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Discussion Starter · #1 · (Edited)
What changes in motor characteristics can I expect if I change camshaft as illustrated, and keeping everything else as is.
Engine is a Chevy small block 350 factory roller block.
Holley carb.
Vortec heads that are prepared for the lift.
Compression was 9,3:1 with stock GM gasket. Have changed to 0,015" shim gasket that should pump it up to app 9,8:1
Manual transmission T56 w/ overdrive.
2700 lbs car.
4,09:1 rear axle ratio.

It works pretty well today, but I want to optimize it up to the maximum lift that the heads are cleared for ( around 0,.525)
Is this change worth the effort?

I could of course change to a GM HOT cam as well, but to reach 0,525" lift with that one, I would have to change to 1.6 rockers as well.
And I already have a nice set of 1.5 ratio full roller rockers.

617458
 

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that slight change is exactly that. You might not even feel it.
Whet end results do you want? Maybe you are looking in the wrong spot?
What are you using for exhaust and fuel management currently?
Change the camshaft after you upgrade the other stuff
 

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It should work fine, but it’s not really simple to change cams, and it’s not going to change your performance much. Considering your gears, manual transmission and the light weight of your car, you could go for a bigger cam and it should work fine.

Howards also has a 231/235 @ .050 and a 233/241 @ .050 (but maybe too much lift) cam that might work well. Howard’s also has cams with the same duration but different LSA. It just depends on whether you want a smooth idle or a little more torque.
 

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Discussion Starter · #5 ·
Thank's for your answers!

I have already changed the cam once on this motor, so changing one more time, should not be a problem.

I don't want higher lift than around .525" because the total clearance is .571.
Safety margin app .040 - .050" = max lift app .525.

From what I have read, the Vortec heads respond very well on lift up to app .525.
Test done by sevaral hot rod magazines show noticeable hp increase when changing from 1.5 to 1.6 rockers on the GM HOT cam and Vortec tops.
That's a change from .495 to .525.

I don't want to change to 1.6 rockers on my present combination. That wil be too much lift for my safety margin.
That's why I thought maybe my suggested cam change would make a difference.

I know lift isn't all that matters, but my knowledge is limited hen it comes to camshafts.
 

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The absolute best thing you can do it buy a custom cam. Let Mike or Chris or Chad pick it for you. Be honest and trust them. They know WAY more than you do and you won't be dissapointed OR having to change things again.
 

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What company is that? Comp Cams?
NOT Comp Cams, ....they coudn't find their butts with both hands and a map, at least as far as the typical "Tech" employee goes.
Lunati is now owned by the same investment group as Comp(and Crane too), so they are worthless now too.

Mike is Mike Jones, Jones Camshaft Designs(forum name is "CamKing" on most forums),....
Chris is Chris Straub of Straub Technologies, who deals with Clay Smith Cams for custom work.

Chad might be Bullet Cams?.
 

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What changes in motor characteristics can I expect if I change camshaft as illustrated, and keeping everything else as is.
Engine is a Chevy small block 350 factory roller block.
Holley carb.
Vortec heads that are prepared for the lift.
Compression was 9,3:1 with stock GM gasket. Have changed to 0,015" shim gasket that should pump it up to app 9,8:1
Manual transmission T56 w/ overdrive.
2700 lbs car.
4,09:1 rear axle ratio.

It works pretty well today, but I want to optimize it up to the maximum lift that the heads are cleared for ( around 0,.525)
Is this change worth the effort?

I could of course change to a GM HOT cam as well, but to reach 0,525" lift with that one, I would have to change to 1.6 rockers as well.
And I already have a nice set of 1.5 ratio full roller rockers.

View attachment 617458
You have a manual T56? I have the Alex's parts valve train setup which allows up to .550 lift. You are right the Vortecs are really only good to around .525.

With a stick you can get away with more duration. You have low gears as well so highway should not be a problem either in 6th . Is that your Rod on you avatar pic? If so a Lightweight car no problem with longer duration as well. If you go with more like the suggested 230-240 duration, I think you see a big jump in HP.

My experience to yours?...
I had a 97 Vette LS1 with a T56. The rear gear was a 3.55. As you know 5th is .70 and 6th .050. However the LS1 has a shorter duration cam so torque is at a lower rpm. 70 was 1500 in 6th.

I think with your lower gearing you should have enough torque for cruising in 6th. I would say you are running like my 700r4 .070 4th gear and 3.73s 2400 at 70 in 6th?

Cam jump comparison - Also I built a Big Bore & Stroked Air Cooled VW. Change it later wanting more like your scenario. I went from an 247 @.050 cam to a 267 @.050 cam. W110 - 430/ 284 to a W130 460/308. Huge diffference.. Power came on big at 3500 and to about almost 7000. But I could cruise in 4th at 2500 easily. (VW's have a 4.12 R&P and a .70 OD 4th) With the smaller cam it was about 1500 to but all over at 5500. Big increase in HP going longer duration! Go bigger Duration.
 

