408 Magnum Stroker Build...cam selection

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Nash Stanton

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Hi everyone,

These place has always been a superb wealth of information. I thought I would also ask you guys for advice again. I'd like to confirm one last thing: Cam + converter. I am hoping to reuse my factory 1970 "high stall" converter from my 340. The specs in the FSM shows that it has a stall speed of 2250-2450 behind the 340 motor. The same converter (apparently) will have a stall speed of 2350-2650 put behind a 383.

I've recently *mostly* decided on the Comp XE274 roller rocker cam. My builder was questioning if the XE280 would work, but some of the advice I've been getting from some is that the XE274 should be seen as the biggest. Specs:

Magnum 360 -> 408, internally balanced, forged pistons, cast crank
EQ Ported heads with 1.94/1.6 valves. 1.6 ratio rockers
LD340 intake
Carter 440 AVS carb
Factory 340 Hipo manifolds (ceramic coated in OE grey)
TTI 2.5" exhaust w/ super turbos
3.73 Eaton rear end
Factory air cleaner

The goal obviously is to create an identical looking 340 (minus the LD340 and the EQ heads) while the original 340 gets refurbished and safely stored.

So with this combo, what do you guys think about the XE274 w/ factory Hi Performance converter in a 3500lb e-body? Hot street is really what I'm going for. It may see the track once in awhile, but just a good street driver is what I'm aiming for.
 
There are several threads that 274 comp degrees is too big for the stock converter
btw
what is a roller rocker cam?
XE274 roller rocker cam.?
If you already have roller tip rockers you will need a shaft relocation kit from B3racingindustries
go to his tech page and read all 4 tech articles
If you decide to with 1.6 rockers get cup adjusters and oil through the pushrods lifters and pushrods to help your adjusters live lube saver style lifters in any case
or did you mean a roller lifter cam?
are you up for a solid lifter cam with edm lifters?
did you mention your compression?
stock exhaust you have to hold the overlap down
so no THUMPER :) just the opposite
that comp squeezes the LCA together so too much overlap
If hyd cam think Lunati VOODOO 262 with 112 LCA .507 jn .527 ex compared to .529 intake with the too big comp- close enough the 10 degrees - would make a bigg difference
(compare the .200)
anything else would have to be custom
do you have or can get your flows
 
I have read as much as I could about the 274, but it's a little inconclusive because lots of people are throwing it into 300-350 CUI engines. I would think a 408 would treat it different.

I will be ordering new lifters with the XE274 (or whatever I decide). Going to stay with hydraulic roller lifters--the whole reason for going to the magnum. The cams I am told to stick with are the hydraulic roller lifter retrofit XE cams due to builders experience. Going to confirm with Comp that they have the long snout because I want to run the mechanical fuel pump.

I already got 1.6 adjustable rockers, so that's locked in. We plan to reuse pushrods and I think we are doing what you're saying there.

Compression will be mid 9s probably. Exact number we'll know during assembly.

Sadly, I don't have my flow numbers for the heads.

Regarding the manifolds, I wouldn't treat them as I am going to run them forever, but I do want to run them for a several years.

Do you still think the XE274 will be too big for factory converter? I am pretty sure mine is the 10 3/4 performance one.
 
Nash Stanton said:
I have read as much as I could about the 274, but it's a little inconclusive because lots of people are throwing it into 300-350 CUI engines. I would think a 408 would treat it different.

I will be ordering new lifters with the XE274 (or whatever I decide). Going to stay with hydraulic roller lifters--the whole reason for going to the magnum. The cams I am told to stick with are the hydraulic roller lifter retrofit XE cams due to builders experience. Going to confirm with Comp that they have the long snout because I want to run the mechanical fuel pump.

I already got 1.6 adjustable rockers, so that's locked in. We plan to reuse pushrods and I think we are doing what you're saying there.

Compression will be mid 9s probably. Exact number we'll know during assembly.

Sadly, I don't have my flow numbers for the heads.

Regarding the manifolds, I wouldn't treat them as I am going to run them forever, but I do want to run them for a several years.

Do you still think the XE274 will be too big for factory converter? I am pretty sure mine is the 10 3/4 performance one.
Click to expand...


