Im in the process of porting my stock tpi and 601 heads, xr-258hr-12 cam(Im trading a set of $200 LCAS for possibly), headers, msd,,,,, I came across an HSR for a good price and was wondering what you guys think of putting it on my 305 instead of the stock TPI,, the 258 cam is rated to make power up to 5000rpm,,, should I ditch the 258(206/212...512/.520) for a bit bigger cam or not use the HSR? thanks for any opinions..

 

I am no expert by any means and am sure that there are plenty of people here that can give you a more sound advise, but the xr258hr12 is designed to increase low and torque. This cam I think would be more suitable to an intakes with a longer runner design, such as the TPI. It could most definitely benefit from a better flowing intake, but above 5k rpm you may be getting into problems with valve float. On the other hand, people have gotten an increase in power with the HSR and a stock cam, so you may see power gains with the HSR and the xr258hr12. These gains however, may not be worth the swap. If you are set on going with the HSR, you may want to look into getting a cam that makes power up to 6000 rpm, but you may end up sacrificing some bottom end torque and drivability. The big question is: Do you want a good daily driver = TPI based intake and xr258hr12, or a high revving drag car = HSR and a larger duration cam?
Also when you end up putting your power up higher in the rpm with a bigger cam and the HSR, you are probable going to need to install gears with a higher ratio in the back and a torque converter with a higher stall speed.
You may also want to consider calling comp cams and talking to one of their technical service people. Tell them what you want to do and they will suggest a suitable cam for you. I found them to be very helpful. You will need to know what compression you would be running, rear gear ratios, converter stall speed, computer, etc. I hope this helps, but like I said, I am no expert.

 

with the 53cc heads that are goin on it Ive come up with @ 10:1, its got a 700r4 with a 2200-2400stall, and Im putting a 3.42 10bolt. Its a sunday driver and will hopefully see some auto-x this summer. Im not set on the 258 or the HSR. Just wondering what some of you more experienced guys would do in my position.

 

Are the 601 heads aluminum or cast iron? If cast iron, you may run in to problems if you are running pump gas with that compression. You never know when you might get a bad batch of fuel. With that high of a compression you may also consider a good quench, something like a .045". It will help prevent detonation.

 

There iron. Ive heard 10:1 with iron heads is good as long as you run 93 octane,, Im not sure what the gasket thichness is, just a cheap felpro regasket kit for an 87 305.. Im assuming its @ .041 but not sure. I know guys have run 601s on 305s with good results, also the cam has more duration and a tighter lsa than stock,, not much but I think itll bring the static compression down a bit to help with the 5cc less in the combustion chamber. I maybe wrong though, not def. sure that will be the case.

 

Yes, it would be fine if you are running 93 octane, but what happens if you happen to get bad gas somewhere and you start detonating? The best way to protect against detonation is to have a good quench. If you have a .041" head gasket, your piston must be .004" in the hole in order to accomplish a .045" quench. It is not a problem and can be done, you may just need to deck the block.
I don't know that the cam is going to affect your static compression that much, it will definitely lower your dynamic compression, which is what probably counts.
You can accomplish whatever it is that you want. Just make sure that you give it enough thought. Select a cam that best matches your heads, intake, etc. and keep in mind what your goals for the car are.

 

I believe its stock deck height... .025 I think, I dont have $$$ for new heads so the 601s are staying,, what Im really asking is which setup do you guys think I should run.....

1. Ported GM TPI with xe258

2. HSR with xe258

3. HSR with ? cam (best cam in your opinion for my setup)

thanks guys, Ive searched and searched but theres not alot of info on the hsr and cam combo options for 305s.

 

What do you want to do with the car? Is it going to be a track car, or a more of a daily driver with a bit of umph to it? If you want more of a daily driver, go with something that is going to give you more of a low end and mid range power, not to mention reasonable fuel economy. For that purpose the xr258hr12 is a good cam choice. A ported and port matched stock intake with the long runner lengths would complement a low rpm cam, like the 258, pretty well.
If you want something that is going to go to the strip a bit more, you would definitely want to go with something like a stealth ram. You may want to select a cam that is going to make power in the 6000 rpm range, but such a combo may not be very practical for a daily driver. You can call comp cams and talk to them about what cam they would suggest for this kind of combination.
My car is a daily driver and I like how the 258 is working for my application. The car has good low and mid range power, and pulls pretty hard all the way to about 5000 rpm (yellow line). With some work to the intake and full exhaust this kind of a combo would probably be good for around 300 hp and perhaps over 350 lbs of torque and the crank with proper tune.

 

He`ll be ok on 93. I used those same castings on my 350, which made over 11:1 CR, and I never had any detonation issues. And we only have 91 up here. Its a pretty good chamber design, and isn`t very detonation prone like some others are.

 

Ive got to get some junk valves so I can polish the comb chambers as well. Thanks for the info so far, I really appreciate it. I just bought the HSR so thats a definate option now. The car may see the drag strip/auto-x once and awhile but will remain a mostly Sunday driver . Anyone on here running a 305 with the HSR? what cam are you using?

 

Another old thread that I just dug up looking for other info...

Treat the HSR as basically an untuned (harmonically) intake, that just does ram tuning, so you don't really have to worry about it WRT to the rest of your combination choice. Yes, it will make less low end than something with smaller in diameter runners just because of a relative loss in velocity over something like that, but it won't actually hurt low end like some intakes might.

(FWIW, the length of the runners on a HSR is getting long enough to move harmonic resonance tuning into a useful RPM range, but the shape of the runners is such that it basically disturbs that tuning effect... OTOH, if you did something like gasket matched it to a 1206 and then carefully blended that you will start seeing some harmonic tuning effect)

 

As far as the 10:1/iron heads thing... those and the 416 heads are really quite decent. If you keep quench reasonable and are careful about tuning you should be OK, _especially_ on a 305 where the smaller bore diameter is working for you.

Even back in the early 80's, when engine controls weren't that good, GM ran 9.8:1 compression with these iron heads on the crossfire engines, and I can tell you from experience, they ran fine on 87 octane even at sea level. With a good combination you can get away with mid 11's on pump gas, I have on a 350 with a set of these heads, and even high 10's on 87 with a well matched combination in a heavily loaded fullsize truck.

I don't get the "what if you get a bad batch of gas" argument... that can happen with any combination and you could end up with an unhappy engine. So? If it's really a problem just don't push the car hard for that tank of gas, if that's a problem siphon as much of it it off into your truck, your lawnmower... whatever you don't care about and then dilllute what's left with the best stuff that you can find. Or try a decent octane booster.

 

I ended up trading the hsr for an edelbrock tpi set up + some cash since I already had the 258 cam. The cam and intake combo should work well and with the small duration...206/212... and high lift .512/.520... the torque should be pretty decent

 

I also have experience with the 601 heads in a 1983 G20 Van. They were on the original 305 first and then a 350. This is with the 80s CCC Q-Jet setup which ran a knock sensor. I calculated out the factory compression ratio on my 1983 G20 vans 305 and it was 9.85:1. The cam was only 194/203 @ .050. The dynamic compression ratio was up there and it ran GREAT on 87, even towing a load.

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