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woj's72lemans 02-18-2013 03:00 PM

1972 pontiac lemans 350 build
 
i ahve a 72 lemans 350 stock with 7h1 heads and i am looking for #48 heads can anyone offer me a good path to follow if i find a set of these heads and what i should do along with them thank you

MouseFink 02-18-2013 03:06 PM

If you manage to find a pair of good #48 heads, get a 400 CI engine to go with them.

LATECH 02-18-2013 04:51 PM

48 s would put you at 9.0 to 1 static. Nice.
I have a set of 46 s which are the same size, but the in and ex valve are the smaller variety. They are the 1969 # 46 heads not the 1973 ones.
Trouble is... they are bolted to the 1969 428 I bought and I dont want to part it out.
Ido have another set of #46 heads ...from a 1973 350 BUT they are 90 pluss CC chamber size. To big for where you are going.
Here is the thing...I have been down the road on a pontiac head hunt before. It really sucks. Problem is , a lot of the published data about chamber size is wrong. Especially when it comes to not so popular heads like the 7H1. One site listed them as 80 CCs. I thought....Perfect.
I got mine home CC'ed them.....91 CCs. I had to mill .045 off to get them to 82 CC for my 400. At least they had the big exhaust valves allready in.
What are your goals for your Build. You may want to rething going to high on CR as you can get a Comp XE grind or a Voodoo grind from lunati that will wake up your 350, nicely...without many costly mods.
Chime in with your Idea/build goal. I would love to hear it. LA Tech :thumbup:

Kal81 02-18-2013 08:38 PM

If I remember correctly a #48 head was a 400 head with 2.11" x 1.77" valves. The 350 bore is 3.875. In other words it won't work.

WDCreech 02-18-2013 11:28 PM

Quote:

Originally Posted by Kal81 (Post 1647879)
If I remember correctly a #48 head was a 400 head with 2.11" x 1.77" valves. The 350 bore is 3.875. In other words it won't work.

#48 heads were factory installed on '69 350 HOs.

MouseFink 02-19-2013 06:29 AM

A 1969 Pontiac Firebird 350 H-O with a 3.88" bore and 3.75" stroke was "me too" competition for the 1969 Chevrolet 350 Z-28 with a 4" bore and 3.48" stroke in the showroom.

Mr. P-Body 02-19-2013 07:38 AM

In '69, a few 350HOs DID come with 48s. I've CC'd a couple sets and their chamber was a bit smaller than the 400, coming in at 68. We've found the 350 "likes" the small valve heads better, as there's not enough bore to make the larger intake valve "work". I've also seen where too much lift runs the intake valve into the top of the block (bad).

350 Pontiac was never a "me too" engine (introduced at the beginning of the '67 models). Is has the capability of far more low-end torque and not as much high-end horsepower as 350 Chevy (apples to donuts). '69 Z/28s had 302. '69 T/As had 400 Ram Air III or Ram Air IV engines, and the little Chevy had no chance against them. The "race" version of T/A had a 303 CID Pontiac based on the 400 block (4 1/8" bore) and a 2 7/8" stroke, with Ram Air V "tunnel port" heads on them. The 302 had a BIG advantage until someone took the Vs off and put Ram Air IV heads on. The little Pontiac REALLY came alive then, but didn't win anything until Chevy and Ford quit putting money in the Trans-Am (Trans-American Challenge Cup) series. Pontiac didn't put money in it (no factory "sponsorship") except to develope the "legal" displacement (5.0 lr. max). It wasn't 'til '75 that Jerry Titus ran the Radial T/A "Tirebird" to a championship. The same was true of the '69 Camaro SS350 against the Firebird "400". Granted, the Firebird came with a bigger engine. The 350 cars were a "downgrade" from the 400 cars. No one I know ever tried to REALLY race the 350 against the small blocks "heads up". We DO have guys doing well in NHRA "Stock" with 350 Firebirds. They're "factored" lower than the 350 Chevy, as it (the Chevy) is better at making horsepower. NHRA doesn't seem to pay much attention to "torque".

FWIW

Jim

MouseFink 02-19-2013 08:01 AM

If the 1969 Pontiac 350 H-O was not a "me too" engine, why did GM put #48 heads on it.

Mr. P-Body 02-19-2013 11:12 AM

It's a good question, MF. The only rationale I've ever heard was they ran out of 47s. In the "pecking order", the Firebird "400" was THE performance model made in high volume. The 350 cars have always been considered "also rans" or "poor man's 400". Not literally, of course, but the general attitude among Pontiac peiople. The 350 has gained popularity in recent years due to the perceived rarity of 400s (not rare at all!).

Jim

MouseFink 02-19-2013 12:02 PM

I prefer to think the reason 48 heads were used on the 1969 Pontiac 350 was because of the "me too" sales policy. The "me too" sales policy was to compete with the 1969 Chevy Z28 on the showroom floor. The 48 heads are some of the best heads you can use but only on a 400 or 455 engine.

