331 Stroker

[MY77Z]

if i do get the trickflow package because i'm thinking about it eventhough i dont like the 61cc i would rather a 58cc, what do you guys think?? and should i stick with the cam that comes with it or switch to another one?? if switching is a good idea, what cam would you guys recommend??? knowing that i'll be spraying a 150hp dry shot?

[blueovalz]

To the best of my recollection, the LeMans cam was a mid .500 lift, 238 I/232 E at 050" cam (funny that it had more duration on the intake).

 

The heads I'm running are the old Alan Root J302 heads (has the Cleveland style exhaust bolt pattern). They were one of the very first aluminum SBF heads (came out in the late '80s), and back then, they did not advertise intake port volume. All I remember about them when I bought them was that they were the best at the time, but a lot of improvements have been made since, so I would say they are mid pack heads now days.

These heads are coupled to a Victor Jr intake, 1 3/4 equal length headers, and a 780 DP. It pulls hard to 7500, so I think I pushed the peak of the curve too high (plus the mixture was too rich that day, WAY too rich). Anyway, these same parts on a larger motor will help lower the peaks a bit.

 

Static CR is 10.2

 

My objectives: Well, I was hoping for closer to 340+ at the rear wheels. I'm taking a little different approach (away from the high winder) and looking for more usuable torque in the stroker.

[Kevin Shasteen]

Sorry to temporarily hi-jack this thread, but..,

 

Terry it looks to me that your combo is a perfect Street/Strip engine set up. Your parts combo is perfect for this category. The problem is the amount of peak hp you want from your displacement, 1.35 hp per ci, will force you to put together a combo that will cause your engine to be in the weekend warrior category/moderate race engine.

 

That LeMans cam is a race cam - requiring a higher SCR...much higher SCR to reach the same output that the LeMans engine's reached. Yet you are running a lower SCR in order to utilize pump gas.

 

Not knowing anything else about your engine combo other than what you have given me - I'ld say your SCR is too low. Since you have alluminum heads and your engine revs to the 7500+ rpm range I'ld also say your combo is pretty close to what it needs to be with the exception of your SCR. Again, recognizing that your current combo is perfect for a Street/Strip pump gas friendly, hot day/high humidity w/no detonation engine makes for a nice performance engine.

 

Camshafts and Cylinder Heads have come along way in the last 20 years and engine builders have learned to utilize this newer tech.

 

Recall that when a race team, in the past, would get hold of a pair of cyl. heads like yours, they would send them off to someone like David Vizard who would spend hours and hours to make them breathe properly. A few weeks and $40K later - the race team had a pair of heads that couldnt be beat.

 

Now days we have these layouts plugged into a cnc machine and it spits out the needed heads in a matter of a few hours for 2k. Your heads are good heads but as you said - a lot of xtra potential in the head dept has been uncovered in the cyl head dept in the past 20 years. You really need to know what your heads breathe prior to purchasing them in order to know what to expect from your engine before it is built.

 

Cyl. Head Mfg, in the past, were stuck on the Intake's Cross Sectional Opening formulas as to identify peak rpm, then they would utilize the cfm at valve lift to identify peak hp. We are still bascially stuck w/this approach to this day w/slight variations. Knowing how to match the Intake Port to the desired output based on a specific displacement is not that hard.

 

This is my beef with ignoring the Cyl.Head's Intake Port Volume as a whole, (evidently the aftermarket's beef also); the Cross Sectioinal Opening formula is only 2 dimensional which is Length x Height and measured in a square measurement. Whereas the Cylinder Head's Intake Port Opening is 3 dimensional as in Length x Width x Height and measured in a cubic measurement - so if all we need is a Cross Sectional Opening (sq. in.) which all the performance magazine articles throw out at us, then why aren't all Cylinder Head Intake Port Volumes the same with only the actual opening of the port being different? Well this would be rediculous, of course it would! Therefore, the 3 dimensional Intake Port Volume is the key to matching your cam to the displacement of the cyl based on your desired output at a specific rpm. Knowing yout Intake Port Volume is imperative and knowing how to utilize that data is even more important.

