G Atsma

They'd be even hotter if they weren't priced in the stratosphere....

1973 STEP A SIDE

iTrader: (4)

blk00ss

iTrader: (66)

You should price some real heads like their ls7's...

big hammer

They have some Jim Dandy cathedral stuff too

Patron

You say Mast 240's are costly. Wonder what you think of with All Pro heads. $3200 is the starting point bare. Or the CID ls7 heads $2800 starting point bare. You wanna play but not pay. Wrong hobby or stick to building factory DD engines with factory parts. Waiting for some results on these. https://www.mastmotorsports.com/coll...ium-bore-4-000

Patsy57

iTrader: (37)

How do you think the mast heads would work out on a 4.140 bore LS3 FI engine? It has pistons setup for Ls1/LS3 hence why it's not an LS7.

Thoughts?

big hammer

I have the medium bore ls3 heads on a 4.130 bore and they seem to work really good NA.

Patsy57

iTrader: (37)

Specifically these mentioned previously

LS3 240 CC 3.890"+ CNC CYLINDER HEAD

Patron

Small bore ls3 heads would perform like TFS 235/245 with F/I. I know for a fact Je asymmetric flat top pistons can use Lsx 1/3/ or 7 heads.

big hammer

Using the ls3 small bores would give you access to better flowing plastic intakes too

Patsy57

iTrader: (37)

I have custom diamond -28cc Pistons the valves won't clear correctly for LS7

So I'm considering after ready this thread going with these guys instead of my cathedral port AFR225 heads which are too restrictive.

The motor is a 430LSX with a Procharger F1R.

After reading this I'm pretty sold on:

https://www.mastmotorsports.com/coll...oducts/ls3-240



The installed cam is in the attached picture. The rockers will change and so will the pushrod length etc.

Right now at 9:1 she makes 550 Rwhp, the the F1R she is going to make more power I need bigger flowing heads for boost she needs to be around 700rwhp without spinning the blower like crazy .

G Atsma

Actually I was being a little(??) facetious. Mast heads are good stuff if one is serious about getting the most from a setup and is not afraid to spend what is necessary to do it.

Darth_V8r

iTrader: (4)

This is one of the coolest tidbits I've picked up from you. I had never thought about it but you're right. Think of a runner like a cylinder, I tend to assume someone says larger runner volume, that it's the CSA. Never thought about the raised runners adding volume from length. Thanks for that!

Here we agree. If the intended RPM range is 6000-8000, then the 30-40 lbs of torque you won't feel by the time you gear it down, etc.

This is off topic, but related.... On mine, I swapped a FAST102 for a MSD airforce on back to back dynos. The MSD lost about 25 lbs of torque in the worst spot, and gained about 9HP up top. But it moved the HP peak out to 7000, and the torque curve went from lumpy to smooth and broad. SOTP, I never felt the torque drop, and I actually left the MSD on the car, because I like the way it pulls clear out to 7400 without falling off.

So, I can completely see what you're saying. Anyway, I'm starting to think that "losing torque" is really a poor description. HP = TQ x RPM / 5252. If HP increased, TQ increased SOMEWHERE. Really, to be correct, one should say "Lost torque at xxxx RPM" AT 6400 to 7400 RPM, the MSD is making more TQ on my car than the fast102 did. Like you said, cam it so it peaks in the intended range. The larger CSA allows you to move that peak to the right.

Darth_V8r

iTrader: (4)

Why not look at the Mast LS3 280cc heads? Specifically designed for big cube and boosted LS, which you are. You'd make more power with lower PSI.

Rise of the Phoenix

iTrader: (27)

I'm sold on those heads after seeing your results. I'd love to replicate your build.

Patron

I knew you'd get it that's why I type sometimes.


Darth_V8r that's why I say the factory can do everything needed most times. I'd only buy aftermarket if I had the $ to spend or needed for F/I no reason in chancing it. I'll ask you this how many members are on this site? Then ask if everyone donated say 5 bucks we could do our own heads. With No Compromises( that 1 guy did those SPM ls3 heads). Yet I defer, most people just like talking or raising up the subject about heads. They Are not about that life. Would rather just go Buy something that everyone Else has and never truly learn something. There's nothing Wrong with that. But any Idea that makes sense can or should be done if it's Cost doesn't affect you or break you. You can't learn nothing just being a follower. You've got to spend for
R & D to get something new which knocks most people off the list. So I say or recommend that most go ahead and jump on the bus with everyone else. Again there's nothing wrong with that. Just not intended for me. So that's where all the common sense came from? I can't even call it knowledge. As it all came from R & D.
Or general Knowledge from someone who does heads and gives you the Basic blue print about heads and you spend $ to see the Results. It's not new if someone has already done it before so there's no learning curve.

