Playing with cam timing

[glhs875]

I was going to suggest "work on Engine, play with self...
Better not

Thanks
Randy

PS: This from Gary, gold as usual:

"I discovered the wonders of cam centerlining and the effects of rolling the timing from as low as 106 to 114. One would give me buckets of torque that would blow the tires away.. and the other end of the range would make the car soggy down low but have a hell of a top end charge. The trick is to find that sweet spot with just enough torque to keep the tires from getting blown away on the bottom end of the track while having enough juice for the top end charge."

This holds true if a person is not willing to make changes to the combo like final drive ratio and or converter stall speed if an auto. Or play around with the compression ratio, etc.

[glhs875]

The gist of what i posted in my van thread was that i was limited to ~230hp by the tiny inducer on the stock mitsu turbo, and i retarded the cam 6 degrees and still was able to make 230hp. The only reason i did it was to limit midrange torque (typically the highest cylinder pressures it would see) because i was trying to tiptoe around my tbi pistons at first. In the end the cam retard slowed my spool up, but my turbo is so small it still spools early, full boost by ~2400. On the top end i was able to move my powerband enough that i go to the 6200 limiter on a completely stock top end whereas before i NEVER EVER hit the rev limiter in a 2.5 because it didn't feel like it made any power up there. It was a pretty dramatic change according to the seat of the pants. I didn't make any more power (limited by the turbo) but it changed the way it drove and where i shifted it.

I always wanted to experiment with increasing the compression ratio enough after retarding a cam so that the cranking psi would at least equal the factory cranking psi. I have a thinner .027 headgasket just for this purpose. Raising the compression ratio may bring back some or all of the lost low end power and also help with the turbo spool up and also increase the upper RPM HP even more!

[Vigo]

I always wanted to experiment with increasing the compression ratio enough after retarding a cam so that the cranking psi would at least equal the factory cranking psi. I have a thinner .027 headgasket just for this purpose. Raising the compression ratio may bring back some or all of the lost low end power and also help with the turbo spool up and also increase the upper RPM HP even more!

I'm going to experiment with this myself. I've been planning to build a 10:1 G-head engine with carb pistons, a big cam, and an upgraded vnt turbo to see if i can build something that makes at LEAST stock power down low but keeps working up to ~7500+. I have everything but the cam and valvetrain (decisions..) but haven't done any of the work!

[glhs875]

I'm going to experiment with this myself. I've been planning to build a 10:1 G-head engine with carb pistons, a big cam, and an upgraded vnt turbo to see if i can build something that makes at LEAST stock power down low but keeps working up to ~7500+. I have everything but the cam and valvetrain (decisions..) but haven't done any of the work!

I like where you are headed! I was having problems with rocker arms being spit out above 7500 rpm (w/ Taft S3 cam)! The cause could of been the valve springs. Anyhow I was looking into using the mousetrap spring setup from a 2.3/2.0 Ford engine to help with the problem. Warren Stramer got with me asking about any problems I might be having with increased RPM's. And he went with a setup that he designed to help keep the rockers planted on the lifter. Maybe check his idea out!

[OmniLuvr]

I'm going to experiment with this myself. I've been planning to build a 10:1 G-head engine with carb pistons

I ended up using t3 pistons, they worked awesome with stock g-head and my block decked 15 thou. Not sure how close the valve clearance might get if there was excessive machining on the head gasket surface or large cam... but I'm bout to try both shortly...

[GLHS60]

This holds true if a person is not willing to make changes to the combo like final drive ratio and or converter stall speed if an auto. Or play around with the compression ratio, etc.

I don't understand your point. Gary explained how he fine tuned his cam timing at the track with the final drive, converter and compression he had at that point in time. He always gives excellent, precise, direct advice.

Thanks
Randy

[mopar-tech]

I don't understand your point. Gary explained how he fine tuned his cam timing at the track with the final drive, converter and compression he had at that point in time. He always gives excellent, precise, direct advice.

Thanks
Randy

Thank you Randy- I have to point out that I did play with some factors like compression (minor) and final drive ratios. Low ET was always the goal and lowering the short time drove most of the changes along with making more power in general.

Balancing the chassis = equalizing the traction to the front wheels
Changing the gear ratio in the final drive = reduce wheel spin/torque multiplication
Removing mass = faster short time and less parts breakage

etc, etc.

[glhs875]

I don't understand your point. Gary explained how he fine tuned his cam timing at the track with the final drive, converter and compression he had at that point in time. He always gives excellent, precise, direct advice.

