Don Terrill’s Speed-Talk

My tests on stock un molested 062 GM vortecs is 228 cfm @28" (more than one set tested)

My current self ported GM 062's with Manley 2.02 x 1.60's are right at 250-255cfm @28"
I did not do a MAX race full effort on them.

Yup Randy is pretty sharp no doubt but he does not do himself any favors. Sometimes.

i should have kept my old Nova like Randy's.. a great car for Drag Racing.

F-BIRD'88 wrote: ↑Sun Oct 29, 2017 12:54 pm My tests on stock un molested 062 GM vortecs is 228 cfm @28" (more than one set tested)

My current self ported GM 062's with Manley 2.02 x 1.60's are right at 250-255cfm @28"
I did not do a MAX race full effort on them.

Yup Randy is pretty sharp no doubt but he does not do himself any favors. Sometimes.

i should have kept my old Nova like Randy's.. a great car for Drag Racing.

"My tests on stock un molested 062 GM vortecs is 228 cfm @28" (more than one set tested)"


That's exactly what I've seen, although I did have one go 240 one time factory stock, but I did not test every port. I'm a big fan of Randy and his kid.

skinny z wrote: ↑Sun Oct 29, 2017 12:26 pm Are there unbiased published flow numbers available for the Bowtie Small Port Vortecs? Anything I've found puts them on par (from purely a CFM standpoint) with my ported RHS heads. The Vortecs in the posted video and supplemental dyno sheet were done and tested by the same shop. I was informed (by the owner of the 383, who's also the manager of the shop) that the RHS fared better than did his reworked OEM heads.
That provides some optimism going forward in that the heads won't be as limiting as I first suspected.

Well, theres 3 ways to look at it
Magazine specs
.1 67
.2 136
.3 182
.4 223
.5 251
.6240
.7 240
My flow bench Left port
.1 59
.2 126
.3 184
.4 232
.5236
.6 240
.7 239
Right port
.1 61
.2 127
.3 185
.4 233
.5 232
.6 239
.7 239
Randys bench and my bench seem to test pretty close to each other, the fact that you are getting "it cant be done without high rpm, more flow, super charger , ect" responses shows you the caliber of the builder, 500 hp out of a 385 is no sweat,Randy already led you to the water in the other thread
Tom

I'd have no problem making 500HP with 11.4:1cr and a big racing single plane intake
etc etc etc.

remember and note:
It runs on 100 octane LL....it will self destruct on the street on street pump gas without power killing ignition retard to let it live.

Ask Randy how may dyno tests sessions total to come to that point.

You are not working with the GMPP Bowtie Vortec heads. Do not equate.
do not equate with that Xe Hr street cam you got or anything like it.

Some of us were born at night...but not last night.

you COULD get a real deal 500hp out of a 383 with those heads but you will need to seriously "step on it".


supercharging is a great path and will get you there and then some using most of what you got and 355cid and your heads and stuff.
You can essentially just freshen up what you got.

You will SPEND less money total and go MUCH faster for a LOT Longer. And on true pump gas.

Edmonton is a ideal spot for supercharging on the street. (if you want to go fast)
There are specific reasons why.

randy331 wrote: ↑Sun Oct 29, 2017 12:11 pm Yes fbird, you are right ( as always ) it CAN'T be done.

Randy

F-BIRD'88 wrote: ↑Sun Oct 29, 2017 2:38 pm I'd have no problem making 500HP with 11.4:1cr and a big racing single plane intake
etc etc etc.

remember and note:
It runs on 100 octane LL....it will self destruct on the street on street pump gas without power killing ignition retard to let it live.

Ask Randy how may dyno tests sessions total to come to that point.

You are not working with the GMPP Bowtie Vortec heads. Do not equate.h
do not equate with that Xe Hr street cam you got or anything like it.

Some of us were born at night...but not last night.

you COULD get a real deal 500hp out of a 383 with those heads but you will need to seriously "step on it".


supercharging is a great path and will get you there and then some using most of what you got and 355cid and your heads and stuff.
You can essentially just freshen up what you got.

You will SPEND less money total and go MUCH faster for a LOT Longer. And on true pump gas.

Edmonton is a ideal spot for supercharging on the street. (if you want to go fast)
There are specific reasons why.