If you have pushrods and don’t have the geometry correction kit, those pushrods will be too short.

As stated above, you need to reAd the 4 tech articles on the B3 racing engines web site. He covers a lot of things about geometry.

It’s worth the read and if you are using a roller tipped rocker and more than OE lift you will need to correct the geometry.
 
yellow rose said:
If you have pushrods and don’t have the geometry correction kit, those pushrods will be too short.

As stated above, you need to reAd the 4 tech articles on the B3 racing engines web site. He covers a lot of things about geometry.

It’s worth the read and if you are using a roller tipped rocker and more than OE lift you will need to correct the geometry.
Click to expand...

It's a magnum, says so right in the title. No shaft mounted rockers. Stud mounted rockers on EQ Magnum heads.
 
ok magnum
but "roller rocker cam" threw me
so roller tip rockers or not?
anyway 274 HR is bigger than a 274XE
your best shot if you want that lift
stock exhaust
and shorter duration and less overlap (the 274xe sucks for that)
is to go here
Street Performance | Jones Cams
and get one his inverse profile hr grinds
He can do the same top end with 8 degrees less duration which solves your problem
no one else can do it
He's done 3 stock exhaust cams for me and they flat work
 
Thanks. Yes, I believe they are roller rockers as well. My builder would like me to stick with a comp cam on that list.

I don't necessarily want to "optimize" for my stock manifolds, but I don't want something to seem wrong or incorrect. Like I stated the manifolds are there for the near to medium term.

What kind of stall should I expect with the factory performance TQ converter with my build? Too low for the XE274? That's the crux of my question. I don't mind a little bit of choppy idle.
 
you should get more detailed information. The XE274 cam is a hydraulic flat tappet. What you want in your Mag is a hydraulic roller. You can go back to hft, but i see no reason to. So first of all, what kind of cam are you lookin for?

Michael
 
90595200_237711917277636_426828244944158720_n.jpg


Sorry about that, yep, the "XR". Kinda confusing because they are "XR" in the "XE" line, heh!

I want something very street-able, but also can unleash. My hopes for this build is getting into the 13s while still looking very stock. Hope to have something very durable as well. Like a little bit of a choppy idle. Love the idea of reusing my factory converter if possible. So far I've been building this on a really good budget.

My builder thinks XR274 or XR280.

My racer friend in PA thinks XR268 until I change the converter.

The crux of the question is how my factory torque converter would perform in a 408 kit w/ the XR274.
 
https://protorque.com/ re stalled my factory converter to work with that very cam but only in 360 cubic inches. Good cam for the street.
Torque converters respond with a higher stall with more torque and the stroker will make a bunch more.

Speak with a pro on this.
 
you do not want a 110 lca with stock exhaust
It's your build you need to throw that catalog in the trash
comp's 110 fits all is just so wrong
 
Wyrmrider said:
you do not want a 110 lca with stock exhaust
It's your build you need to throw that catalog in the trash
comp's 110 fits all is just so wrong
Click to expand...
For best results I agree however, it is just a catalog and the 110 has that popular rhythm everyone loves.

It’s not Comps idea. Most everyone has there basic cam groups on a 110.
 
Wow, this thread is going nowhere on answering my question. It went from having to describe I have a magnum, to saying I have to get a custom cam otherwise nothing will work (hogwash), to 110 will not work with exhaust manifolds so I should get a less efficient 114 cam (hogwash), and to now defying my builder by throwing his "catalog" in the trash, which would mean the end of my 408 build.

Thanks rumblefish360 for one of the only helpful responses. The problem will calling converter companies is of course my factory converter will not work, because I need to get theirs!

I'll try to ask my question (that I've posted at least 3 times so far) somewhere else because this is going into a ditch.
 
Nash Stanton said:
Wow, this thread is going nowhere on answering my question. It went from having to describe I have a magnum, to saying I have to get a custom cam otherwise nothing will work (hogwash), to 110 will not work with exhaust manifolds so I should get a less efficient 114 cam (hogwash), and to now defying my builder by throwing his "catalog" in the trash, which would mean the end of my 408 build.