Patron

Darth_V8r

Your kinda right, so you won't notice a gear change of 3.42 to 3.73 or 4.11's with the same engine that lost TQ in the lower RPM band? Just think about it. It could peak at 6800 and a gear change could help for that lost 30 ft-lbs of Tq. May cost you a few MPG...LMAO!

99 Black Bird T/A

iTrader: (4)

Regarding the OP's question about CD.

I would want flow numbers from the same flow bench and same operator for both cylinder heads. Different flow benches and operators can vary by 15-25 cfm. That's enough to skew the CD calculations.

Likewise, it would be good to have flow numbers with the intake manifold(s) being used or considered and compare the CD based on flow numbers with intake manifold in place.

As always flow numbers are just a starting point ...

That's my .02 worth.

speedtigger

iTrader: (16)

A few more things to consider for this conversation. That is the relationship between displacement, RPM and the intake manifold. The debate always gets going on head size for a given engine. I offer that you must consider how those 3 design parameters are related for optimal results.

A certain displacement cylinder requires a certain amount of cross sectional area and flow to fill it in a given amount of time. Time is the important factor here. The amount of time it has is determined by the engine RPM. The higher the RPM, the less time you have to fill the cylinder.

The flow vs time, which can be expressed as CFM, is but one determining factor as to how much volumetric efficiency you can achieve with a certain displacement at a given RPM.

In addition, it takes a certain amount of time for this air to travel from the plenum to the cylinder through an intake tract with a given amount of cross sectional area or flow. The longer the runner is, the longer it takes for air from the plenum to get to the cylinder.

If the cross sectional area is too small to flow the requisite air in the amount of time at a given RPM, the volumetric efficiency will be poor. In addition, if the runner is too long for the air from the plenum to travel to the cylinder in a given amount of time, the volumetric efficiency will be poor.

So, the game is not only cross sectional area, it is choosing the correct length intake runner. You must tune the engine power curve with both and then choose a camshaft that tunes the engine to the same RPM range as the entire intake tract.

If you have an engine that is relatively small to a larger cylinder head, it will take a lot of RPM before that cylinder head becomes efficient. If you put a long runner intake manifold that is tuned to a lower RPM on that combination it will never be happy at any RPM. This is because at low RPM where the long runners are efficient, the air speed will be too low in the larger cross sectional runner. When the RPMs get high enough for optimal air speed, the long runner will no longer be efficient as the air charge cannot make it to the cylinder in time from the plenum before the intake valve needs to close.

I would offer that you cannot fix too long of a runner with cross sectional area, and conversely, you cannot fix too little cross sectional area with runner length. You can slightly crutch one with the other, but it will never be anywhere close to as good as having each parameter correct.

At the risk of generalization, which often backfires, I will offer that the cross sectional area of the head is more related to the displacement of the engine whereas runner length is more related to target RPM range.

If you look at Big Hammer's build, it is the perfect example of when everything is in balance. His larger cylinder head is exceptionally efficient with the shorter runners and appropriate cam design in the RPM range in which he operates the engine.

Darth_V8r

iTrader: (4)

I didn't want to quote tiggers post, but I do see very much that can, heads, intake all need to be in balance.

If I understand correctly, longer runners allow air to pick up more momentum, making for VERY good cylinder fill at lower RPM. The velocity of the air mattering quite a lot for filling the cylinder as it is in its way back up from bdc.

But at high rpm, where you've got far less time (milliseconds) to fill the cylinder, that momentum is less important vs raw mass flow, favoring shorter, wider runners.

I guess if I read you correctly, one cannot use shorter runners to help narrow runners flow better, nor can one use broader runners to make up for too much length.

In all actuality, I'd think longer, narrow runners go quite well for low and midrange rpm volumetric efficiency, and shorter, broader runners for high rpm volumetric efficiency.

Then add the cam to the mix. The cam should be chosen to match the runner design and the runner design to match the intended purpose of the engine.

Is that approximately correct? If maybe oversimplified.