Viper Head Mods

JeepTherapy

JeepTherapy

New member
Joined
Dec 26, 2005
Messages
533
Age
64
Location
Negaunee
Since I bought my viper I have been wanting to add triple pipes to it. When I do it I am more concerned about reliability than bleeding edge performance. With that in mind I went with the bender pipes that run at a bit lower RPM. I have a rear heat exchanger and plan to add an opticool gasket. I was also thinking that I needed to add a modded head.

It is my understanding with the DCS the head needs to be modded to keep it functional. Can someone tell me what that modification entails? Does CPR modify the Viper heads the same way that Bender modifies the Viper heads? Should I just save a few extra coins and buy an aftermarket head?

Is there any information web sites ect. that anyone can point me to that I can read up on head modifications?

Thanks in advance,
Chris
 

I kind of expected more responces to this. When I searched pipes many said that a head mod was needed also.
 
getting the benders just cause they run at a lower rpm, doesnt mean they are better or safer (pipe design and timing are viper problems). there are alot of posts on the subject. and alot of varying opinions. you can mod your head, or get an aftermarket unit(s), or opt for srx heads. you are looking for better dome design and cooling capacity. extra heat exhanger, and better base gasket and head gasket will help greatly too. good luck in your quest. it is worth it once you get it all together. pipes, cooling, jetting and clutching. vipers run very well in the right hands. ski
 
K I was pondering this at work, is it REALLY NEEDED to have the stock Viper head cut when running pipes. Will it still be a realible set up wit the stock head running on top a optic-cool head gasket? Just curious even though I'm running a aftermarket head. Lets hear the pros and cons of keeping the stock head on a Piped Vip.
 
Everything I know about modding two strokes will fit in the palm of my hand. I have been trying to read everything I can on here and elsewhere about the viper. Finding there isn't much elsewhere. Thanks ski, that is kind of what I was looking for.

I have learned thus far that for sure I either need to use an opticool, or an aftermarket head that addresses the cooling port size. I will do some searching on SRX heads. I didn't know that was an option.

I have also come to the conclusion that my odds of getting an viper with DCS to work with pipes is pretty slim. From what I have seen (read on hear) the DCS is kind of a luck of the draw thing. Some work others need work. Bender tells me they modd the head to address the DCS. At least that is the way I understood it. I very well may have misunderstood.

What I would like to know now, What is different between a bender modded head, a cpr modded head and aftermarket heads. There is a head available in the for sale section that has been cpr modded. My question is more what has cpr done different with the head for their pipse that peak at 9100 vs the what bender would do for their pipes that peak at 8750. I do realize the aftermarket heads come in varying sizes (cc) to adjust compression. I think I got somewhere that the viper starts with two domes of one size and one dome of another. That sound right? 22 and 23 CCs are in my mind for some reason.

I would think that a head of lesser CCs will raise the compression to the point of requiring much higher octane fuel. What are the right size/compression ratio to run on medium to good quality pump gas for a mostly trail sled?
 
hopefully mr viper and others will see this and chime in for some more help. the head mods done by all shops are to open the tighter squish domes on the viper to lower compression and make them equal on all cylinders.

the opticool gasket is an option but not the be all, end all, fix all problems. can you run pipes without the head mod or aftermarket heads? yes, will it perform flawless and and peak performance and reliability??? only time will tell.

i like to error to the side of cuation. for me i run srx base gasket, megapower heads, br9ecs plugs, and premium fuel. other than the add on heads, this is spec stuff for srx's.

vipers have tighter cc volume domes than an srx but doesnt require premium fuel per the manual (that doesnt make sense to me so i run premium) the ecs plug is better at dissapating heat and required on the srx, again the viper has these tighter cc chambers, why arent they recomended for the viper?

this year i got tired of worrying about it all, had don rework my cylinders and pistons including adding oring grooves so i can run orings v.s a head gasket (like the srx).

the main thing is to listen to the guys the run and know these vipers and follow their guidelines. if you listen then do your own thing, you are just fighting yourself dont over think the process.

srxspec, and mr viper700, betheviper to name a few, know these motors. the head(s) mod, and using an srx base gasket, and carb brass. comes right from them. if you follow the precautions, you can make the sled last and perform at it's peak for years to come. ski
 
