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hi-po heads

2169 Views 21 Replies 10 Participants Last post by  opnwide
I'm seriously thinking of having the high performance heads installed. I've done the exhaust thing and would like more power while staying NA. Anyone done this? How did it affect power (dyno and seat of pants) and drivability? I also figured I'd go with the aluminum flywheel; does this adversely affect the idle?
Thoughts and comments appreciated.
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I have the alum flywheel. Best track mod I ever did. It doesn't affect the idle at all, but you will need to give it a touch more gas to get off the line. This is because you don't have as much rotational mass in the driveline to move you forward, so you need a little more rpms to make up for it. Nothing major though.

I'm not sure what heads per se would net you. If you want more power, you may want to go with a set of t&d 1.7 ratio rockers first. I believe these are good for another 25 or so horses. Heads would likely be the step after that but I'm no expert.
I went on BTR's website and they have a dyno chart on a viper that had the usual exhaust mods plus heads and they got more than 500 hp (520 or so I think) at rear wheels and even greater torque. Looked like about 70 more hp over a comparable car without the modified heads...not bad I thought. Don't know if it adversely affects daily drivability though.
It shouldn't. The only thing that usually affects driveability is an agressive cam change, or a turbo or s/c that comes on like a hammer.
There seems to be a variety of vendors that can do a good job with heads/cam packages. No one supplier stands out. There are a gathering of customers that rave about their respective results, and very few that report disappointments.

I have been thinking a long time about this mod as well. I live far away from any vendor and would prefer to do the install myself. To take advantage of the heads, a cam change would benefit, but it seems to jack up the price quite a bit (if labor and down time is considered). It is hard to decide whether or not a SC is in the future as this would influence compression. I wonder if a group purchase is realistic?
S/C vs heads/cam seems to be the fork in the road. Seems like you need to decide if you want to keep the car NA or not at the outset. Since I track the car (road race) I don't need the kind of power that S/C provides and in fact don't need ANY more power (i do need better suspension setup, brakes and seat time/lessons). But, I've fallen under the spell of the viper and want some of both. So, I'll stay NA and get some more reasonable power at a reasonable price so I have some money left over for the other necessary mods. I also do not live on either coast so I'm not near any major tuner which makes it more difficult; so I'll keep it as simple as possible. I'll probably work toward increased flow without changing compression so the options are kept open. I also have to do the lighter flywheel so it'll spool up quicker and have yet to put in the 1.7 rockers, all in the plan.
I am leaning toward NA and mild bump in compression. I figure the 1.7's may as well go along with the package.

If anyone has dyno or track times with just heads/headers/exhaust/k&n, etc, please post the vendor and some specs (valves, rockers, stage, etc) as well as model yr. I'm especially interested in creampuff yrs.
I see you live in Illinois.

All the major tuners offer packages that are capable of turning 500-600rwhp from cam, heads and exhaust and a retune - most use a piggy back to the ECU like the Roe software so they can recalibrate air/fuel etc.

If these packages are outside your budget - there is another option that will be cheaper but they are not Viper specialists.

Hughes Engines Inc are near Washington Illinois - Dave Hughes is a guru on heads and engine building. He specialises in Mopar and will build you anything you want. A lot of what I know was taught to me by that man - he is one of the best. If you need bang for buck but still want top workmanship - I'd call him. At that level of skill - he doesn't need to have done Vipers before to do a good job on the heads - he designs his own heads!!! He can also build a tight quench engine for you - much less prone to detonation, more compression, more power.

Cam wise - stick to the 98GTS stock cam - it works well - unless you are willing to go to a solid roller - THEN you'll make some power - but you'll also need the computer upgrade to retune and you'll need regular valve lash maintenance and solid roller lifters with beefier springs. if I recall - if not run a search on that name.
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I live a few hours from Woodhouse and know he knows racing. Is it safe to assume that they can do the engine work that Cornholio and I are talking about? I was planning to go there sometime later this fall for some suspension work and other tidbits anyway. I have a '97 GTS. I'm not clear on whether bigger valves are beneficial or not for someone who wants to stay NA vs just porting, polishing, etc. I don't want to lose too much low end torque but am willing to sacrifice some if the overall product will benefit me for road racing. I'm thinking that going with 3:55 gears would help in this regard. Thanks for your thoughts.
I'm sorry - but I know nothing about Woodhouse re engine work - but I'm sure others on the forum do.