Thanks rumblefish360 for one of the only helpful responses. The problem will calling converter companies is of course my factory converter will not work, because I need to get theirs!

I'll try to ask my question (that I've posted at least 3 times so far) somewhere else because this is going into a ditch.
Click to expand...

It’s not in the ditch. You just don’t like the answers you’re getting. I very rarely ever suggest a cam out of a catalog. Ever. Too many compromises and since I joined this forum that has been what I have suggested.

If you already know what you want why ask here? I have never liked any Comp lobes in those families.

Your lack of converter makes cam selection even more critical.

Do what you want. Just don’t get pissy becuase you don’t like the answers you’re getting.

BTW, if you’ve read much around here you’d know I HATE hydraulic lifters. For very slow, soft lobes they are fine, but start getting agressive and they make noise and all that. And I’ll add in I’m not a fan of stud mounted rockers. I get the ease of the magnum block and hydraulic rollers it the draw backs just aren’t worth the squeeze to me.
 
Call all of the cam grinders/companies out there and get their recommendations - then decide amungst those. They'd be A LOT more qualified to provide an expert opinion than a bunch of internet heroes anyway. That's what I would do.
 
Your welcome Nash, Pro Torque to MY stock OE ‘67 converter and re stalled it to suite.

Nash Stanton said:
Wow, this thread is going nowhere on answering my question. It went from having to describe I have a magnum, to saying I have to get a custom cam otherwise nothing will work (hogwash), to 110 will not work with exhaust manifolds so I should get a less efficient 114 cam (hogwash), and to now defying my builder by throwing his "catalog" in the trash, which would mean the end of my 408 build.

Thanks rumblefish360 for one of the only helpful responses. The problem will calling converter companies is of course my factory converter will not work, because I need to get theirs!

I'll try to ask my question (that I've posted at least 3 times so far) somewhere else because this is going into a ditch.
Click to expand...
 
While you try to be helpful your often insulting and belittling without realizing it. Not ever build has to be precise and built to the maximum.

Yes! Sometimes good enough Chevy lobes will do just fine. Rocker geometry off? Sometimes it will just have to do.

You can bash the issue, the OE poster, me and anyone else that has an opposing opinion or lack of money to “Do it your way, the right way, or be bashed and ridiculed to death but in the long run, your not helping.

Sometimes, is just getting it going....


yellow rose said:
It’s not in the ditch. You just don’t like the answers you’re getting. I very rarely ever suggest a cam out of a catalog. Ever. Too many compromises and since I joined this forum that has been what I have suggested.

If you already know what you want why ask here? I have never liked any Comp lobes in those families.

Your lack of converter makes cam selection even more critical.

Do what you want. Just don’t get pissy becuase you don’t like the answers you’re getting.

BTW, if you’ve read much around here you’d know I HATE hydraulic lifters. For very slow, soft lobes they are fine, but start getting agressive and they make noise and all that. And I’ll add in I’m not a fan of stud mounted rockers. I get the ease of the magnum block and hydraulic rollers it the draw backs just aren’t worth the squeeze to me.
Click to expand...
 
rumblefish360 said:
While you try to be helpful your often insulting and belittling without realizing it. Not ever build has to be precise and built to the maximum.

Yes! Sometimes good enough Chevy lobes will do just fine. Rocker geometry off? Sometimes it will just have to do.

You can bash the issue, the OE poster, me and anyone else that has an opposing opinion or lack of money to “Do it your way, the right way, or be bashed and ridiculed to death but in the long run, your not helping.

Sometimes, is just getting it going....
Click to expand...

I wasn’t bashing anyone. The OP asked for opinions and didn’t like what he got so he got pissy and said the thread was in the ditch.

If you don’t want honest opinions don’t ask. I did say I missed the magnum head part of it, so that’s that.

It’s been my opinion and and will continue to be my opinion that for the extra few bucks and a little more time, even someone with a combo like the OP can benefit from CALLING (not an email, not a text but a phone call so you can have a fluid conversation) several cam grinders with tech guys that know what they are doing or the guy that answers the phone is grinding the cams, or at least has done it.

Unless you are someone special you won’t get that from Comp. You get a minimum wage guy who looks at the same catalog as everyone else.

