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Help with 350 Combo

  
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Help with 350 Combo

 
lpaulmorgan lpaulmorgan
New User | Posts: 28 | Joined: 01/14
Posted: 01/19/14
04:56 AM

Hey guys I'm new to the sight, and new to Ponchos to be honest. I just bought a 68 Firebird and I am looking to get some more power out of it. It currently has a .030 rebuilt 350 with stock #17 heads with about stock 8.6:1 cr, SpeedPro 1038 cam, Performer Intake, Edelbrock 600 carb, dougs longtubes, TH350 with a 2000 stall and not sure on the rear gear but it feels around 3.55.

I was planning on swapping to a RPM intake and a different cam, but curious on you guys' thoughts.

Thanks  

shyrgfuh70 shyrgfuh70
User | Posts: 93 | Joined: 12/13
Posted: 01/19/14
05:45 AM

hi;

welcome.

what is the advertised duration on that? it is a low rpm cam.


COMPRESSION - i would boost my compression up first. the "bigger" the cam the lower the compression.

your 17 heads should be 72 cc, this gives you a static comp of 9.1. if you mill them .026" from stock, you will have 9.45 comp.

this will increase you hp and tq by around 2.75% throughput the entire rpm range.
it all adds up.

it will also increase your mileage slightly but you might need to run 91 octane.



HEAD PORTING - I would get the heads pocket ported and have the intake valves back cut while they were off. A cam needs good flowing heads to operate to its fullest potential.



CAM - basically, installing a bigger cam simply raises the entire operating range of an engine. this must be compensated for by installing lower gears.

i suggest you verify your gear ratio before buying a bigger cam unless you don't mind changing gears.

for a bit more fun with a different cam, i might use comp xe262h or a comp xe268h and advance it 4 degrees or a lunati voodoo 60202.



RPM INTAKE - this will cost you a little bottom end. I might run what you have and try a 1" spacer to see if it helps or hurts your perf.


CARB - What type is it.


GEARS - You need at least 3.31's to 350's to get a sense of "quick" acceleration.  

lpaulmorgan lpaulmorgan
New User | Posts: 28 | Joined: 01/14
Posted: 01/19/14
07:55 AM

Cam Specs are: Basic Rpm: 1500-4000 Adv Dur. Int/Exh: 278/288
Dur @ .050 Int/Exh: 204/214 Lobe Sep. 110 Valve Lift Int/Exh: 420/443

The carb is an Edelbrock 600cfm electric choke.

I plan on jacking up the rear and counting rotations on the tires and driveshaft to calculate the exact gearing.

I bought the RPM intake because I have a converter that stalls to 2000 so I thought I would better in the slightly higher RPM range.

For what it's worth, I called Comp and they suggested the XE268 Cam with the RPM intake. Thanks for the reply  

shyrgfuh70 shyrgfuh70
User | Posts: 93 | Joined: 12/13
Posted: 01/19/14
08:15 AM

hi;


no prob, hapy to help spend your money, lol.


i am actually extremely familiar with all those xe series cams and have been a comp dealer since they first opened their doors.

the stock eddy is a very good manifold, it is no slouch.

the rpm will do exactly what I mentioned it would. you might prefer a little less bottom in exchange for a little more top. the reason i suggested the spacer is because i think in your particular case it will perform better overall than a 6500 rpm manifold will with a 5500 rpm cam. the spacer will raise the rpm range of your intake slightly so its like splitting the diff and its only $15.00.

you might also prefer to compensate for the loss of bottom with some gearing.

its all good.

if you tell us exactly what you do and do not like about your current set up and what you want and are willing to give up in exchange we can get you what you want much better than comp can i guarantee it.


the xe268h cam is on the threshold of being a hair to big for 9.1 compression in a 350 ci engine imo. a 262 would be ideal but it will lack excitement and will not feel like a very big change from your current cam.


you could run a 268 in a 400 with only 8.5 compression and it would still run "good" because the extra cubes will compensate for the low compression.  

lpaulmorgan lpaulmorgan
New User | Posts: 28 | Joined: 01/14
Posted: 01/19/14
08:28 AM

Well to be honest I just want the car to be faster. It's a dog off the line, unless I power brake it to get the RPM's up, and it just seems slow throughout the powerband. In comparison I had a Mustang with a 302 that made about 300 RWHP and it would blow the doors off this Firebird. What I plan to eventually do is build a 455 but I want to get a bit more out of this 350 without dumping a ton of money into it. I just feel that the 350 can do a lot more than it currently is right now. I bought the RPm intake because I have read that the Performer is worse than a stock intake and that the RPM is far superior. That and the fact that I have a 2000 stall and even my current cam is rated at 1500-4000 RPM I thought the RPM intake would improve things.

Maybe it's the current tune? If you think that the Performer intake is good and my cam is a low RPM cam, then maybe it's just poorly tuned. Do you have recomendations on timing and where I should set it both at idle and at which RPM. It's a MSD distributor so it's a good piece, but maybe I should start simple. What are your thoughts on the carb?  

Pontiacman8 Pontiacman8
Moderator | Posts: 5775 | Joined: 02/08
Posted: 01/19/14
08:36 AM

With a 9:1scr I would look for a camshaft with at least 216 duration @.050 and no more than 222-224 duration @.050  
Engine builder,self taught auto body guy.
Horsepower sells engines and torque wins races

Pontiacman8
Pontiacman8
Pontiacman8

Pontiacman8 Pontiacman8
Moderator | Posts: 5775 | Joined: 02/08
Posted: 01/19/14
08:38 AM

don't believe everything you read because the eddy performer intake is a good intake.

