Hot Rod Forum : Hotrodders Bulletin Board

Hot Rod Forum : Hotrodders Bulletin Board (
-   Engine (
-   -   Pistons and rods for sbc 350 ? (

Icejeep 09-22-2012 06:54 AM

Pistons and rods for sbc 350 ?
Hello guys, I'm getting ready to put together this engine I have, but I have to buy some pistons for it, I'm not sure if if should go with hypereutectic or forged pistons, dished or flat top. (does anybody know how deep dish there is in std cast dish piston) ? That's what was in the engine last time along with standard X-rods that had original rod bolt's which are the cause the engine was torn apart. It spun a rod bearing because the stock bolts could not hold the bearing tight enough at 7000 rpm's

So now I'm wondering if I should just put some Arp bolts into them original rods, or if I should buy some forged I beam rods with Arp cap screws from either Eagle or Scat.
Now I need to bore the engine 0.030" over and then I need new pistons for it as I said above, what is your recommendation in this case ?

The engine is based on a 4bolt mains block and has 235cc Rhs aluminum heads with 2.08"/1.6" valves, camshaft is comp cams solid street roller #12-769 -
Rocker arms are 1.6 ratio comp's gold. intake manifold is now going to be Edelbrock Victor, but last time the engine was together it had Edelbrock Performer intake, headers are 1.3/4" with 18" collectors. Ignition will be taken care of by tried and true Gm hei distributor, it will have Holley 850 hp carburetor.

Last time it was together it was installed into 3000lbs car that went to the track once and ran 118 mp/h in 1/4 mile. This engine had good manifold vacuum at idle, 15in/hg at 750 rpm.

So this engine is probably making somewhat close to 400 hp as it was, with it's low compression and performer intake. And max rpm's are near 7000...

If you need some more/better information about my engine, to help me choose the right pistons and rods, please just ask.

Best regards.

vinniekq2 09-22-2012 07:19 AM

first thats not a 7,000 rpm cam,second,if you want to run 7,000 rpm get forged pistons.Eagle/scat rods are decent rods.check your crank to see if its forged or cast,forged is preferred for 7,000 rpm. Put on smaller heads,200 to 210 cc for a mild to moderate 355
vic Jr and 850 is great! flat top pistons will get you around 10:1 depending on CC of heads and head gasket.
If your crank is cast and you are considering buying a forged crank,you can now go for a few more cubes with a longer stroke,depending on engine application? 366-401 depending on block.
383 is the most popular and most reasonable. A bigger engine will also make that cam seem more mellow.

also if you plan to run 7,000 rpm,I really recommend a full blue print and balance.Get an after market S.F.I. approved balancer. Because you had bearing issues before,machine block for deck and square and align hone.
this is just a start of a plan,think it out.even with that small roller cam,500hp is with in reach.Find someone close by and have your heads flow tested.If hes also a head porter he can tell you what to do for your application,example,I had a set of brodix heads that flower over 300 cfm that went on a street car,we closed up the intake ports a little

Icejeep 09-22-2012 08:00 AM

Running it to 7000 rpm's is not something I insist to do, in fact I choose this mild cam to keep the rpm's down, but that does not change the fact that with these big heads it does pull very easily to 7000 rpm's and does not seem to fall on it's face at all. Changing heads is not an option for me now, but I might consider that option later, these heads do come off my racing engine and will be put on that engine before next racing season. These heads do have 64cc chambers, here in Iceland we don't have a flow bench, so we are not able to go to some major modification on these heads. The main reason I choose to use these heads are because I think it's better to use these well flowing aluminum heads, even though they are This big for moderate 350 CID engine, rather than using some poor flowing small valve Smog heads with bad combustion carachteristics and big bath tub chambers.

The crank is cast piece. But I don't quite think that's the main issue here, in fact there are local racer's here in Iceland that are running a nitrousd 8000+ rpm 355 CID engine in the 5.60's in 1/8 mile with cast crank, and lightweight rotating assembly. But maybe their pushing it to the limit..!
In fact I'm do already have a sfi approved balancer that I'm going to use and the block deck is pretty good, last time this engine was together I did use fel pro #1094 head gaskets that do measure 0.015" thick without problems.

You say that with flat top pistons this engine might be around 10:1 compression ratio, depending on heads and head gasket, deck height etc. this engine must run on 91 oct gas. But with this moderate size cam and aluminum heads that's maybe no issue with 10:1 comp ratio ?

I'm dead on that the only reason I had bearing issues is because these stock rod bolts didn't held up at these rpm's. But since we are started to talk about bearings, what kind of bearings do you advice me to use in this mild build ?

Best regards from Iceland.

machine shop tom 09-22-2012 11:31 AM

Heads and headers way too big.

What is your intended purpose for this engine?


vinniekq2 09-22-2012 02:01 PM

You wont feel the roll off in hp with a roller cam as much as others.I use quite a bit bigger cam and my peak horse power is at 6,500 rpm.(6470 on the dyno)It will easily run past 7,000 rpm maybe losing 60 hp? your cam will do the same.

