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Old 01-12-2010, 03:05 PM   #1
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Default S1 3800 (L27) heads

I've been considering an engine swap in my 95 Regal to an L67 for more power, because that 170-190hp (mods included, who knows how much they add) simply isn't as fun as it was 8 years ago when I was 16.

I've been doing some research and came across a few project threads, one of which was a guy named James on a my w-body discussion board who decided it would be beneficial as far as engine design to use Series 2 heads on a Series 1 3800. The advantage would be that the S1 block has a 1" taller deck height, and therefore is more suitable for stroking, but also has a better rod length to piston ratio.

The idea was that Series 2 heads flow better than Series 1 heads, that the belief was that the S1 3800 shortblock was the peak evolution of the 3800.

The major pitfalls to this project was the need for a custom ground camshaft due to the different valve locations, and the 1" extra deck height created extra clearance from the manifold to the heads. Last he posted in that thread, he was still working on it, and I haven't heard from him since.

"Now besides the fact that the SII heads have much better engineering of the port design and excellent crossectional area/flow the SII heads feature 1.8 and 1.52 inch intake and exhaust valves, and they measure 4.7212/4.7133 inches overall length on the intake and exhaust respectively. While the SI heads have 1.71 and 1.487 inch diameter intake and exhaust valves, and measure 4.727 inches overall length each."

My curiosity was peaked when I was given information on 3x00 valve sizes.

"the 3800 and LP3100 exhaust are damn near identical, but the LP3100 flows ~220cfm at .600, while the L67 heads flow ~194 at .600..."

I was told that there are considerable gains to be made by porting L67 heads.

"if you do decide to go 3800, do yourself a favor and port the living **** out of the heads. they suck for flow. large port 3100 heads flow roughly the same air with 22% less displacement, which is why the powerband of a 3800 favors low-rpm while a 3100 favors the top."

"flow tests were done with heads only. the L67 had 1.92/1.57 valves while the 3x00 heads had 1.76/1.42 valves..."

I can now start to see why the L27 has such low performance numbers (170hp) given its displacement in comparison to the 3100.




I don't wish to venture into creating a S1/S2 hybrid as James wanted to do in that thread I posted, but this all got me thinking. How much do I stand to gain from porting my L27 heads? I already have roller rockers on, and the LIM is ported as well. I don't have a flow bench, but I would consider my porting experience to be adequate.

Consider my work with my Jaguar V12 heads and manifolds:


Here'* what the throttle bodies looked like stock:
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And after I finished with them:
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Stock manifolds:
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Ported and polished (after injectors) manifolds:
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Stock head intake ports:
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Port and polished head intake ports:
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Eplanations are in my previous post, but for those who didn't catch it, I didn't really port much of the heads. On the head intake ports, the gasket is 1.5". I gasket matched the ports on the intake manifolds. The very surface of the head ports is a hair under 1.5", but the ports have a sharp taper into 1.25" for the size of the head ports. I smoothed out that taper so it funnels into the bowl of the head port smoothly, thereby increasing velocity and eliminating the turbulence that the stock machining creates. The ridges you see on the sides of the ports are from the factory welds, as these are not cast aluminum heads.

I smoothed the edges of the throttle bodies to also help maintain some velocity and reduce turbulence. They're not beautiful, but they'll be worlds better than stock. The stock throttle bodies are slightly over 2.5" in diameter, while the intake manifold entry is 3", and my new intake pipe will also be 3".




So, what do you think? With roller rockers and a ported LIM, will I stand to gain much from porting the L27 heads if I do work like I did above?
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Old 01-12-2010, 09:47 PM   #2
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Has nobody here ever ported heads on a series 1 3800?
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Old 01-13-2010, 08:19 AM   #3
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Long ago ...sure.

But not that many try to push a Series I that far these days.
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Old 01-13-2010, 10:53 AM   #4
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Quote:
Originally Posted by BillBoost37 View Post
Long ago ...sure.

But not that many try to push a Series I that far these days.
Given the inherent advantage of the taller teck, one would only imagine that aside from tuning deficiencies, it would be a better block to work on, if for stroking purposes alone. I don't know the exact numbers, but I don't believe 4.2L would be out of the question. What does an extra inch of piston travel give you in a 3800? A conversion to OBD2 alone and properly ported heads would make it quite an animal. Seems to me the possibilities are greater than with the Series 2, save for the lack of aftermarket.

A turbo stroked 4.2L Series 1 with an OBD2 conversion would scream, but the heads are what'* holding you back. That'* where I'm trying to start here, but if there isn't much progress that can be made with the heads, I might as well just swap in an L67 and call it a day.

That, and these engines don't seem to want to die. Mine has 213k and I don't expect it to start failing any time soon.

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Old 01-13-2010, 04:36 PM   #5
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if you do end up going the l67 swap route and are looking for an engine tranny, and ecu, i have them in my garage atm(pulled it out of a 98 regal). wouldnt mind selling either =] let me know or good luck on the 4.2 turbo =0 defonatley would be a sweet project
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Old 01-13-2010, 09:24 PM   #6
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you are correct about the 4.2 stroker

http://www.3800stroked.com/

a bit pricey for me though lol
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Old 01-14-2010, 12:37 AM   #7
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Quote:
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you are correct about the 4.2 stroker

http://www.3800stroked.com/

a bit pricey for me though lol
That'* a bit disappointing. It seems you can't go farther than 4.2L as there won't be enough clearance for the crankshaft. So much for that idea.

I do wonder what you'd gain from an additional .4L of displacement. I'm thinking the gains are not worth $2500 unless you're building a racing engine.

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Old 01-24-2010, 11:25 PM   #8
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Does anyone here have flowchart information regarding how well Series 1 heads flow? I know they're pretty bad, but I'd like to know how bad.
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Old 01-25-2010, 07:45 AM   #9
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It'* been a while since folks were discussing the S1 from a performance side, Try searching Dr. Jay and some of the items, maybe there'* an old one kicking around.
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Old 01-25-2010, 07:59 PM   #10
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Stroking is a whole lot more intail than just adding .4 liters, its bringing the pistons closer to the valves and or farther away for more or less comp. Depending on what you want to make it, is up to you. I see alot a 383 stroker chev'* putting out 400+ hp with a cheap reliable build. 6,000.00 can get you around 420hp to the wheels. There is alot to benefit from stroking if you port and polish everything. Headers, cam, ecm, and everything thing possible will bring in alot of numbers. I can see making 280hp on a NA motor possible probably even more. There are alot of guys out there with little tricks and tips that can guide you along. I had a 5.0 ho mustang pushing around 515hp with stock pistons and crank. The top end was a crazy build and was still on pump gas. You have to throw around alot of numbers and ideas to get a great combo.
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