As for head work - bigger valves and porting does not need to drop torque at all - that would be a bad job!! A good porter like Dave Hughes and I'm sure the good Viper Tuners (who possibly sub out anyway) will go for improving air velocity not just more port cc. In other words - a good package will add power and torque from 2500rpm up - under that who cares - it's an 8 litre engine it's never going to be gutless off idle.

The .588" lift cam with good heads that breathe over 300cfm at good velocity and good exhaust with 3.55 gears will really snap your head back when the tires bite... :thumb:
I don't want to steal the thread but I want some gtsr heads. Where do I find them and how much? Also a good set of heads will give you alot more power any way you go supercharged, turbos or na.
Thanks for the headsup on Hughes. I'm probably going to buy a set of heads from Greg Good (TNT), J Heffner (if I don't win a set), or other well regarded vendor and ask a Viper tech to do the install. I would like to do the install myself, but I have not even done a set of rockers yet. Murphy's law would probably have me end up sending the engine to Arrow for a rebuild for forgetting some special must have fastener or shim. I just need to decide how much reliability and power increase should cost me.
My business partner has a new SL55 AMG that I have to keep ahead of. My Vette friend has 405 RWHP after some head and cam work. When will the power wars ever end?
I got my heads from Jeff Morys who works in the DCX flow lab. He's actually the one that supplies to West Coast Vipers and some other tuners. I got 50cfm more flow and 60 extra RWHP. I added T&D at the same time as the heads and that netted me another 20RHWP. I dyno'd before and after the install to correlate the mods. So for around $4000 I gained 80RWHP.
I think that is a good deal, an extra 50cfm is a good gain and will support more cam, more compression, boost - whatever you want to do.
GTSnake, do you have a tel number or web address for Jeff Mory?
Thanks for the info.
Now that's what I'm looking for! /images/graemlins/headbang.gif
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His work number is (248)576-9204. Best time to call is between 8-2 EST.

Sorry for the delay responding....I don't get to this site as much as I should.

Our Stage II Cylinder heads are flowing in excess of 300 cfm (our website data is being updated as it is over a year old) and we have several Vipers making in excess of 530 RWHP (before nitrous or s/c but set up for those applications) without drivability issues. I also believe our prices to be the greatest value in the industry in that we offer a warranty and a performance guarantee on all of our cylinder head work....included in the price.

Keep in mind that cylinder head and cam choice are based upon user application. Most of our users are planning on having some type of forced air induction installed at some point in the future(nitrous, s/c, tt). What this boils down to is designing the combustion chamber, static compression, intake and exhaust port and valve shape for these applications. As an example, our average 520+ rwhp Naturally aspirated Viper engine makes well over 750 RWHP and well over 900 RW Torque with the addition of a simple and cost efficeint nitrous system. I refer to this well thought out and proven combination as "Total Horsepower" and you can read about this on my website.

Your other choice is a higher compression engine with a larger cam that exibits maybe 30 more Naturally Aspirated RWHP but has poor drivability, higher maintenance to the valvetrain, more frequent need to replace parts, and I have even seen some that were so lacking in vacuum from poor cam design that they could hardly idle and the airconditioning system could not be engaged.

In summary, there are lots of choices these days for modifications for your Viper and I am happy about it keeps lowering the price for the end user. I sell products based upon actual proven performance. I invite you to compare our 770 RWHP nitrous assisted Vipers to those with over 100 hp more, that for some reason can't prove themselves on the pavement. It's all about the combination that makes our engines(SIMPLE AIR PUMPS)work. Our combinations, whether Naturally aspirated or supplemented by Nitrous or other forms of forced air have proven themselves over and over again. Our cylinder head and camshaft profiles play an intricate role in our......and possibly YOUR success.

Best of luck in your search.

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i see you have proven your heads make good power for nitrous. anyone using your heads on a blown application?
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