Go ahead and put arp bolts in your rods and go racing. 118 mph = low 11s or maybe high 10s.Have fun,,,(headers are not too big) I used 1 3/4 headers on my old roller 355.

Ruthlessmr 09-22-2012 05:25 PM

speed pro pistons are decent for this and if you use the 400 block use 350 rods
clevite bearings are pretty good too and decent priced

Icejeep 09-23-2012 08:44 AM

Machine shop tom : intended purpose is to put the engine into an off road Jeep.

Vinniekq2 : so this camshaft that i have will make peak power around 6000 rpm's, And should I limit max rpm's to 6500 for longevity ? Would it be better for me to use hi rise dual plane intake manifold rather than single plane Victor ? As I said above it had Edelbrock Performer intake When it ran 118 mp/h at the strip, the compression ratio was only 8.75:1-9:1 at the best. (does anyone know how deep the dish in stock cast piston is ?) so I would say that there's was some power left on the table in the intake manifold and compression ratio alone.

Ruthlessmr : I've been looking at speed pro pistons, I'm just not quite sure if I should use hypereutectic pistons or forged pistons. And yes, I'm using 350 block so of course i will use 5.7" rods. You said clevite bearings, they offer both P and H series bearings, what's the main difference and what's best suited for my mild build ?
Does anyone have experience of these sealed power digital diamond profile hypereutectic pistons ?

Best regards

vinniekq2 09-23-2012 08:58 AM

The dual plane intake Vs vic is debateable. I choose open plenum intakes for my type of driving. Piston question has been answered.Get rid of hei and use a multi spark unit with a rev limiter. If a driveline part ever breaks at w.o.t. then the engine is safe.10:1 compression is a good goal to achieve with aluminum heads and 91 octane. I use 10.75:1 and I can get 94 octane at the pump.If you no longer use the car on the track then the dual plane will respond better at low rpm. fuel injection is much better for off road.

Icejeep 09-23-2012 09:56 AM

Thanks for your reply sir. The main reason I insist that it must run on 91 oct pump fuel is because the only place we can get 93 oct on pump is in or near the capital city, however we can get 91 oct everywhere in the country, so if in emergency I must be able to use 91 oct fuel. Is there any particular dcr ratio I should aim for ?

Carb vs Efi, well of course we can discuss that for hours. But I like the Holley carb very well and choose to use one in the jeep for simplicity. Also we mainly drive on snow so there's no serious rock climbing involved. So if well tuned carbs do ok in our environment.

Best regards

ap72 09-23-2012 10:05 AM

for that rpm you'll want a flat top with a small valve reliefs- shoot for about 10:1 compression, maybe a hair over.

I'd go for 6.125" rods and forged flat top pistons with a thin ring package. It'll last a lot longer and make more power.

Ruthlessmr 09-23-2012 11:48 AM

i would run the hyper pistons flat tops all day long ,they should work great for the build .i have used many sets of speed pro hyper pistons and had great luck .
this should be a great budget motor
clevite p series have held up good
for what you are going to use this for should be fun and cool

cdminter59 09-23-2012 01:04 PM

Pistons and rods for sbc 350 ?
If the problem was spinning too many rpms I would purchase these rods. Eagle Specialty Products 5700B3DL19 - Eagle ESP H-Beam Connecting Rods - Overview - To go along with the beefy rods check out these Probe forged pistons. Your compression ratio with these pistons and 64cc heads using .015 head gasket will be 9.55:1. A set of Clevite P bearings will be fine to use.

Icejeep 09-27-2012 06:08 PM

Well guy's I have decided what i'm going to do..
I'we got my hands over a set of GM rods that have been worked, Arp bolts, beam polished and weight matched, so they should be up for the task. As far as piston's goes i'm decided to buy flat top pistons from speed pro.
I can get a set of ported 461 Double hump heads that are in good condition. would that be acceptable choice for this mild engine, and work well with my other components ?

So what we are talking about here is 350 sbc w. 10.25:1 compression ratio.
Ported #461 double hump heads, Edelbrock Performer or Edelbrock Victor intake manifold, haven't decided yet. Holley HP 850 carburetor
Camshaft is street roller from comp cams #12-769 -
1.3/4" headers with dual 3" exhaust.

Best regards.

vinniekq2 09-27-2012 06:27 PM

I would think about the performer and 750 if you dont plan on bouncing the tach past 5k regularly.both intakes are a good choice,I would use the vic for myself because I do look for a little more on top.Most drivers are better off with the performer.

(My car has a vic and a 950 holley)

Icejeep 10-05-2012 08:16 AM

What kind of combo are you running if i may ask Vinnie ?
But anyways there's been a change of plans, and this engine is going back into my strip car. So i'm really considering about going with a bigger camshaft. And i can use 93 oct pump gas on this engine.

All times are GMT -6. The time now is 05:45 AM.

Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0 PL2
vBulletin Security provided by vBSecurity v2.2.2 (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright 1999 - 2012. All Rights Reserved.