Firebreather

Hi guys. I know some of you have swapped in 400 ci sbc. However, I've heard both good and bad reviews about these engines. The thing is, I have a chance to buy a 4-bolt 408. My questions are:

1. Is it true the 2-bolt blocks are stronger? I'm kind of skeptical
2. Is overheating an issue?
3. Are the AFR 195 Eliminators too small or should I get 210?
4. Is this wise, or should I just build my 350?
5. Is a 500hp+ 408 going to last?
6. Is header selection and/or installation going to be a problem?

Thanks

rjt76

i would say it will be reliable based on camshaft and valve train choices more than about 350 or 400 cubic inches. The 400 will need steam holes drilled in the heads as the 350 will not. Some starter/header problems may come up. The 2 bolt blocks after 1973 seem to be the hot ticket. Afr 195 is what i would use for a street engine. That engine in a camaro will run alot hotter than a stock engine. certainly if running without an overdrive like 3000rpm cruise speeds. That 700r4 behind a stout 400 is going to die. better step to a th350 if you want to play at the strip ect...450-500hp is alot of power so prepare your vehicle for the stress or you will be unhappy when the rear is broken or the trans is smoked ect...

Brennan

500 horsepower in a unibody car? your probably gonna want a roll cage or somethin at least some sfcs

bjankuski

-A 400 will drop right in place of the 350
-The two bolt block may be stronger if it is equiped with splayed caps, the stock 4-bolt block will be fine at 500 HP
-Overheating is not an issue
-AFR195 heads will work fine, if you are targeting 500 HP
-Durability will not be an issue

I run a 1973 4-bolt 406 in my vette at 550+ HP and it has never given me any problems in 15,000 miles of street use and many 1/4 passes.

AlkyIROC

About the only issue to punching it out to 408 is cylinder wall thickness. 0.030" over is safe. Pushing it to 0.040" over in a 400 block starts to make thin cylinder walls. Factory block castings are not performance castings.

Firebreather

I really want to do this with the 700R4. It has already been upgraded with B&M clutches, power pack, 13 vane pump, corvette servo, shift kit, cooler, etc. I will install Corvette HIgh-Intensity band, 4L65E 5-pinion planetary and Beast Sun Shell before I do so. I really like this trans and I think it can be built to keep up with the 400. Also, I will install TA differential cover, weld the axel tubes and go to church every Sunday so nothing will break so soon, at least.



I already have SFCs.

rjt76

I really think that the 700r4 even built up is a heap of junk for hard performance use. I had one with all the performance parts ect... $3000 dollars later it still failed like the stock 700r4. Dont assume it will hold up to that amount of power. My 383 is in the 425 crank hp range and it killed those overdrives like nothing. 1st to 2nd shifts suck due too much drop in rpm. you end up overreving 1st gear to get it to shift into 2nd gear more in the power band. Also 4th gear sucked unless i was reving 2300 rpm or higher due to the engine build i have. In other words a 500hp 406 might like a little rpm to be happy. A 308 rear with a nice torque cuve from a 450hp 406 would be the hot ticket for a street bruiser with a th350trans. I understand that the od trans is where its at but all the fun starts to be misery when parts keep failing when your trying to have fun. By the way i have a 3.42 rear and have a 3000rpm cruise on the highway and i average 17 to 19 highway mileage.

bjankuski

I am running a modified 700 R4 behind my 550+ Hp 406 and it works great. I bought the parts from PATC and built the transmission myself and it has worked very well. I used the parts from their 600 HP kit.

Firebreather

Is that the Level 3 package? What's included in your tranny package? Wow, they have everything for the 700R4. I can find better prices but that hardened drum and shaft look tempting. I posted the mods already done to my transmission and the still to come mods. I think I will also upgrade the front planetary to the 4L65E 5-pinion unit.

bjankuski

I do not remember what level it is but it is the same package as the rapter 700 except it does not have the 5 pinion planetary.