Last edited:
The Viper PTO chamber size is 24.55 - 24.85. Center and Mag are 21.35 -21.65. What they do when modding the head is lower the compression ratio on the center and mag. By machining the center and mag chambers to the 24 cc (same as PTO).
The RPM difference between the the different pipe brands, is due to the design of that pipe. The head mod has very little to no difference in operating RPM per say.
If you can always run good premuim fuel, the head mod may not be required. However it's a very good idea to run a rear cooler, and the head gasket cant hurt either.
 
skidooboy said:
i like to error to the side of cuation....

the main thing is to listen to the guys the run and know these vipers and follow their guidelines. if you listen then do your own thing, you are just fighting yourself dont over think the process...
Click to expand...


I agree to error on the side of caution. But right now I have gotten to the point of fear. Why are there so many that have engine melt downs. Are they doing something wrong?

I read a searched out post today about someone running stock jetting with pipes... I would have thought that would last about 5 min before meltdown.

I did a search today on the SRX heads. I didn't really find much on that either.

I think for me the best thing to do for peace of mind is just let Bender set it up for me. I already have the bender pipes and plan to use them. Like Ski said, listen to what the guys that know say. Bender tells me I need their head mods. If I run their modded head then they will also know my configuration well enough to recomend proper jetting and clutching.

I do kind of understand pipe design from my nitro two stroke RC cars. But I don't mind taking a chance with a $200 RC motor...

http://www.m-performance.com/Sidor/dyno_yamaha.htm
What I got out of that is the Bender pipes seem to perform a little better at lower RPMs making more torque earlier on. AAEN has a flatter torque curve but doesn't make their big power till the motor is wound out pretty good. The SLP pipes have a bit of a midrange flat spot but make the highest HP number. Am I misunderstanding something there or am I correct in thinking the bender pipes are going to feel a little stronger from low to midrange?
 
I agree to error on the side of caution. But right now I have gotten to the point of fear. Why are there so many that have engine melt downs. Are they doing something wrong?

The reason for this is real easy, some are trying to get the most they can out of there setup and go just a tad to far. The others, don't take the time to research it enough. Maxdlx JMO
 
it all boils down to one problem, too much timing. plain and simple. if the pipe manufacturers sold the pipes with a cdi box to make them run safe, all this conversation would never exsisted.

from what i have seen myself and read, i would run slp pipes, with the timing retarded 4deg, run it at 8800, cut the head to 24cc straight accross, leave the base gasket the same and install a rear cooler. your gas milage will still be crap but the sled will be safe er ish.
 
I started off by reading post #1 here, the thing I think the original poster may have a clouded vision is on the operating rpm versus the relability factor.
Just because your running the engine at 8700 rpm instead of say 9100rpm isnt going to affect the reliability of it nor the gas mileage I might add.

The reason that the "other " pipes are run at 89-9100rpm is from the cdi box as others have mentioned, it just gets into a range of the box where the timing isnt as high and this reduces the chances of detonation. The viper has a design flaw in the one peice mono head and it doesnt cool all the cylinders equally, the mag cylinder runs the hottest in them. The compression was staggered to help the average consumer run straight jetting across the carbs, yamaha thought that was a large conveinace...lol, instead of always stagger jetting them richer in the pto usually from the added heat of the clutch. Yamaha actually used to run a richer main in the mag side but changed that to the PTO.

Bender pipes actaully have the worst reputation for burn downs due to the fact your right in the meat of the timing curve(lots of advance) at operating rpm along with a margianl cooling head and the piston gets melted as a end result, thats why they came out with the rear cooler, and opti-cool head gasket. The head mod that everyone likes to do is to lower the center and mag cylinders down to the same as the PTO, this LOWERS the compression in the engine and reduces heat...again aids in reducing detonation.

I like to either use srx heads on a viper or better yet a set of meag power heads that hold even more water then a srx head does.
 