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Discussion Starter · #13 · (Edited)
You have a manual T56? I have the Alex's parts valve train setup which allows up to .550 lift. You are right the Vortecs are really only good to around .525.

With a stick you can get away with more duration. You have low gears as well so highway should not be a problem either in 6th . Is that your Rod on you avatar pic? If so a Lightweight car no problem with longer duration as well. If you go with more like the suggested 230-240 duration, I think you see a big jump in HP.

My experience to yours?...
I had a 97 Vette LS1 with a T56. The rear gear was a 3.55. As you know 5th is .70 and 6th .050. However the LS1 has a shorter duration cam so torque is at a lower rpm. 70 was 1500 in 6th.

I think with your lower gearing you should have enough torque for cruising in 6th. I would say you are running like my 700r4 .070 4th gear and 3.73s 2400 at 70 in 6th?

Cam jump comparison - Also I built a Big Bore & Stroked Air Cooled VW. Change it later wanting more like your scenario. I went from an 247 @.050 cam to a 267 @.050 cam. W110 - 430/ 284 to a W130 460/308. Huge diffference.. Power came on big at 3500 and to about almost 7000. But I could cruise in 4th at 2500 easily. (VW's have a 4.12 R&P and a .70 OD 4th) With the smaller cam it was about 1500 to but all over at 5500. Big increase in HP going longer duration! Go bigger Duration.
-Manual T56, yes.
-Alex's parts valetrain setup, yes.
-But I measured only 0,571" total clearance on my heads. Can't have a 0.550" lift cam with only .571" in total clearance. Way too small safety margin.
I don't want to go much below .050" in safety margin. That leaves me with around .525 max chamshaft lift.

But since the Vortecs flow best up to around .525" anyway - and I only have 2 bolt main block, where maximum recommeded hp is around 400, all this actually makes sense. A well suited camshaft with app .525" lift will make around 400 hp - more or less.

It's the car in the avatar, yes.
The rear tires have a rather large diameter. 275/45-18.
I cruise easily in 60 mph with less than 2000 rpm's.

Enclosed a photo of anothe cam I consider.
This is the cam GM use in their ZZ 383.

617513
 

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Grind the top of the valve guide down another .030 or so then lightly dress the top of the guide i.d. with a chamfer bit. That’s essentially the crux of a ghetto grind, if you’re not an ape with basic hand power tools it works pretty damn well.

Bogie
 

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Little to no difference. Added duration would be noticeable especially at higher rpm.
 

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Discussion Starter · #16 ·
Grind the top of the valve guide down another .030 or so then lightly dress the top of the guide i.d. with a chamfer bit. That’s essentially the crux of a ghetto grind, if you’re not an ape with basic hand power tools it works pretty damn well.

Bogie
i have bought springs, locks & retainers from Alex’s Parts, that according to him should clear Safety for up to .550 lift. They should therefore be «ghetto grinded» already. But still I measure only .571 of total clearance.
One possible explanation is that I haven’t managed to knock the valve seals long enough down, even if I where aware of this issue.
Another explanation is that my heads have a cast that make for Extra small clearance.
 

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The cam swap you listed in the 1st post is not worth the effort IMO. If you want to keep the lift below .525, then you need a custom grind to see much of any benefit. Someone else mentioned going into the 230 on duration. I agree. But remember, as the duration goes up the low rpm performance goes down and the rpm range goes up.

Your Vortecs are needing more than .550, but they would benefit from more duration if you want to spin it to find the improvement. If you're interested in tire burning/launching fun, then I'd stick with what you have.

Want some extra sauce? - laughing gas (nitrous) in 50hp shot increments should help.
 

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Vortec heads without porting probably don't need more than .520 lift.

I would stay with about 220 duration at 0.050 and reduce lobe separation to 108---will pick up mid-range power without losing much peak power---idle will be more choppy
 

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Less motor more rear.

By running more rear end ratio you will feel the diffrence even a 10% jump is noticable. Also by running a a lower ( numerically higher) ratio you will place less stress through the transmission.

I am not a T-56 fan. The issues and required costly upgrades are known. So lowering my top speed a bit to "baby" a T-56 would be a fair trade to keep my shoulders pressed against the seat.

Depending on what t-56 (and carrier) you have you may be good with ratios in the mid 4's or even low 5's giving you the acceleration you want while still being able to cruise in high
 

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NOT Comp Cams, ....they coudn't find their butts with both hands and a map, at least as far as the typical "Tech" employee goes.
Lunati is now owned by the same investment group as Comp(and Crane too), so they are worthless now too.

Mike is Mike Jones, Jones Camshaft Designs(forum name is "CamKing" on most forums),....
Chris is Chris Straub of Straub Technologies, who deals with Clay Smith Cams for custom work.

Chad might be Bullet Cams?.
Curious as to why Isky is never mentioned ?
 
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