Thanks
Randy

If a change is made to an engine combo and lets say the change makes more power up top but loses some down low. A person can then play with other things (stall speed,final drive,etc.) to compensate for the loss in lower RPM power but will take advantage of the top end power increase. Not doubting Gary's abilities, but what works for him may not work for someone else. If molds are not broken how can progress be made. I know I most likely get frowned upon by many for not always agreeing with what Gary says or do, but that is okay with me!

[MILKCARTON]

∆∆∆ what this guy said

[Vigo]

I ended up using t3 pistons, they worked awesome with stock g-head and my block decked 15 thou. Not sure how close the valve clearance might get if there was excessive machining on the head gasket surface or large cam... but I'm bout to try both shortly...

I just mounted up some t3 pistons on LW rods for my spirit but it is 782 head. They are still out so i can compare them to the carb pistons i have as far as compression height. Anyone know the total 'dish/valve relief' volume of a t3 piston? As far as valve clearance i don't care about freewheeling if the belt skips. In all this time i can only think of one time i had a belt skip or break out of all the shitty cars and builds ive done, and i cant remember the last time i bought a new 8v timing belt! lol

[GLHS60]

If a change is made to an engine combo and lets say the change makes more power up top but loses some down low. A person can then play with other things (stall speed,final drive,etc.) to compensate for the loss in lower RPM power but will take advantage of the top end power increase. Not doubting Gary's abilities, but what works for him may not work for someone else. If molds are not broken how can progress be made. I know I most likely get frowned upon by many for not always agreeing with what Gary says or do, but that is okay with me!

I don't want to sound disrespectful but your not making any sense in criticizing Gary for fine tuning his combination, whatever it might be, at the track.

Anyone who is consistent enough and smart enough to fine tune cam timing at the track is very talented.

I'm sure, without even asking Gary, that if he changes a torque converter, or gearing or anything else, he considers where his cam is at.

I cant understand the criticism towards someone who shares his success.

I don't mean to speak for Gary but I appreciate and trust what he says.

Actually, I think this trend of retarding the cam is breaking the mold, and here is Gary and Vigo confirming my theory to some extent with their testing.

I'm not frowning on any of your accomplishments, I just don't understand the criticizing.

However, if you have a good reason to not fine tune cam timing then I will have to eat my words!!

Thanks
Randy

[mopar-tech]

If a change is made to an engine combo and lets say the change makes more power up top but loses some down low. A person can then play with other things (stall speed,final drive,etc.) to compensate for the loss in lower RPM power but will take advantage of the top end power increase. Not doubting Gary's abilities, but what works for him may not work for someone else. If molds are not broken how can progress be made. I know I most likely get frowned upon by many for not always agreeing with what Gary says or do, but that is okay with me!

What I get a chuckle about is people assume why I did something and have lengthy discussions without asking me why or for more data. I take no offense, questions are always good, more data is always good assuming the input is sound.

Feel free to play with cam timing; as I stated with the GTX it was a valuable tuning aid for street racing and with the Reliant a valuable for for maximizing elapsed time. Different venues that have their own unique requirements IMHO.

I was also clear that there are 2 schools of thought regarding engine tuning- Tune for peak power and seal the bay and tune the chassis or if you can't tune the chassis very much then tune the engine to the track. I'm for which ever gets you the lowest E.T.

[glhs875]

I don't want to sound disrespectful but your not making any sense in criticizing Gary for fine tuning his combination, whatever it might be, at the track.

Anyone who is consistent enough and smart enough to fine tune cam timing at the track is very talented.

I'm sure, without even asking Gary, that if he changes a torque converter, or gearing or anything else, he considers where his cam is at.

I cant understand the criticism towards someone who shares his success.

I don't mean to speak for Gary but I appreciate and trust what he says.

Actually, I think this trend of retarding the cam is breaking the mold, and here is Gary and Vigo confirming my theory to some extent with their testing.

I'm not frowning on any of your accomplishments, I just don't understand the criticizing.

However, if you have a good reason to not fine tune cam timing then I will have to eat my words!!

