Stock Heads/Cams... Joel Check it.

[Fox Slaughter]

I remember me and Joel were talking about stock heads and them being underrated.

Well I looked over some numbers.

A set of stock Aluminum LT1 heads were flow tested.

.100 61 52
.200 120 106
.300 169 135
.400 204 151
.500 223 157
.600 223 158

The stock LT1 cam is a .447/.459 lift. So average the difference between .400 and .500 tests is 213.5/154cfm.
A 224/236 AI Cam will lift .566/.566 lift. So average the difference between .500 and .600 is 223/157.5cfm.

Thats an extra 10cfm on the intake and 3.5cfm on the exhaust.
Now you might wonder why we were talking about they were underrated.
Here is stock LS1 head flow numbers.

.100 67 52
.200 122 97
.300 178 133
.400 215 156
.500 219 170
.600 227 180

So looking at these, the LT1 heads will flow better at .500 on the intake, and .100, .200, and .300 on the exhaust side. Otherwise these heads are pretty closely matched.
The stock cam on a LS1 is .496/.496 lift. So it flows ~219/170. Right around the same as the AI 224/236 cam will flow on stock LT1 heads.

Of course there is obviously improvement for the heads of any engine but this just is discussing how these heads are a pretty good design and underrated.



SIDE NOTE:

The LT1 stock uses 1.5RR and the LS1 uses 1.7RR.
If you put 1.7RR on the LT1 head it would lift .506/.520 which would give you 223/157cfm.
So by using the 1.7RR you would out flow the stock LS1 cam on the intake but not the exhaust.


Just some food for thought next time someone says the LT1 heads are garbage.

[JoeliusZ28]

Nice job putting some numbers to that TJ. It all seems pretty aligned with reality from what ive seen.

The LT1 sheep started out prioritizing headwork from the beginning (probably an old sbc habit) and thus we saw the phenomenon of everyone assuming they needed ported heads. I am of the opinion that if you have a 90 degree intake elbow and a single exhaust, heads arent your limiting factor. LT1s like to breathe easy and respond well to overkill on the basics.

[Fox Slaughter]

Stock heads still have power to offer. Case in point yours with whatever were done to them and the AI cam laid down 372. Most guys with elbows and single exhaust with like a CC503 are in the 350 range with M6s.

[c0ncEpT]

Where did you get the LS1 head flow numbers?

Hotrod Magazine tested a bunch of LS heads a few years back and there stock 241 casting numbers are quite a bit off in a few areas of the results you posted.

0.050 32 24
0.100 64 55
0.200 137 106
0.300 190 141
0.400 216 179
0.500 228 193
0.600 238 203
0.650 242 204
0.700 244 206

[sman]

Kinda what I was wondering, what castings were those?

[Nocooler]

Remember - head flow isn't everything guys. Port, valve angle, and chamber design has a lot to do with the power a head makes. And the LS head is a clear winner on those aspects.

[DETROITMUSCLE]

unless they were both flowed on the same bench the numbers are hard to compare different flow benches differ just like dynos do and what bore were they flowed on? Valve angle is a big factor as well not like some old school SBC 23 heads.

[JoeliusZ28]

Remember - head flow isn't everything guys. Port, valve angle, and chamber design has a lot to do with the power a head makes. And the LS head is a clear winner on those aspects.

Agreed that there is a lot more to it. I dont need to comment on the capabilities of an LS head though. The point of this thread is that LT1 heads arent junk, not to debate exact specs of an LS1 head. GM isn't going to take a step backwards, obviously its better than an LT1 casting for you soldiers defending the lsx kingdom

[Nocooler]

Agreed that there is a lot more to it. I dont need to comment on the capabilities of an LS head though. The point of this thread is that LT1 heads arent junk, not to debate exact specs of an LS1 head. GM isn't going to take a step backwards, obviously its better than an LT1 casting for you soldiers defending the lsx kingdom

Ok - I read this as an A to B comparison of the LT/LS heads.

The LT1 stuff works well - the heads wouldn't be the 1st thing I'd change

[c0ncEpT]

unless they were both flowed on the same bench the numbers are hard to compare different flow benches differ just like dynos do and what bore were they flowed on? Valve angle is a big factor as well not like some old school SBC 23 heads.

True that. I guess the size and length of exhaust piping if any has a big effect on the numbers also.

I wish we had access to cool shit like flow benches and chassis dynos. Would make testing stuff a lot easier.

Ok - I read this as an A to B comparison of the LT/LS heads.

The LT1 stuff works well - the heads wouldn't be the 1st thing I'd change

Agreed. You can go very fast cam only with an LT1. Problem is a lot of people jumped ship to go to the LSx platform and guys aren't really pushing the envelope with the LTx stuff anymore.

[birdie2000]

Joel, did you follow any measurements about the distance of the H-pipe or the mufflers from the header collector, or just put it in there how it would fit best? I'm just wondering if the mufflers were further away from the collectors (like behind the axle in a dual setup that goes out the back) would affect power in anyway.

I've always wanted to try David Vizard's method of having an "expansion chamber" a certain distance from the collector to simulate open atmosphere to the engine, but it's ultimately too hard to package in most situations. He claimed that if you sized and placed that right, you could put any sort of muffler behind it as long as it met the flow requirements for that particular engine. Claimed you could have a super quiet street exhaust with no power loss.

[JoeliusZ28]

I tried to put it where it fit while keeping it as symmetric as possible. Not sure what it is but my car runs a LOT better with my dual setup than anything else ive tried.

[birdie2000]

Out of curiosity, did you ever try 2.5" duals? If you did, what was the setup and what mufflers?

I'd like to do 3" duals in the future, problem is I have a Trans-Am and absolutely hate not having the holes in the bumper filled, plus I need the ground clearance. Proper 3" duals out the back is a pain in the ass to say the least, at least if you want it reasonably quiet.

[JoeliusZ28]

I might be looking into a modification soon that would make such an endeavor more possible . Im still split on whether or not i want to take mine over the axle. It was always my intention but i feel like i shouldnt mess with perfection. My only motivation to do it is to quiet the interior down.

I never tried 2.5". I went straight to 3" because i wanted the bassy sound.

[DETROITMUSCLE]

not defending anything just trying to get the facts straight there is more than just flow numbers at play here and I don't think the LT1 is junk just friendly discussion.