I run 11:1 with iron heads on pump gas and run full timing. It's not impossible. In fact, to keep static CR is foolish. It wastes power.

skinny z wrote: ↑Wed Oct 25, 2017 11:08 am
Subject: Gen 1 SBC. Currently 355 CID. Contemplating moving up to 385 CID
I have a set of cylinder heads. Freshly ported with verified flow numbers.
Intake: 253 CFM @ .500". 170 cc before porting. 2.02" valve. Specifics beyond the advertised port volume I don't have.
I have seen and witnessed 355 cubic inches produce 440 HP with heads less than these (Vortec heads). Dyno engine (with the usual lack of accessories) 224@.050", .500", 108 LSA,104 ICL, decent dyno headers. Peak HP @ 6200 RPM.
Now my question is: to what extent should I be able to produce the same HP/CI with the above mentioned heads? Is the CFM going to limit RPM to the point where HP would also be limited? Is 500 HP an unreasonable expectation? For this application, max RPM would be 6500. Assume a cam spec'd to suit. Something along the lines of 282 ADV. 106 LSA,102 LCA.
Thanks in advance.

After 5 pages of dialogue (!) and I appreciate all of the replies, I think a recap is in order.
There were really two questions buried in the original post.
The first question: Can 255 CFM @ .500-.550" port flow work in a 385 and produce the same HP/CID as the 355 listed above?
It seems, universally, the answer is yes. 477 HP from 1.23 HP/CID.
The second question: Is 500 HP an unreasonable expectation?: Reading back, there was no clear cut answer although you could say the answer is yes but it came with a number of caveats. From various sources factors such as compression ratio, pump gas compatibility, RPM, how the horsepower was measured (by who and where ) were all thrown into the mix at one time or another. There was one very compelling example but it may be beyond my reach to duplicate. Items outside the scope of the original post, in particular 500 HP is doable with better heads, while appreciated, didn't address the question in it's intent.
My summary: With the heads in question, a cam to suit (and as I've mentioned I had contacted Mike Jones and Terry Walters) and the other supporting bits, maybe not 500 HP but certainly the same HP/CID as with the 355. Now that said, (and I've deliberately avoided including my current driving combination so as to not turn this into a "build this for a drag racer" thread), I know that my own 355 is desperately under performing. With a mismatched cam and compression ratio (and I don't want to bring stall speed, gearing and suspension into this) improving on that part of the spec alone and adding another 30 cubic inches will make a measurable difference in performance.
Anyway, that's my take on it.
Still more research to do too.

Two simple answers in my opinion to those two original questions:

1. To achieve the output shown on the original 355 version engine 255CFM at .500" lift was adequate for the results and at the rpms that peak horsepower was produced.

The problem that will arise in my opinion is that to achieve that 50-60 additional horsepower needed to get completely to 500HP the addtional 28 cubic inches in the 383 is not enough to get there and any real increase in power over this point is going to be STUNTED by the facts that these existing heads CFM flow pretty much caps at .500" lift. The extra lifts will most likely approach .600" needed along with rpms needed will be restricted by the maximum flow of these heads and prevent a true 500HP power production.

2. The second question answer is CERTAINLY! But with a caveat , the engine will have to produce additional power beyond just the increase in cubic inches. The engine will have to have an improvement in induction in the form of better flowing heads, changes in camshaft and that flow increase will have to come at a rpms in excess of 6000rpms.

The final form of this 383 can and will produce 500HP if spec'd built correctly, but it will have different personality. JMO

The target was never to build to 500 HP and the answers and responses regarding the likelihood didn't surprise me.
Truth is, (and I'm possibly repeating myself here) the shortblock currently in use is done. My initial leakdown test revealed values that are far in excess as to what can be considered reasonable. So much so, I intend to re-test if for nothing more than my own edification.
That said, seeing as a rebuild is in order, I'm loathe to just move "sideways". As I mentioned, the heads are fresh (and I hope still) so the engine is half spec'd so to speak. A camshaft selection is all that remains really. While I could reuse the current cam, it's a poor choice and will select something more appropriate for the application.
While the current combination has seen it's end, it did deliver in the areas where I expected to see an improvement when I ported the heads and added the larger cam, namely in acceleration. It also, and somewhat surprisingly, delivered the best highway mileage I've ever attained with respect to a hot rod SBC. If all I managed to accomplish with the stroker was on par performance with the additional cubes, I'd be happy. But with a more suitable cam, I believe there will be even more.
It wasn't my 355 that made the 440 HP so the theoretical 475 HP looks pretty good and I'm OK with that.

skinny z wrote: ↑Mon Oct 30, 2017 8:53 pm While I could reuse the current cam, it's a poor choice and will select something more appropriate for the application.

Why is it a poor choice, and what would be a better choice ?

