment with this setup.

Get a set of AFR 205 or TW 190 heads, an Ed Curtis cam and rockers matched to the heads.

 

f8tlfiveo

My wife likes my spool and blow-off valve.

Aug 8, 2007

1,585

102

64

Lancaster, PA

Dec 21, 2014

#12

• Dec 21, 2014

• #12

Gt40 heads are not horrible, they just make no sense mating them with a 347.. Fine for a budget build 302 looking for 260-270rwhp..

 

C

CaptainJack_7

New Member

Dec 21, 2014

9

0

1

Dec 21, 2014

#13

• Dec 21, 2014

• #13

Let me share with you all the rest of this build. So it is going in a 90 f150 5spd 4x4. Don't tell me to get a 351 because I'm not going to do it! From the ground up so far I've go a canton 8qt rear sump oil pan fr high volume high pressure pump. canton stud girdle and windage tray. Like I said above scat full forged rotating assembly with 10.5-1 compression I did the math right its not a guess. The cam and heads are up in the air now thanks to y'all lol. But the motor will be using an rpm air gap intake manifold with Holley 750 double pumper msd ignition 6al box. The exhaust is just going to be straight headers found a nice hooker set I'm going to run.

 

C

CaptainJack_7

New Member

Dec 21, 2014

9

0

1

Dec 22, 2014

#14

• Dec 22, 2014

• #14

so if i run 185cc AFRs with a decent cam I should be in the 450 Range?

 

A5literMan

At least it is lumpy...

5 Year Member

Jul 30, 2011

4,674

2,343

194

Illinois

Dec 22, 2014

#15

• Dec 22, 2014

• #15

CaptainJack_7 said:

so if i run 185cc AFRs with a decent cam I should be in the 450 Range?

Click to expand...

400-450 flywheel hp would be my guess. With it being a 4x4 build concentrate on making torque in the mid range. I still would run a custom cam also. Afr's are very good heads(I prefer trick flow. It not much difference) would be a very stout performer.

 

C

CaptainJack_7

New Member

Dec 21, 2014

9

0

1

Dec 22, 2014

#16

• Dec 22, 2014

• #16

Torque is important but I am building it for the mud so wheel speed is king. Im Hoping to safely turn at least 7500rpm is that realistic? and with 10.5-1 compression 93 or race gas? If figured up the total build price at around $8200 in motor alone speed costs $ lol. I could get a decent crate motor for that price but nothing in that price range would have everything i would want like the way I'm going to build it.

 

RangerJoe

I leave the horn on while driving

15 Year Member

Apr 26, 2010

2,560

1,146

184

Georgia

Dec 22, 2014

#17

• Dec 22, 2014

• #17

7500 rpms is not going to happen with the gt40's. And in a stock block, 7500rpms will make short work of your motor. Not saying the motor could not physically see 7500, but it will make no power and the block will be short lived. Also, at 7500, valve train is going to probably need to start changing to something more robust.

Joe

 

Reactions: A5literMan

A5literMan

At least it is lumpy...

5 Year Member

Jul 30, 2011

4,674

2,343

194

Illinois

Dec 22, 2014

#18

• Dec 22, 2014

• #18

Without a doubt you will have to change heads,cam,and have a superior valve train to turn 6500rpms not alone 7500! Block durability is a major concern above 6500. It will not hold up! Your "all forged" internals will be worthless in a stock block. If you're going to turn high speeds you'll need a solid roller cam and probably a shaft mount rocker system. You also will need a lot of ignition upgrades. With a high end head,studs,valvetrain,etc you're talking about 4000$ in parts to run anywhere close to that rpm level. You also need an aftermarket block which is about 2-2.5k. The engine you are describing is about 12k-15k not 8! A good stock block build still needs heads,cam,etc and can produce close to 500hp but will be limited to around 6500. Hyd roller cams tend to have valve float around 62-6500.

 

Boosted92LX

It's only an inch or two. What's the big deal?

15 Year Member

Dec 19, 2010

5,721

4,244

224

Dec 22, 2014

#19

• Dec 22, 2014

• #19

I'd have to find it, I've posted it here before, but it's on you tube. Horsepower tv did a bit on edelbrock rpm 2 top end packages with a carb on a 347. They took all parts out of a box, heads, cam, intake, and carb... put them on a 347 short block and dynoed right at 500/500. I was astounded.

 

Boosted92LX

It's only an inch or two. What's the big deal?

15 Year Member

Dec 19, 2010

5,721

4,244

224

Dec 22, 2014

#20

• Dec 22, 2014

• #20

http://www.stangtv.com/tech-stories/engine/edelbrocks-ford-crates-a-look-inside/ Not finding the video right away, albeit a bunch of ppl hating on it and calling bs on it... however I did find this write up on the edelbrock crates with specs. Seems you could find some of the top end parts used and get good results. I'm not by any means saying these heads are better than afr or tfs, but they can be found for next to nothing and perform well when coupled with the right stuff. I've got rpm 2 heads on my car I picked upfor 400 bucks. Just sayin.