Thanks
Randy

Never did I say I was against fine tuning cam timing! I have been changing/playing with cam timing since at least the early 1980's! I am not new at this! BTW I was the one who brought up cam timing in another recent thread. And I don't feel that I am criticizing Gary! Things that I have posted goes for myself as well! And I agree Gary has done a lot for our hobby and never said that he didn't! But that does not make me a blind follower of Gary! I like to question things that others may have done with MY OWN experiences! Personally I was wondering why you went off the deep end! I feel I made a mistake on commenting on your post in the first place! Normally If I disagree with a post I tend to just let it go! I need to keep doing that! And the comment that I made about your post about Gary's thoughts on cam timing was not directed at just Gary! It was for anyone! I am getting real close to kissing Turbo-Mopar goodbye!

[glhs875]

I don't want to sound disrespectful but your not making any sense in criticizing Gary for fine tuning his combination, whatever it might be, at the track.

Anyone who is consistent enough and smart enough to fine tune cam timing at the track is very talented.

I'm sure, without even asking Gary, that if he changes a torque converter, or gearing or anything else, he considers where his cam is at.

I cant understand the criticism towards someone who shares his success.

I don't mean to speak for Gary but I appreciate and trust what he says.

Actually, I think this trend of retarding the cam is breaking the mold, and here is Gary and Vigo confirming my theory to some extent with their testing.

I'm not frowning on any of your accomplishments, I just don't understand the criticizing.

However, if you have a good reason to not fine tune cam timing then I will have to eat my words!!

Thanks
Randy

I wanted to add that the whole purpose of my post was not to be disrespectful to anyone or even disagree with anyone but only to maybe make others aware that there are things a person can do to their combo to work with or to compensate for whatever effect the cam timing changes may have to engine power output. I feel as though you have added MANY WORDS to my post that I didn't even say or even mean!

[Gaboon]

Fine tuning for max power on a dyno is fine but keep in mind nobody races a dyno. All a dyno is, is a tool.
Fine tuning at the at the track for quickest et is what I look for and what all racers should be shooting for.



We are taking about cam timing and it's affects on power output. Yes there are loads of other things we can change that will have an affect on ET but this conversation is about cam timing.

[Shadow]

Fine tuning for max power on a dyno is fine but keep in mind nobody races a dyno. All a dyno is, is a tool.
Fine tuning at the at the track for quickest et is what I look for and what all racers should be shooting for.



We are taking about cam timing and it's affects on power output. Yes there are loads of other things we can change that will have an affect on ET but this conversation is about cam timing.

Like it!

[Vigo]

Well i think we should decide whether we're really talking about tuning for POWER (trap speed) or tuning for ET since referring to both in the same post can be confusing. I think cam timing can affect either one but you may not necessarily gain on both unless you can hook up all the power you're making, so at some point you may have to decide which one is more important to you, as Gary was saying about different venues.

[GLHS60]

I wanted to add that the whole purpose of my post was not to be disrespectful to anyone or even disagree with anyone but only to maybe make others aware that there are things a person can do to their combo to work with or to compensate for whatever effect the cam timing changes may have to engine power output. I feel as though you have added MANY WORDS to my post that I didn't even say or even mean!

When you said this about my post that quoted Garys input on cam timing:

"This holds true if a person is not willing to make changes to the combo like final drive ratio and or converter stall speed if an auto. Or play around with the compression ratio, etc.?

It sounded like you were disagreeing with Garys input on cam timing. It doesn't add anything to the cam timing discussion is why I said I don't understand your point.

If for example you would have stated you found advancing the cam was beneficial at 7500 RPM that would have been on point.

Anything you learned since the 1980's about cam timing would have been of interest !!

I usually don't post much but the cam timing topic has been of great interest.

I wasn't trying to add any words in your post only trying to understand your point and I still don't.

Sorry if I offended you or anyone else, that wasn't my intention.

Thanks
Randy

[Gaboon]

My camshaft is bigger than your camshaft...


That's all I got and of no value to this thread.

[glhs875]

When you said this about my post that quoted Garys input on cam timing:

"This holds true if a person is not willing to make changes to the combo like final drive ratio and or converter stall speed if an auto. Or play around with the compression ratio, etc.?

It sounded like you were disagreeing with Garys input on cam timing. It doesn't add anything to the cam timing discussion is why I said I don't understand your point.

If for example you would have stated you found advancing the cam was beneficial at 7500 RPM that would have been on point.

Anything you learned since the 1980's about cam timing would have been of interest !!

I usually don't post much but the cam timing topic has been of great interest.

I wasn't trying to add any words in your post only trying to understand your point and I still don't.

Sorry if I offended you or anyone else, that wasn't my intention.

Thanks
Randy

No problem! All is forgiving on my end! I agree cam timing is interesting!