Randy

F-BIRD'88 wrote: ↑Sun Oct 29, 2017 2:38 pm I'd have no problem making 500HP with 11.4:1cr and a big racing single plane intake
etc etc etc.

The un ported GMPP vortec bowtie intake is a " Big racing single plane " ??

F-BIRD'88 wrote: ↑Sun Oct 29, 2017 2:38 pm remember and note:
It runs on 100 octane LL....it will self destruct on the street on street pump gas without power killing ignition retard to let it live.

No it wouldn't. The Vortec fast burn stuff can run a higher comp than the other 23* stuff.

F-BIRD'88 wrote: ↑Sun Oct 29, 2017 2:38 pm Ask Randy how may dyno tests sessions total to come to that point.

18 pulls. But some were just for my, education. Like the 1.3 to 1.6 rocker testing. Not much need for that with hyd roller, but I wanted to see it anyway.

F-BIRD'88 wrote: ↑Sun Oct 29, 2017 2:38 pm You are not working with the GMPP Bowtie Vortec heads. Do not equate.
do not equate with that Xe Hr street cam you got or anything like it.

I have used the RHS vortecs before, and I have a set here now that's going on a 355. (be on the dyno in 2-3 weeks) and they act and run a lot like the GM heads. RHS vortecs ported correctly will make 500 HP on 383 cubes, in very streetable trim. As steve316 said, walk in the park.

F-BIRD'88 wrote: ↑Sun Oct 29, 2017 2:38 pm you COULD get a real deal 500hp out of a 383 with those heads but you will need to seriously "step on it".

You still haven't said what " stepping on it " involves. The OP may be ok with "stepping on it"
He may have "stepped on it " before.
It may not be that big of step to "Step on it" ????
I, and most certainly most others on this forum would sure be interested in learning the technical details involved in "stepping on it"
Is "stepping on it" one of your racing seCreTZ ??
Please enlighten us that have most likely spent our entire lives "Stepping over it" !!!
Is "stepping on it" anything like "rugging it" ??? Kinda the same thing ?

Randy

I am sorry but my reading of your post on Oct 26 quite clearly said your target goal was 500HP !!

My caveats are only that you build your new 383 cu.in engine with a good decent compression ratio , nice lightweight forged pistons with a 1.5,1.5,3.0 ring set and 6.0" H-beam rods, good flowing aluminum heads in the 225cc range with flows in the 275-285 cfm range at .600" lift, use a good matched camshaft with decent dynamic compression for pump gas, a good set of proper size and length headers and a properly matched intake manifold and carb and a 500 pump gas streetable horsepower should be easily attainable somewhere between 6000-6500 rpms. Your target does not need to move, you just need to build the correct package! Many here know it can be done just make yourself a believer.

randy331 wrote: ↑Mon Oct 30, 2017 11:13 pm

skinny z wrote: ↑Mon Oct 30, 2017 8:53 pm While I could reuse the current cam, it's a poor choice and will select something more appropriate for the application.

Why is it a poor choice, and what would be a better choice ?
Randy

I have been told by the people referred to from those here at SpeedTalk (and other forums) that the specs are not ideal for particular pursuits. Those pursuits being within the confines of what's been discussed here.
For the record, the specs on the CC XR288HR are 288/294, 236/242@.050", 110 LSA, 106 ICL., .520/.540.
Do you have a recommendation? I'd be very interested in what you have to say.

Newold1 wrote: ↑Mon Oct 30, 2017 11:52 pm I am sorry but my reading of your post on Oct 26 quite clearly said your target goal was 500HP !!

skinny z wrote: ↑Fri Oct 27, 2017 12:07 am ...to moving forward with these heads and will make the most of it. I doubt that my 500 HP target is reachable...

I'll give you that. The wording should have been "... I doubt that A 500 HP target is reachable...
I understood going in that given the constraints of the heads that that HP result was unlikely.
As you said...

Newold1 wrote: ↑Mon Oct 30, 2017 11:05 am The final form of this 383 can and will produce 500HP if spec'd built correctly, but it will have different personality. JMO

And that to me, writes the RHS heads off in terms of reaching 500 HP and having the kind of engine characteristics I would like.

Newold1 wrote: ↑Sat Oct 28, 2017 6:18 pm The fact I know is that your 170cc-253cfm heads flowing at .500 lift ain't gonna get you there and at the 6200-6500 rpms you will need they are done at 5500 on a 385.

Going back over the posts, I had meant to respond to this.
I suppose by respond I mean, really? From a HP peak point of view, you think 5500 is about it?

Not knowing your exact cam specs., I think I am pretty close where the horsepower @ rpms will peak, yep.