[BWeir49221]

Originally Posted by pbSS

I have BTR 225 on my M6. The driveability is perfectly fine (it's my weekend/track car) since it's still in the "mild" range. I wouldn't be worried about losing driveability, it feels like stock to me but with chop chop.

I'm FBO with e85 (ported LT1 heads, ported MSD, 103 TB, JLT 5", ARH catless). I also went with the Johnson lifters and CHE trunion kit.

Over the last few days of thinking all this through, my plan is to pull the motor to do the work. Since access will be easiest this way, I may just spring for the 225 and have the heads milled and fly cut the pistons. At that point, why not do everything you can to help out?

Everyone is telling me that you really won’t notice a low-end difference between the 220 vs 225, and that with the M6, it’s really all about the tuner’s ability to do their job. If they are good, they can make it drive like stock in the low rpm’s.

Did you change your oil pump when mods were added? I’m on the fence about it. Seems like it’s a mixed bag of opinions. Some say you must do it, while others say these aren’t as prone to failures as people act like they are.

[KingLT1]

Isn't there is only like a 5-7hp peak difference between the 220 and 225. Imo, there is really no point in going larger unless you plan up upping the compression, msd manifold, and shifting the car around 7200 rpm. When you go larger with the cam the power curve is shifted to the right. If you don't address the combination to utilize the higher rpm power, the smaller cam with more power under the curve will be faster. That is the part many seem to overlook. If you don't care about that and just want more cam chop, then have at. The 225 will still drive fine with a Manual trans. The Autos ideally need a converter.

[BWeir49221]

Originally Posted by KingLT1

Isn't there is only like a 5-7hp peak difference between the 220 and 225. Imo, there is really no point in going larger unless you plan up upping the compression, msd manifold, and shifting the car around 7200 rpm. When you go larger with the cam the power curve is shifted to the right. If you don't address the combination to utilize the higher rpm power, the smaller cam with more power under the curve will be faster. That is the part many seem to overlook. If you don't care about that and just want more cam chop, then have at. The 225 will still drive fine with a Manual trans. The Autos ideally need a converter.

As far as cam chop, I wouldn’t mind a little, but I’m not looking for massive amounts.

I understand what you mean about the power curve. I’ve have went back and forth in my head over these two camsfor weeks. I think the problem I run into with seeking advice from others who have experience with these, is that the large majority of them drag race use them on a track. That crowd is using their car differently than I am. Mine is strictly a fun weekend street car. That extra <10hp that you gain from the 225 doesn’t mean anything to me if I have to be 7k+ to see it. You just can’t really enjoy that side of the motor on the street, at least not long, before you end up in jail or in the ground. So you’re probably the most correct in that I need the 220 for the rpm range I’ll be using most often.

Let me ask you this King, while the heads are off, would you mill them with the 220 to keep compression at stock, or do you think a thinner gasket would suffice? I appreciate the sound advice you offer! This is why I’m not an impulse buyer. I have to think stuff like this through thoroughly before I pull the trigger, so I don’t end up wasting money.

[KingLT1]

I would leave that up to James Short. He is a knowledgeable guy. Like I said the 225 makes more above 6500rpm with an MSD manifold. The 220 works well with stock compression and LT2 manifold. I don't know of any results off hand with the trinity/220 cam combo. My instincts tell me that manifold would be better with the 225. I just know for best driving manners, reliability, and all-around fun factor, the closer you stay to OEM the better. Lol

[BWeir49221]

Does anyone have any experience to share regarding adding compression? If I run the 225 cam, I know the overlap will cause some compression loss, so what I want to do is raise the compression to where it will be back to stock level with the cam. I was recommended to run a .040” gasket, but at what compression will that put it at? I guess what I need to know is, does anyone know what compression drops to with the 225? I’m trying to plan it out to see if the heads will need milling as well.

[Dynamical]

Racer X is doing the 225 with trinity. Not sure if he's talked it over with the shop about how that will drive with the stock stall though Lol.

[KingLT1]

Originally Posted by BWeir49221

Does anyone have any experience to share regarding adding compression? If I run the 225 cam, I know the overlap will cause some compression loss, so what I want to do is raise the compression to where it will be back to stock level with the cam. I was recommended to run a .040” gasket, but at what compression will that put it at? I guess what I need to know is, does anyone know what compression drops to with the 225? I’m trying to plan it out to see if the heads will need milling as well.

Here is a compression chart for a SBE LT1 posted by James @ GPI. Just a .040 gasket will put you just under 12:1. I know some have run 12.5:1 supposedly with pump gas but I believe that is with the best 93 octane in the country. Now if you are going to run E85 then it doesn't matter. Run as much compression as you can but you will run into PTV issues at some point. Don't quote me but I think .040 / .040 puts you on edge of PTV and that is around 13:1. There are calculators out there to figure this all out.

[BWeir49221]

Is there a calculator that will tell you how much compression loss there is with certain cam overlap? Maybe I’m overthinking this or just not catching on to the details. Do smaller cams drop the compression very much?

[BWeir49221]

Originally Posted by Dynamical

Racer X is doing the 225 with trinity. Not sure if he's talked it over with the shop about how that will drive with the stock stall though Lol.

I think I watched that video the other day. I may reach out to him and see what he can tell me about that setup.

[KingLT1]

Originally Posted by BWeir49221

Is there a calculator that will tell you how much compression loss there is with certain cam overlap? Maybe I’m overthinking this or just not catching on to the details. Do smaller cams drop the compression very much?

A cam doesn't drop static compression, but it will drop dynamic compression. There are calculators out there to figure out both. I believe summit racing has one, just have to search it.

[BWeir49221]

Thanks for that info. I reached back out to James Z. at BTR, and I think I’ll just run a .040” gasket and not touch the heads. That way compression won’t get to be too much. I’ll just have to test-fit the heads to see what the ptv clearance is and to double check for pushrod length.

[KingLT1]

That was going to be my recommendation.