Hey guys,i need some info on a build.
Before i start,i know it would be best to get a aftermarket block but i want to work with what i have and make it look like a typical 350 build.

I picked up a 87 350 1 piece rear main block.Its standard bore,will go .030 over.
I seen alot of guys do a 396 from a factory block but i want to see who has done a 408.
4.00 stroke,4.030 bore.

I see eagle makes a 4.00 stroke 4340 crank for the 1 piece rear seal blocks(#435340006000)
I see they make a 6" stroker clearenced h-beam rod(#crs6000bst).
Would i need a 1.00" compression height piston for this combo?

What other parts combo's have you used?
Im not looking for crazy$ billet rods or cranks.

Who do you use to make a custom piston for this?

I know a couple guys on here have done large strokes in factory blocks(AKS RACING,TPI 421 VETTE) and im looking for a 408 parts combo that works.
I will be doing a 1/3 fill on the block.
Thanks!

 

Sounds like your on the right track. A key part is a set of good stroker rods. If your trying to keep your rods somewhat economical, I would recommend the Crower sportsman stroker rod, They have 7/16" bolts, and are just over $600. Lunati isn't bad either. But I like a rod with the bigger bolts. I also use a .900" basecircle cam. Rod to cam clearance gets real close.You can use a 1.00 compression height piston with the 6.0" rod mentioned. But that does put the pin way up there. 1.00 compression height is shortest I've seen. You can also go with a 5.85 rod and a 1.150 compression height piston. But with the shorter rods, you will probably have to have the counterweights on the crank shaved for crank to piston clearance. And that will make it a little harder to balance. But the ones I have done have still been internal balance. Both 1.0" or 1.150" C.H. pistons are off the shelf parts. I personally would check JE/SRP. That's what I use. Just check everything close while assembling. You will have to notch the oil pan gasket, and I usually use a Canton pan . I haven't tried a stock pan and 4.0 stroke. A 408 really isn't that hard to do. It's obviously more involved than a 383, but when you feel the torque when it's done, it will be worth it. At least that how I feel about it.

 

I'd rather see that slightly higher compression height piston but it should work ok with 1". I never did like the idea of a stroke that big in these blocks as they arent all that strong but many have done it. Could also recommend a half fill of the block with hard block so you dont leave too thin water jackets.
T&L engines makes a crate 408. My buddy has one and has been spraying it just fine. granted it dont run anywhere near as fast as my 383 but thats probly because he doesnt have the heads/cam he should have for that motor. But its running strong and hasnt blown up

I myself wanted that motor but decided 383 was better/cheaper/easier. Now going 400 with aftermarket Dart SHP block. Much stronger than GM blocks and better foundation to build a 400-408 inch motor on. The amount of machine work for a GM block you could have a SHP block for a few hundred more and its money well spent for security. But tpi421 above has a strong 408 and does well with it... so you should be ok

 

Thanks for taking the time to reply!
I read many old threads where you said you have gotton a 4.125 stroke crank in a factory 350 block and that is what i wanted to try but i dont see anyone that makes a 4.125 stroke crank for a 1 piece seal block.A 421 would be killer and i dont plan on reving this thing to the moon so i think it would last with good internals.

Do you have any exp with the eagle h-beam stroker clearanced rods i listed above?They say they are clearanced for a 4.00 stroke and are only $430 without upgradeing bolts and in the $500's with upgraded bolts.

Also,what size basecircle is a stock cam?Im not to familiar with all the small base circle cam stuff so i dont want to sound dumb but can you explain it a little.

Thanks again guys!

 

Yeah,i know aftermarket block would be best but i want it to look like a 350.
Also,my buddy works for Shaffrof Race engines so he is hooking me up as far as machine,prep work.He is there balancer.

Im gonna look into the 5.85 rod with 1.150 ch piston but if those clearanced eagle rods clear or only need a little work,id rather go with the 6.00 and 1" ch combo.

 

I've run the h beam eagles in my 383 and they clear very well. Very strong rod too, i was pushing over 500whp with mine for a little while with the nitrous and no problems but i only made 7 passes on the bottle at the track and about 5-6 on the street. I was running 400whp all the way to 6800 rpm on occassion tho with no problems either.

I run a smaller base circle cam as well, i believe mine is on a 1.00" circle and i THINK stock is in th 1.3" range, atleast thats what my stock L98 cam approximately measured

If you run a .900-1" base circle it should clear as long as the lift aint super huge. I was running .600" lift just fine with my 6" rods/3.75" stroke. I dont think 4" stroke will have any more problems than my 3.75"

 

OK,Thanks!
I guess my next question is,whats the biggest Lobe i can run with the small base circle cam(.900) and the 4" stroke,6" rod combo.

Im not sure on the rest of combo but it will prob be afr heads(maybe 210 elim) and a miniram intake.
Cam i have not thought about but it would be nice to know how big of a lobe i can go with.

 

I run a 248/254° @ 0.050 SR cam with just over 0.670" lift in my 408. I run the 0.900 base circle cam. I am using 5.85" Oliver billets, due to the large dish required to get 9.4:1SCR. I ran with the AFR215CPs with a MRII and 58MM and produced just barely over 480WHP NA.

Also, these larger cube motors will suck up cam duration much better than their smaller brethren.