All successful performance engines are "over-square", meaning, the bore is larger than the stroke. I cannot think of one thing a Pontiac 350 engine would be good for except for fish structure. You cannot even bore a Pontiac 350 engine so it will accept high performance heads. The "under-square" (small bore) of the Pontiac 350 severely limits its RPM potential.

There may be a rare occasion that a Pontiac 350 engine will be competitive at the track but I don't see how they can be compared to a Chevrolet 350 "over-square" engine.

V8&4spd 02-19-2013 02:22 PM

Quote:

Originally Posted by MouseFink (Post 1648048)
I prefer to think the reason 48 heads were used on the 1969 Pontiac 350 was because of the "me too" sales policy. The "me too" sales policy was to compete with the 1969 Chevy Z28 on the showroom floor. The 48 heads are some of the best heads you can use but only on a 400 or 455 engine.

All successful performance engines are "over-square", meaning, the bore is larger than the stroke. I cannot think of one thing a Pontiac 350 engine would be good for except for fish structure. You cannot even bore a Pontiac 350 engine so it will accept high performance heads. The "under-square" (small bore) of the Pontiac 350 severely limits its RPM potential.

There may be a rare occasion that a Pontiac 350 engine will be competitive at the track but I don't see how they can be compared to a Chevrolet 350 "over-square" engine.

Don't forget the cost to build a Pontiac 350 verses a Chevy 350. What would you do with it? It's not a collectors item. Scrounging parts for a Pontiac 350 is a lost cause.

Mr. P-Body 02-20-2013 08:13 AM

"Scrounging" is not a "Pontiac thing". Parts are available at every engine parts warehouse, just like Chevy. Yes, they DO cost a bit more, but they are NOT hard to find. 326 pistons can be an adventure...(:-

Considering the Firebird 400 and T/A had ALL the small block Camaros "covered with a blanket", I really don't see Pontiac's marketing people worried AT ALL about Camaro in '69. Pontiac was #3, far "ahead" of where they were at any time in recent memory. If they really wanted a slice of the "Camaro pie", I think they would have flooded the market with T/As instead of severely limiting them. I think the 350HO cars were just a "bone" thrown to more economically-minded Pontiac buyers. With the exceptin of GTO in that era, for the most part, Pontiac wasn't trying to outsell Chevy. They didn't NEED to "try" with GTO until 1970, when GTO sales took a dive (strange, too, as the '70 is among the finest of all muscle cars) and SS FINALLY swept "up".

In some ways, "48" is considered the "second best" D-port head. 12 takes "top honors" ('70 350HP-366HP 400s). 12 has about the same intake flow as 670 and 48 (210 @ .500, untouched). The exhaust, however, goes an additional 25 CFM over ALL the other D-ports, at just over 175 @ .500. Some 48s were also machined with an "odd" chamber, similar in shape to the Ram Air IV heads ("compact wedge"). I've only seen a few, and those on KNOWN Ram Air III (simply called "Ram Air" in '69) 366HP 400s. 48s are getting VERY rare these days, and is NOT a good head for a 455 unless drastic steps are taken to reduce compression (12:1 with a flat top), OR it's a dedicated "race" engine, using only 100-plus octane race gas. Without porting, a 455 will "run out of breath" with these heads before 5,500 RPM. Once ported, a d-port is a d-port is a d-port...

PAX

Jim

V8&4spd 02-20-2013 05:58 PM

Scrounging sure is a Pontiac thing. You want Chinese no problem. #48 heads were not made since 1969, how many different cars you think the average set of #48 heads have been on? Anything he finds will be used and in who knows what condition. Add the cost to have them rebuilt. The problem is you can buy a new Chevy engine from GM with a warranty. What kind of warranty is going to be on used Pontiac parts or Chinese Pontiac parts?

LATECH 02-20-2013 06:05 PM

The set of # 48 s I have arent what you might think. I CCed them and they are at 96 CC s. Not what I expected to be on a 350...but thats what it was.
I have plenty of pontiac ...engines - heads etc. LOL
I just bought a 1969 428 . Wish I had found it before I bought the 400, or the 389...or .....:thumbup:
To The OP ....shove a Comp cams XE 256 in that bad boy and rework that 2GC rochester a little. They can be made to run 500 CFM which is right for a stock 350. Dual exhaust with a crossover would be a definite plus also.
You would be suprised.:thumbup:
That would be on target for a budget street ride.
If you want NORS Pontiac engine parts ...I know a guy in Lansing, mi. He has 4 warehouses full of nors stuff for all makes.

V8&4spd 02-20-2013 06:14 PM

I wouldn't try hopping up a Pontiac 350 on a dare. It's not even worth messing with unless it's 400 cu in or larger. It just cost too much, no bang for the buck. If they were such good engines, Nascar would have used them. $5.00 a gallon gas will kill them off. If you want somethiing different then by all mean build a Pontiac 350, it will never be a 400 or 455 and you will always know it. :sweat:


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