Also that camshaft you have is on the lazy side.  
Engine builder,self taught auto body guy.
Horsepower sells engines and torque wins races

Pontiacman8
Pontiacman8
Pontiacman8

shyrgfuh70 shyrgfuh70
User | Posts: 93 | Joined: 12/13
Posted: 01/19/14
08:46 AM

hi;

i added to my previous post.



Well to be honest I just want the car to be faster. It's a dog off the line, unless I power brake it to get the RPM's up,


you absolutely positively must change gear ratios, a bigger cam will make it even slower off the line i promise you. very few want to spend money on gearing but thats where it starts unless you simply drop in a 455, lol.

you most likely have taller gears than 350's. a 6 cyl will seem sort of fast off the line with 3.50's.


xxxxx


In comparison I had a Mustang with a 302 that made about 300 RWHP and it would blow the doors off this Firebird.


oh, i know way more about mustangs than pontiacs. that would be around 375 hp at the crank which is massive for a 302.

either way, unfortunately, a mildly built 302 ford will TROMP a built 350 pontiac and will cost less to build.


xxxxx


What I plan to eventually do is build a 455 but I want to get a bit more out of this 350 without dumping a ton of money into it. I just feel that the 350 can do a lot more than it currently is right now.


yes it can for a LOT more money.


xxxxx


I bought the RPm intake because I have read that the Performer is worse than a stock intake


someone is smokin crack, its about the same but lighter.


xxxxx


and that the RPM is far superior.


only when used for the right app. it will not totally kill your bottom end. you might prefer it.


xxxxx


That and the fact that I have a 2000 stall and even my current cam is rated at 1500-4000 RPM I thought the RPM intake would improve things.


No.


XXXXX


Maybe it's the current tune?


No, its because it's a 350 pontiac with probably 3.0 gears and a tiny cam with slightly low compression.


xxxxx


If you think that the Performer intake is good and my cam is a low RPM cam, then maybe it's just poorly tuned.


see answers above


xxxxx


Do you have recomendations on timing and where I should set it both at idle and at which RPM. It's a MSD distributor so it's a good piece, but maybe I should start simple.


i or another can give more detail later but disconnect the dist vac.

set idle to around 12 degrees.

set max timing to 34 - 36.

set timing so it maxes out at around 2400 - 2600 rpm.

connect dist vac to ported vac not manifold vac.


xxxxx


carb


i hate those carbs but if they are  set up properly they work well. i like the old leaking holleys.

an annular booster carb will benefit you.  

shyrgfuh70 shyrgfuh70
User | Posts: 93 | Joined: 12/13
Posted: 01/19/14
09:02 AM

hello lpaulmorgan;

From pontiacman8

"With a 9:1scr I would look for a camshaft with at least 216 duration @.050 and no more than 222-224 duration @.050"


These are the specs on the cams i suggested in my earlier post.

xe262h = 218  224

.60202 = 219  227

xe268h = 224  230  

lpaulmorgan lpaulmorgan
New User | Posts: 28 | Joined: 01/14
Posted: 01/19/14
09:03 AM

The MSD distributor on the car now does not have a vacuum advance so I'll have to adjust the curve with the internal springs only. Does that change your recomendation?  

shyrgfuh70 shyrgfuh70
User | Posts: 93 | Joined: 12/13
Posted: 01/19/14
09:06 AM

Nope.

the vacuum works mainly at steady throttle and decelerating in gear. its mainly to improve mileage, some people also use it to increase idle timing.  

lpaulmorgan lpaulmorgan
New User | Posts: 28 | Joined: 01/14
Posted: 01/19/14
09:23 AM

So to sum things up, it sounds like you guys are recommending...

-Check/set timing
-Figure out current rear gears, and if tall gears swap to lower gears
-Keep the Performer intake and go with a faily small cam like the XE262

Like I stated I really don't want to dum much money in this motor as the long term plan is a 455 or stroked 400. Thanks for the tips and I am really looking forward to waking this motor up a bit!  

shyrgfuh70 shyrgfuh70
User | Posts: 93 | Joined: 12/13
Posted: 01/19/14
09:39 AM

yank the heads and at least get the compression up, its your labor [free] and 80.00 to surface two heads and 65.00 for the gaskets.

THEN toss the lunati or xe268 in it, advance it 4 degrees and try the spacer on the stock intake.

you can still run the 268 without increasing compression because you will be running low gears AND advancing the cam timing by 4 degrees.

this will wake the bejesus out if it compared to what you have now, lol.

the 262 cam is still a bit "girly" but better than what you currently have.


to advance the cam, simply buy a good double roller adjustable cloyes or similar timing gear set from summit for 55.00. do not buy a comp cam one.

checking can with degree wheel is helpful but not necessary imo since you aren't building a funny car.

your saving money by keeping your intake and carb.



timing chain sets

good
http://www.summitracing.com/parts/edl-7812/overview/make/pontiac

better
http://www.summitracing.com/parts/clo-9-1112/overview/make/pontiac  

lpaulmorgan lpaulmorgan
New User | Posts: 28 | Joined: 01/14
Posted: 01/19/14
10:02 AM

So mill the heads .026? That won't effect the fitment of the intake? I was going to pull the heads anyway and switch to screw in studs over the stock pressed ins ones. Which intake are you recommending with the either of those cams? Rightnow I have both so I can run either one.  

Pontiacman8 Pontiacman8
Moderator | Posts: 5775 | Joined: 02/08
Posted: 01/19/14
10:12 AM

Sure it will.

I have a ported eddy performer on mine and it makes plenty of power.  
Engine builder,self taught auto body guy.
Horsepower sells engines and torque wins races

Pontiacman8
Pontiacman8
Pontiacman8

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