[88CapriceSS]

Thanks for reading.

I have a 350 SBC in a 1988 Chevrolet caprice. Weighs around 4200 lbs. 3.23 rear gears. 200r4 OD transmission. 2000 stall converter.. Factory smog heads.

STOCK highly restrictive exhaust. Stock aluminum dual plane intake.

Must keep these things and a bunch of other stuff due to smog.

The car is a daily driver, and I was going for increased grunt over stock. But gas mileage is more important than ever.

I can get away with a mild cam. At the moment I have a comp cams X4270HR truck cam in the car right now. And truthfully it's over cammed.

The specs are 220/224 @0.050. .474/.474 lift. On 111 LSA


I'm mostly debating between the X42458HR, XR252HR, and XR258HR

Specs X4258HR 206/210 @0.050, .458/.458 lift. On 111 LSA

XR252HR 200/206 @0.050 .472/.480 lift. On 110 LSA

XR258HR 206/212 @0.050 .480/.487 lift. On 110 LSA.

If anyone with more experience could recommend what route I should take and why, I would really appreciate the input.

Thank you.

 

[Moosecountry]

198-200º duration in a roller with .420" lift. Tight intake centerline

 

[1979Malibu]

Do you know what the 350 originally came out of and/or what pistons it has? Depending on what it is you may find that some inexpensive factory heads would work well in a combination using the specs Moose outlined. Options that work with the intake/exhaust set up you already have. With some casting number information and some number crunching you could possibly yield an increase in performance AND fuel economy. Given the tear down you will already have to swap the cam, the heads would be an easy thing to consider.

 

[88CapriceSS]

The engine was actually an ATK performance engine I bought from a friend.

It has dart iron eagle SS heads. 165cc runners. 76cc chambers. Engine is supposed to be a 9.1:1 CR. I've read these are basically a stock replacement head.

The truth is budget is the driving factor in the build right now. Along with drive ability. I have enjoyed the mildly cammed sound of the current setup, but it doesn't drive as nice as I'd like, and it is clearly inefficient for my semi-daily driving use.

With the current cam it doesn't seem happy until around 2200 rpm, and with the exhaust it's out of steam around 3700 rpm.

 

[1979Malibu]

Those numbers add up. 76cc chambers, .030 flat tops with valve reliefs and a good quench yields that compression ratio.

Moose nailed it on his recommendation. The V8 in my daily driver S10 is the same compression with similar cam specs (GM ramjet cam) to what he outlined above. I have no issues with detonation and it runs great.

 

[BogiesAnnex1]

I see you live in my ex home town (Pacific Beach for me) so youre subject yo California SMOG restrictions. However, evidently the cam you have gets past them? You can put anything on that engine that has CARB approval which are many fine intakes, different carbs or I guess with a 88 fuel njections that have Carb approval or sneak past them with the 650 CFM 454 TBI if that’s what’s on your Caprice.

You can use headers if they are ported for AIR. AIR is necessaey to furnish oxygen for burning HC’s to water and CO2. Also aids the 3 way converter in reducing NOx to N2 and O2. Oxygenated fuel with ethyl alcohol is assisting this as well an alcohol goes through several decomposition phases with leaves free oxygen late in the burn to convert CO into CO2 which leaves more free oxygen from the AIR system to react unburnt HC’s to water and oxygen where the oxygen helps the CO to CO2 reaction and NOx reaction to N2 and O2. Often you can find a cat back exhaust that while not reducing the resistance of the converter does eliminate those resistances in the tail pipes and mufflers.

Generally the larger the LSA of a cam the less overlap is present, this greatly reduces unburnt fuel pulling over to the exhaust during overlap by reducing the overlap period.

The cam you have would like more compression GM advertised these engines at 8.2 to 8.5 of the seeming half million I opened up I have yet to find a factory combination of head gasket and chamber size on these 1980’s SMOG engines that beats 7.9 and usually less. The less expensive moves available are to whack .030 off the head’s, they after-all are thin wall castings so maybe .040 but probably not .060 just to leave some meat. That with .015 coated Fel Pro would inch you up around 8.7 to 9.0 would do a lot for picking up torque.

