OK, I guess I'm stuck building a 350, I looked at a 302/400/ 331 but it looks like I'm stuck with a 350. I've never been a fan of these but I guess I'll have to make the best of it.
Here's the criteria:
Non computer Q-jet
Has to use the L69 ramshorn exhaust manifolds (sorry)
The car is an 83 Z28/t5/3.73 that is autocrossed.
The car also has a Mallory HEI replacement distributor.
That's about it, I need 325 rwhp without juice.

 

I'll give you a comparison point:

A 400 with a Comp XE274, double-hump heads with good port work, Edelbrock TES, Performer intake, Holley 800 DP, T-5; made 284 RWHP and 373 RW ft-lbs.

You're not likely to get anywhere near 300 RWHP out of a 350 through manifolds.

 

Why do you have to use exhaust manifolds? Such a universal performance upgrade is crutial if you want to make any power at all.

 

Let's just say I'm trying to avoid any unecessary administrative input.

 

For the sake of technical correctness, L69's didn't have rams horn manifolds.

However...

I have seen a 3700 lb '37 Chevy pickup with huffed 383 run low 13's at altitude through rams horns.

I have seen a street driven, emissions-legal '90 RS w/ZZ4 crate (on which entirely too much money was spent upgrading) TPI run high 13's at altitude through L98 manifolds.

In both cases, the manifolds had been thoroughly internally massaged with a die grinder.

 

Well, OK. I guess what I meant was that they don't have the 57 style rams horn exhaust manifolds (which if I recall were actually quite a good flowing manifold) But they do go over the top of the spark plugs rather than under them like most later style SBC's.
I have 2 of these L69 and they both look the same.
I have used a die grinder on heads, etc before so that is not an issue. Have you ever heard of an "extrude" hone process?

 

Oh, yeah. Forgot to mention that this ZZ4 guy had his plenum to chambers extrude honed together, and chambers through manifolds extrude honed.

To the best of my knowledge, no 3rd gen exhaust manifold went over the plugs. Got pics?

'57 rams horns were pretty poor, for what that's worth.

 

Stand by..................

http://www.fl-thirdgen.org/blacksheep1-3.html

Scroll down.
It's the best I can do, I'm not a big computer wiz.
Back in the day, we used to hunt for the rams horns because we had to run "stock" manifolds on a roundy round car. Now they may not have been the 57 manifolds but they were rams horn. I know the 265 stuff was tiny compared to later engines. The 283 were bigger and if I'm not mistaken the early vette exhaust were the good ones. (327)

 

I'm pretty sure all 3rd gen manifolds go over the top of the plug, it's a straight log though unlike the rams horn. I can tell you from my experience of circle track racing a class restricted to manifolds that the over top log style manifolds are probably the worst flowing of all. The log style that goes underneath the plugs can be made to flow better but the rams horns are the best not sure if either of those styles will fit in the chassis of a third gen though. castheads.com has some information about exhaust manifolds and porting them, it's a shop that specializes in cheating parts for circle track racing.

 

Guess I need to get out more.

My '86 LG4 and '87 LB9 manifolds go under the plugs.

I think.

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Great, now I'm going to have to get out to the garage attic and check again.

Dang, it's cold out there, too...

 

I guess it's snowing out there by now, I saw it on the news.
Here in Fla it's a "balmy" 70. Of course it was a little windy this summer!!

hhmmm castheads.com, I'll check that out.

 

Boy, do I feel sheepish...

Guess I'm losing it.

Yes, the logs go over the top. Been too long since I saw them installed (excuses, excuses).

But, if you have to go with manifolds, do the L69's and clean them up as much as possible.

(They're still not ramshorns...)

 

I guess that's the plan, I looked on that website, (I wonderred what ever happened to Brezinski), just like a bunch of racers, they make a rule to use stock parts (to save $$)and then the racers cheater them up to where they cost more than the parts they outlawed. Some things never change.
Anyway, if chevy could build a 365hp 327(at the flywheel) with manifolds I should be able to hit 300 at least.
If I have to run headers, to do that I will, but I'd rather not.

 

I run the LB9 manifolds and the differance after headers was amazing. It's not just the manifolds but the Y pipe too that sucks.
Do your self a favor and ditch the manifolds or lower your power goals.

 

Ditto.

It has been a long time ago (the 80's) but I thought that the cast iron manifolds for the... (RB83L69, you can jump all over this if you want, lol!), Vette in the mid to late 80's had a larger (like 2.25in) outlet.

If they didn't then my memory is blurred from smoking too much wacky tabacky back then:lala:

 

Could you use the style that are on the 4th gens? Are they like ram horns? If so, then you could probably get them off of ebay for a song. I'd bet they probably flow better than our stock "log" type maifolds.

Just found a set on there....http://cgi.ebay.com/ebaymotors/ws/eB...spagename=WDVW

 

Alright, alright, you guys are killin' me.......what about everything else?

 

We really need to know the nature of your constraints. If it is sanctioning body rules, that's one thing. If it's justifying costs to the spousal unit, that's another.

The truth is they didn't. They used to "fudge" those numbers, so the 327 they actually pulled on the dyno had headers, velocity stack on the carb, no accessories being powered by the engine, etc. They never made 365 horse through cast iron manifolds.

Since "net" HP is now required, they have to dyno the engine like it is in the car, and that's why you can have different ratings for the same engine when all that changed between models was exhaust or air cleaner.

 

Couldn't say about the Vette manifolds; I don't think they'll fit this chassis, but I could be wrong; but the L69 manifolds are 2¼". At least, the set I have sitting around is that size. LG4 ones were 2".

The difference doesn't sound like much difference.... until you realize that the thickness around the flange is about 3/8"; which means that the 2¼" ones have an ID of about 1-7/8", while the 2" have an ID of 1-5/8"; if there's 1/8" of casting irregularity or whatever anywhere, that takes them down to 1¾" & 1½" repsectively; that gives the LG4 ones an effective cross-sectional area of a little over 1¾ sq in, while the L69 ones have a cross-section of almost 2½". Almost a 50% increase in flow at that extremely critical point.

 

LOL, I no longer have a spousal unit, I now have a very understanding girlfriend. I was just trying to pass the car off as a stock engine, if I go the header route, I might as well step up in other places as well. But I refuse to give up my beloved Q-jet and my cold air intake