Heads Cam Journey Has Begun

**Sniper** · 02-20-2023

On the way to get a little rowdy!

IMG_5461.jpg

**Old School** · 02-20-2023

Rowdy is a good thing

**Space Truckin** · 02-20-2023

Who is doing the work?

**Sniper** · 02-20-2023

JMB Performance

**StrokerAce** · 02-20-2023

Specs of cam?

**AAA96** · 02-21-2023

Interested in this thread. Post as much as you can as you go along please!

**Mikey** · 02-21-2023

I'm jealous

**Sniper** · 02-21-2023

Spec of cam: it is aggressive
Not much to post as it's getting work on about 4 hours away from me so I will not have anything until I get the car back.

Car has arrived at the shop.

IMG_5463.jpg

**Fulltilt** · 02-21-2023

Dumb question but..............I know some companies use completely different heads as part of the heads/cam package. If so, do you keep your oem heads and can the car be turned back to stock?

**Sniper** · 02-21-2023

The shop is doing this: CNC port, valve job, and surface cylinder heads.
So, they are using my heads.

**bullitt2735** · 02-21-2023

nice! what are the goals with the car? drag racing, road racing, street?

**Sniper** · 02-21-2023

Just for street

**StrokerAce** · 02-21-2023

Originally Posted by Sniper

Spec of cam: it is aggressive
Not much to post as it's getting work on about 4 hours away from me so I will not have anything until I get the car back.

Car has arrived at the shop.

Aggressive is a relative term. Just curious to some general specs. Some guys think a 250/260 duration cam is aggressive and others think it's too tame. I would imagine the cubic inches eats up the larger cam pretty easily making it more streetable.

Your car looks good.

**Aevus** · 02-21-2023

aggressive is north of 20 deg valve overlap, more or less.

So 250/260 with say 114 LSA : 255-228 = 27 deg.

**Lawineer** · 02-22-2023

Originally Posted by StrokerAce

Aggressive is a relative term. Just curious to some general specs. Some guys think a 250/260 duration cam is aggressive and others think it's too tame. I would imagine the cubic inches eats up the larger cam pretty easily making it more streetable.

Your car looks good.

The rough idle is generally attributed to overlap, more than duration. When the intake and exhaust are both open, as you might expect, you're not going to build up much pressure. At low RPM and high intake restriction (closed throttle body) you're barely getting enough air in there to support combustion as it is. Letting a bunch of the air leave through the exhaust stroke makes it worse.

And, ironically, StrokerAce, it's more stroke that eats up cam, but yeah, it's all relative. I never really thought about it, but I'm not really sure why. I can't intuitively think of an explanation for why stroke makes the idles smoother. Obviously has something to do with piston velocity.

**Jack B** · 02-22-2023

I did the Prefix HC, then, later added the 9L. The idle did not change.

The car will be up for sale this spring.

Originally Posted by Lawineer
The car is ;468461

The rough idle is generally attributed to overlap, more than duration. When the intake and exhaust are both open, as you might expect, you're not going to build up much pressure. At low RPM and high intake restriction (closed throttle body) you're barely getting enough air in there to support combustion as it is. Letting a bunch of the air leave through the exhaust stroke makes it worse.

And, ironically, StrokerAce, it's more stroke that eats up cam, but yeah, it's all relative. I never really thought about it, but I'm not really sure why. I can't intuitively think of an explanation for why stroke makes the idles smoother. Obviously has something to do with piston velocity.

**13COBRA** · 02-22-2023

Vroom vroom!

**StrokerAce** · 02-22-2023

Originally Posted by Aevus

aggressive is north of 20 deg valve overlap, more or less.

So 250/260 with say 114 LSA : 255-228 = 27 deg.

Makes sense. My last had only a 14 split and has a good lope but nothing major. I'd say it's relatively tame compared to the other builds I researched. If it wasn't a street car I'd have gone a slightly different route.

Originally Posted by Lawineer

The rough idle is generally attributed to overlap, more than duration. When the intake and exhaust are both open, as you might expect, you're not going to build up much pressure. At low RPM and high intake restriction (closed throttle body) you're barely getting enough air in there to support combustion as it is. Letting a bunch of the air leave through the exhaust stroke makes it worse.

And, ironically, StrokerAce, it's more stroke that eats up cam, but yeah, it's all relative. I never really thought about it, but I'm not really sure why. I can't intuitively think of an explanation for why stroke makes the idles smoother. Obviously has something to do with piston velocity.

Agreed on all points but usually you don't see as much overlap on tame cams and goes hand in hand with the cams with more duration, with variation of course.

My experience has been primarily with LS and SBC BBC stuff but I'm not well versed on what these big V10's like and what makes the best power. Of course power at different RPM's need different specs. So for a streetcar like the OP's I wasn't sure how wild the specs would be, if wild at all.

Rarely do you see a long stroke small bore V8 engine built for performance. There are some long stroke LS3 bore engines out there but they have issues with rocking at the bottom. That's why I went larger bore and kept a 4" stroke on my last build.

Do the stock Gen V valvetrain do well with more aggressive camshafts? How far can you go without modifying the heads and intake?

**Aevus** · 02-22-2023

''Agressive cam'' = there's also the question of the lift, but I don't know any stock or ported Viper heads that benefits from a lift of more than 0.630'' and even that it's pushing it...

Too much lift is counter productive, not to mention the strain of the valvetrain..

**Aevus** · 02-22-2023

Do the stock Gen V valvetrain do well with more aggressive camshafts? How far can you go without modifying the heads and intake?

Gen 3-4-5 I think all greatly benefits from lighter valvetrain components and conical springs, especially of you want to reach 6,500-ish rpm and more

The best upgrades are:

- 3/8 pushrods (or thicker/bigger)
- Conical springs w/ Ti retainers and locks
- Hollow SS or Ti valves (very difficult to get for the Viper)
- Shaft mount rocker
- Hyd lifters with tru-arc

And of course the camshaft must fit the air flow (in and out) otherwise you're losing time and money

It's either that or you stay in the moderate +/- 10 deg valve overlap zone...

**Aevus** · 02-22-2023

So for a streetcar like the OP's I wasn't sure how wild the specs would be, if wild at all.

Mine is modified as a track car but will be used 95% on the street and I went with 24 deg overlap (248/256 114LSA) which is pretty much the max I could go anyway while having enough valve clearance and 11:1 compression, with the pistons I wanted to use.

Dyno tune mandatory. At the moment I can't drive the car at all. Truth to be told, I might've been too far...

Bottomline, be careful with ''agressive cam'' on a Dodge Viper. Ain't that easy.