roller block with gt40 heads.. valvetrain/airflow questions. - MustangForums.com



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Old 07-10-2013, 02:02 AM   #1
spearson712
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Default roller block with gt40 heads.. valvetrain/airflow questions.

I don't know much about these engines. I'm going to run a carb setup, but that doesn't matter so much right here. I'm only asking a few questions about the cam/lifter/pushrod/rocker setup(s) that I can use. My block, cam, lifters, and pushrods are all from a town car hydraulic roller 5.0, rockers came on the gt40 heads. I traded a set of wheels for this motor, which a friend put together but has not started since changing the heads.

1. Will this work as it is?

2. If I were to change the cam to a cheap performance flat tappet setup, would I need both pushrods and lifters, or just lifters for compatability? Does anyone know where I can get a better roller cam for cheap instead for this setup?

3. exactly how much air can the gt40 heads flow? I wanna buy the right parts for my carb setup. I don't care what everyones favorite brand is, I wanna know about the relationship between airflow ratings of carb, intake manifold, heads, headers, and cam lift/duration.
I understand how all the parts work and what's going on, I just wanna know how close I should keep the ratings on all my parts and what I can reasonably expect to get through the gt40s without machine work.

Links are helpful, as are answers or explanations. I want numbers and facts, stories are okay too. Will disregard opinions. Sorry for asking so many questions on one thread, please answer question(s) 1, 2, or 3.
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Old 07-10-2013, 07:01 AM   #2
mjr46
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1.yes
2. no don't try a flat tappet in a roller block, you'd have to change all valvetrain parts = not worth it for a roll back in performance. A "b" cam is what you need and cam change = spring change

3. your stuck on price = cheap so matching all the right stuff will cost, just throw the almighty b cam in , a rpm air gap intake and 600-650 carb and swap springs on heads for cam choice and be done with it. = easiest solution for you and your budget
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Old 07-10-2013, 07:48 AM   #3
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I don't think Ive ever even heard of any one wanting to down grade to a flat tappet on a roller block . The cost of a B cam will be cheaper in the long run.

By the way , you will get a lot of opinions . Don't disregard all of them. As most opinions here are formed from facts.
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Old 07-10-2013, 01:45 PM   #4
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Listen to Mjr, he's definitely steering you in the right direction. As for question #3, read read read, then read some more. These engines are one of the easiest to work on, you just need a little know-how. Google is your friend here, and a lot of us learned by trial & error, you'll learn pretty quick which opinions to rule out. Is this going in that RX-7?
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Old 07-10-2013, 03:40 PM   #5
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Quote:
Originally Posted by mjr46 View Post
1.yes
2. no don't try a flat tappet in a roller block, you'd have to change all valvetrain parts = not worth it for a roll back in performance. A "b" cam is what you need and cam change = spring change

3. your stuck on price = cheap so matching all the right stuff will cost, just throw the almighty b cam in , a rpm air gap intake and 600-650 carb and swap springs on heads for cam choice and be done with it. = easiest solution for you and your budget
Thank you, I figured I would have to find a roller cam, but only really found found flat tappet cams. I'll look into the b cam, and I was gonna get an rpm, performer, or similar dual plane manifold, possibly a larger (750?) cfm carb and run jets sized for a smaller carb, because I live at 7200' and want to make decent power.

What is the rpm range of the b cam with some good springs and possibly roller rockers on a gt40 head?
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Old 07-10-2013, 03:44 PM   #6
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Quote:
Originally Posted by Duncan_GT View Post
Listen to Mjr, he's definitely steering you in the right direction. As for question #3, read read read, then read some more. These engines are one of the easiest to work on, you just need a little know-how. Google is your friend here, and a lot of us learned by trial & error, you'll learn pretty quick which opinions to rule out. Is this going in that RX-7?
Yes, this is going in the rx7, running a t5 and my rear end is mazda 4.10 LSD, so I need to rev pretty high to make use of the 4.10 rear through the t5. You guys think the gt40 heads with good springs and a b cam could be usable for that?
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Old 07-10-2013, 03:58 PM   #7
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Ive seen what stock 5.0 can do in a rx7 , I almost bought one a couple years ago, but the guy wanted to much for it. Was a really quick car. And don't worry about having to rev high with the 4.10 gearing youll be red lining almost as fast as you can blink an eye in first with the t5. A 650 or 750 carb will make all the power the thing can take , in fact your probly gonna go through some tires till you get the suspension dial in.
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Old 07-10-2013, 04:34 PM   #8
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Originally Posted by dawson1112 View Post
Ive seen what stock 5.0 can do in a rx7 , I almost bought one a couple years ago, but the guy wanted to much for it. Was a really quick car. And don't worry about having to rev high with the 4.10 gearing youll be red lining almost as fast as you can blink an eye in first with the t5. A 650 or 750 carb will make all the power the thing can take , in fact your probly gonna go through some tires till you get the suspension dial in.
haha yeah it should be fun, and I am building the car with the intention of going through tires, but I want enough power to spin big grippy tires haha so I'm at least gonna be getting rid of the towncar hydro cam.. I just want to rev higher and make power around 4k-6200 so 2nd 3rd and 4rth are a bit more useful.
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Old 07-10-2013, 06:36 PM   #9
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tfs stage 1 cam and for springs for the gt-40 heads www.alexsparts.com
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Old 07-10-2013, 06:40 PM   #10
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