I would agree the cam you have given the restrictions of compression, head choice, exhaust restrictions and rear gearing is too much. You could gain up on launch out of low by swapping the 200R4 for the deeper low gears of a 700R4. For putting around on the street torque is your friend and if the engine can’t produce it you can pump it up at the rear wheels with stiffer gears.

But really to dig deeper requires more info about this engine especially if it’s injected what kind is on it as in TBI or TPI and if it’s injected and you put this cam in it was the computer reprogrammed? EFI is not like a carburetor you can’t make changes that take the fueling and ignition requirements off the computer’s map of these things. Where a carb is fixed with a few dollars in jets, EFI requires a few hundred in reprogramming and I’m not talking those over the counter hot rod chips.

Bogie

 

[88CapriceSS]

The camshaft I have has been through smog twice so I am confidant a smaller but non-stock cam will be no problem.

I think I have a good sense of direction now and really appreciate the input.

My car came stock with the e4me qjet which I use for smog. The rest of the year I use a holley sniper setup which is very tunable.

AIR headers for my car are very expensive. And are not presently a realistic option for the gains they would provide.

I eventually intend to upgrade to a 4l60e with thr deeper first gear, but that's not in the budget for the moment.

Again I really appreciate the input. Thank you.

 

[wave1957]

I would say you do not need headers for what you want, but you sure need a cat-back exhaust system, an aftermarket CARB-approved intake, and a distributor recurve, that is where I would start. I had really good (seat of the pants sensations) results with those mods on my '87 QJet Caprice.
Of course, a camshaft on top of all this will make it all even better, as well as the 4L60.

 

[lmsport]

what do you do for timing when the Sniper is installed?

 

[88CapriceSS]

For timing with the sniper installed, I have the sniper controlling the stock small-cap HEI.

I could have also just used a mechanical hei. But I liked to have the control.

 

[88CapriceSS]

For timing with the sniper installed, I have the sniper controlling the stock small-cap HEI.

I could have also just used a mechanical hei. But I liked to have the control.

 

[lmsport]

for cam I would consider Isky 201258

Product Features:

• RPM-Range 1500-4800
• 1.5:1 Rocker Ratio
• Grind No./Type 256-Supercam Hydraulic
• Best Torque And Economy in 305 CI
• 9.5:1 Compression
• Passenger Cars And Trucks
• Standard Axle Ratio
• Standard to 600 CFM Carb
• Smooth Idle

 

[KirkM!chapman]

I would go with a cam with 1000 to 4000 to 5000 rpm range with a 111 or 112 lobe separation this would be simple and sweet, not high price and would bring the toque range down lower in rpm range given more grunt on take off should bring gas mileage up some, with properly tune carb with timing at ideal at 12 to 14 degree, with 10 degree mechanical advance at 3000 RPM with back in advance unhooked and let vacuum advance carry you up to 40 to 45°. When hooked up just my opinion some may disagree but like I said just my opinion

 

[BogiesAnnex1]

OK so if this isn’t originally a 9C1 cop car it didn’t start life with a 350. I guess the Reman 350 is sliding past the emissions people because they haven’t checked casting and ID numbers?

So this potential masquerade has to hide from them by looking and sounding stock which puts a hurt on the exhaust system. I’m surprised they don’t hear the cam.

Is the reman engine a roller or flat tappet block?

If a flat tappet the good old stand by GM p/n 3896929 195/202 @ .050 with .390/.410 lift at the valve with a 1.5 rocker and uses a 112 LSA is a good and common choice lots of duplicates in the aftermarket as well.

If the reman block can take an OEM roller since you need to run a mechanical fuel pump then the L30/31 Vortec marine cam part number 14097395 times at 190/195 @.050 with .414/.428 lift at the valve with a 1.5 rocker and uses a 111.64 ~ 112? LSA and this cam has a fuel pump lobe.

Bogie

 

[KirkM!chapman]

You are correct bogie 👍👍