Spare parts engine build

[user-612937456]

Probably just under 10-1

[randy331]

Every component is probably ok if you get the perimeters in the ball park. But on a camshaft as little as 3-4 degree's can make the difference of 40 Horsepower or more.

No way. I've never seen a 40 HP difference from even big differences in cams, much less a small change like 3*-4*

Maybe going from a stock hyd flat tappet to a solid roller on an engine with ported heads,...maybe?

To OP, run one of the cams you have and save your money for your main car.

Randy

[turdwilly]

I really do appreciate the replies from you guys. I do have a question though. If the pistons are rated at 11:1 with a 62 or 64 cc head like the double humps, then what would my compression be around with the 75cc head? I'm not sure of the dome cc.

From 62cc to 75cc you will drop about 1.55 points of compression. 64cc to 75cc you will drop about 1.3 points.

[user-612937456]

Every component is probably ok if you get the perimeters in the ball park. But on a camshaft as little as 3-4 degree's can make the difference of 40 Horsepower or more.

No way. I've never seen a 40 HP difference from even big differences in cams, much less a small change like 3*-4*

Maybe going from a stock hyd flat tappet to a solid roller on an engine with ported heads,...maybe?

To OP, run one of the cams you have and save your money for your main car.

Randy

Oh Contraire Mon Frere you can realistically take a 355 engine making 500 horsepower move the intake lobe 4 degrees in the wrong direction you can turn a really good combination into a really sucky *** motor. 40 hp may have been streaching it to the extreme but i stress the point of how much difference a mildly different cam can be.

[rfoll]

I really do appreciate the replies from you guys. I do have a question though. If the pistons are rated at 11:1 with a 62 or 64 cc head like the double humps, then what would my compression be around with the 75cc head? I'm not sure of the dome cc.

It won't matter much what the pistons are rated for, only what the parts measure up to when installed. Install some pistons, CC them at TDC, and CC your various heads. Using advertised gasket volumes will get you close. 1 CC is worth about a tenth compression point, so any advertised piston volumes are usually off by a half compression point or more. Many of the 76 CC chambers are 80 CC or larger.

[randy331]

Oh Contraire Mon Frere you can realistically take a 355 engine making 500 horsepower move the intake lobe 4 degrees in the wrong direction you can turn a really good combination into a really sucky *** motor. 40 hp may have been streaching it to the extreme but i stress the point of how much difference a mildly different cam can be.

I've never seen it. Have you?
I mean you personally same day on the dyno back to back test, witness a 40 HP difference with a 4* or less cam duration change, with lift and aggressiveness the same on both cams?
Not what you read or heard, but your own test.

My experience has been cams that close will look the same on the dyno when both cams are adjusted to optimum position.

Randy

[user-612937456]

Randy

with lift and aggressiveness the same on both cams?

I was not specifically referring to duration change nor suggested "lift and aggressiveness the same on both cams" I didn't mean to be controversial and get anyone stirred up either. It was just a general emphasis on the importance of event timing (or choosing a random but similar specs camshaft) I have no specific data in mind so don't beat me up for using the alleged exaggerated #'s. If you move the intake lobe in particular 4 degree's wider from 108 to 112 separation in a hypothetical engine combination you can kill the peak #'s whether it be 23 HP or 45 Hp there are way too many variables to say what loss you will suffer by choosing the wrong camshaft spec's.

Not trying to take away from phantomfab intelligence or knowledge either. I was attempting to make an effort to steer him away from mistakes I had made 30-40 years ago by reasonong that I have this cam so I think I will just use it. Also considering not knowing more background than he initially shared.

Cams I have are a 300 crane, cant remember specs, ill check later and a cam that I'm unsure of the only thing on it is a 1z206 and its a 550/545 lift, both are solid lift cams and an isky sl2 details as follows

Although if they are cams he has had experience with he may very well be making informed decisions.

[randy331]

I was not specifically referring to duration change nor suggested "lift and aggressiveness the same on both cams" I didn't mean to be controversial and get anyone stirred up either. It was just a general emphasis on the importance of event timing (or choosing a random but similar specs camshaft) I have no specific data in mind so don't beat me up for using the alleged exaggerated #'s. If you move the intake lobe in particular 4 degree's wider from 108 to 112 separation in a hypothetical engine combination you can kill the peak #'s whether it be 23 HP or 45 Hp there are way too manyvariables to say what loss you will suffer by choosing the wrong camshaft spec's.

Personally I think your exaggerating the effect small changes in cam have on the power.
And a 108*-112* LSA change doesn't mean you necessarily moved intake valve events. You can install both on the same ICL.

Soon I'll be testing a 20* duration difference in cams, I'll bet after we find best position on both, and tune them both up, there won't be 40 HP difference.
I'll be a little surprised at a 25 HP difference.

Not saying there are no very well developed engines that are sensitive to valve events, but very few are that developed.

Randy

[user-612937456]

Personally I think your exaggerating the effect small changes in cam have on the power.
And a 108*-112* LSA change doesn't mean you necessarily moved intake valve events. You can install both on the same ICL.

Soon I'll be testing a 20* duration difference in cams, I'll bet after we find best position on both, and tune them both up, there won't be 40 HP difference.
I'll be a little surprised at a 25 HP difference.

Not saying there are no very well developed engines that are sensitive to valve events, but very few are that developed.