 

Convert your engine cylinder's displacement into a cc measurement and then divide the Cylinder Head's Intake Port Volume, also in a cc measurement, by your cylinder's cc displacement to obtain a Cylinder to Intake Port intercomponent value. This value will help you to identify when a cylinder head is too large or too small. Anything greater than the .29 is a dedicated race value and require 12.0:1 SCR's or higher. Anything in the .28 to .29 is in the Weekend Warrior range and can utilize pump gas. Anything in the .26 to .27 is in the Steet/Strip range and can also utilize pump gas.

 

Regardless of the displacement of an engine, if you want 390 hp at the flywheel, then your heads need to breathe 190cfm at 3/5ths valve lift; which a premium head for the SBF does quite easily (especially now days). Your head may even reach this mark - but we wont know w/out said heads being put on a flow bench.

 

You gave your cam specs but you didnt say if it was a mechanical or hydraulic roller. Due to the high rpms your engine will rev - I'll assume it is a mechanical roller. You already said in a previous post that your LSA was 112. So with your LSA and the duration given, your cam's overlap should be in the 46* degree range. As stated earlier, this is a perfect Street/Strip engine. With your engine's smaller displacement and your desired 390 peak hp, your cam's overlap really needs to be in the 60* degree range and your SCR needs to be in the 11.0:1 range.

 

This would then move your engine combo from where it is now, in the Street/Strip category, to the higher end of the Weekend Warrior category barely scating by on pump gas and might require a gas additive on those really hot/humid days as in 90+ F* w/.90 humidity.

 

If you like your engine and want the 1.35 hp per ci, which is obtainable - then I would change your SCR to the 11.0:1 and put in a cam w/a 60* overlap that has a 285 duration in it. This cam would allow you to run around town at lower rpms, due to the cyl. pressure bleeding off at low rpms brought about by the overlap - so no detonation, and run like the dickens at the higher rpms.

 

I know you know there's no replacement like displacement hence your cause for looking into a stroker engine. The higher your displacement - the easier you will reach the 400 hp mark; and with each increase of displacement - that 400 hp mark will be seen by the engine as less radical.

 

So, your 331 or 347 will reach that 400 hp mark much easier and remain in the Street/Strip range with less stress to the components than say a 390 hp 289.

 

The problem you run into is that enough is never enough; now with a stroker at 1.35 hp per ci, you will need to put together a combo than makes 331 = 446hp and 347 = 468hp..., what a horrible problem to have.

 

Kevin,

(Yea,Still an Inliner)

[Kevin Shasteen]

I re-read the thread, I see where you are not using the LeMans cam.

 

Everything else still applies. In order to get your 289 into the 390peak hp range you need a top of the range Street/Performance overlap of 60*degrees which will require a 280 duration.., maybe 285.

 

A cam swap and increase your SCR and you will be in the 390 hp range.

 

Kevin,

(Yea,Still an Inliner)

[blueovalz]

Thanks for that enlightening post. :2thumbs: Too bad you don't make yourself more usefull on this site

 

BTW, the stroker has a little more SCR, and a little more cam (in spite of the larger displacement), so it appears I'm headed in the right direction.

 

Thanks again for the great post!

[cup]

if i do get the trickflow package because i'm thinking about it eventhough i dont like the 61cc i would rather a 58cc, what do you guys think?? and should i stick with the cam that comes with it or switch to another one?? if switching is a good idea, what cam would you guys recommend??? knowing that i'll be spraying a 150hp dry shot?

 

ive got 2 custom cams for sale if intested.. 1 by buddy rawls and is a beautiful 302 (not 331/347) street cam. and a radical (302) cam motions cam that would suit a 331/347 great.. ran the both w. the tfs tw heads.. btw the TFS package is a really nice combo on a 302.. wouldnt spec it for a stroker... btw.. i know this will stir up a bunch of ♥♥♥♥... but.. i wouldnt worry toooooo much bout the dynamic CR.. 3cc isnt enough to bicker bout.. if anything it lowers static cr and i see yor may be a poweradder guy.. stay w/ the lower cr.. your not shooting for a high hp/per leiter motor.. if so you wouldnt be using a 302 block.. ive had a n/a 302/ a nx/ a turbo 302 and have a grasp on what works for a 302 based motor.. theory is great but 3cc dosnt win a race...