These large cube set-ups will be plenty reliable if you start with good components.
Aaron

 

Nice setup.I might be duplicating it if you dont mind.
I pretty much ruled out the 421ci,i cant find someone that makes a 4.125 stroke crank for 1 piece seal blocks.

Looks like the 408 is my best option.
I have to decide on a 6" rod,1"ch piston or
5.85" rod and 1.150ch piston.

I guess i need to decide the rest of combo before picking between the two choices.Eagles does make the stroker clearenced rods for a 4" stroke in 6" and 5.85".
I dont know if i want to run on motor or build it for the option to supercharge it.
Looks like you got some nice power out of your 408 combo even with low compression.
Care to tell me the whole combo with which parts you used?
Thanks!

 

Come on guys...call it a 409, a good ole' Chevy number. I thought most folks used this designation anyway. Lunati also makes some good "stroker" Rods. I believe Ski and others have used them. Don't know the lengths or prices though.

 

Everytime i see this i still go into shock. 9.4 compression and makes more hp than most combos i've ever seen. that cam duration wise isnt huge for a 408 but the lift is pretty healthy. I cant imagine what it would do with 11 to 1 compression

FWIW, i'm predicting 360ish whp n/a with a 233/233 hydraulic roller 400 motor at 9 to 1 compression before the boost comes in. thats only 40 or so lower than my 383 with 11 to 1

 

If you use a crank with the smaller Honda Rod Journals (1.888) you have less clearance issues than with a usual 383 stroker combo and you don't have to use a small base circle cam... That's what Allen Motorsports told me an that's what they are doing on their 408 and 410 LT1 blocks.

I know callies makes these cranks, but they are big $$$!

Regards
Rico

 

OK,I m back on the 421 C.I thing!LOL

I see you can use an adapter to install to 2 piece rear main crank in a 1 piece rear main block and they make a 4.125" stroke crank for the 2 piece block.
So...4.030 bore block with 4.125" stroke would give me 421C.I.

I know its been done before.
Now back to the rod/piston thing.
I think im gonna go eagle h-beam on the rods.Great price and i have had good luck with them in my 468 pontiac build.

They sell 4"stroker clearenced rods in 6" and 5.85" in large journal.

Or if i go to small journal or honda journal,my choice is reg h-beam rods not the stroker clearenced ones.
I think 6" or 5.85 is aval.I have to check.
Then i would need to clearence them myself if i still need to with the smaller journals.

TPI 421 VETTE?????I know you have done this.

 

I used a 5.85" Oliver billet rod with the 4.125" stroke. These rods have some of the best contouring on the big end preventing excess clearancing compared with many other "stroker" rods. And still, the clearancing was ridiculous!

I would steer others away from a 421CID build in a 4.030" bore block. If you want a 421, build the 400 base block.

The clearancing to make this all fit (even with high quality parts) in a 350 base block is excessive. Jim will probably 2nd that opinion.
Aaron

 

I have built 4 of these motors i took them all to .040 over and call them a 410. The scat 7/16 cap screw I beam rod works very good also, And can be had for a little under $300 a set. I also recomend at least a half fill block like mentioned above. The best et we saw with that combo was mid 10.40s in a 3400lb malibu, through exhaust and on pump gas.

 

If it was an LTX block, and you were going to stick with all the LT electronics, I might recommend the 4.125 stroke in a 350 block. But if you have a first gen block, and can run the bigger 4.155 bore, I would build the 421 the way Aaron recommended it. 4.155X3.875. And 400 based block. It is much easier, and has a much better rod ratio. But if your one of those guys that wants to do something different... and I am also guilty of this, it sounds like you have most of the info to do it. You will need a 2 piece seal adapter. I used small journal rods (2.00" Crower billet maxilite stroker rods) and still had to do slight clearancing on them, but Honda rods would probably be better. And don't go low budget on the rods. You still need a stroker design rod. It seems like half the rods want to hit the cam. And some hit real hard with a regular 2.10" stroker rod. And there is major clearancing on the block. And block filler as mentioned. You still need a small base circle cam. And with a 4.125 stroke, you will need a 5.85 rod, and a 1.062 compression height piston. The pistons would be the same as a 396 with a 6" rod. So they are off the shelf. And the crank will need the counterweights turned down so the pistons will clear it, and the rod journals turned down for the smaller journal rods. This will make it harder to balance with the counterweights cut. Mine ended up being external balance on the rear half, but took a small counterweight on the flywheel. I was able to get the front half of the crank internal balance.And the crank took several sticks of mallory metal. And you can expect an expensive machine shop bill. You will also need a oil pan that will handle a 4.0" stroke. I used a Canton. Then I still had to clearance the crank scraper in the pan to clear the rods. And of course clearance the oil pan gasket. It's alot of work and money, but it's your decision.

 

Dart SHP block for 1800 fully blueprint machined. 4.125" bore and they recommend only 3.75 stroke but you can get away with more i'm sure. thats your best bet to build a bigger inch motor in the 400-420" range

 

Your right, and I fully agree. But some guys like to go off the beaten path. I am sure a 4.00" or 4.125" stroke would be no problem with that block. But I have been guilty of building motors (mainly for myself) that would have been easier and cheaper to do different. I wouldn't do it to a paying customer. But with your own stuff experimenting does come into play. Anybody else... if you want a 421 go the 4.155 x 3.875 route.