who has put a blower on a 302?

[tomcat27]

I was given a good 302 block from 1969 and my son and I would like to build it for fun. and, of course, we would like to add 8psi of boost with a Weiand 174. I recognize that, especially since we are stroking it, we are pushing the limit of block design with this (many examples of cracked 302's). and that the best solution is to use a Dart block. but who here has actual experience with boosting a 302? we are not putting this baby on the bottle.....

We had the block checked and it is being bored .030 over. will use a forged stroker crank, H-beam rods, and forged pistons. also adding a main bearing girdle and main studs. street use.

 

[Johnny2Bad]

You can replace an iron block for a lot cheaper than buying a DART. A used ("seasoned") iron block is usually a better candidate for boring / machining / blueprinting than a new one. I say "run her".

This one kind of reminds me of the panic in the 70's and 80's over the switch to unleaded fuel, the loss of lubricity with lead that the older valve seats depended on, and the advice to pull your heads and install hardened valve seats on a perfectly good running motor. Ummm ... why not wear the old seats out first at $0 cost, THEN replace the seats when it's time to rebuild the head?

 

[CT8]

The Dart blocks are heavier duty than the factory blocks when trying to really push the power up. If you want to spend the $$$$

 

[CT8]

I beams rods are stronger.

 

[The_Eric]

Originally Posted By: Johnny2Bad
You can replace an iron block for a lot cheaper than buying a DART. A used ("seasoned") iron block is usually a better candidate for boring / machining / blueprinting than a new one. I say "run her".

This one kind of reminds me of the panic in the 70's and 80's over the switch to unleaded fuel, the loss of lubricity with lead that the older valve seats depended on, and the advice to pull your heads and install hardened valve seats on a perfectly good running motor. Ummm ... why not wear the old seats out first at $0 cost, THEN replace the seats when it's time to rebuild the head?


That's true BUT- things tend to get REALLY expensive when highly stressed parts fail catastrophically. Then that Dart doesn't look so expensive.

tomcat- what kind of RPM are you looking at turning? It seems like stresses imparted inside an engine from RPM are greater than those from power/torque. An example- some years back a guy logged a build of a stock 100k mile cast everything 2 bolt main Chevy 350. It was a twin turbo build that he chassis dyno tuned to around the 750hp mark at the wheels. Accounting for drive train losses, he was knocking on the door of 1000hp at the crank! The engine never blew, but the mains were squirming around quite a bit... IIRC, he only turned 5500 rpm with it, and many times 5000 rpm.

 

[tomcat27]

I actually don't know what kind of rpm I will want. it will probably run through an auto (we don't have a car yet) so I suppose I could limit the rpm via the ignition very easily to 5500. I also could leave the blower out of the equation and save that for a more stout block later. The 302's don't really have a lot of material under the mains. and you are correct, the cost of the gamble is not the $2k for the Dart block, but rather the cost of anything it would take with it when it breaks. besides, the point of this endeavor is to see what we CAN do with the block we have.

we built a 408 last summer - but I have no idea what rpm we run with that - the factory tach does not work with the msd ignition. I need to get my tach converted or get an msd-compatible tach. of course, the 408 is a dart block, so it's very stout; definitely overkill for my use of it.

 

[t1snwrbrdr12]

I had a newer 302 in an 87 fox body. It was injected but still same motor, had good pistons and rods but stock crank stock bore. I detuned it a bit because it pulled 550 to the wheels. The stock blocks are good for about 500 to the wheels. I never experienced an issue but I got rid of the car within 2 years or so of putting the blower on it. It was only run to race or cruise to get ice cream or something, which I'm sure you'll be in a similar boat.

 

[Trav]

What kind of blower do have in mind? Is this for big belt look and blower noise like that from a 6-71? Unless its a Boss block with 4 bolt mains, ford racing or Dart I wouldn't even think about a serious blower. A 4-71 is more than enough for the SBF if you can find a manifold for it and will give you the big blower look and sound, you still need a strong block though just not as strong.
Call Dyer's blowers they can help you with blower questions and correct block info for what you want to do.

 

[A_Harman]

Originally Posted By: Trav
What kind of blower do have in mind? Is this for big belt look and blower noise like that from a 6-71? Unless its a Boss block with 4 bolt mains, ford racing or Dart I wouldn't even think about a serious blower. A 4-71 is more than enough for the SBF if you can find a manifold for it and will give you the big blower look and sound, you still need a strong block though just not as strong.
Call Dyer's blowers they can help you with blower questions and correct block info for what you want to do.


The OP said he wanted to use a Weiand 174 blower with 8 psi boost.

 

[A_Harman]

8 psi boost on a stock cast iron block with a main bearing girdle added seems reasonable to me.
As long as you limit it to street use, and the occasional day at the drag strip.

 

[Trav]

Originally Posted By: A_Harman
Originally Posted By: Trav
What kind of blower do have in mind? Is this for big belt look and blower noise like that from a 6-71? Unless its a Boss block with 4 bolt mains, ford racing or Dart I wouldn't even think about a serious blower. A 4-71 is more than enough for the SBF if you can find a manifold for it and will give you the big blower look and sound, you still need a strong block though just not as strong.
Call Dyer's blowers they can help you with blower questions and correct block info for what you want to do.


The OP said he wanted to use a Weiand 174 blower with 8 psi boost.


I didn't see that but yeah now I read the thread again I do. 8 psi should be okay with the stock block depending on the compression ratio, any more than 8.0:1 would be pushing it, the effective ratio would be 12.4:1 which is a little high.

 

[OVERKILL]

Keep the RPM down to around 6K, and the power below 550 to the tires and you should be OK. Conservative, keep the RPM max below 6K and the power below 500 to the tires.

I've got several friends that have boosted stock block 302's and they've all held together. The highest was 534HP to the tires.

 

[asand1]

I doubt a 174 blower will make 8PSI on a 302. I suck at math, but I know a two stoke single 74CI cylinder is only a 1/4 of the dispacement of a 302. And the blowers on GM two strokes dont make positve pressure in stock form, they are merely scavenging pumps. I would go 371 or better and gear it up some. If you meant 471, then yes.

 

[Robenstein]

Over a small blower on a 302, I would probably do something like this.

http://www.jonkaaseracingengines.com/html/kaase_p-38_canted_valve_small_block_ford_heads.html