Don, just wondering but I was told that the PTO cylinder runs hotter by a Moderator from this site, whats the deal on that. I can see why the mag side would run hotter cause the pipes and silencer are right next to it. And 1 question I have is it necessary to run 24cc straight across, when running srx base gasket, srx rear cooler, opticool head gasket, and peak head with 22cc domes straight across? I know the jetting will need to be starggered but which ones will need a richer jetting? But Mega Power heads will be added in the near future cause I already have them lined up.
 
In a viper with stock head the mag side runs the hottest because of the water flow from the head design. The mag has more compression also then the pto does, compression makes heat faster. The reason yamaha did the lower compression on the pto cylinder was to enable the use of straight jetting across the carbs and eliminate the stagger jetting, so by lowering the compression it already cooled off the pto cylinder.

with aftermarket heads you can run the straight higher compression across the engine, you may need to stagger jet it slightly if your pto shows signs of being leaner then the other 2, you may be fine straight across the cylinders, its gonna depend on how good of cooling the heads you add give you.

again, with the head mod that people do this lowers the compression on the other 2 to match the pto, this in turn takes away heat which added with timing leads to detonation, its just a another way to help the engine live a little bit better without burn down risk.
 
Last edited:
I have Benders with the stock head on it still with the opti cool gasket and rear heat exchanger. 1500 miles on them so far with no issues. I will complete the head mod when I get a chance. So far it's been solid.
 
I have a 2004 so I have the DCS to contend with. I look at it as a good thing. Forces me to do it right the first time. I spoke with Bender an additional time. They tell me the differance in what they do to the head and what CPR does to the head is significant enough that the CPR modded head will not work with their pipes and DCS. I don't know if they are blowin smoke up my a$$ or if they do something special to the head. I can't afford to do the testing required to find out.

So for my application I have decided to follow the Bender instructions to the letter. I have a set of 165/55 jets and pilots. They (Bender) told me to run the next size up for my application. They also recomended premium pump gas. Again, going to follow their recomendations to the letter.

Now I have one further question; if I have modded my head to lower compression (24cc's across the board) why is it that I now have to step up to run premium? Is it the exhaust pulse improvement that effectively highers the engines compression when running?
 
mrviper700 said:
I started off by reading post #1 here, the thing I think the original poster may have a clouded vision is on the operating rpm versus the relability factor.
Just because your running the engine at 8700 rpm instead of say 9100rpm isnt going to affect the reliability of it nor the gas mileage I might add.

The reason that the "other " pipes are run at 89-9100rpm is from the cdi box as others have mentioned, it just gets into a range of the box where the timing isnt as high and this reduces the chances of detonation. The viper has a design flaw in the one peice mono head and it doesnt cool all the cylinders equally, the mag cylinder runs the hottest in them. The compression was staggered to help the average consumer run straight jetting across the carbs, yamaha thought that was a large conveinace...lol, instead of always stagger jetting them richer in the pto usually from the added heat of the clutch. Yamaha actually used to run a richer main in the mag side but changed that to the PTO.

Bender pipes actaully have the worst reputation for burn downs due to the fact your right in the meat of the timing curve(lots of advance) at operating rpm along with a margianl cooling head and the piston gets melted as a end result, thats why they came out with the rear cooler, and opti-cool head gasket. The head mod that everyone likes to do is to lower the center and mag cylinders down to the same as the PTO, this LOWERS the compression in the engine and reduces heat...again aids in reducing detonation.

I like to either use srx heads on a viper or better yet a set of meag power heads that hold even more water then a srx head does.
Click to expand...

What do i have to do to get SRX heads to fit on my -03 Viper ?
 
5000 hard miles on slp stock head no fancy gasket,no dented pipe or hood shim to make them fit,also am able to hold it to the bar for way more than a qtr mile.very happy w/my choice and would recomend them.
 
I'm running the hauck loud pipes and had a meltdown on the PTO side, both other cylinders were fine, checked the mains and they were all 151.3 across.... no head mod, no head gasket, and no rear heat exchanger.

I'm planning to get the head gasket and rear heat exchanger, also richen up the PTO cyl.

Also i was running regular fuel (which was a mistake) and NGK BR9ES all across.

Any suggestions rather than the obvious mods to make it run cooler.

And any explanations as to why this might have happened if PTO is supposed to be the "safe" cylinder.
 
You must log in or register to reply here.


Back
Top