That’s why I say CALL around, see who you get along with the best. Tell them exactly what you want and what you have and you’ll always get a better cam. You may not see it in peak numbers, but area under the curve and driveability is where this shows up. And this is exactly what most guys claim they want.
 
yellow rose said:
I wasn’t bashing anyone. The OP asked for opinions and didn’t like what he got so he got pissy and said the thread was in the ditch.

If you don’t want honest opinions don’t ask. I did say I missed the magnum head part of it, so that’s that.

It’s been my opinion and and will continue to be my opinion that for the extra few bucks and a little more time, even someone with a combo like the OP can benefit from CALLING (not an email, not a text but a phone call so you can have a fluid conversation) several cam grinders with tech guys that know what they are doing or the guy that answers the phone is grinding the cams, or at least has done it.

Unless you are someone special you won’t get that from Comp. You get a minimum wage guy who looks at the same catalog as everyone else.

That’s why I say CALL around, see who you get along with the best. Tell them exactly what you want and what you have and you’ll always get a better cam. You may not see it in peak numbers, but area under the curve and driveability is where this shows up. And this is exactly what most guys claim they want.
Click to expand...

I didn't ask your opinion about how you felt about comp cams. I didn't ask your opinion about whether you like hydraulic rollers or not. It was your choice to come **** on these things that will not change. In-fact, I don't want your opinion at this point, so please scroll by.

What I am asking here, is how well a 2350-2650 converter (behind a 383) or 2250 - 2450 converter (behind a 340) would fare behind a XR274 cam for a street driven stroker vehicle wanting to hit in the 13s with the specs above.
 
Nash Stanton said:
I didn't ask your opinion about how you felt about comp cams. I didn't ask your opinion about whether you like hydraulic rollers or not. It was your choice to come **** on these things that will not change. In-fact, I don't want your opinion at this point, so please scroll by.

What I am asking here, is how well a 2350-2650 converter (behind a 383) or 2250 - 2450 converter (behind a 340) would fare behind a XR274 cam for a street driven stroker vehicle wanting to hit in the 13s with the specs above.
Click to expand...

Your converter will run tight dude and you know this. Call PTC ask for 3500 stall and I implore you to google this excellent subject.

On another quote:

'Don't ask questions you don't really want to know the answers to'. Comes to mind here.

The 'tough guy' insecurities doesn't inspire others to give you their best answers. This isn't a shop that did you dirty, we don't owe you an answer. I say **** around and find out dude. If you haven't got the memo, 65% of the hobby is experimentation with combinations and having fun.

Since you don't like the FREE responses you've gotten from the most knowledgeable, gifted and accomplished on here who have given their most important resource, TIME. Who also have helped many who have come before, and after you. We really don't need you here contributing drama and climbing the ladder of liability in his 37th post. Have enough of it as is, take your bitterness over to 'News and Politics' instead. Seen them come, watched them go!
 
Nash Stanton said:
I didn't ask your opinion about how you felt about comp cams. I didn't ask your opinion about whether you like hydraulic rollers or not. It was your choice to come **** on these things that will not change. In-fact, I don't want your opinion at this point, so please scroll by.

What I am asking here, is how well a 2350-2650 converter (behind a 383) or 2250 - 2450 converter (behind a 340) would fare behind a XR274 cam for a street driven stroker vehicle wanting to hit in the 13s with the specs above.
Click to expand...


Don’t be a baby.
 
You don't need a stroker and big cam to run 13s in the qtr! Back in the mid seventies I built a 360 with high compression pistons but standard 360 cam and heads and home made extractors (I was a twenty year old apprentice)The car ran a 13.7 the first run. With 4 speed and 3.23 diff.
 
Nash Stanton said:
What I am asking here, is how well a 2350-2650 converter (behind a 383) or 2250 - 2450 converter (behind a 340) would fare behind a XR274 cam for a street driven stroker vehicle wanting to hit in the 13s with the specs above.
Click to expand...
You obviously aren't looking for performance. So stick with manifolds, stock converter and the xr274... It will probably still run better than 13's at sea level. But with the heads, cam and combo that engine is being choked to death.
 
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