Randy

Ok randy I will let you win and reascend my previous suggestions that 2 similar cams could be as different as nite and day, considering you can't look at the big picture and want to put it all into a bottle with preconceived assumptions. I agree with you and suggest that there is no sense overthinking a camshaft. If you are OK with coming within 25 horsepower of your combination max potential, just use any cam as long as the events happen to fall within 20 degree's of spot on. Can you agree with this?

Edit: What I am saying randy when you look at it in your specific context you are technically correct. But from my point of view in a broad application there can be a big difference in the performance personality of the same engine with similar cams that where one peaks at a higher RPM and another peaks at a lower RPM there can be a significant difference in a 4 degree change to one of 5 perimeters and an unknown difference in aggressiveness and lift.
Also look at the way I worded my original post

as little as 3-4 degree's can make the difference of 40 Horsepower or more.

I did not say that it will it said can as in a worst case scenario

[randy331]

Ok randy I will let you win and reascend my previous suggestions that 2 similar cams could be as different as nite and day, considering you can't look at the big picture and want to put it all into a bottle with preconceived assumptions. I agree with you and suggest that there is no sense overthinking a camshaft. If you are OK with coming within 25 horsepower of your combination max potential, just use any cam as long as the events happen to fall within 20 degree's of spot on. Can you agree with this?

Edit: What I am saying randy when you look at it in your specific context you are technically correct. But from my point of view in a broad application there can be a big difference in the performance personality of the same engine with similar cams that where one peaks at a higher RPM and another peaks at a lower RPM there can be a significant difference in a 4 degree change to one of 5 perimeters and an unknown difference in aggressiveness and lift.
Also look at the way I worded my original post

as little as 3-4 degree's can make the difference of 40 Horsepower or more.

I did not say that it will it said can as in a worst case scenario

Ok, what I'm asking is,... have you personally seen this in your own testing ?
Same engine, small change in cam, big change in power ?
Not what someone else claims, but your own results.

And, I'm not trying to win anything, just here about your own testing.


Randy

[wyrmrider]

I think Joe Sherman said he saw large differences moving from older Herbert? to new designs
what say you Joe? I don't want to miss attribute
All I know is that you can go from losing to winning

[user-612937456]

I think I have previously answered your question Randy.

I have no specific data in mind so don't beat me up for using the alleged exaggerated #'s.

I have had several experiences with installing a cam that a friend gave me with High praises only to have disappointing results. After the fact a days work lost, add $$$ to the budget, go to Jerry's Auto Parts and have Jerry call Crower, Comp, or another manufacturer and have them spec and order a cam with satisfactory results. Giving me prejudice toward any used camshafts laying around.

Randy yes I have had varying experiences that lead's me to this conclusion. No data to speak of as I have never had access to a dyno up until the last few years. I don't have motivation or finances to do a back to back test of 2 extreme cases of subtle changes in camshaft design.

I will stand by my suggestion. Lets take a common example of a 10.5-1 383 and you use a hypothetically optimal for the desired results cam of 228/232 @.050 at 106 lsa compared with a similar cam with a shorter intake duration lets say 224 at 110 LSA the engine will fall far short compared to the first. But how much? I can not say you will have a 28 HP difference or 40 Hp.

What do you think Randy, what do you think? Do you think it will be a lot less than a 20 HP peak? Lets say with the first cam the HP is 490 @6200 RPM. Where will the second cam peak at **00 RPM? How much HP?

[randy331]

I will stand by my suggestion. Lets take a common example of a 10.5-1 383 and you use a hypothetically optimal for the desired results cam of 228/232 @.050 at 106 lsa compared with a similar cam with a shorter intake duration lets say 224 at 110 LSA the engine will fall far short compared to the first. But how much? I can not say you will have a 28 HP difference or 40 Hp.

What do you think Randy, what do you think? Do you think it will be a lot less than a 20 HP peak? Lets say with the first cam the HP is 490 @6200 RPM. Where will the second cam peak at **00 RPM? How much HP?

If they are the same speed and lift of lobes,less than 20 for sure, probably less than 5, if both are tested for best position.
That's the part left out in these situations most of the time, the testing for best position.
In the scenario you mentioned, If you test for best position both cams will end up with the IVC at the same location would be my guess.
To me it's inaccurate to say one cam is better because of LSA etc until both are tested for position for best average power.
I see that claim a lot, yup, my engine likes 106* LSA VS 110* when both were just put in at the position on the card.
In that case your chasing IVC even if you don't realize it.

What do you expect on my up coming cam change on Tommy Boy ?
It's a 20* duration change same lift. If there's 40 HP with a 3*-4* cam change there should be 200-266 HP with 20* shouldn't there ?? LOL

Randy

[Kbails]

I built a 400 last year and I'm hoping going from 10.5:1 to just under 11:1 from a solid ft cam to a solid roller addling 12 int. and 10 ex.degrees duration I will pick up at least 20 hp we will see, i should of just went solid roller right from the start.... everybody told me to go roller and I wanted to ''save money" but Iv learned in the past couple years if your going build something build it rite one time

[user-612937456]

It's a 20* duration change same lift. If there's 40 HP with a 3*-4* cam change there should be 200-266 HP with 20* shouldn't there ?? LOL

I would care to bet if you changed the lsa 20 degree,s you would see the 200 + HP loss as a mater of fact i think you may have difficult getting it to start. Or maybe you can twist this response into another if scenario that will turn my description of a cucumber into a water mellon if you resequence the gene strand for optimal nutricion lol